ALBERT

Description: 〈h3〉Abstract〈/h3〉 〈p〉A fluorimetric and colorimetric method is described for the determination of glutathione (GSH) and silver (I). It is based on the use of MnO〈sub〉2〈/sub〉 nanosheets that were prepared by solution mixing and exfoliation. They display oxidase-mimicking activity and can catalyze the oxidation of o-phenylenediamine (OPD) to form yellow 2,3-diaminophenazine (DAP) with an absorption maximum at 410 nm. DAP also has a yellow fluorescence (with a peak at 560 nm). The MnO〈sub〉2〈/sub〉 nanosheets can be rapidly reduced to Mn〈sup〉2+〈/sup〉 by GSH. This reduces the efficiency of the oxidase mimic MnO〈sub〉2〈/sub〉 and causes a decrease in fluorescence and absorbance intensity. However, on addition of Ag〈sup〉+〈/sup〉, a complex is formed with GSH. It prevents the destruction of MnO〈sub〉2〈/sub〉 nanosheets so that the enzyme mimicking activity is retained. A dual-method for the determination of GSH and Ag(I) was developed. It has excellent sensitivity for GSH with lower detection limits of 62 nM (fluorimetric) and 0.94 μM (colorimetric). The respective data for Ag(I) are 70 nM and 1.15 μM. The assay was successfully applied to the determination of GSH and Ag(I) in spiked serum samples.〈/p〉 〈p〉 〈span〉 〈caption〉 〈strong〉Graphical abstract〈/strong〉 〈em〉 〈div〉Schematic presentation of a method for colorimetric and fluorometric determination of glutathione (GSH) and silver(I). MnO〈sub〉2〈/sub〉 nanosheets are reduced to Mn(II) by GSH. This reduces the enzyme-mimicking activity of MnO〈sub〉2〈/sub〉 nanosheets and causes a decrease in fluorescence and absorbance. On addition of Ag(I), the enzyme-like activity is increasingly retained. A decrease in fluorescence and absorbance is not observed any longer.〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/604_2019_3613_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Carboxylic acids (CAs) have been reported as potential biomarkers of specific diseases or human body odors. A visual sensor array is described here that is based on indicator displacement assays (IDAs). The arrays were prepared by spotting solutions of the following metal complexes: Murexide-Ni(II), murexide-Cu(II), zincon-Zn(II) and xylenol orange-Cu(II), with the capability of discrimination of 15 carboxylic acids (CAs) and the quantitation of pyruvic acid (PA). Clear differences can be observed through distinctive difference maps obtained within 5 min by subtraction of red, green and blue (RGB) values of digital images after and before exposure to analytes. After an analysis of multidimensional data by pattern recognition algorithms including HCA, PCA and LDA, excellent classification specificity, and accuracy of 〉96% were obtained for all samples. The IDA array exhibited a linear range from 10 to 1500 μM with a theoretical detection limit of 3.5 μM towards PA. Recoveries of real samples varied from 84.8% to 114.3%. As-fabricated IDA sensor array showed an excellent selectivity among other organic interfering substances and a good batch to batch reproducibility, demonstrating its robustness. All these observations suggested that the IDA sensor array is one of the most promising paths for the discrimination of CAs.〈/p〉 〈p〉 〈span〉 〈caption〉 〈strong〉Graphical abstract〈/strong〉 〈em〉 〈div〉Schematic diagram of indicator displacement assay (a), the procedure for acquisition of difference maps (b), and pattern recognitions for CAs (c). The method uses hierarchical cluster analysis (HCA), principal component analysis (PCA) and linear discriminant analysis (LDA)〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/604_2019_3601_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉A multifunctional nanoprobe is described for dual sensing of acidic pH values and glutathione (GSH) by combining the pH-responsive fluorescent probe 3-acetyl-7-hydroxy-2H-chromen-2-one (AHC) and MnO〈sub〉2〈/sub〉 nanosheets. The fluorescence of the MnO〈sub〉2〈/sub〉/AHC composite is weak due to an inner filter effect. If, however, the MnO〈sub〉2〈/sub〉 nanosheets are reductively decomposed by GSH, the blue fluorescence of the pH probe AHC (with excitation/emission maximum at 417/456 nm) will be restored. The MnO〈sub〉2〈/sub〉 nanosheets also are decomposed by acidic pH values, and the fluorescence of AHC is decreased. According to absorbance and fluorescence signal changes, the pH and GSH induced responses can be easily distinguished. Thus, the nanoprobe can be used for logical analysis of acidic pH values and GSH. The nanoprobe works in the pH range from 4 to 7, and GSH can be determined in the concentration range from 0.5 to 200 μM.〈/p〉 〈p〉 〈span〉 〈caption〉 〈strong〉Graphical abstract〈/strong〉 〈em〉 〈div〉Schematic presentation of a multifunctional nanoprobe for dual sensing of acidic pH values and glutathione by combining a pH-responsive fluorescent probe and MnO〈sub〉2〈/sub〉 nanosheets. According to absorbance and fluorescence signal changes, the nanoprobe can be used for logical analysis.〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/604_2019_3590_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Two kinds of aptasensors for ampicillin (AMP) are described. The assay strategies include the use of gold nanoparticles (AuNPs) that were modified with (a) a thiolated aptamer (T-Apt), and (b) a non-thiolated polyadenine aptamer (polyA Apt). The AuNPs and the aptamers were brought to interaction prior to addition of AMP. T-Apt and polyA Apt are adsorbed on the AuNPs by different mechanisms. The adsorbed aptamer was able to bind the target while preventing non-specific interactions. Remarkably different optical absorbances (measured at 520 and 680 nm) are produced the absence and presence of AMP. The assay can selectively recognize AMP even in the presence of species of similar chemical structure. The T-Apt based assay has a linear response in the 1–600 nM AMP concentration range and a 0.1 nM limit of detection. The respective data for the polyA Apt assay are 1–400 nM and 0.49 nM.〈/p〉 〈p〉 〈span〉 〈caption〉 〈strong〉Graphical abstract〈/strong〉 〈em〉 〈div〉Schematic presentation of the colorimetric aptasensor for ampicillin detection using two kinds of anti-ampicillin aptamers and gold nanoparticles. Polydiallyldimethylammonium chloride (PDDA) acts as aggregation agent.〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/604_2019_3524_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉The authors describe an immunosensor for the prostate specific antigen (PSA). It was obtained by modifying a glassy carbon electrode (GCE) first modified with gold nanoparticles and then with reduced graphene oxide that was decorated with gold nanoparticles. The AuNPs on reduced graphene oxide provide a suitable surface for attachment of antibodies. On binding of the antigen, the square wave voltammetric signal (measured by using hexacyanoferrate as a probe) reduced. This method has two logarithmically linear analytical ranges that extend from 25 to 55 fg.mL〈sup〉−1〈/sup〉 and from 1 to 36 ng.mL〈sup〉−1〈/sup〉, respectively. The lowest detection limit is 2 pg.mL〈sup〉−1〈/sup〉. Electrochemical impedance spectroscopy was also carried out for PSA determination. EIS works in the 0.0018 to 41 ng.mL〈sup〉−1〈/sup〉 concentration range and has an LOD of 60 pg.mL〈sup〉−1〈/sup〉. This method was applied to the determination of PSA in (spiked) human serum samples. In order to survey the selectivity of immunosensor, determination of PSA was performed in human serum samples, and finally sensitivity and reproducibility were examined.〈/p〉 〈p〉 〈span〉 〈caption〉 〈strong〉Graphical abstract〈/strong〉 〈em〉 〈div〉Facile label free immunosensor based on reduced graphene oxide decorated with gold nanoparticles for early diagnosis prostate cancer via ultrasensitive detection of PSA biomarker: application in human serum.〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/604_2019_3565_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉A non-enzymatic hydrogen peroxide (H〈sub〉2〈/sub〉O〈sub〉2〈/sub〉) electrochemical sensor material was prepared from silver nanoparticles and a 2D copper-porphyrin framework (MOF). The structure and morphology of the nanocomposite were characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy. The results showed that the MOF has a two-dimensional sheet structure, and a large number of Ag NPs are uniformly attached to it. The MOF also acts as a peroxidase mimic. The sensor has excellent catalytic performance in terms of H〈sub〉2〈/sub〉O〈sub〉2〈/sub〉 reduction. Figures of merit include (a) an electrochemical sensitivity of 21.6 μA mM〈sup〉−1〈/sup〉 cm〈sup〉−2〈/sup〉 at a typical working potential of −0.25 V (vs. SCE), (b) a detection limit of 1.2 μM (at S/〈em〉N〈/em〉 = 3), and (c) a linear response range that extends from 3.7 μM to 5.8 mM. Compared to other sensors of the same type, the linear range of the sensor is extended by an order of magnitude.〈/p〉 〈p〉 〈span〉 〈caption〉 〈strong〉Graphical abstract〈/strong〉 〈em〉 〈div〉Silver nanoparticles (Ag NPs) were reduced with sodium borohydride (NaBH〈sub〉4〈/sub〉) on the surface of copper(II)-porphyrin (Cu-TCPP) nanosheets prepared with the assistance of polyvinylpyrrolidone (PVP). Their synergistic effect improved the performance of H〈sub〉2〈/sub〉O〈sub〉2〈/sub〉 sensor fabricated by immobilizing Ag NPs/Cu-TCPP nanocomposites on glassy carbon electrodes (GCE).〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/604_2019_3551_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Two adsorbents with covalently bound aminomethylenephosphonic acid functions (and referred to as MNPs/AMPA and MNPs/SiO〈sub〉2〈/sub〉-AMPA) were synthesized from two types of amino-functionalized magnetic nanoparticles (MNPs) via Moedritzer-Irani reaction. The sorbents with anchored dopamine ligand (MNPs/dopa) or aminopropyl groups (MNPs/SiO〈sub〉2〈/sub〉-NH〈sub〉2〈/sub〉), and the MNPs/AMPA were characterized by X-ray diffraction, FTIR, transmission electron microscopy and vibrating sample magnetometry. Surface modification does not adversely impact the physical properties of the starting magnetite. Compared to the size of the unmodified Fe〈sub〉3〈/sub〉O〈sub〉4〈/sub〉 (magnetite) nanoparticles (7–12 nm), the average size of functionalized nanoparticles is increased to 10–16 nm. Similarly, the magnetic saturation decreased from 67.5 emu g〈sup〉-1〈/sup〉 to 42.0 emu g〈sup〉−1〈/sup〉, and the surface area is increased up to 205 m〈sup〉2〈/sup〉 g〈sup〉−1〈/sup〉 for MNPs/SiO〈sub〉2〈/sub〉-AMPA. The kinetics of the adsorption of Eu(III) on the sorbent is ultra-fast, and equilibria are attained within 5–10 min at room temperature. The adsorption kinetics can be described by a pseudo-second-order model. Adsorption and desorption conditions were tested with respect to the removal of Eu(III) ions from water solution. The adsorption capacities for Eu(III) at pH 7.0 are 77 mg g〈sup〉−1〈/sup〉 and 69 mg g〈sup〉−1〈/sup〉 for MNPs/AMPA and MNPs/SiO2-AMPA nanoparticles, respectively. Eu(III) was quantified by ICP-MS. The limit of detection (LOD) for Eu(III) is 0.05 ng L〈sup〉−1〈/sup〉 (based on the 3σ criterion), with an enrichment factor of 150. The selectivity over ions such as Tb(III), Fe(III), Zn(II), Cu(II), and Ca(II) ions was studied. Under optimal condition the distribution coefficient for Eu(III) relative to these ions is near 10〈sup〉5〈/sup〉 mL g〈sup〉−1〈/sup〉. The sorbents can be easily retrieved from even large volumes of aqueous solutions by magnetic separations. The method was tested for spiked water samples (with recoveries from 96.6–102.5%) and for rock minerals.〈/p〉 〈p〉 〈span〉 〈caption〉 〈strong〉Graphical abstract〈/strong〉 〈em〉 〈div〉A schematic showing the regeneration of magnetite nanoparticles (MNPs), core-shell (MNPs/SiO〈sub〉2〈/sub〉), and the structures with covalently bonded aminomethylenephosphonic acid (AMPA) after preconcentration of Eu(III) from largewater sample volumes onto a small specimen.〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/604_2019_3520_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉A ratiometric electrochemical aptamer-based assay is described for the ultrasensitive and highly specific determination of adenosine triphosphate (ATP). It is based on ATP aptamer-mediated triple-helix molecular switch (THMS). The method uses (a) a hairpin DNA (MB-DNA-SH) labeled with the redox probe Methylene Blue (MB) at the 3′ end, and a thiol group at the 5′ end, and (b) a single strand ATP aptamer modified with two ferrocenes at each end (Fc-DNA-Fc). The labeled probe of type MB-DNA-SH was self-assembled onto the surface of a gold electrode via gold-thiol binding. On exposure to Fc-DNA-Fc, it will hybridize with MB-DNA-SH to form a stable THMS structure on electrode surface. In the presence of ATP, it hybridizes with the loop portion of Fc-DNA-Fc, and this results in the unwinding of the THMS structure. Such variation caused the changes of the differential pulse voltammetry (DPV) peak currents of both MB (at around −0.25 V) and Fc (at around 0.39 V; both vs. Ag/AgCl). A significant enhancement is found for the ratio of the two DPV peaks. Under the optimum experimental conditions, this assay has a response that covers the 0.05 to 100 pM ATP concentration range, and the detection limit is 5.2 fM (for 〈em〉S〈/em〉/〈em〉N〈/em〉 = 3). The method is highly selective for ATP over its analogs.〈/p〉 〈p〉 〈span〉 〈caption〉 〈strong〉Graphical abstract〈/strong〉 〈em〉 〈div〉Schematic presentation of a novel ratiometric electrochemical aptasensor for ATP via triple-helix molecular switch (THMS) strategy. MB-DNA-SH was self-assembled on GE surface through gold-thiol binding. Fc-DNA-Fc hybridized with MB-DNA-SH to form THMS structure. ATP specifically bond with its aptamer sequence of Fc-DNA-Fc to unwind the THMS structure. The ratio of DPV peak currents of MB and Fc was applied to monitor the concentration of ATP in real samples over its analogs.〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/604_2019_3630_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Core-shell nanoparticles (NPs) consisting of a gold core and a metal-organic framework shell (type MOF-74) were synthesized via one-pot synthesis. The NPs exhibit highly sensitive and stable SERS activity for the detection of 4-nitrothiophenol, with a specific band at 1337 cm〈sup〉−1〈/sup〉. The method has a linear response in 0.10–10 μmol·L〈sup〉−1〈/sup〉 analyte concentration range and a lower detection limit of 69 nmol·L〈sup〉−1〈/sup〉. The potential application of this novel SERS substrate was evaluated by two model reactions involving 4-nitrothiophenol. The first involves in-situ SERS monitoring of the surface plasmon-induced nitration of aromatic rings without adding conventional acid catalyst. The second involves the photocatalytic reduction of 4-nitrothiophenol to 4-thioaminophenol in the presence of Au/MOF-74 under 785-nm laser irradiation. The plasmon-assisted dimerization of 4-nitrothiophenol to form 4,4′-dimercaptoazobenzene can also be monitored simultaneously.〈/p〉 〈p〉 〈span〉 〈caption〉 〈strong〉Graphical abstract〈/strong〉 〈em〉 〈div〉Schematic presentation of a nanoparticle SERS substrate consisting of gold core and MOF-74 shell, which was applied to detection of 4-nitrothiophenol. The Au/MOF-74 was successfully used for in-situ monitoring of two model reactions involving 4-nitrothiophenol by SERS.〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/604_2019_3618_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Light-harvesting nanoprobes were developed by self-assembly of nanoscale metal-organic frameworks (NMOFs) and stimuli-responsive polymers for fluorometric sensing of pH values and temperature. Two kinds of fluorescent NMOFs (acting as the energy donor) and stimuli-responsive polymers conjugated to fluorophores (acting as energy acceptors) were prepared and characterized. The NMOFs include zirconium(IV) and 〈em〉π〈/em〉-conjugated dicarboxylate ligands. The fluorophores inclued cyaine dyes and a Bodipy dye. The energy donor and energy acceptor form a Förster resonance energy transfer (FRET) nanosystem. In the light-harvesting system, the chain lengths of the stimuli-responsive polymers vary when the local pH value or temperature change. Ratiometric sensing of pH and temperature was accomplished by monitoring fluorescence. pH values were can be sensed between 3.0 and 8.0 under 420 nm excitation and by ratioing the emission peaks at 645 and 530 nm. Temperature can be sensed in the range from 25 to 50 °C under 550 nm excitation and by ratioing the emission peaks at 810 and 695 nm. The nanoprobes display excellent water dispersibility and cell membrane permeability. They were applied to image pH values and temperature in HeLa cells.〈/p〉 〈p〉 〈span〉 〈caption〉 〈strong〉Graphical abstract〈/strong〉 〈em〉 〈div〉Schematic presentation of an effective strategy to fabricate light-harvesting nanoprobes by self-assembly of MOFs and stimuli-responsive polymers for ratiometric pH and temperature sensing. The distance as the polymer length between energy donor and acceptor is crucial for energy transfer efficiency.〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/604_2019_3608_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉A paper-based electrochemical sensor is described that is based on the use of thiol-terminated poly(2-methacryloyloxyethyl phosphorylcholine) (PMPC-SH) that was self-assembled on a gold nanoparticle-modified screen-printed electrode (SPE). The SPE sensor was used for label-free detection of C-reactive protein (CRP). Gold nanoparticles (AuNPs) were first electrodeposited on the SPCE, followed by the self-assembly of PMPC-SH on gold. The electrochemical response of the modified SPE to CRP was measured by differential pulse voltammetry (DPV). If the CRP on the paper device is contacted with Ca (II) ions, the current (measured by using hexacyanoferrate as the electrochemical probe) decreases. The signal drops in the 5 to 5000 ng·mL〈sup〉−1〈/sup〉 CRP concentration range, and the lower detection limit (at 3 SD/slope) is 1.6 ng·mL〈sup〉−1〈/sup〉. The use of a PMPC-modified surface also reduces the nonspecific adsorption of proteins. The sensor is not interfered by bilirubin, myoglobin and albumin. It was successfully applied to CRP detection in certified human serum. This sensor is applicable as an attractive protocol for an inexpensive, highly sensitive, and disposable material for electrochemical detection of CRP.〈/p〉 〈p〉 〈span〉 〈caption〉 〈strong〉Graphical abstract〈/strong〉 〈em〉 〈div〉Schematic presentation of highly sensitive and disposable paper-based electrochemical sensor using thiol-terminated poly(2-methacryloyloxyethyl phosphorylcholine) in the presence of Ca〈sup〉2+〈/sup〉 for the label-free C-reactive protein detection. The current was measured by differential pulse voltammetry.〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/604_2019_3559_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉A sandwich-type electrochemical aptasensor is described for detecting the carcinoembryonic antigen (CEA) with high sensitivity and accuracy. Two kinds of nanomaterials are used. The first was obtained by modifying gold nanoparticles with reduced graphene oxide and hemin (Hemin-rGO-AuNPs). The second consists of horseradish peroxidase-modified organic-inorganic hybrid nanoflowers linked to gold nanoparticles to obtain an architecture of type HRP-Cu〈sub〉3〈/sub〉(PO〈sub〉4〈/sub〉)〈sub〉2〈/sub〉-HNF-AuNPs). These serve as carriers for two aptamers (apt1 and apt2) against CEA. Simultaneously, they were used to catalyze the precipitation reaction between 4-chloro-1-naphthol(4-CN) and H〈sub〉2〈/sub〉O〈sub〉2〈/sub〉. A sandwich-type assay linked to enzyme inhibition amplification was established for electrochemical determination of CEA. Under optimal experimental conditions and by using differential pulse voltammetry, the response peak currents (best measured at −0.34 V vs. Ag/AgCl) increases linearly with the logarithm of the CEA concentration in the range between 100 fg mL〈sup〉−1〈/sup〉 and 100 ng mL〈sup〉−1〈/sup〉. The detection limit is as low as 29 fg mL〈sup〉−1〈/sup〉.〈/p〉 〈p〉 〈span〉 〈caption〉 〈strong〉Graphical abstract〈/strong〉 〈em〉 〈div〉Schematic representation of the sandwich-type electrochemical aptasensor based on signal inhibition amplification from biocatalytic precipitation reaction. (HRP-Cu〈sub〉3〈/sub〉(PO〈sub〉4〈/sub〉)〈sub〉2〈/sub〉 hybrid nanoflowers: Horseradish Peroxidase-Cu〈sub〉3〈/sub〉(PO〈sub〉4〈/sub〉)〈sub〉2〈/sub〉 hybrid nanoflowers; AuNPs: Gold Nanoparticles; Hemin-rGO-AuNPs: Hemin-Reduced Graphene Oxide-Gold Nanoparticles; BSA: Bovine Serum Albumin; CEA: Carcinoembryonic Antigen; CEA〈sub〉apt1〈/sub〉: 5′-SH-(CH〈sub〉2〈/sub〉)〈sub〉6〈/sub〉-ATA CCA GCT TAT TCA ATT-3′; CEA〈sub〉apt2〈/sub〉: 5′-NH〈sub〉2〈/sub〉-(CH〈sub〉2〈/sub〉)〈sub〉6〈/sub〉-AGG GGG TGA AGG GAT ACC C-3′; GCE: Glassy carbon electrode; 4-CN: 4-Chloro-1-naphthol; DPV: Differential pulse voltammetry).〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/604_2019_3542_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Polyaniline and its composites with nanoparticles have been widely used in electrochemical sensor and biosensors due to their attractive properties and the option of tuning them by proper choice of materials. The review (with 191 references) describes the progress made in the recent years in polyaniline-based biosensors and their applications in clinical sensing, food quality control, and environmental monitoring. A first section summarizes the features of using polyaniline in biosensing systems. A subsequent section covers sensors for clinical applications (with subsections on the detection of cancer cells and bacteria, and sensing of glucose, uric acid, and cholesterol). Further sections discuss sensors for use in the food industry (such as for sulfite, phenolic compounds, acrylamide), and in environmental monitoring (mainly pesticides and heavy metal ions). A concluding section summarizes the current state, highlights some of the challenges currently compromising performance in biosensors and nanobiosensors, and discusses potential future directions.〈/p〉 〈p〉 〈span〉 〈caption〉 〈strong〉Graphical abstract〈/strong〉 〈em〉 〈div〉Schematic presentation of electrochemical sensor and biosensors applications based on polyaniline/nanoparticles in various fields of human life including medicine, food industry, and environmental monitoring. The simultaneous use of suitable properties polyaniline and nanoparticles can provide the fabrication of sensing systems with high sensitivity, short response time, high signal/noise ratio, low detection limit, and wide linear range by improving conductivity and the large surface area for biomolecules immobilization.〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/604_2019_3588_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉New green-emissive carbon dots (G-CDs) are described here and shown to be viable fluorescent nanoprobes for the detection of changes in cellular pH values. By using 〈em〉m〈/em〉-phenylenediamine as the carbon source, G-CDs with an absolute quantum yield of 36% were solvothermally synthesized in the presence of strong H〈sub〉2〈/sub〉SO〈sub〉4〈/sub〉. The G-CDs have an average size of 2.3 nm and display strong fluorescence with excitation/emission peaks at 450/510 nm. The fluorescence intensity depends on the pH value in the range from 6.0 to 10.0, affording the capability for sensitive detection of intracellular pH variation. The nanosensor with excellent photostability exhibited good fluorescence reversibility in different pH solutions, and showed excellent stability against the influence of other biological species. The nanoprobe was successfully used in confocal fluorescence microscopy to determine pH values in SMMC-7721 cells.〈/p〉 〈p〉 〈span〉 〈caption〉 〈strong〉Graphical abstract〈/strong〉 〈em〉 〈div〉Schematic presentation of green-emissive carbon dots (G-CDs) synthesized using 〈em〉m〈/em〉-phenylenediamine and sufuric acid through a solvothermal method for real-time fluorometric monitoring of intracellular pH values. Mechanism can be ascribed to PET process from the electron lone pair in amino group to the CDs.〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/604_2019_3569_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉An ultrasensitive and highly reliable ratiometric assay is described for the determination of microRNA-155. It works at the attomolar concentration level and has high selectivity which warrants its potential application in cancer biomarker tracking. The excellent performance of this method results from (a) the use of a hybrid conjugate prepared from Rhodamine B (RhB), carbon dots (CDs) and probe-microRNA, and (b) from the measurement of fluorescence resonance energy transfer (FRET) that is observed in the AuNP/target-microRNA system as a result of RNA hybridization. The dye RhB (emission peak at 580 nm) serves as an internal reference. The sensitivity of this assay is increased by about 30% because of the broad emissions of CDs (489 nm and 665 nm) through a sequential FRET phenomenon. RhB-CDs were covalently bio-conjugated to probe microRNA. In the presence of AuNPs, the fluorescence of the CDs is quenched, while in the presence of microRNA-155, the ratio of fluorescences at 489 and 665 nm (I〈sub〉489〈/sub〉/I〈sub〉665〈/sub〉) is enhanced again. A linear relationship exists between the ratio of fluorescence and the concentration of microRNA-155 in the range from 1 aM to 0.1 μM, and the detection limit is 0.3 aM. The assay was applied to quantitative studies of target microRNA-155 in multiple pathways associated with cancer progression in biological fluids include human serum samples and cancer cells. The nanoprobe also deliver clear signal to microRNA target in fixed and lived MDA-MB-231 cells.〈/p〉 〈p〉 〈span〉 〈caption〉 〈strong〉Graphical abstract〈/strong〉 〈em〉 〈div〉A ratiometric FRET sensing method used for microRNA-155 detection at aM concentration level using CDs and AuNPs as donor–acceptor respectively and Rhodamine B as amplification reagent. The application of assay for imaging of microRNA-155 in fixed and live MDA-MB-231 cells is demonstrated.〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/604_2019_3446_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉An amperometric nonenzymatic dopamine sensor has been developed. Cobalt oxide (Co〈sub〉3〈/sub〉O〈sub〉4〈/sub〉) nanoparticles were uniformly dispersed inside mesoporous SiO〈sub〉2〈/sub〉/C. A sol-gel process was used for the preparation of this mesoporous composite material (SiO〈sub〉2〈/sub〉/C). This mesoporous composite has a pore size of around 13–14 nm, a large surface area (S〈sub〉BET〈/sub〉 421 m〈sup〉2〈/sup〉·g〈sup〉−1〈/sup〉) and large pore volume (0.98 cm〈sup〉3〈/sup〉·g〈sup〉−1〈/sup〉) as determined by the BET technique. The material compactness was confirmed by SEM images which showing that there is no phase segregation at the magnification applied. The chemical homogeneity of the materials was confirmed by EDX mapping. The SiO〈sub〉2〈/sub〉/C/Co〈sub〉3〈/sub〉O〈sub〉4〈/sub〉 nanomaterial was pressed in desk format to fabricate a working electrode for nonenzymatic amperometric sensing of dopamine at a pH value of 7.0 and at a typical working potential of 0.25 V vs SCE. The detection limit, linear response range and sensitivity are 0.018 μmol L〈sup〉−1〈/sup〉, 10–240 μmol L〈sup〉−1〈/sup〉, and 80 μA·μmol L〈sup〉−1〈/sup〉 cm〈sup〉−2〈/sup〉, respectively. The response timé of the electrode is less than 1 s in the presence of 60 μmol L〈sup〉−1〈/sup〉 of dopamine. The sensor showed chemically stability, high sensitivity and is not interfered by other electroactive molecules present in blood. The repeatability of this sensor was evaluated as 1.9% (RSD; for 〈em〉n〈/em〉 = 10 at a 40 μmol L〈sup〉−1 〈/sup〉dopamine level.〈/p〉 〈p〉 〈span〉 〈caption〉 〈strong〉Graphical abstract〈/strong〉 〈em〉 〈div〉Schematic presentation of the preparation of a nanostructured composite of type SiO〈sub〉2〈/sub〉/C/Co〈sub〉3〈/sub〉O〈sub〉4〈/sub〉 for electrooxidative sensing of dopamine.〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/604_2019_3605_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉A highly sensitive colorimetric assay is described for the determination of glutathione (GSH). It is based on the use of tungsten disulfide (WS〈sub〉2〈/sub〉) which is a peroxidase mimic. It catalyzes the oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB) by hydrogen peroxide to form a blue-colored product (oxTMB) at near neutral pH values. In the presence of the analyte GSH, it is transformed to its oxidized form (GSSG), while the blue oxTMB is increasingly reduced and eventually is converted to colorless TMB. This can readily be detected with bare eyes. GSH can be determined spectroscopically (at 652 nm) by this method at concentrations down to 61 pM, and the response is linear in the 100 pM to 10 nM GSH concentration range. The assay is cost-effective and simple. Conceivably, it provides a promising tool for the determination of GSH in food and medical samples.〈/p〉 〈p〉 〈span〉 〈caption〉 〈strong〉Graphical abstract〈/strong〉 〈em〉 〈div〉Schemaric of a sensitive method for colorimetric detection of glutathione (GSH) based on WS〈sub〉2〈/sub〉-catalyzed oxidation of TMB by H〈sub〉2〈/sub〉O〈sub〉2〈/sub〉 and the reduction of blue oxTMB by GSH.〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/604_2019_3365_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉A fluorometric method was developed for the determination of the insecticide cartap. It is based on the use of green emitting carbon dots (CDs) and gold nanoparticles (Au NPs). The CDs were prepared from phenol and ethylene diamine by a hydrothermal route. They have excitation/emission maxima at 410/513 nm) and a fluorescence quantum yield of 29%. They were characterized by TEM, Raman, XRD, XPS, FT-IR, UV and fluorescence spectroscopies. The green fluorescence of the CDs is strongly reduced by the red-colored Au NPs because of an inner filter effect. Upon addition of cartap, it will cause the aggregation of the Au NPs owing to Au-N interaction between Au NPs and cartap to form purple colored aggregates with spectra that do not overlap the green emission of the CDs. Hence, their fluorescence is restored. Under optimum conditions, the method allows for the quantitation of cartap in the 5–300 nM concentration range, and the detection limit is 3.8 nM. The method was successfully applied to the determination of cartap in spiked real samples and gave satisfactory results.〈/p〉 〈p〉 〈span〉 〈caption〉 〈strong〉Graphical abstract〈/strong〉 〈em〉 〈div〉Schematic presentation of green emitting carbon dots for sensitive fluorometric determination of cartap based on its aggregation effect on gold nanoparticles.〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/604_2019_3361_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Cellulose paper was coated with the metal-organic framework MIL-101(Cr) in a chitosan matrix and utilized for thin-film microextraction (TFME). The coated paper possesses excellent extraction efficiency for the triazine herbicides atraton, desmetryn, secbumeton, prometon, ametryn, dipropetryn, and dimethametryn. High-performance liquid chromatography-tandem mass spectrometry was applied to quantify target analytes. The effects of mass ratio of MIL-101(Cr) to chitosan, sample pH value, time of adsorption and desorption, and type and volume of desorption solvent on extraction efficiency were optimized. Under the optimal conditions, the method has limits of detection between 1.5 and 22 ng·L〈sup〉−1〈/sup〉. The recoveries of triazines from spiked tap water, drinking water, lake water and river water range from 77.0 to 125.3%, with relative standard deviations of 〈17.4%.〈/p〉 〈p〉 〈span〉 〈caption〉 〈strong〉Graphical abstract〈/strong〉 〈em〉 〈div〉Cellulose paper was modified with metal-organic framework MIL-101(Cr)/chitosan by using a simple, efficient and environmentally friendly approach. The modified cellulose paper was then used as a novel extraction phase in thin-film microextraction (TFME).〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/604_2019_3889_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉This work describes the synthesis of a nanocomposite consisting of Ag〈sub〉2〈/sub〉O, silver nanoparticles and N,S-doped carbon quantum dots (Ag〈sub〉2〈/sub〉O/Ag@NS-CQD). The NS-CQD were prepared by hydrothermal treatment of p-aminobenzenesulfonic acid. They act as both the reducing and stabilizing agent for synthesis of Ag〈sub〉2〈/sub〉O/Ag@NS-CQD. The composite was characterized by UV-vis spectroscopy, transmission electron microscopy, X-ray diffraction and X-ray photoelectron spectroscopy. The glassy carbon electrode (GCE) was modified by coating it with Ag〈sub〉2〈/sub〉O/Ag@NS-CQD. It exhibits excellent amperometric response to catechol, typically at a low working potential of around 0.25 V. Under the best experimental conditions, the sensor has a wide linear response (0.2 to 180 μM) and a low detection limit (13 nM; at S/〈em〉N〈/em〉 = 3). The method was applied to analysis of spiked water samples and gave satisfactory results.〈/p〉 〈p〉 〈span〉 〈caption〉 〈strong〉Graphical abstract〈/strong〉 〈em〉 〈div〉Schematic representation of the preparation of the Ag/Ag2O@N,S-doped carbon quantum dots composite using 〈em〉p〈/em〉-aminobenzenesulfonic acid and silver nitrate as the starting materials. The corresponding modified glassy carbon electrode exhibits the excellent amperometric sensing performance toward catechol at pH 7.0 with low detection limit and good selectivity.〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/604_2019_3848_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉A flower-like Fe〈sub〉3〈/sub〉O〈sub〉4〈/sub〉/GO/CdSe nanodot magnetic hybrid material was produced and applied to magnetic solid-phase extraction of ibuprofen from pharmaceuticals, water, and urine samples. The material was characterized by X-ray diffraction, Raman spectroscopy and field emission scanning electron microscopy and SEM-EDX. The pH value, volume of sample solution, amount of sorbent, type and volume of elution solvent and extraction time were optimized. Following elution with acetone, ibuprofen was quantified by HPLC-DAD detection. The recoveries of ibuprofen from spiked real samples ranged between 87 and 109%, and the intra-day and inter-day relative standard deviations from 1.25 to 3.02%. The limit of detection, limit of quantification and preconcentration factor are 0.36 ng·mL〈sup〉−1〈/sup〉,1.20 ng·mL〈sup〉−1〈/sup〉 and 150, respectively.〈/p〉 〈p〉 〈span〉 〈caption〉 〈strong〉Graphical abstract〈/strong〉 〈em〉 〈div〉Schematic representation of the combination of flower-like Fe〈sub〉3〈/sub〉O〈sub〉4〈/sub〉/GO/CdSe nanodot-based magnetic solid phase extraction (MSPE) and high-performance liquid chromatography (HPLC) procedure for the extraction and analysis of ibuprofen in pharmaceuticals, water, and urine samples.〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/604_2019_3875_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉A luminescent metal organic framework (LMOF) of type UiO-66-NH〈sub〉2〈/sub〉 was chosen for specific and sensitive detection of trace levels of hypochlorite. Hypochlorite causes the quenching of the blue fluorescence of nano-UiO-66-NH〈sub〉2〈/sub〉 (with excitation/emission maxima at 325/430 nm), and this finding forms the basis for a fluorometric assay for hypochlorite. The method overcomes disadvantages of conventional redox-probes which are interfered by oxidants with oxidation capability stronger than that of hypochlorite. Compared with other fluorescent probes for sensing hypochlorite, UiO-66-NH〈sub〉2〈/sub〉 has a comparable detection limit of 0.3 μmol L〈sup〉−1〈/sup〉 and a broad linearity relationship in the range of 1–8 μmol L〈sup〉−1〈/sup〉. The probe was successfully applied to the detection of hypochlorite in complex water samples and living Hela cells.〈/p〉 〈p〉 〈span〉 〈caption〉 〈strong〉Graphical abstract〈/strong〉 〈em〉 〈div〉Schematic representation of hypochlorite induced quenching of the blue fluorescence of nano-UiO-66-NH〈sub〉2〈/sub〉 (with excitation/emission maxima at 325/430 nm) through energy transfer. It overcomes disadvantages of conventional redox-probes which are interfered by oxidants with oxidation capability stronger than that of hypochlorite.〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/604_2019_3806_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉A protocol is described for chemical modification of graphene oxide with a Schiff base derived from diethylenetriamine and 2-hydroxy-4-methoxybenzophenone. The base was grafted onto an indium tin oxide (ITO) film and applied to electroanalytical determination of arsenite. Successful grafting was confirmed by Fourier transform-infrared spectroscopy, spectrophotometry, field emission scanning electron microscopy and cyclic voltammetry. Secondly, the coated ITO film served as a working electrode for the stripping voltammetric determination of arsenite. The analytical signal is generated by selective oxidation of metal species via multi-donor sites present in the derivatized Schiff base. The electroanalytical protocol was optimized by investigating the effects of deposition time, working potential, frequency and amplitude of square wave anodic stripping voltammetry. The method has attractive features including (a) the usage of a non-metallic, non-toxic and cost-effective material; (b) improved sensitivity (with limit of detection as low as 156 pM) due to better adsorption of arsenite in the Schiff base pockets on the ITO, and (c) the application to the determination of arsenite in real samples.〈/p〉 〈p〉 〈span〉 〈caption〉 〈strong〉Graphical abstract〈/strong〉 〈em〉 〈div〉Schematic representation of the fabrication of a Schiff base-functionalized graphene oxide on an indium tin oxide (SB@SiO2@GO@ITO) electrode for selective electrochemical sensing of arsenite due to adsorption on multi-donor sites.〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/604_2019_3807_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉A self-powered photoelectrochemical (PEC) aptamer probe is presented for the determination of oxytetracycline (OTC). The assay is based on the use of g-C〈sub〉3〈/sub〉N〈sub〉4〈/sub〉 and NiO nanocrystals (NCs) which form a heterojunction. The latter was prepared by two-step hydrothermal pyrolysis by using the ionic liquid 1-hydroxyethyl-3-methylimidazole chloride which functions as a morphological template to form NiO NCs. The heterojunction exhibits much better electronic conductivity, wider absorption range, higher electron-hole-separation productivity, and stronger photocurrent compared to plain g-C〈sub〉3〈/sub〉N〈sub〉4〈/sub〉. The heterojunction was adopted to construct a self-powered PEC aptamer probe for OTC detection. An OTC-binding aptamer was immobilized on the heterojunction and the probe was constructed. The aptamer on the probe binding with OTC can form steric hindrance for transmitting of electrons and cause the PEC signal change depending on the OTC concentration. The photocurrent decreases with increasing OTC concentration in the 0.01 to 100 nM concentration range and its detection limit is 4 pM (at S/〈em〉N〈/em〉 = 3).〈/p〉 〈p〉 〈span〉 〈caption〉 〈strong〉Graphical abstract〈/strong〉 〈em〉 〈div〉Schematic representation of a self-powered photochemical aptamer probe. The probe performs enhanced ability for oxytetracycline (OTC) determination due to the formation of NiO nanocrystals/g-C〈sub〉3〈/sub〉N〈sub〉4〈/sub〉 (NiO NCs/g-C〈sub〉3〈/sub〉N〈sub〉4〈/sub〉) heterojunction and the specification recognition of the aptamer.〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/604_2019_3856_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉The peroxidase-like activity of hollow Prussian Blue nanocubes (hPBNCs) is used, in combination with the enzyme alcohol oxidase (AOx), in a colorimetric ethanol assay. Different from other nanozymes, the large cavity structure of the hPBNCs provides a larger surface and more binding sites for AOx to be bound on their surface or in the pores. This extremely enhances the sensitivity of the assay system. In the presence of ethanol, AOx is capable of catalyzing the oxidation of alcohols to aldehydes, accompanied by the generation of hydrogen peroxide (H〈sub〉2〈/sub〉O〈sub〉2〈/sub〉). The hPBNCs act as peroxidase mimics and then can catalyze the oxidation of 3,3′5,5′-tetramethylbenzidine (TMB) by H〈sub〉2〈/sub〉O〈sub〉2〈/sub〉, resulting in a color change of the solution from colorless to blue with a strong absorption at 652 nm. The lower detection limit for ethanol is 1.41 μg∙mL〈sup〉−1〈/sup〉. Due to the high catalytic activity of hPBNCs in weakly acidic and neutral solutions, the system was successfully applied to the determination of ethanol in mice blood. This is critically important for studying the alcohol consumption and monitoring the ethanol toxicokinetics.〈/p〉 〈p〉 〈span〉 〈caption〉 〈strong〉Graphical abstract〈/strong〉 〈em〉 〈div〉Schematic representation of hollow Prussian Blue nanocubes (hPBNCs) used as both a peroxidase mimetic and as a carrier for alcohol oxidase. Utilizing hPBNCs along with the ethanol conversion enzyme, a sensitive colorimetric assay for ethanol was developed and applied to blood samples with satisfactory results.〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/604_2019_3826_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Prussian Blue nanoparticles were deposited on g-C〈sub〉3〈/sub〉N〈sub〉4〈/sub〉 nanosheets. The resulting nanocomposite possesses peroxidase-like (POx) activity and can catalyze the oxidation of 3,3′,5,5′-tetramethylbenzidine at room temperature in the presence of H〈sub〉2〈/sub〉O〈sub〉2〈/sub〉. This leads to formation of a blue product with an absorption maximum at 650 nm. The formation of the Prussian Blue nanoparticles on the g-C〈sub〉3〈/sub〉N〈sub〉4〈/sub〉 nanosheets, and the POx-like activity of the composite were characterized in detail. The POx mimic was used for determination of L-lactic acid via detection of H〈sub〉2〈/sub〉O〈sub〉2〈/sub〉 that is produced by the enzyme lactate oxidase (LOx). The assay has a linear range that extends from 5 to 100 μM, and the detection limit is 2.2 μM. The method was successfully applied to the determination of L-lactic acid in spiked human serum.〈/p〉 〈p〉 〈span〉 〈caption〉 〈strong〉Graphical abstract〈/strong〉 〈em〉 〈div〉Ultra-small Prussian Blue (PB) nanoparticles were used to modify g-C〈sub〉3〈/sub〉N〈sub〉4〈/sub〉 nanosheets, and their peroxidase-like activity was explored for detection of L-lactic acid. LOx represent L-lactate oxidase, and TMB represents 3,3′,5,5′-tetramethylbenzidine.〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/604_2019_3834_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Walnut shell was processed for preparing nanoporous carbon, which further underwent element doping in order to boost its performance. A novel electrochemical sensor was then built by using the nitrogen and sulfur co-doped walnut shell carbon (N,S-WSC). Morphology and microstructure of the materials were characterized by scanning electron microscopy and Brunauer-Emmett-Teller (de)sorption which showed that N,S-WSC has a large specific surface with abundant pores. Electrochemical properties of differently modified sensors were investigated by cyclic voltammetry and electrochemical impedance spectroscopy. They demonstrated enhanced conductivity and enlarged surface after N,S co-doping. The modified electrode exhibits good catalytic ability towards paracetamol (ACOP) and p-aminophenol (PAP), and baseline separation of their oxidation peaks (peak potential difference is 0.24 V) allows for simultaneous detection of these two compounds. Under the optimal conditions, the calibration plot is linear in the 0.1 to 220 μM ACOP concentration range, with a 26 nM detection limit. Response to PAP is linear from 1.0 to 300 μM, and the detection limit is 38 nM (at S/N = 3). The sensor was successfully applied to quantify ACOP and PAP in tablets, and the accuracy of results is validated by HPLC.〈/p〉 〈p〉 〈span〉 〈caption〉 〈strong〉Graphical abstract〈/strong〉 〈em〉 〈div〉Schematic representation of a novel electrochemical sensor based on N, S co-doped walnut shell carbon modified glassy carbon electrode for determination of paracetamol and 〈em〉p〈/em〉-aminophenol.〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/604_2019_3870_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉This paper presents an electrochemical sensor for Cr(VI) (chromate ion) in water. A disposable screen-printed electrode was modified with gold nanostars (AuNSs) that were synthesized by Good’s buffer method. Linear sweep voltammetry (LSV) was employed for the detection of Cr(VI) in 0.1 M sulfuric acid solution. The AuNSs are shown to provide higher current response to Cr(VI) than spherically shaped gold nanoparticles. The sensor gives the strongest response at a scan rate of 0.05 V (vs Ag/AgCl) and exhibits minimal interference from other electroactive species. The linear range extends from 10 to 75,000 ppb, and the limit of detection is 3.5 ppb. This is well below the provisional guideline value given by the World Health Organization. Excellent recoveries (ranging between 95 and 97%) were found when analyzing contaminated ground water samples obtained from a site situated in Wellesley, MA.〈/p〉 〈p〉 〈span〉 〈caption〉 〈strong〉Graphical abstract〈/strong〉 〈em〉 〈div〉Schematic presentation of preparation of gold nanostars (AuNS) on carbon paste screen printed electrode (CPSPE) by drop casting and electrochemical detection of chromium (VI) using linear sweep voltammetry (LSV).〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/604_2019_3847_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Fluorescent polymer dots (PDs) with maximum excitation/emission wavelengths of 410/515 nm were prepared in water solution from 1,4-benzoquinone and ethylenediamine. The green fluorescence of these PDs is screened off by the red-colored oxidation product (PPDox, maximum absorption at 510 nm) formed by horseradish peroxidase (HRP)-catalyzed oxidation of 〈em〉p〈/em〉-phenylenediamine (PPD). It causes the reduction of the fluorescence intensity of the PDs due to spectral overlap and an inner filter effect (IFE). If glucose is enzymatically oxidized under the formation of H〈sub〉2〈/sub〉O〈sub〉2〈/sub〉, the formed H〈sub〉2〈/sub〉O〈sub〉2〈/sub〉 can be quantified by the above IFE. The assay for HRP activity and glucose have detection limits of 0.2 U·L〈sup〉−1〈/sup〉 and 0.1 μM, respectively. The nanoprobe was further extended to an immunosorbent assay (ELISA) for the determination of insecticidal Cry1Ab/Ac protein with a detection limit of 0.25 ng·mL〈sup〉−1〈/sup〉. The ELISA was applied to rice leaf analysis.〈/p〉 〈p〉 〈span〉 〈caption〉 〈strong〉Graphic abstract〈/strong〉 〈em〉 〈div〉Schematic representation of fluorometrict enzyme-linked immunosorbent assay for Cry1Ab/Ac protein detection based on horseradish peroxidase (HRP)-triggered fluorescence quenching of polymer dots (PDs). Quenching is caused by an inner filter effect (IFE) caused by PPDox, the oxidation product of 〈em〉p〈/em〉-phenylenediamine (PPD).〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/604_2019_3831_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉The authors describe an electrochemical and an optical method for the determination of As(V) by using iron oxyhydroxide (FeOOH) nanorods that display peroxidase-mimicking activity. The nanorods catalyze the oxidation of substrate ABTS by H〈sub〉2〈/sub〉O〈sub〉2〈/sub〉 to form a green product with an absorption maximum at 418 nm. If, however, As(V) is electrostatically adsorbed on the nanorods, the oxidation is gradually inhibited. A colorimetric assay was worked out based on these findings. Response is linear in the 0 to 8 ppb and 8 to 200 ppb As(V) concentration range, and the detection limit is 0.1 ppb. Even higher sensitivity is achieved in an electrochemical method which is based on the excellent electrical conductivity of FeOOH nanorods. Electrochemical analysis of As(V) was achieved by first adsorbing As(V) on the nanorods. This inhibits the ABTS reduction current signal, best measured at a potential of 150 mV (vs. Ag/AgCl). The linear range extends from 0.04 to 200 ppb, and the detection limit is as low as 12 ppt.〈/p〉 〈p〉 〈span〉 〈caption〉 〈strong〉Graphical abstract〈/strong〉 〈em〉 〈div〉Schematic representation of FeOOH nanorod-based colorimetric and electrochemical assays for arsenate (As(V)). As(V) adsorbed on FeOOH nanorods inhibits the peroxidase-mimicking activity of nanorods, and a colorimetric and electrochemical dual-signal assay was constructed to achieve sensitive determination of As(V).〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/604_2019_3863_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉The inconsistent thermal quenching performance of manganese(II)-doped Cs〈sub〉3〈/sub〉Cu〈sub〉2〈/sub〉I〈sub〉5〈/sub〉 microparticles is exploited in a highly sensitive noninvasive optical thermometer. The ratio of the emissions of Cu(II) and Mn(II) ions in the microparticles is highly temperature dependent in the range from 298 to 498 K. The best absolute and relative sensitivities are 0.547 K〈sup〉−1〈/sup〉 and 0.525% K〈sup〉−1〈/sup〉, respectively. The emission spectrum, under 300-nm photoexcitation, has emission peaks at 448 and 556 nm. This is the result of energy transfer between the Cu(II) and Mn(II) ions whose efficiency can reach up to 57% when the Mn(II) ion concentration is 2 mol%. The emission color of the microparticles changes from cyan to green when increasing the temperature from 298 to 498 K.〈/p〉 〈p〉 〈span〉 〈caption〉 〈strong〉Graphical abstract〈/strong〉 〈em〉 〈div〉Synthesis of novel Mn(II)-doped Cs〈sub〉3〈/sub〉Cu〈sub〉2〈/sub〉I〈sub〉5〈/sub〉 thermochromic halides with admirable luminescent behaviors for high sensitive ratiometric thermometry and safety sign in high temperature environment.〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/604_2019_3881_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉An optical method for determination of Hg(II) is described that exploits the aggregation of gold nanoparticles (AuNPs) under dark-field microscope (DFM) observation. This assay is based on the use of a Hg(II)-specific aptamer, AuNPs modified with complementary DNA strands, and exonuclease I (Exo I). In the absence of Hg(II), the added dsDNA prevents salt-induced aggregation of the green-colored AuNPs. If Hg(II) is added, the aptamer will capture it to form T-Hg(II)-T pairs, and the complementary strand is digested by Exo I. On addition of a solution of NaCl, the AuNPs will aggregate. This is accompanied by a color change from green to orange/red) in the dark-field image. By calculating the intensity of the orange/red dots in the dark-field image, concentration of Hg(II) can be accurately determined. The limit of detection is as low as 36 fM, and response is a linear in the 83 fM to 8.3 μM Hg(II) concentration range.〈/p〉 〈p〉 〈span〉 〈caption〉 〈strong〉Graphical abstract〈/strong〉 〈em〉 〈div〉Schematic representation of a colorimetric assay for Hg(II) based on the use of a mercury(II)-specific aptamer, gold nanoparticles modified with complementary DNA strands, and exonuclease I.〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/604_2019_3876_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉An electrochemical method is described for ultrasensitive determination of protein tyrosine kinase-7 (PTK7). It is based on (a) the use of positively charged gold nanoparticles (AuNPs) and negatively charged graphene oxide (GO), and (b) of toehold-mediated strand displacement amplification. A hairpin probe 2 (HP〈sub〉2〈/sub〉) containing the sgc8 aptamer was used to modify a glassy carbon electrode (GCE). Its hairpin structure is opened in the presence of PTK7 to form the PTK7-HP〈sub〉2〈/sub〉 complex. The exposed part of HP〈sub〉2〈/sub〉 partly hybridizes with hairpin probe 1 (HP〈sub〉1〈/sub〉) that was immobilizing on the AuNPs and GO modified GCE. On addition of the hairpin probe 3 that was labeled with the redox probe Methylene Blue (MB-HP〈sub〉3〈/sub〉), toehold-mediated strand displacement occurs due to complementary hybridization of HP〈sub〉1〈/sub〉 with MB-HP〈sub〉3〈/sub〉. This causes the release of PTK7-HP〈sub〉2〈/sub〉 into the solution and makes it available for the next reaction. Under optimal conditions, PTK7 can be quantified by voltammetry (typically performed at −0.18 V) with a detection limit of 1.8 fM. The assay possesses high selectivity for PTK7 due to the employment of the aptamer. It was successfully applied to the determination of PTK7 in the debris of malignant melanoma A375 cells.〈/p〉 〈p〉 〈span〉 〈caption〉 〈strong〉Graphical abstract〈/strong〉 〈em〉 〈div〉Schematic representation of the enzyme-free electrochemical sensor for ultrasensitive determination of protein tyrosine kinase-7 (PTK7) based on the toehold-mediated strand displacement reaction amplification on gold nanoparticles and graphene oxide.〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/604_2019_3849_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Pyrophosphate-modified carbon quantum dots (PP-CDs) are demonstrated to be a viable fluorescent nanoprobe for mercury(II) (Hg〈sup〉2+〈/sup〉) detection. Hg〈sup〉2+〈/sup〉 reacts with the pyrophosphate groups on the surface of PP-CDs to form a non-fluorescent complex. This results in quenching of the green fluorescence which has excitation/emission peaks at 400/513 nm. Static quenching is shown to be the dominant mechanism. The probe works in 0.1 μM to 1.4 μM Hg〈sup〉2+〈/sup〉 concentration range, and the limit of detection is 2 nM. The PP-CDs were also used to visualize Hg〈sup〉2+〈/sup〉 inside human hepatocyte LO2 cells.〈/p〉 〈p〉 〈span〉 〈caption〉 〈strong〉Graphical abstract〈/strong〉 〈em〉 〈div〉Schematic representation of pyrophosphate-modified carbon quantum dots (CDs) for selective and sensitive fluorometric determination of mercury(II). Hg(II) quenches the blue fluorescence of the CDs, and glutathione restores it. The method was used to detect Hg(II) in spiked tap water and inside cells.〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/604_2019_3872_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉A fluorometric aptamer based assay is described for rapid and sensitive detection of aflatoxin B1 (AFB1). It is making use of a fluorescein (FAM) labeled anti-AFB1 aptamer and complementary DNA-modified gold nanoparticles (GNPs). In the absence of AFB1, the FAM-labeled aptamers hybridize with complementary DNA strands that were covalently immobilized on GNPs. This results in quenching of the green fluorescence (with excitation/emission peaks at 485/525 nm). In the presence of AFB1, the aptamer probe binds AFB1 and is released from the GNPs. Hence, fluorescence is restored. Under optimized conditions, AFB1 in the concentration range from 61 pM to 4.0 μM can be detected, and the detection limit is 61 pM. This assay is highly selective for AFB1. It was applied to the determination of AFB1 spiked into 50-fold diluted wine and 20-fold diluted beer.〈/p〉 〈p〉 〈span〉 〈caption〉 〈strong〉Graphical abstract〈/strong〉 〈em〉 〈div〉Schematic presentation of fluorometric detection of AFB1 using a fluorescein (FAM) labeled anti-AFB1 aptamer and complementary DNA-modified gold nanoparticles (GNPs).〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/604_2019_3838_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉A reusable fiber optic chemiluminescent aptasensor (FOCA) is reported for the rapid and sensitive on-site detection of 17β-estradiol (E2), an endocrine-disrupting compound frequently found in water samples. The E2-ovalbumin conjugate (E2-OVA) was covalently immobilized onto the optical fiber as a biorecognition element as well as a transducer. The affinity constant of the E2/aptamer complex was determined to be 1.35 × 10〈sup〉6〈/sup〉 M〈sup〉−1〈/sup〉 using the FOCA. An indirect competitive assay was then developed for E2 detection. A certain concentration of HRP-E2 aptamers pre-reacted with samples containing E2 in various concentrations. Part of HRP-E2 aptamers specially bound to the sensor surface after introduction of the mixture. This catalyzed the chemiluminescece reaction of a chemiluminescent system composed of luminol and H〈sub〉2〈/sub〉O〈sub〉2〈/sub〉. A higher concentration of E2 led to less HRP-E2 aptamer bound to the biosensor surface, thus resulting in less chemiluminescence. Highly sensitive detection of E2 was achieved under optimal conditions, and the limit of detection is 48 ng ·L〈sup〉−1〈/sup〉 (0.18 nM). The whole analytical process, including measurement and regeneration, can be performed in 〈15 min. The robustness of the biosensor allows its application to multiple assays with little activity loss. The selectivity, recovery, and accuracy of the sensor was demonstrated by evaluating its response to potentially interfering endocrine disruptors in spiked water samples.〈/p〉 〈p〉 〈span〉 〈caption〉 〈strong〉Graphical abstract〈/strong〉 〈em〉 〈div〉Schematic diagram of the fiber optic chemiluminescent aptasensor system (A), detection mechanism of 17β-estradiol (B), and its application for detection of 17β-estradiol with rapidity and sensitivity (C and D).〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/604_2019_3813_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉This review (with 115 refs) summarizes applications of 3-dimensional graphene (3DGs) and its derivatives in the fields of preconcentration, extraction, and sorption. Following an introduction into the field (including a definition of the materials treated here), the properties and synthetic strategies for 3DGs are described. The next section covers applications of 3DG-based adsorbents in solid phase extraction of organic species including drugs, phthalate esters, chlorophenols, aflatoxins, insecticides, and pesticides. Another section treats applications of 3DGs in solid phase microextraction of species such as polycyclic aromatic hydrocarbons, alcohols, and pesticides. We also describe how the efficiency of assays may be improved by using these materials as a sorbent. A final section covers conclusions and perspectives.〈/p〉 〈p〉 〈span〉 〈caption〉 〈strong〉Graphical abstract Graphical abstract contains poor quality and small text inside the artwork. Please do not re-use the file that we have rejected or attempt to increase its resolution and re-save. It is originally poor, therefore, increasing the resolution will not solve the quality problem. We suggest that you provide us the original format. We prefer replacement figures containing vector/editable objects rather than embedded images. Preferred file formats are eps, ai, tiff and pdf.Tiff file of graphical abstract was attached.〈/strong〉 〈em〉 〈div〉Schematic presentation of synthesis of three-dimensional graphene (3DG) from two-dimensional graphene (2DG) with self-assembly, template-assisted and direct deposition methods. Application of 3DG-based nanoadsorbents in direct immersion-solid phase microextraction (DI-SPME), headspace-SPME (HS-SPME), magnetic-solid phase extraction (Magnetic-SPE), dispersive-SPE, and magnetic sheet-SPE.〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/604_2019_3324_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Magnetic ZnFe〈sub〉2〈/sub〉O〈sub〉4〈/sub〉 nanotubes (ZFONTs) with numerous pores on their walls were synthesized and characterized. They are shown to be a viable sorbent for dispersive micro-solid phase extraction of the trivalent ions of rare earth elements (REEs), specifically of lanthanum, praseodymium, europium, gadolinium, holmium and ytterbium. The specific surface area of ZFONTs is large (57 m〈sup〉2〈/sup〉⋅g〈sup〉−1〈/sup〉) and much bigger than that of ZnFeO〈sub〉4〈/sub〉 nanoparticles (16 m〈sup〉2〈/sup〉⋅g〈sup〉−1〈/sup〉). It is shown that REEs are quantitatively retained on ZFONTs in the pH range of 7.0–9.0. The separation of the sorbent from the aqueous phase was achieved by an external magnetic field. Following elution with 0.5 mol⋅L〈sup〉−1〈/sup〉 HNO〈sub〉3〈/sub〉, REEs were quantified by inductively coupled plasma mass spectrometry. The main parameters influencing preconcentration and determination of the REEs were studied. Under optimum conditions, detection limits for REEs range from 0.01 (Ho) to 0.75 (La) pg⋅mL〈sup〉−1〈/sup〉. Relative standard deviations are less than 6.5% (for 〈em〉n〈/em〉 = 9; at 1.0 ng⋅mL〈sup〉−1〈/sup〉). The method was applied to the determination of trace REEs in spiked biological and environmental samples and gave satisfactory results.〈/p〉 〈p〉 〈span〉 〈caption〉 〈strong〉Graphical abstract〈/strong〉 〈em〉 〈div〉Schematic presentation of a new adsorbent for dispersive micro-solid phase extraction (DMSPE) combined with ICP-MS. Magnetic ZnFe〈sub〉2〈/sub〉O〈sub〉4〈/sub〉 nanotubes with many pores on their walls were used for preconcentration and determination of rare earth elements (REEs) in environmental and biological samples.〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/604_2019_3342_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉A colorimetric assay is presented for the detection of 〈em〉Stachybotrys chartarum〈/em〉 proteases as biomarkers. The assay comprises a gold film acting as solid support and carrying an immobilized peptide substrate that is specific for 〈em〉S. chartarum〈/em〉 protease. The substrate was conjugated to black magnetic nanoparticles (MNPs) to form a monolayer on the gold film. Hence, detection nanoprobe is black. If, however, the peptide-MNP fragments are cleaved by 〈em〉S. chartarum〈/em〉 proteases present in a sample, the golden color of the detecting nanoprobe becomes apparent so that positive visual readout is enabled. The method was applied to the determination of 〈em〉S. chartarum〈/em〉 in (spiked) environmental samples. The limit of detection ranges from 10 to 100 spores·mL〈sup〉−1〈/sup〉 depending on the kind of sample (culture, dust, mold and soil). Assay specificity was examined for 〈em〉Aspergillus flavus〈/em〉, 〈em〉Fusarium solani〈/em〉. 〈em〉Penicillin chrysogenum〈/em〉, and 〈em〉Saccharomyces cerevisiae〈/em〉, and negative readouts were observed visually for all samples, except for those also containing 〈em〉S. chartarum〈/em〉.〈/p〉 〈p〉 〈span〉 〈caption〉 〈strong〉Graphical abstract〈/strong〉 〈em〉 〈div〉Schematic presentation of 〈em〉S. chartarum〈/em〉 colorimetric nanoprobe.〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/604_2019_3313_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Hierarchical Co〈sub〉3〈/sub〉O〈sub〉4〈/sub〉@NiMoO〈sub〉4〈/sub〉 core-shell nanowires (NWs) were synthesized utilizing a two-step hydrothermal method. The NWs show a high chemiresistive response (at a temperature of 255 °C) to xylene, with an R〈sub〉gas〈/sub〉/R〈sub〉air〈/sub〉 ratio of 24.6 at 100 ppm xylene, while the response towards toluene, benzene, ethanol, and acetone, CO, H〈sub〉2〈/sub〉S and NO〈sub〉2〈/sub〉 is much weaker. In contrast, pure Co〈sub〉3〈/sub〉O〈sub〉4〈/sub〉 nanowires exhibit weak responses to all the vapors/gases and poor selectivity. The new NW sensor displays an almost linear response (1–100 ppm) to xylene and a lower detection limit of 424 ppb. The remarkable gas sensing characteristics are attributed to the synergistic catalytic effect and the formation of a heterostructure between Co〈sub〉3〈/sub〉O〈sub〉4〈/sub〉 and NiMoO〈sub〉4〈/sub〉.〈/p〉 〈p〉 〈span〉 〈caption〉 〈strong〉Graphical abstract〈/strong〉 〈em〉 〈div〉Schematic presentation of a xylene vapor chemiresistive sensor based on Co3O4@NiMoO4 core-shell nanowires. The Co3O4@NiMoO4 core-shell nanowires-based sensor exhibits a high response (24.6) to 100 ppm xylene at 255 °C and high response/recovery speed (13–15 and 25–29 s).〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/604_2019_3335_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉The authors describe the preparation of two kinds of periodic mesoporous organosilicas (PMOs). The first kind is monofunctional and has a bridged alkyl imidazolium framework (PMO-IL). The other is a two-dimensional (2D) hexagonal bifunctional periodic mesoporous organosilica (BFPMO) with bridged IL-phenyl or -ethyl units. The CPMOs were utilized as highly sensitive and stable sorbents for microextraction by packed sorbent. The materials were characterized by SEM, TEM, FT-IR, and N〈sub〉2〈/sub〉 adsorption–desorption analysis. The adsorption capacities of the sorbents were investigated by using phenoxy acid herbicides as model analytes. The effects of bifunctionality and type of additional surface groups (phenyl or ethyl) on the efficiency of the extraction is emphasized. Three kinds of environmental contaminants, viz. phenoxy acid herbicides (CPAs), polycyclic aromatic hydrocarbons and chlorophenols were then studied with respect to their extraction by the sorbents. The interactions between the CPAs and the sorbents were evaluated by pH-changing processes to explore the interactions that play a major role. The selectivity of the sorbents was investigated by extraction of other types of analytes of with various polarity and charge. The BFPMOs display the typical good chemical stability of silica materials. The extraction properties are much better compared to commercial silicas. This is assumed to be due to the highly ordered mesoporous structures and the different types of probable interactions with analytes. The performance of the method was evaluated by extraction of CPAs as model analytes from aqueous samples, and quantification by GC with FID detection. Under optimized conditions, low limits of detection (0.1–0.5 μg.L〈sup〉−1〈/sup〉) and a wide linearity (0.5–200 μg.L〈sup〉−1〈/sup〉) were obtained. The method was applied to the trace analysis of CPAs in farm waters and rice samples.〈/p〉 〈p〉 〈span〉 〈caption〉 〈strong〉Graphical abstract〈/strong〉 〈em〉 〈div〉Monofunctional periodic mesoporous organosilica with bridged alkyl imidazolium frameworks and bi-functional periodic mesoporous organosilica containing bridged ionic liquids and phenyl or -ethyl, have been successfully synthesized and utilized in microextractions by packed sorbent sorbents.〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/604_2019_3355_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Multifunctional nanodots represent an emerging platform for overcoming the delivery challenges of poorly water-soluble drugs for use in the diagnosis and treatment of cancer. The authors describe the preparation of nanocrystallites composed of the water-insoluble photosensitizer zinc(II)-phthalocyanine in the form of nanodots by applying a cryodesiccation-driven crystallization approach. Modification of the surface of the nanodots with Pluronic F127 and folic acid endows them with excellent water solubility and stealth properties in blood. Under near-infrared (NIR) photoexcitation at 808 nm, the nanodots are shown to produce singlet oxygen, which is widely used in photodynamic therapy of cancer. The nanodots exhibit strong NIR absorbance at 808 nm and can be used as a non-toxic contrast agent for photoacoustic imaging of tissue.〈/p〉 〈p〉 〈span〉 〈caption〉 〈strong〉Graphical abstract〈/strong〉 〈em〉 〈div〉Schematic presentation of the preparation of ZnPcNDs by droplet-confined/cryodesiccation-driven crystallization.〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/604_2019_3286_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Water-soluble nitrogen-doped carbon quantum dots (C-dots) were fabricated by microwave-induced decomposition of the precursor materials citric acid and N,N′-bis(2-aminoethyl)-1,2-ethanediamine. The C-dots were placed on portable paper strips with novel origami designs to simplified user operations. The intensity of the blue fluorescence, best measured at excitation/emission wavelengths of 330/420 nm, depends on the pH value in the range from pH 2 to 12. The C-dots on the paper stripe are shown to be a sensitive fluorescent probe for chromium(VI) via an inner filter effect. Response is linear in the 0.08 to 1 mM concentration range, and the detection limit (at S/〈em〉N〈/em〉 = 3) is 0.14 mM. The test was applied to the determination of chromium(VI) in (spiked) environmental water samples.〈/p〉 〈p〉 〈span〉 〈caption〉 〈strong〉Graphical abstract〈/strong〉 〈em〉 〈div〉Schematic presentation of the water-soluble nitrogen-doped carbon dots (C-dots) as a fluorescent probe for Cr〈sup〉6+〈/sup〉 based on an inner filter effect. The three-dimensional paper analytical device integrating C-dots was applied to the determination of Cr〈sup〉6+〈/sup〉 in (spiked) environmental water samples.〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/604_2019_3337_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉A method is described to enhance the sensitivity of an immunochromatographic assay for clenbuterol (CLE) by making use of dually-labeled gold nanoparticles (GNPs), background fluorescence blocking, and immunomagnetic separation. The GNPs were labeled with biotinylated antibody and streptavidin, respectively, and dually labeled GNPs were obtained via the biotin-streptavidin interaction to amplify the detection signal. The fluorescent signal was blocked by dually labeled GNPs and decreased as the dually labeled GNPs aggregation increases on nitrocellulose membrane, which derived from fluorescent polyvinylchloride card. However, fluorescence (measured at excitation/emission wavelengths of 518/580 nm) recovers when CLE reacts with dually labeled GNPs. Immunomagnetic separation was first applied for sample pretreatment. This can offset the matrix effect and improves the sensitivity and accuracy of the assay. Under the optimal conditions, the limits of detection of CLE visually were 0.25 μg·L〈sup〉−1〈/sup〉. In addition, clenbuterol can be quantified in swine urine with a 0.03 μg·L〈sup〉−1〈/sup〉 detection limit. This is 60-fold lower than current immunochromatography. Response is linear in the 0.06–0.59 μg·L〈sup〉−1〈/sup〉 concentration range, and the recoveries from spiked swine urine range from 81 to 115%.”〈/p〉 〈p〉 〈span〉 〈caption〉 〈strong〉Graphical abstract〈/strong〉 〈em〉 〈div〉Schematic presentation of the strategies for improving sensitivity of immunochromatographic assay. It includes immunomagnetic separations, dually-labeled gold nanoparticles and background fluorescence blocking. The assay was applied to detect clenbuterol (CLE) in swine urine with an excellent performance.〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/604_2019_3326_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉The authors have fabricated reduced graphene oxide nanosheets (rGO) supported with Fe〈sub〉3〈/sub〉O〈sub〉4〈/sub〉 nanoparticles and Ag/Au hollow nanoshells. The material was placed on a glassy carbon electrode which is shown to enable highly sensitive determination of As(III) which is first preconcentrated from solution at a potential of −0.35 V (versus Ag/AgCl) for 100 s. The electrode, typically operated at a working potential as low as 0.06 V, has a linear response in the 0.1 to 20 ppb As(III) concentration range and a 0.01 ppb detection limit. The electrochemical sensitivity is 52 μA ppb〈sup〉−1〈/sup〉. The high sensitivity is assumed to be the result of various synergistic effects. The method was applied to ultratrace (0.1 ppt) determination of As(III) in real water samples.〈/p〉 〈p〉 〈span〉 〈caption〉 〈strong〉Graphical abstract〈/strong〉 〈em〉 〈div〉The hybrid displays a wide linear response in the 0.1 to 20 ppb As(III) concentration range and a 0.01 ppb detection limit. The high sensitivity is attributed to various synergistic effects. The method was applied to ultratrace determination of As(III) in real water samples.〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/604_2019_3328_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉An electrochemical method is described for the determination of the activity of the DNA methyltransferase (MTase). The assay was based on the use of a commercially available customized electromagnetic modular detector, which consisted of a magnetic switch, electrical connectors and a screen-printed electrode modified with graphene oxide. The biotinylated single-strand DNA (ss-DNA) S1 was absorbed by streptavidin-modified magnetic beads (MBs) via streptavidin-biotin interaction. The biotinylated ss-DNA S1 was hybridized with the complementary ss-DNA S2. After the symmetrical sequences 5′-CCGG-3′ of the duplex DNA (ds-DNA) were methylated by M. 〈em〉Sss〈/em〉I CpG methyltransferase (M. 〈em〉Sss〈/em〉I MTase), the symmetrical sequences 5′-CCGG-3′ in the ds-DNA were recognized by glutathione S-transferase (GST) tagged methyl CpG binding protein 2 (MeCP2). The unmethylated 5′-CCGG-3′ sequences were specifically cleaved by 〈em〉Hpa〈/em〉II restriction endonuclease. After magnetic separation and washing, HRP-labeled GST tag monoclonal antibody and H〈sub〉2〈/sub〉O〈sub〉2〈/sub〉 were used as a tracer label and enzyme substrate, respectively. Electrochemical measurement was carried out at pH 7.4 in the presence of 50 μM thionine and 0.5 mM H〈sub〉2〈/sub〉O〈sub〉2〈/sub〉. Stepwise changes in the microscopic features of the SPE surface upon the formation of each layer were studied by scanning electron microscopy. Cyclic voltammetry and differential pulse voltammetry were used to characterize the electrochemical behavior of the different modified electrodes. Under the optimal conditions, the activity of M. 〈em〉Sss〈/em〉I MTase can be determined in the activity range of 0.5–125 unit〈strong〉·〈/strong〉mL〈sup〉−1〈/sup〉 with a detection limit of 0.2 unit〈strong〉·〈/strong〉mL〈sup〉−1〈/sup〉 (at an S/N ratio of 3). The sensitivity of the immunoassay is 0.489 μA·μM〈sup〉−1〈/sup〉·cm〈sup〉−2〈/sup〉〈sub〉.〈/sub〉〈/p〉 〈p〉 〈span〉 〈caption〉 〈strong〉Graphical abstract〈/strong〉 〈em〉 〈div〉Schematic presentation of the electrochemical immunosensor for the determination of the activity of M. 〈em〉Sss〈/em〉I CpG methyltransferase (M. 〈em〉Sss〈/em〉I MTase). It is based on an electromagnetic modular detector and the use of glutathione S-transferase tagged methyl CpG binding protein 2 (GST-MeCP2).〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/604_2019_3309_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉A carbon paste electrode (CPE) modified with a metal-organic framework composite of type MIL-101(Fe) is described for determination of citric acid (CA). The electrochemical activity of the modified CPE was studied by cyclic voltammetry and differential pulse voltammetry. Scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, N〈sub〉2〈/sub〉 adsorption-desorption isotherms and X-ray powder diffraction were used for characterization of the MIL-101(Fe). Under optimized electrochemical conditions, the anodic peak current, best measured at working potentials around 0.02 V (vs. Ag/AgCl); decreases linearly in the 5.0 to 100 μM CA concentration range, and the detection limit is 4.0 μM (at S/〈em〉N〈/em〉 = 3). The electrode exhibits good selectivity for CA, with no significant interference in the wide pH range of 3.0 to 9.0. The electrochemical sensitivity of the MIL-CPE is −0.67 μA·μM〈sup〉−1〈/sup〉·cm〈sup〉−2〈/sup〉. The method was successfully applied to the determination of CA in some commercial beverages. The good recoveries (98–102%) and the agreement of data with those obtained by HPLC indicate the applicability of the method.〈/p〉 〈p〉 〈span〉 〈caption〉 〈strong〉Graphical abstract〈/strong〉 〈em〉 〈div〉Schematic presentation of a new modified carbon paste electrode based on the metal-organic framework of type MIL-101(Fe) for the simple and sensitive determination of citric acid. The results show the MIL-101(Fe)-modified electrode to have good selectivity for citric acid and to enable real sample analysis.〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/604_2019_3585_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉The authors report on the synthesis of carboxy functionalized graphene oxide (fGO) decorated with magnetite (Fe〈sub〉3〈/sub〉O〈sub〉4〈/sub〉) nanoparticles. The resulting nanomaterial was used to prepare a composite with polyaniline (PANI) which was characterized by UV-vis, Fourier transform-infrared and Raman spectroscopies. Its surface morphologies were characterized by atomic force and scanning electron microscopies. A screen-printed carbon electrode was then modified with the nanocomposite to obtain an enzyme-free glucose sensor. The large surface of fGO and Fe〈sub〉3〈/sub〉O〈sub〉4〈/sub〉 along with the enhanced charge transfer capability of PANI warrant a pronounced electrochemical response (typically measured at 0.18 V versus Ag/AgCl) which is suppressed in the presence of glucose. This reduction of current by glucose was used to design a sensitive method for quantification of glucose. The response of the modified SPCE is linear in the 0.05 μM – 5 mM glucose concentration range, and the lower detection limit is 0.01 μM.〈/p〉 〈p〉 〈span〉 〈caption〉 〈strong〉Graphical abstract〈/strong〉 〈em〉 〈div〉Schematic illustration of in-situ anchoring of Iron oxide on functionalized graphene oxide and synthesis of its polymeric nanocomposite for non-enzymatic detection of Glucose. The nanocomposite modified screen printed interface enabled monitoring of glucose at lower potential with higher precision. GO (graphene oxide), fGO (functionalized graphene oxide), PANI (polyaniline).〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/604_2019_3364_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉The authors are presenting a novel strategy for global phosphoproteome recognition in practical samples. It integrates metal oxide affinity chromatography (MOAC) and immobilization metal ion affinity chromatography (IMAC). This resulted in a kind of titanium dioxide/ion-based multifunctional probe (dubbed T2M). The T2M combines the features of MOAC and IMAC including their recognition preferences towards mono- and multi-phosphorylated peptides. Hence, they exhibit an outstanding recognition capability towards global phosphoproteome, high sensitivity (the limit of detection of which is merely 10 fmol) and excellent specificity in MALDI-TOF MS detection. Their performance is further demonstrated by the identification of the phosphoproteome in non-fat milk and human saliva. By combining T2M with nano LC-MS/MS, remarkable results are obtained in the tryptic digestion of healthy eye lens and cataract lens phosphoproteomes. A total of 658 and 162 phosphopeptides, respectively, were identified. This indicates that phosphorylation and the appearance of cataract can be related to each other.〈/p〉 〈p〉 〈span〉 〈caption〉 〈strong〉Graphical abstract〈/strong〉 〈em〉 〈div〉Schematic presentation of the preparation of titanium dioxide/ion-based multifunctional magnetic nanomaterials (T2M). The T2M based enrichment protocol exhibits outstanding recognition capability towards global phosphoproteome. This protocol shows great prospect for clarifying mechanism of phosphorylation-related diseases via further information acquisition.〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/604_2019_3346_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉An aptamer based impedimetric assay for the mycotoxin patulin (PAT) is described. A glassy carbon electrode (GCE) was modified with black phosphorus nanosheets (BP NSs) and modified with PAT aptamer by electrostatic attraction. Detection is based on the variations of electron transfer resistance at the modified electrode surface. This assay can detect PAT over a linear range that extends from 1.0 nM to 1.0 μM with a 0.3 nM detection limit. To improve the performance of the sensor, the BP NS-GCE was further modified with gold nanoparticles and then with thiolated PAT aptamer. This modified electrode, operated at an applied potential of 0.18 V (vs. Ag/AgCl), has a wider linear range (0.1 nM to 10.0 μM) and a lower detection limits (0.03 nM). Both assays were successfully applied to the analysis of (spiked) genuine food samples.〈/p〉 〈p〉 〈span〉 〈caption〉 〈strong〉Graphical abstract〈/strong〉 〈em〉 〈div〉Black phosphorus nanosheets (BP NSs) were used to fabricate an aptamer based assay for patulin. To further improve the performance of the electrode, gold nanoparticles (AuNP) were placed on the surface of black phosphorus nanosheets (AuNP-BP NSs) by electrostatic attraction for patulin aptasensing.〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/604_2019_3339_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉A fluorometric method is described for the determination of the tumor biomarker mucin 1 (MUC1). It is based on signal amplification of the hybridization chain reaction (HCR), and the interaction between a luminescent ruthenium(II) complex and CdZnTeS quantum dots (QDs). If MUC1 bind to the biotin-labeled aptamer, it will initiate HCR with hairpins H〈sub〉1〈/sub〉 and H〈sub〉2〈/sub〉 to form a long-range dsDNA. The long nucleic acid chains are then linked on the surface of streptavidin-modified magnetic microparticles (MMPs) through streptavidin-biotin interaction. The luminescent ruthenium(II) complex is then embedded in the long dsDNA linked to the MMPs. Hence, there is little Ru complex in the supernatant after magnetic separation, and the fluorescence of the CdZnTeS QDs (best measured at excitation/emission wavelengths of 350/530 nm) is only slightly quenched. In the absence of target, the fluorescence of the CdZnTeS QDs is strongly quenched. Fluorescence increases linearly in the 0.2–100 ng·mL〈sup〉−1〈/sup〉 MUC1 concentration range, and the LOD is 0.13 ng·mL〈sup〉−1〈/sup〉 (at S/〈em〉N〈/em〉 = 3). The method was applied to the determination of MUC1 in spiked human serum samples.〈/p〉 〈p〉 〈span〉 〈caption〉 〈strong〉Graphical abstract〈/strong〉 〈em〉 〈div〉A fluorometric turn-on aptasensor for mucin 1 is described that is based on the interaction between a Ru(II) complex and quantum dots (QDs). The detection system includes biotin-labeled aptamer-H〈sub〉0〈/sub〉, hairpins H〈sub〉1〈/sub〉 and H〈sub〉2〈/sub〉, streptavidin-modified magnetic microparticles (MMPs), Ru(bpy)〈sub〉2〈/sub〉(dppx)〈sup〉2+〈/sup〉 and CdZnTeS QDs.〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/604_2019_3347_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉This short review (with 72 refs.) summarizes the state of the art in fluorometric methods for targeted imaging of cancer cells and tumor tissues in order to differentiate between normal cells and cancer cells. Following an introduction into the field and after presenting an overview on the most commonly used carbon dots and graphene quantum dots, we describe methods based on peptide based targeting, aptamer based targeting, antibody based targeting, and ligand-based targeting. A concluding section summarizes the current state and challenges, and discusses future perspectives.〈/p〉 〈p〉 〈span〉 〈caption〉 〈strong〉Graphical abstract〈/strong〉 〈em〉 〈div〉An overview is given on the applications of carbon dots (CDs) in target-specific imaging and differentiation of cancerous cells from normal cells. Several classes of ligands (including aptamers, peptides, antibodies), especially small molecules (such as FA)) have been reported for functionalizing of CDs.〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/604_2019_3338_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉The authors describe a fluorometric immunoassay for alternariol monomethyl ether (AME). It is making use of magnetic nanoparticles and quenching of the fluorescence of mercaptopropionic acid-capped CdTe quantum dots (MPA-CdTe QDs) by H〈sub〉2〈/sub〉O〈sub〉2〈/sub〉. Catalase (CAT) was labeled with AME as a competitive antigen to competitively bind to magnetic nanoparticles carrying monoclonal antibodies (mAbs) with free AME in samples. The effects of the concentration and pH value of buffer, the concentrations of H〈sub〉2〈/sub〉O〈sub〉2〈/sub〉 and CAT-AME, and the incubation time of H〈sub〉2〈/sub〉O〈sub〉2〈/sub〉 and MPA-CdTe QDs were optimized. Under optimal conditions and in combination with magnetic separation, the quenching of the fluorescence of the MPA-CdTe QDs (excitation at 310 nm, emission at 599 nm) can be used to quantify AME with a detection limit of 0.25 pg·mL〈sup〉−1〈/sup〉 and the linear range from 0.25 to 7.5 pg·mL〈sup〉−1〈/sup〉. The immunoassay also has a lower cross-reactivity to AME analogues. It was evaluated by analyzing fruit samples spiked with AME. The recoveries from spiked fruits ranged from 87.2% to 92.0%.〈/p〉 〈p〉 〈span〉 〈caption〉 〈strong〉Graphical abstract〈/strong〉 〈em〉 〈div〉Schematic presentation of a fluorometric immunoassay for alternariol monomethyl ether (AME) using magnetic nanoparticles (MNPs) for the rapid separation and purification. The method is based on quenching of the fluorescence of mercaptopropionic acid-capped CdTe quantum dots (MPA-CdTe QDs) by H〈sub〉2〈/sub〉O〈sub〉2〈/sub〉 for the fluorescence signal output, and on the use of catalase (CAT) with its high catalytic activity.〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/604_2019_3334_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉An electrochemical sensor that can resist biofouling even when operated in complex biological medium is developed for the determination of dopamine. It is based on the use of the conducting polymer poly(3,4-ethylenedioxythiophene) (PEDOT) that is doped with the water insoluble ionic liquid (IL), 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide. A glassy carbon electrode modified with PEDOT/IL is shown to enable accurate determination of dopamine, as a model analyte in the presence of high concentrations of proteins, and resist biological fouling even in native serum. It exhibited a low limit of detection of 33 nM for the detection of dopamine, with a wide linear range from 0.2 to 328 μM (at 0.2 V vs. saturated calomel electrode). The PEDOT/IL modified glassy carbon electrode has a porous microstructure, high electrical conductivity and good stability. The sensor can be used to quantify dopamine in human urine samples with satisfying accuracy.〈/p〉 〈p〉 〈span〉 〈caption〉 〈strong〉Graphical abstract〈/strong〉 〈em〉 〈div〉An antifouling electrochemical sensor capable of detecting target in complex biological samples was developed based on the use of a conducting polymer (PEDOT) that was doped with a water insoluble ionic liquid.〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/604_2019_3340_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉An antifouling electrochemical aptasensor for ATP is described that has a zwitterionic self-assembled sensing interface on a glassy carbon electrode modified with a reduced graphene oxide carbon nanofiber (GO-CNF). The GO-CNF was first modified by self-polymerization of dopamine which provided a platform for simultaneously self-assembly of the ATP aptamer and cysteine. By using hexacyanoferrate as the electrochemical probe, in the presence of ATP, the aptamer strands fold around ATP molecules, thus leading to the variation of the electrochemical signal. The aptasensor has a linear response in the 0.1 pM to 5 nM ATP concentration range, and a 13 fM lower detection limit. The electrode is strongly resistant to nonspecific adsorption and biofouling. This enabled the detection of ATP even in spiked human plasma.〈/p〉 〈p〉 〈span〉 〈caption〉 〈strong〉Graphical abstract〈/strong〉 〈em〉 〈div〉An antifouling electrochemical aptasensor employing reduced graphene oxide carbon nanofiber as conductive substrate and zwitterionic cysteine as antifouling material for adenosine triphosphate detection.〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/604_2019_3343_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉The activity of terminal deoxynucleotidyl transferase (TdTase) is a biomarker for routine diagnosis of acute leukemia. A method has been developed for the determination of TdTase activity. It is based on the use of silver nanoclusters (AgNCs) whose yellow fluorescence is enhanced by an in-situ grown DNA tail of TdTase-polymerized and guanine-rich DNA at the 3′ end of a hairpin DNA. The fluorescence, best measured at excitation/emission peaks of 530/585 nm, increases linearly in the 1 to 35 mU mL〈sup〉−1〈/sup〉 TdTase activity range. The detection limit is 0.8 mU mL〈sup〉−1〈/sup〉. The method is cost-efficient, selective and convenient. It integrates enhancement of the fluorescence of AgNCs and target recognition into a single process.〈/p〉 〈p〉 〈span〉 〈caption〉 〈strong〉Graphical abstract〈/strong〉 〈em〉 〈div〉Schematic presentation of a method for determination of TdTase activity. It is based on AgNCs fluorescence enhanced by in-situ grown TdTase-polymerized G-rich DNA tail. The method integrates AgNCs fluorescence enhancement and the target recognition into a single process.〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/604_2019_3288_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Gold nanobipyramids were synthesized by a seed-mediated growth method and then supported by multi-walled carbon nanotubes (denoted as AuNBP/MWCNTs). The electrocatalytic activity of the AuNBP/MWCNTs on a glassy carbon electrode (GCE) towards direct glucose oxidation and hydrogen peroxide reduction was superior to that of AuNBPs and MWCNTs. The modified GCE, operated at a typical working voltage of +0.15 V (vs. SCE) and in 0.1 M NaOH solution, exhibits a linear response in the 10 μM to 36.7 mM glucose concentration range with a 3.0 μM detection limit (at S/〈em〉N〈/em〉 = 3) and a sensitivity of 101.2 μA mM〈sup〉−1〈/sup〉 cm〈sup〉−2〈/sup〉. It also demonstrates good sensitivity towards hydrogen peroxide in at pH 7 solution at a working potential of −0.50 V (vs. SCE), with a linear response range from 5.0 μM to 47.3 mM, a sensitivity of 170.6 μA mM〈sup〉−1〈/sup〉 cm〈sup〉−2〈/sup〉 and a detection limit of 1.5 μM.〈/p〉 〈p〉 〈span〉 〈caption〉 〈strong〉Graphical abstract〈/strong〉 〈em〉 〈div〉A electrochemical sensing platform based on the use of gold nanobipyramids and multi-walled carbon nanotubes nanocomposites (AuNBP/MWCNTs) is described for the determination of glucose and hydrogen peroxide.〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/604_2019_3272_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉A nanocomposite was hydrothermally prepared from C-dots and V〈sub〉2〈/sub〉O〈sub〉5〈/sub〉 nanowires, and characterized by TEM, FTIR and XRD. Due to the synergistic effects between C-dots and V〈sub〉2〈/sub〉O〈sub〉5〈/sub〉 nanowires, the nanocomposite is found to possess peroxidase-mimicking activity. This finding was exploited to design colorimetric methods for determination of H〈sub〉2〈/sub〉O〈sub〉2〈/sub〉 and glucose (via glucose oxidase) by using of 3,3′,5,5′-tetramethylbenzidine (TMB) as the chromogenic substrate. The C-dot/V〈sub〉2〈/sub〉O〈sub〉5〈/sub〉 nanocomposite catalyzes hydrogen peroxide to oxidize TMB and the resultant product, i.e., TMB* produces a blue color in the solution. Also for glucose determination, at first glucose reacts with dissolved oxygen in the presence of glucose oxidase and generates H〈sub〉2〈/sub〉O〈sub〉2.〈/sub〉 Then, produced H〈sub〉2〈/sub〉O〈sub〉2〈/sub〉 was monitored by the C-dot/V〈sub〉2〈/sub〉O〈sub〉5〈/sub〉 nanozyme in the presence of TMB. Intensity of the blue color in the solution at wavelength of 650 nm is an indication of H〈sub〉2〈/sub〉O〈sub〉2〈/sub〉 or glucose concentration. The response to H〈sub〉2〈/sub〉O〈sub〉2〈/sub〉 is linear in the 0.5–520 μM concentration ranges, and that for glucose from 0.7 μM to 300 μM.〈/p〉 〈p〉 〈span〉 〈caption〉 〈strong〉Graphical abstract〈/strong〉 〈em〉 〈div〉Schematic presentation of peroxidase mimicking activity of C-dot/V〈sub〉2〈/sub〉O〈sub〉5〈/sub〉 nanocomposite and its application as sensitive colorimetric H〈sub〉2〈/sub〉O〈sub〉2〈/sub〉/glucose assay by using of 3,3′,5,5′-tetramethylbenzidine (TMB) as chromogenic substrate to induce a typical blue color reaction.〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/604_2019_3344_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈p〉The online version has been available; however, the corrections that have been suggested in a separate file apart from e.proofing were not carried out. Given here is the corrected article.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Field effect transistor (FET) based sensors have attractive features such as small size, ease of mass production, high versatility and comparably low costs. Over the last decade, many FET type biosensors based on various nanomaterials (e.g. silicon nanowires, graphene, and transition metal dichalcogenides) have been developed to detect various classes of biomolecular targets due to their integration into portable and rapid test systems, both for use in the clinical lab and in point-of-care testing. This review (with 197 refs.) starts with an introduction into the specific features of FET biosensor technology. This is followed by a description of the essentials of methods for immobilization of recognition elements. The next section discusses the progress that has been made in FET based biosensors using semiconducting nanostructures composed of silicon, graphene, metal oxides, and transition metal dichalcogenides. A further section is devoted to microfluidic systems combined with FET biosensors. We then emphasize the biosensing applications of these diagnostic devices for analysis of clinically relevant biomarkers, specifically to sensing of neurotransmitters, metabolites, nucleic acids, proteins, cancer and cardiac biomarkers. Two tables are presented which summarize advances in applications of 1D and 2D nanomaterial-based FETs for biomarker sensing. A concluding section summarizes the current status, addresses current challenges, and gives perspective trends for the field.〈/p〉 〈p〉 〈span〉 〈caption〉 〈strong〉Graphical abstract〈/strong〉 〈em〉 〈div〉Field effect transistor devices based on the use of 1D and 2D semiconductor nanostructures (so called nano-FETs) are making use of materials including silicon nanowires, graphene, zinc oxide, indium oxide, titanium oxide, and molybdenum disulfide that are further modified with recognition elements for biosensing application.〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/604_2019_3850_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Lignin nanoparticles (LNPs) were employed as the reducing and stabilizing agent in the preparation of silver nanoparticles (Ag NPs) from silver nitrate under solar light. The Ag NPs were characterized by spectrophotometry, TEM, HRTEM, element mapping, XRD and XPS. The formation of Ag NPs and the structural changes of lignin during the reaction was monitored by analysis via 〈sup〉31〈/sup〉P NMR, 〈sup〉1〈/sup〉H NMR and 〈sup〉13〈/sup〉C NMR. The Ag NPs have uniform shape and an average size of ~14 nm. They were loaded onto the surface of LNPs and entangled in lignin. The resulting Ag NP-LNP suspension displays an ultrasensitive and selective optical response to Hg (II) in giving a color change from yellow to colorless. The assay was performed by spectrophotometry at 450 nm. The analytically useful range extends from 5 nM to 100 nM of Hg (II), and the limit of detection is 1.4 nM in deionized water and 1.8 nM in spiked tap water. This is lower than the threshold level (10 nM) in drinking water specified by the US Environmental Protection Agency.〈/p〉 〈p〉 〈span〉 〈caption〉 〈strong〉Graphical abstract〈/strong〉 〈em〉 〈div〉Schematic representation of the solar light induced synthesis of sliver nanoparticles (Ag NPs) by lignin nanoparticles (LNPs) and their application to colorimetric determination of Hg〈sup〉2+〈/sup〉.〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/604_2019_3832_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Graphene quantum dots (GQDs) were prepared via pyrolysis of citric acid and glutamic acid, then reacted with chlorauric acid to form a gold/graphene quantum dot hybrid (Au/GQD), and finally connected with hairpin DNA probe 1 (H1) and thionine (Thi). The H1-Au/GQD-Thi composite is found to be a viable redox probe for electrochemical and aptamer-based determination of vascular endothelial growth factor VEGF165. A dual amplification strategy is employed based on the use of molecular machine and the Au/GQD. Each single VEGF165 molecule can bind two DNA probes via specific aptamer-target recognition to produce a molecular machine. Surface-tethered hairpin DNA 2 (H2) hybridizes with the molecular machine through proximity effect, and the prelocked toehold domain of H2 becomes exposed. This part binds to H1-Au/GQD-Thi to release the molecular machine which then moves to the neighboring H2 upon which a surface programmatic chain reaction is initiated. By continuous molecular machine travel, many H1-Au/GQD-Thi probes are present on the gold electrode surface. This implies an efficient signal amplification capability. The Au/GQD based redox probes in-situ catalyzes the redox activity of thionine and further enhances the detection signal. The aptasensor exhibits ultrahigh sensitivity and selectivity for VEGF165. The square wave voltammetric signal, best measured at −0.18 V vs. Ag/AgCl, increases linearly in the 1.0 fM to 120 pM VEGF165 concentration range, and the detection limit is 0.3 fM. Conceivably, the method may be applied to other target proteins if the corresponding high-affinity aptamers are available.〈/p〉 〈p〉 〈span〉 〈caption〉 〈strong〉Graphical abstract〈/strong〉 〈em〉 〈div〉This study report one dual amplification strategy for ultrasensitive electrochemical detection of VEGF165 based on gold-graphene quantum dot hybrid (Au/GQD) and bipedal molecular machine (BMM) powered surface programmatic chain reaction (SPCR).〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/604_2019_3336_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉The authors describe a fluorometric method for the quantification of tannic acid (TA). MoO〈sub〉3-x〈/sub〉 quantum dots (QDs) can selectively capture TA via the formation of an organic molybdate complex. This causes an electron transfer effect and an inner filter effect to result in synergistic quenching of the fluorescence of the QDs. TA can be detected via this effect with a linear response in the of 0.1–10 μM concentration range and a lower detection limit of 30 nM within 1 min. The use of such QDs as a quenchable fluorescent probe warrants good selectivity even in the presence of relatively high concentration of potentially interferents and makes the method suitable for real sample analysis.〈/p〉 〈p〉 〈span〉 〈caption〉 〈strong〉Graphical abstract〈/strong〉 〈em〉 〈div〉Tannic acid can be rapidly and selectively detected in food using a MoO〈sub〉3-x〈/sub〉 quantum dots based fluorometric assay.〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/604_2019_3311_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Magnetic nanoparticles (MNPs) modified with β-cyclodextrin and mono-6-deoxy-6-(1-methylimidazolium)-β-cyclodextrin tosylate (an ionic liquid), which called MNP-β-CD and MNP-β-CD-IL, were coated into the capillary inner wall. Compared to an uncoated capillary, the new systems show good reproducibility and durability. The systems based on the use of MNP-β-CD or MNP-β-CD-IL as stationary phases were established for enantioseparation of Dns-modified amino acids. Improved resolutions were obtained for both CEC systems. Primary parameters such as running buffer pH value and applied voltage were systematically optimized in order to obtain optimal enantioseparations. Under the optimized conditions, the capillaries exhibited excellent chiral recognition ability for six Dns-amino acids (the DL-forms of alanine, leucine, lsoleucine, valine, methionine, glutamic acid) and provided a promising way for the preparation of chiral column.〈/p〉 〈p〉 〈span〉 〈caption〉 〈strong〉Graphical Abstract〈/strong〉 〈em〉 〈div〉Schematic presentation of the open-tubular capillary electrochromatography systems with MNP-β-CD and MNP-β-CD-IL as stationary phases for enantioseparation of dansylated amino acids.〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/604_2019_3318_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈p〉The original version of this article unfortunately missed Prof. A.T. Ezhil Vilian’s project number in Acknowledgements. The missing project number is 2017R1D1A1B03034977.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉An efficient non-enzymatic electrochemical sensor for hydrogen peroxide (H〈sub〉2〈/sub〉O〈sub〉2〈/sub〉) was constructed by modifying a glassy carbon electrode (GCE) with a nanocomposite prepared from cobalt nanoparticle (CoNP) and tungsten carbide (WC). The nanocomposite was prepared at low temperature through a simple technique. Its crystal structure, surface morphology and elemental composition were investigated via X-ray diffraction, transmission electron microscopy and X-ray photoelectron spectroscopy. The results showed the composite to be uniformly distributed and that the CoNP are well attached to the surface of the flake-like WC. Electrochemical studies show that the modified GCE has an improved electrocatalytic activity toward the reduction of H〈sub〉2〈/sub〉O〈sub〉2〈/sub〉. H〈sub〉2〈/sub〉O〈sub〉2〈/sub〉 can be selectively detected, best at a working voltage of −0.4 V (vs. Ag/AgCl), with a 6.3 nM detection limit over the wide linear range from 50 nM to 1.0 mM. This surpasses previously reported non-enzymatic H〈sub〉2〈/sub〉O〈sub〉2〈/sub〉 sensors. The sensor was successfully applied to the determination of H〈sub〉2〈/sub〉O〈sub〉2〈/sub〉 in contact lens solutions and in spiked serum samples.〈/p〉 〈p〉 〈span〉 〈caption〉 〈strong〉Graphical abstract〈/strong〉 〈em〉 〈div〉Schematic presentation of a method for electrochemical sensing of hydrogen peroxide in real samples using cobalt nanoparticle decorated tungsten carbide (WCC) modified glassy carbon electrode (GCE).〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/604_2019_3377_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉The presented voltammetric mercury(II) sensor is based on the specific interaction between Hg(II) ion and thymine-thymine base pairs. Reduced graphene oxide is functionalized with gold nanorods and then loaded with thionine and streptavidin (RGO@AuNR-TH-SA). A T-rich thiolated DNA (S1) is firstly immobilized on a gold electrode. In the presence of Hg (II), the T-rich biotin-DNA (biotin-S2) binds to S1 via T-Hg(II)-T interaction. Then, the RGO@AuNR-TH-SA is linked to the gold electrode by specific binding between SA and biotin-S2. This produces an electrochemical signal (at −0.208 V vs. Ag/AgCl) of TH that depends on the concentration of Hg (II). The peak current increases linearly in the 1 to 200 nM Hg (II) concentration range, and the detection limit is 0.24 nM. The sensor is highly selective for Hg (II) over other environmentally relevant metal ions, even at concentration ratios of 〉1000.〈/p〉 〈p〉 〈span〉 〈caption〉 〈strong〉Graphical abstract〈/strong〉 〈em〉 〈div〉Schematic representation of a voltammetric biosensor for mercury(II) using reduced graphene oxide@gold nanorods (RGO@AuNRs) and thymine-Hg(II)-thymine interaction. It is based on the fact that RGO@AuNR can strongly adsorb thionine (TH) and streptavidin to realize the signal amplification.〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/604_2019_3372_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉A turn-on fluorometric method is described for the determination of adenosine-5′-triphosphate (ATP). It is based on the displacement of a dye-labeled oligonucleotide from a cobalt(II) based layered double hydroxide (LDH). Due to the electrostatic and ligand exchange interaction, the FAM-labeled DNA is readily adsorbed on the LDH. This leads to complete and fast quenching of the green fluorescence of the label. However, on addition of ATP, the DNA is detached from the LDH because of the stronger affinity of ATP for LDH. This results in the restoration of the green fluorescence. The effect was used to design a sensitive assay that has a linear response in the 0.5–100 μM ATP concentration range and a 0.23 μM lower detection limit. It was applied to the determination of ATP in spiked serum samples.〈/p〉 〈p〉 〈span〉 〈caption〉 〈strong〉Graphical abstract〈/strong〉 〈em〉 〈div〉Schematic presentation of a fluorometric ATP assay based on the displacement of a dye-labeled oligonucleotide from a layered double hydroxide (LDH).〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/604_2019_3371_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉An ultrasensitive sandwich-type electrochemical immunosensor was developed for the amperometric determination of serum myeloperoxidase (MPO). The method is making use of (a) gold nanoparticles encapsulated in graphitized mesoporous carbons (AuNP@GMC); and (b) horseradish peroxidase (HRP) labeled secondary antibody (HRP@Ab〈sub〉2〈/sub〉) immobilized on AuNP@GMC. MPO capture antibody (Ab〈sub〉1〈/sub〉) was immobilized on the electrode modified with an AuNP-graphene oxide nanocomposite. The sandwich immunoreaction leads to the formation of the complex composed of Ab〈sub〉1〈/sub〉, MPO, and HRP@Ab〈sub〉2〈/sub〉. An amplified electrochemical signal is produced by electrocatalytic reduction of H〈sub〉2〈/sub〉O〈sub〉2〈/sub〉 (at a typical voltage of −0.18 V vs. Ag/AgCl) in the presence of enzymatically oxidized thionine. The peak current of thionine was measured using differential pulse voltammetry. Under optimized steady-state conditions, the reduction peak increases in the 1 to 300 pg.mL〈sup〉−1〈/sup〉 MPO concentration range, and the detection limit is 0.1 pg.mL〈sup〉−1〈/sup〉 (at S/N = 3).〈/p〉 〈p〉 〈span〉 〈caption〉 〈strong〉Graphical abstract〈/strong〉 〈em〉 〈div〉Schematic presentation of AuNP-GO based sandwich-type electrochemical immunoassay for the determination of myeloperoxidase by using gold nanoparticles encapsulated in graphitized mesoporous carbons (AuNP@GMC) as a carrier for horseradish peroxidase (HRP) labeled secondary antibody (HRP@Ab〈sub〉2〈/sub〉)〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/604_2019_3359_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉A nanocomposite consisting of electrochemically reduced graphene oxide, poly(Eriochrome black T) and gold nanoparticles (ERGO-pEBT/AuNPs) was prepared for the simultaneous detection of resorcinol (RC), catechol (CC), and hydroquinone (HQ). The electrochemical oxidation of HQ, CC, and RC was analysed by using cyclic voltammetry and differential pulse voltammetry. Three well-separated potentials were found at 166, 277, and 660 mV (vs. Ag/AgCl) for HQ, CC, and RC, respectively The linear ranges were 0.52–31.4, 1.44–31.2, and 3.8–72.2 μM for HQ, CC, and RC, respectively. The limits of detections (LODs) for both individual and simultaneous detections are negligibly different are (15, 8, and 39 nM, respectively).〈/p〉 〈p〉 〈span〉 〈caption〉 〈strong〉Graphical abstract〈/strong〉 〈em〉 〈div〉Voltammetric determination of hydroquinone, catechol, and resorcinol at ERGO-pEBT/AuNPs resulted in high peak currents and outstanding oxidation potential separation of the analytes.〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/604_2019_3376_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉A rapid method is described for the preparation of a highly uniform and sensitive SERS substrate by an improved ‘drop-and-dry’ method. Gold nanobipyramids (Au NBPs) were prepared inside the nanoholes (nanowalls) of anodic aluminum oxide (AAO) templates with a typically 5-μm nanohole depth. The SERS substrate can be prepared by this method within 40 s and on large scale. The SERS signals obtained with this Au NBPs-AAO substrate is stronger by four-orders of magnitude compared to conventional a silicon wafer substrate. The SERS signal for dopamine (DA; measured at 1311 cm〈sup〉−1〈/sup〉) is found to be enhanced by a factor of 2.2 × 10〈sup〉8〈/sup〉. The response to DA extends from 10 nM to 0.1 mM, and the limit of detection is 6.5 nM (at S/〈em〉N〈/em〉 = 3). The assay was applied to the determination of DA in spiked human serum.〈/p〉 〈p〉 〈span〉 〈caption〉 〈strong〉Graphical abstract〈/strong〉 〈em〉 〈div〉Schematic presentation of a highly active and uniform 3-dimensional substrate composed of gold nanobipyramids and anodic aluminum oxide (Au NBP/AAO). It was used for on-spot sensing of dopamine.〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/604_2019_3357_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉The authors describe an electrochemical immunoassay for simultaneous determination of alpha-fetoprotein (AFP) and glypican-3 (GPC-3) which are important biomarkers for early detection of hepatocellular carcinoma (HCC). Magnetite (Fe〈sub〉3〈/sub〉O〈sub〉4〈/sub〉) nanoparticles (NPs) were decorated with hyperbranched amino functionalized dendrimers. The modified NPs were coupled to the antibodies against AFP and GPC-3. The electrochemical behaviour of the Fe〈sub〉3〈/sub〉O〈sub〉4〈/sub〉 NPs and dendrimer-modified NPs were studied. A glassy carbon electrode was then modified with the NP-conjugated antibodies and biomolecular interactions were studied by using cyclic voltammetry and electrochemical impedance spectroscopy. Dual differential pulse voltammetric sensing was performed by utilizing the redox probes; Prussian blue for AFP and toluidine blue for GPC-3. The biomarkers can be detected best at voltages of 0.25 mV and – 0.54 mV (vs Ag/AgCl) for AFP and GPC-3, respectively. The low working potentials makes the method more selective over other electroactive species present in real human serum samples. Response is linear in 0.02 to 10 ng mL〈sup〉−1〈/sup〉 concentration ranges of both AFP and GPC-3; and the respective detection limits are 50 and 70 pg mL〈sup〉−1〈/sup〉. The method was validated by analysing spiked human serum samples. In our perception, the method is of great clinical significance as combination of GPC-3 and AFP increases the sensitivity of detection of HCC.〈/p〉 〈p〉 〈span〉 〈caption〉 〈strong〉Graphical abstract〈/strong〉 〈em〉 〈div〉Schematic presentation of polyamidoamine (PAMAM) dendrimers modified magnetite (Fe〈sub〉3〈/sub〉O〈sub〉4〈/sub〉) nanoparticles as electrochemical sensing platform using redox dyes Prussian blue and toluidine blue for simultaneous detection of alpha-fetoprotein (AFP) and glypican-3 (GPC-3), respectively by differential pulse voltammetry.〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/604_2019_3354_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Magnetic porous microspheres composed of Fe〈sub〉3〈/sub〉C, MnO and graphitic carbon (Fe〈sub〉3〈/sub〉C/MnO/GC) were prepared by a one-pot method. A polycondensate obtained from urea and formaldehyde served as the carbon source and was calcined in the presence of metallic iron and manganese to yield Fe〈sub〉3〈/sub〉C/MnO/GC. The resultant hybrid has highly mesoporous architecture, large specific surface, graphitic structure and adequate saturation magnetism. It is shown to possess excellent pre-concentration ability for herbicides (monuron, chlortoluron, atrazine and terbutylhylazine). The sorbent can be easily separated and has a long service lifetime (〉25 cycles). Under optimized conditions, the sorbent excels by good recoveries (78–120%), high enrichment factors (45–50) and good precision (RSDs ≤10.7%). The limits of detection are 0.01–0.10 μg L〈sup〉−1〈/sup〉 for (spiked) water samples, 0.22–0.87 μg kg〈sup〉−1〈/sup〉 for grape samples, and 0.18–0.74 μg kg〈sup〉−1〈/sup〉 for potato samples. This work offers a new strategy for the construction of magnetic bimetallic heterostructured GC hybrids.〈/p〉 〈p〉 〈span〉 〈caption〉 〈strong〉Graphical abstract〈/strong〉 〈em〉 〈div〉Schematic presentation of magnetic porous Fe〈sub〉3〈/sub〉C/MnO/graphitic carbon microspheres and their application for the enrichment of trace level herbicides prior to HPLC analysis.〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/604_2019_3358_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉The authors describe an integrated microfluidic chip for immunodetection of the prostate specific antigen (PSA) by using giant magnetoimpedance (GMI) sensor. This chip contains an immunoreaction platform and a biomarker detection system. The immunoreaction platform contains an incubation chamber and a reactive chamber to implement immunological reaction in microfluidics. The system can detect PSA rapidly with ultra-high sensitivity. Both are fabricated by MEMS technology. Immunomagnetic beads (If PSA binds to its antibody (that is labeled with immunomagnetic beads; IMBs) it will be trapped on the surface of self-assembled film. Trapped IMBs generate a stray magnetic field under the magnetization of the external applied magnetic field and can be detected by the GMI sensor. The chip can detect PSA with a detection limit as low as 0.1 ng ∙ mL〈sup〉−1〈/sup〉 and works in the 0.1 ng ∙ mL〈sup〉−1〈/sup〉 to 20 ng ∙ mL〈sup〉−1 〈/sup〉concentration range. Compared to established GMI biosensors, the magnetic microfluidic chip reduces assay time, and lends itself to fast detection. It also avoids complex handling steps, enhances reaction efficiency and decreases experimental errors.〈/p〉 〈p〉 〈span〉 〈caption〉 〈strong〉Graphical abstract〈/strong〉 〈em〉 〈div〉An integrated magnetic microfluidic chip which contains immunoreaction platform and biomarker detection system was designed and microfabricated by micro-electromechanical systems (MEMS) technology to detect prostate specific antigen (PSA) rapidly, and has promise in Point-of-care (PoC) diagnostic applications.〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/604_2019_3349_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Mesoporous molecularly imprinted polymers (MIPs) containing mangnanese-doped ZnS quantum dots (Mn-ZnS QDs) were prepared for specific recognition and detection of 4-nitrophenol (4-NP). The Mn-ZnS QDs display orange room-temperature phosphorescence with excitation/emission peaks at 295/590 nm and a decay time of 2.0 ms. In the presence of 4-NP, the orange phosphorescence is strongly reduced. Phosphorescence drops linearly in the 0.1–100 μM 4-NP concentration range, and the detection limit is 60 nM. The detection limit is far lower than the maximally allowed 4-NP concentrations in surface water and drinking water as specified by the U.S. Environmental Protection Agency. The intraday (〈em〉n〈/em〉 = 5) and interday (〈em〉n〈/em〉 = 6) spiked recovery rates were 96.0–104.5% and 97.9–107.9%, respectively, with relative standard deviations of 0.7–4.8% and 1.8–7.5% respectively. These MIPs integrated the characteristic features of phosphorimetry and molecular imprinting. Potential interference by competitive substances, background fluorescence or scattered light are widely reduced.〈/p〉 〈p〉 〈span〉 〈caption〉 〈strong〉Graphical abstract〈/strong〉 〈em〉 〈div〉Schematic presentation of the synthesis of phosphorescent molecularly-imprinted polymers. A novel probe with manganese-doped ZnS quantum dots (Mn-ZnS QDs) and 3-aminopropyl-triethoxysilane (APTES) as functional monomers and tetraethoxysilane (TEOS) as crosslinking agent was prepared for selective phosphorescence detection of 4-nitrophenol (4-NP).〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/604_2019_3362_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉A sensitive non-enzymatic fluorescent glucose sensor, consisting of vertically aligned ZnO nanotubes (NTs) grown on low-cost printed circuit board substrates, is described. The ZnO NTs were synthesized by a one-step hydrothermal method without using a seed layer. The sensor function is based on the photoluminescence (PL) quenching of ZnO NTs treated with different concentrations of glucose. The UV emission (emission maximum at 384 nm under 325 nm excitation) decreases linearly with increasing glucose concentration. The sensor exhibits a sensitivity of 3.5%·mM〈sup〉−1〈/sup〉 (defined as percentage change of the PL peak intensity per mM) and a lower limit of detection (LOD) of 70 μM. This is better than previously reported work based on the use of ZnO nanostructures. The detection range is 0.1–15 mM which makes the sensor suitable for practical uses in glucose sensing. The sensor was successfully applied to the analysis of human blood serum samples. It is not interfered by common concentrations of ascorbic acid, uric acid, bovine serum albumin, maltose, fructose, and sucrose.〈/p〉 〈p〉 〈span〉 〈caption〉 〈strong〉Graphical abstract〈/strong〉 〈em〉 〈div〉Schematic of the one-step, seedless hydrothermal method utilized for synthesizing vertically aligned ZnO nanotubes on printed circuit board substrates (PCBs). The ZnO nanotubes were used to monitor glucose concentrations in a non-enzymatic fluorescent sensor.〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/604_2019_3353_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉An ultrasensitive electrochemiluminescence (ECL) disposable aptamer sensor (aptasensor) is presented for detection of myocardial infarction biomarker by quantification of troponin I in blood serum. A screen-printed electrode was modified with (a) aptamer-modified gold nanoparticles, (b) cyclometallated iridium(III)-poly-4-vinylpyridine nanoparticles, and (c) nitrogen-doped graphene in order to increase the loading capacity and conductivity of the aptasensor. If the aptasensor is exposed to troponin I, it will bind to the aptamer and desorb the aptamer from gold nanoparticles and the surface of the electrode. This generates an enhancement in ECL emission depending on troponin I concentration. ECL emission is strongly improved by aggregation-induced phenomenon, which is caused by inhibition of the water and oxygen quenching effect on the iridium complex ECL in aqueous media. Under optimum conditions, the aptasensor has a wide dynamic range that extends from 0.1 pM to 10 nM, with a 20 fM detection limit (S/〈em〉N〈/em〉 = 3) and a relative standard deviation of 3.1%. The ECL aptasensor was successfully applied to 20 individual human serum for the detection of troponin I biomarker.〈/p〉 〈p〉 〈span〉 〈caption〉 〈strong〉Graphical abstract〈/strong〉 〈em〉 〈div〉Schematic presentation of electrochemiluminescence aptamer assay fabrication for detection of Troponin I. Carbon screen printed electrode (CSPE) was modified with nitrogen doped graphene (NG), gold nanoparticles (AuNPs), cyclometallated iridium(III)-polyvinylpyridine polymer nanoparticles, ionic liquid and bovine serum albumin.〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/604_2019_3352_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉An ultrasensitive and highly selective method is described for the determination of adenosine triphosphate (ATP) via surface-enhanced Raman scattering (SERS). Two split aptamers are used for specific recognition of ATP. They were attached to two SERS substrates. The first was placed on a nanolayer of gold nanoparticle-decorated graphene oxide (GO/Au3), and the other on gold nanoparticles (Au2). When ATP is introduced, it will interact with the split aptamers on the gold nanostructures to form a sandwich structure that brings the GO/Au3 nanolayer and the Au2 nanoparticle in close proximity. Consequently, the SERS signal, best measured at 1072 cm〈sup〉−1〈/sup〉, is strongly enhanced. The sandwich structure also displays good water solubility and stability. Under optimized conditions, the SERS signal increases in the 10 pM - 10 nM ATP concentration range, and the limit of detection (LOD) is 0.85 pM. The method was applied to the determination of ATP in spiked human serum, and the LODs in serum and buffer are comparable. In our perception, the method has a wide scope in that numerous other aptamers may be used. This may result in a variety of other highly sensitive aptasensors for use in in-vitro diagnostics.〈/p〉 〈p〉 〈span〉 〈caption〉 〈strong〉Graphical abstract〈/strong〉 〈em〉 〈div〉Schematic presentation of a self-assembly sandwich nanostructure as unique SERS assay platform for the sensitive detection of ATP.〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/604_2019_3356_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉It is shown that metallothionein-stabilized copper nanoclusters (MT-CuNCs) display catalase-like activity. In the presence of either lead(II) or mercury(II), the catalase-like activity is converted to a peroxidase-like activity. On addition of Pb(II) or Hg(II), the inhibitory effect of MT-CuNCs on the chromogenic reaction of 3,3′,5,5′-tetramethylbenzidine (TMB) with H〈sub〉2〈/sub〉O〈sub〉2〈/sub〉 is weakened. On the other hand, the catalytic effect of the nanoclusters on the chromogenic reaction is increased. The system MT-CuNCs-Pb(II)/Hg(II) exhibits high affinity for the substrates TMB and H〈sub〉2〈/sub〉O〈sub〉2〈/sub〉. Their catalytic behavior follows Michaelis-Menten kinetics. Based on these findings, a method was developed for visual detection (via the blue coloration formed) and spectrophotometric determination (at 450 nm) of Pb(II) and Hg(II). The linear range for Pb(II) extends from 0.7 to 96 μM, and the linear ranges for Hg(II) from 97 nM to 2.3 μM and from 3.1 μM to 15.6 μM. The detection limits are 142 nM for Pb(II) and 43.8 nM for Hg(II).〈/p〉 〈p〉 〈span〉 〈caption〉 〈strong〉Graphical abstract〈/strong〉 〈em〉 〈div〉Metallothionein-stabilized copper nanoclusters (MT-CuNCs) display catalase-like activity. On addition of Pb(II) or Hg(II), the catalase-like activity is converted to a peroxidase-like activity. The latter catalyzes the oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB) by H〈sub〉2〈/sub〉O〈sub〉2〈/sub〉.〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/604_2019_3360_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉A dual-mode method was developed for the determination of ascorbic acid (AA) and of ascorbic acid oxidase (AA-Ox) activity. It combines the advantages of ratiometric fluorometry and colorimetry. The assay is based on the oxidation of o-phenylenediamine (OPDA) by permanganate (KMnO〈sub〉4〈/sub〉). A yellow substance (referred to as oxOPDA) with an absorption peak at 425 nm is rapidly produced in the presence of the oxidant. oxOPDA reduces the blue fluorescence of carbon dots (C-dots) peaking at 450 nm (upon 380-nm excitation), and a new emission peak is found at 565 nm. If AA is pesent, it consumes a certain fraction of KMnO〈sub〉4〈/sub〉, so that less OPDA will be oxidized. This is accompanied by a decrease in the intensity of the fluorescence at 565 nm and an increase in the intensity at 450 nm. In parallel, the color of the solution changes from yellow to colorless. The determination of the activity of ascorbic acid oxidase (AA-Ox) is performed as follows: AA is oxidized by AA-Ox. This causes the fluorescence and colors to change in the opposite directions compared with AA detection. The ratio of fluorescences (I〈sub〉565〈/sub〉/I〈sub〉450〈/sub〉) becomes larger if the color the solution turns from colorless to yellow. Thus, the fluorescence intensity ratio (I〈sub〉565〈/sub〉/I〈sub〉450〈/sub〉) and colorimetric “bare-eye” readout can be used for determination of both the concentration of AA and the activity of AA-Ox. The fluorometric assay for AA has a linear range that extends from 0.6 to 40 μM, and the colorimetric assay from 0.2 to 70 μM. The respective data for AA-Ox activity are 0.04 ~ 5 mU·mL〈sup〉−1〈/sup〉 and 0.04 ~ 8 mU·mL〈sup〉−1〈/sup〉, respectively. The limits of detection for AA are 9 and 40 nM, and the LODs for AA-Ox activity are 0.017 and 0.012 mU·mL〈sup〉−1〈/sup〉.〈/p〉 〈p〉 〈span〉 〈caption〉 〈strong〉Graphical abstract〈/strong〉 〈em〉 〈div〉Schematic presentation of the assay. Permanganate (KMnO4) rapidly oxidizes ortho-phenylenediamine oxide to form a product (oxOPDA) having a yellow fluorescence peaking at 565 nm. The yellow color of oxOPDA can be detected visually. It also reduces the intensity of the blue fluorescence of carbon dots (C-dots) peaking at 450 nm. Ascorbic acid (AA) can consume permanganate, and this results less oxidation of OPDA. Ascorbic acid oxidase (AA-Ox) catalyzes the oxidization of AA by oxygen, and this - in turn - causes the changes in absorbance and fluorescence to change in the opposite directions.〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/604_2019_3341_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉A colorimetric method is presented for the detection of specific nucleotide sequences in plant pathogens. It is based on the use of CRISPR/Cas9-triggered isothermal amplification and gold nanoparticles (AuNPs) as optical probes. The target DNA was recognized and broken up by a given Cas9/sgRNA complex. After isothermal amplification, the product was hybridized with oligonucleotide-functionalized AuNPs. This resulted in the aggregation of AuNPs and a color change from wine red to purple. The visual detection limit is 2 pM of DNA, while a linear relationship exists between the ratio of absorbance at 650 and 525 nm and the DNA concentration in the range from 0.2 pM to 20 nM. In contrast to the previous CRISPR-based amplification platforms, the method has significantly higher specificity with the single-base mismatch and can be visually read out. It was successfully applied to identify the 〈em〉Phytophthora infestans〈/em〉 genomic DNA.〈/p〉 〈p〉 〈span〉 〈caption〉 〈strong〉Graphical abstract〈/strong〉 〈em〉 〈div〉Schematic presentation of a colorimetric method for detection of 〈em〉Phytophthora infestans〈/em〉 genomic DNA based on CRISPR/Cas9-triggered isothermal amplification. The Cas9 endonuclease cleaves DNA at the design site and the color changes from red to purple with increasing target DNA concentration.〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/604_2019_3348_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉The mesmerizing properties of nanomaterials and the features offered by optical fibers can be combined to result in an attractive new platform for chemical sensing. This review (with 230 refs.) summarizes the progress made in the past five years in the field of fiber-optic sensors: The first group comprises metals and metal oxides and their composites, and the second group comprises graphene, graphene oxides and CNTs, and its composites. By combining these nanocomposites with various optical fiber geometries, numerous sensors have been realized. Following an introduction, first section summarizes fiber-optic configuration for chemical sensing (including Fabry-Perot and Mach-Zehnder interferometry, surface plasmon resonance, and optical fiber gratings of the FBG and LPG type). The second section covers typical nanomaterials used in such sensors, with a first subsection on metals, metal oxides, their composites and nanostructured modifications, and a second subsection on graphenes, graphene oxides, carbon nanotubes, and their derivatives. Section 3 summarizes sensors (i) for various gaseous species (NH〈sub〉3〈/sub〉, H〈sub〉2〈/sub〉, CH〈sub〉4〈/sub〉, H〈sub〉2〈/sub〉S, CO〈sub〉2〈/sub〉, NO〈sub〉2〈/sub〉, O〈sub〉2〈/sub〉), (ii) for volatile organic compounds (such as ethanol, methanol, acetone, toluene, and formaldehyde), and (iii) for heavy metal ions (such as Hg〈sup〉2+〈/sup〉, Pb〈sup〉2+〈/sup〉, Mg〈sup〉2+〈/sup〉, Cd〈sup〉2+〈/sup〉, Ni〈sup〉2+〈/sup〉, and Mn〈sup〉2+〈/sup〉). The merits and limitations of these nanomaterials and numerous examples for nanomaterial-based sensors are discussed and presented in the form of tables. A concluding section addresses technological challenges and future trends.〈/p〉 〈p〉 〈span〉 〈caption〉 〈strong〉Graphical Abstract〈/strong〉 〈em〉 〈div〉Schematic presentation of an optical fiber modified with various nanomaterials such as metal oxides (MOXs), metals, carbon-nanotubes (CNTs) and graphene. Such sensors are based on several fiber-optic configurations like Fabry-Perot interferometers (FPI), Mach-Zehnder interferometer (MZI) (includes an in-line MZI), surface plasmon resonance (SPR) (includes coating on cladding and unclad part of an optical fiber) and fiber gratings (FGs) (includes fiber Bragg gratings (FBGs) and long-period gratings (LPGs), these are explored for detection of various gases (NH〈sub〉3〈/sub〉, H〈sub〉2〈/sub〉, H〈sub〉2〈/sub〉S, CH〈sub〉4〈/sub〉, O〈sub〉2〈/sub〉, CO〈sub〉2〈/sub〉), vapors (VOCs), and ions.〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/604_2019_3351_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Micrococcal nuclease (MNase) is a naturally-secreted nucleic acid degrading enzyme with important role in the spread of the bacteria in an infected host. The content of MNase can be used to estimate the pathogenicity of 〈em〉Staphylococcus aureus〈/em〉 (〈em〉S. aureus〈/em〉). A fluorometric method is described here for determination of the activity of MNase and for identification of 〈em〉S. aureus〈/em〉 using DNA templated fluorescent copper nanoclusters (CuNC). A double-stranded DNA (dsDNA) with AT-rich regions and protruding 3′-termini was identified as a high-selectivity substrate for MNase and as a template for CuNC. In the absence of MNase, the long AT-rich dsDNA templates the formation of CuNC that display bright yellow fluorescence, with excitation/emission peaks at 340/570 nm. However, the substrates are enzymatically digested to mononucleotides or short-oligonucleotide fragments, which fail to synthesize fluorescent CuNC. The method works in the 1.0 × 10〈sup〉−3〈/sup〉 - 5.0 × 10〈sup〉−2〈/sup〉 U mL〈sup〉−1〈/sup〉 MNase activity range, has a 1.0 mU mL〈sup〉−1〈/sup〉 detection limit, and is highly selective over other exonucleases. The assay was successfully applied to the detection of MNase secreted by 〈em〉S. aureus〈/em〉 and to the identification of 〈em〉S. aureus〈/em〉.〈/p〉 〈p〉 〈span〉 〈caption〉 〈strong〉Graphical abstract〈/strong〉 〈em〉 〈div〉A smart dsDNA, with AT-rich regions and 3′-protruding termini, is screened as the high-selectivity substrate for MNase and template for the formation of copper nanoclusters (CuNC). A method is described for determination of the activity of MNase and for identification of 〈em〉S. aureus〈/em〉 via smart DNA templated formation of fluorescent CuNCs.〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/604_2019_3363_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉An electrochemical sensor for paracetamol is described that consists of a glassy carbon electrode (GCE) that was modified with the conducting polymer poly(3,4-ethylenedioxythiophene) (PEDOT) doped with MnO〈sub〉2〈/sub〉 nanoflowers. The hydrothermally synthesized MnO〈sub〉2〈/sub〉 nanoflowers possess a large surface area and can be doped into PEDOT through electrochemical deposition to form a conducting polymer nanocomposite. The nanoflowers are shown to be uniformly distributed within the nanocomposite as revealed by elemental mapping analysis. The nanocomposite displays excellent catalytic activity toward the electrochemical oxidation of paracetamol. The modified GCE, best operated at a working potential of around 0.37 V (vs. SCE) has a linear response in 0.06 to 435 μM paracetamol concentration range and a very low limit of detection (31 nM at a signal-to-noise ratio of 3). The sensor exhibits excellent reproducibility and stability, and satisfying accuracy for paracetamol detection in pharmaceutical samples.〈/p〉 〈p〉 〈span〉 〈caption〉 〈strong〉Graphical abstract〈/strong〉 〈em〉 〈div〉A highly sensitive electrochemical sensor capable of detecting paracetamol with a limit of detection down to 31 nM was developed based on MnO〈sub〉2〈/sub〉 nanoflowers doped conducting polymer PEDOT.〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/604_2019_3614_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Nanofibrous polyporous membranes imprinted with cyhexatin (CYT) were formed via the ordered distribution of the imprints in electrospun nanofibers. The MIPs have a high mass transfer rate and enhanced adsorption capacity. In addition, a printed carbon electrode with enhanced sensitivity was developed via electrochemical fabrication of reduced graphene oxide (rGO) and gold nanoparticles (AuNPs). The molecularly imprinted sensor exhibits excellent selectivity and sensitivity for CYT. The structure and morphology of the nanohybrid films were characterized by using scanning electron microscopy, atomic force microscopy and chronoamperometry. The sensing performances were evaluated by cyclic voltammetry, differential pulse voltammetry and electrochemical impedance spectroscopy by using hexacyanoferrate(IV) as an electrochemical probe. The electrode, best operated at a working potential of around 0.16 V (vs. Ag/AgCl), has a linear response in the 1–800 ng mL〈sup〉−1〈/sup〉 CYT concentration range and a detection limit of 0.17 ng mL〈sup〉−1〈/sup〉 (at S/〈em〉N〈/em〉 = 3). The sensor demonstrated satisfactory recoveries when applied to the determination of CYT in spiked pear samples.〈/p〉 〈p〉 〈span〉 〈caption〉 〈strong〉Graphical abstract〈/strong〉 〈em〉 〈div〉Schematic presentation of the electrochemical sensor for detection of CYT.〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/604_2019_3631_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉A reliable fluorometric assay is described for the determination carcinoembryonic antigen (CEA) using exonuclease III (Exo III) and a 2-aminopurine binding aptamer. In the absence of CEA, dsDNA is degraded by Exo III, and free 2-AP (which has a blue fluorescence with excitation/emission maxima of 310/365 nm) is released. Strong fluorescence is generated after addition of graphene oxide (GO) to the solution. However, the 2-AP modified DNA (T2) cannot be degraded in the presence of CEA by Exo III due to the interaction between CEA and aptamer T1. Hence, only weak fluorescence can be detected after addition of GO. In this system, CEA can be quantified in the 0.05 - 2 ng·mL〈sup〉-1〈/sup〉 concentration range with a detection limit of 30 pg·mL〈sup〉-1〈/sup〉 (at S/N = 3). The method was successfully applied to analyze serum samples for CEA.〈/p〉 〈p〉 〈span〉 〈caption〉 〈strong〉Graphical Abstract〈/strong〉 〈em〉 〈div〉An exonuclease III-assisted fluorometric aptasensor has been developed for the detection of carcinoembryonic antigen using graphene oxide and 2-aminopurine.〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/604_2019_3621_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Magnetic carbon nitride composites were synthesized via a solvothermal reaction and developed as an effective adsorbent for magnetic solid-phase extraction of trace hydroxylated polycyclic aromatic hydrocarbons (OH-PAHs) from urine samples prior to their determination by HPLC. The sorbent was characterized by Fourier transform infrared spectrometry, X-ray diffractometry, scanning electron microscopy, vibrating sample magnetometry and solvent stability experiments. The adsorption of hydroxy-PAHs is better by a factor or 20 to 49 compared to bare Fe〈sub〉3〈/sub〉O〈sub〉4〈/sub〉 and comparable that of a commercial C〈sub〉18〈/sub〉 sorbent. The adsorbent amount, adsorption time and eluting solvent and volume were optimized. The complete extraction for the OH-PAHs at a level of 40 ng·mL〈sup〉−1〈/sup〉 and by using 4 mg sorbent is completed within 3 min. With an enzymatic hydrolyzed urine sample loading volume of 2 mL, enhancement factors in the range of 9–10, and a limit of detection (at 〈em〉S〈/em〉/〈em〉N〈/em〉 = 3) of 0.08 ng·mL〈sup〉−1〈/sup〉 were achieved. The method showed a linear response in the 0.25–250 ng·mL〈sup〉−1〈/sup〉 hydroxy-PAH concentration range, and intra-day and inter-day precisions are 1.5–7.7% and 2.2–8.7%, respectively. The recovery from spiked urine samples ranged from 90.1% to 102%. The sorbent was stable over 10 successive cycles of extraction/desorption of urine sample without significant loss of extraction efficiency. The method was successfully applied for the determination of OH-PAHs in urine samples of smoking volunteers.〈/p〉 〈p〉 〈span〉 〈caption〉 〈strong〉Graphical abstract〈/strong〉 〈em〉 〈div〉Schematic presentation of the preparation of graphitic carbon nitride (g-C〈sub〉3〈/sub〉N〈sub〉4〈/sub〉)/magnetite (Fe〈sub〉3〈/sub〉O〈sub〉4〈/sub〉) using a solvothermal reaction, and application for magnetic solid-phase extraction of three trace hydroxy polycyclic aromatic hydrocarbons (OH-PAHs) in urine samples of smoking volunteers.〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/604_2019_3607_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉The use of carbon black-Fe〈sub〉3〈/sub〉O〈sub〉4〈/sub〉 magnetic nanocomposite (CB-Fe〈sub〉3〈/sub〉O〈sub〉4〈/sub〉) as a probe for surface-enhanced laser desorption ionization mass spectrometry (SELDI-MS) with a high extraction efficiency and sensitive detection is described. The magnetic nanocomposite was synthesized and fully characterized using X-ray photoelectron spectroscopy, X-ray diffraction, Raman spectroscopy, Fourier transform infrared spectroscopy, Ultraviolet-Visible spectroscopy, transmission electron microscopy and nitrogen sorption. The feasibility of the SELDI probe to extract and detect three classes of drugs (labetalol, metoprolol, doxepin, desipramine, triprolidine and methapyrilene) spiked in wine is demonstrated. All the drugs were successfully and reproducibly extracted and detected with high efficiency and with limits of detection (LOD) between 1 and 1000 pg mL〈sup〉−1〈/sup〉. The adsorption capacity of the nanocomposite for the drugs was evaluated by UV-Vis spectroscopy. The results showed that 27.8–36.1% of the drugs were adsorbed on the magnetic probe within 3 min. The nanocomposite was also applied for efficient analysis of amino acids and fatty acids. Both types of analytes can be extracted within a few minutes and then successfully quantified by SELDI-MS.〈/p〉 〈p〉 〈span〉 〈caption〉 〈strong〉Graphical abstract〈/strong〉 〈em〉 〈div〉A schematic presentation of carbon black-Fe〈sub〉3〈/sub〉O〈sub〉4〈/sub〉 magnetic probe for SELDI analysis of small molecules. The probe containing the analyte(s) is collected with the aid of a magnet and deposited on the target plate for mass spectrometry analysis.〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/604_2019_3623_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉The balance between free oxygen radicals and antioxidant defense systems is usually assessed by an antioxidant capacity assay. A rapid and sensitive antioxidant capacity assay is described here. It is making use of NaYF〈sub〉4〈/sub〉:Yb/Er@NaYF〈sub〉4〈/sub〉 core-shell upconversion nanoparticles (UCNPs) and potassium permanganate (KMnO〈sub〉4〈/sub〉). In this strategy, added KMnO〈sub〉4〈/sub〉 reduces the green (540 nm) emission of the UCNPs (under 980 nm photoexcitation) due to an inner filter effect. The antioxidants cysteine, ascorbic acid and glutathione (GSH) reduce the intense purple color of KMnO〈sub〉4〈/sub〉 because it is reduced to Mn(II) ion. Hence, the green upconversion fluorescence is restored after the addition of antioxidants. Figures of merit for this assay (for the case of GSH) include a detection limit of 3.3 μM, a detection range that extends from 10 μM to 2.5 mM, and an assay time of a few seconds. The assay was applied to the evaluation of antioxidant capacity in human plasma samples spiked with GSH and gave satisfactory repeatability and specificity.〈/p〉 〈p〉 〈span〉 〈caption〉 〈strong〉Graphical abstract〈/strong〉 〈em〉 〈div〉Schematic presentation of a fluorometric assay based on inner filter effect (IFE) between upconversion nanoparticles (UCNPs) and potassium permanganate (KMnO〈sub〉4〈/sub〉) for the determination of antioxidant capacity in human plasma.〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/604_2019_3627_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Porous uranium oxide hollow sphere nanoparticles were synthesized in ionic liquids under hydrothermal conditions. Various precipitating agents and ionic liquids were investigated to determine their respective impact on the resultant uranium oxide morphologies. Using hydrazine hydrate as precipitating agent and N-butyl pyridinium bromide as templating agent, a porous-hollow structure was created with a surface area of 1958 m〈sup〉2〈/sup〉.g〈sup〉−1〈/sup〉 and an average pore diameter of 30 nm. The nanoparticles revealed high peroxidase-mimicking activity. This was evaluated by using the peroxidase substrate 3,3′,5,5′-tetramethylbenzidine (TMB) that is catalytically oxidized by H〈sub〉2〈/sub〉O〈sub〉2〈/sub〉 to give oxidized TMB (oxTMB) which is blue (with an absorption peak at 652 nm). The material was used as a nanozyme for colorimetric detection of Sn〈sup〉2+〈/sup〉. Meanwhile, it is found that BSA strongly improves the catalytic activity of the nanozyme, while Sn(II) inhibits its activity. Thus, a colorimetric method for Sn〈sup〉2+〈/sup〉 detection was designed. The method works in the 0.5–100 μM Sn(II) concentration range and has a lower detection limit of 0.36 μM (at S/〈em〉N〈/em〉 = 3).〈/p〉 〈p〉 〈span〉 〈caption〉 〈strong〉Graphical abstract〈/strong〉 〈em〉 〈div〉The catalytic activity of porous-hollow nano-UO〈sub〉2〈/sub〉 toward the oxidation of 3,3′,5,5′-tetramethylbenzidine by H〈sub〉2〈/sub〉O〈sub〉2〈/sub〉 is remarkably improved in the presence of bovine serum albumin, while tin(II) inhibits its activity. This finding has been applied to design a method for colorimetric quantification of tin(II) in water samples.〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/604_2019_3624_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉A method is presented for electrochemical determination of the breast cancer biomarker HER2. A glassy carbon electrode (GCE) was modified with densely packed gold nanoparticles placed on a composite consisting of electrochemically reduced graphene oxide and single walled carbon nanotubes (ErGO-SWCNTs). An aptamer directed against HER2 was then immobilized ono the GCE. The modified GCE was characterized by cyclic voltammetry, differential pulse voltammetry and electrochemical impedance spectroscopy. The immobilized aptamer selectively recognizes HER2 on the electrode interface, and this leads to an increased charge transfer resistance (R〈sub〉ct〈/sub〉) of the electrode when using ferri/ferro-cyanide as the electrochemical probe. The method has a low limit of detection (50 fg·mL〈sup〉−1〈/sup〉) and a wide analytical range (0.1 pg·mL〈sup〉−1〈/sup〉 to 1 ng·mL〈sup〉−1〈/sup〉). The assay is highly reproducible and specific. Clinical application was demonstrated by analysis of the HER2 levels in serum samples, and sera of breast cancer patients were successfully discriminated from sera of healthy persons.〈/p〉 〈p〉 〈span〉 〈caption〉 〈strong〉Graphical abstract〈/strong〉 〈em〉 〈div〉An electrochemical aptasensor for HER2 is described that is based on the immobilization of anti-HER2 aptamer on a glassy carbon electrode modified with a nanocomposite prepred fromreduced graphene oxide, carbon nanotubes and gold nanoparticles.〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/604_2019_3619_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Halloysite nanotubes (HNTs) were functionalized with gold nanoparticles. The morphology and structures of this composite were characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, powder X-ray diffraction, and surface area and pore-size analyses. The material was employed, in conjunction with a syringe pump and an organic filter head, to the enrichment of five triazines (atrazine, desmetryn, prometorn, tebumeton, ametryn) in spiked rice samples. Several parameters that may affect the extraction efficiencies, including type and volume of extraction solvent, amount of sorbent, times of ultrasonic extraction and adsorption, volume and flow rate of elution solvent, were optimized. Following elution with acetonitrile, the herbicides were quantified by using HPLC. Under the optimum conditions, the LODs of the method, when applied to spiked rice samples, are the range from 0.06 to 1.32 ng g〈sup〉−1〈/sup〉 (LODs = 3SD/k). The relative intra-day and inter-day recoveries ranged from 80.6 to 106.5% and 80.4–107.3%, respectively, and relative standard deviations ranged from 0.8 to 8.7% and 3.6–9.6%, respectively.〈/p〉 〈p〉 〈span〉 〈caption〉 〈strong〉Graphical abstract〈/strong〉 〈em〉 〈div〉Packed hybrids of gold nanoparticles and halloysite nanotubes (Au/HNTs) were prepared and applied to the dispersive solid-phase extraction by packed sorbent of five triazine herbicides from rice.〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/604_2019_3578_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Glutathione (GSH) is an important tripeptide that plays an important role in preventing damage to reactive oxygen species. An electrochemical assay was fabricated for this purpose by modification of a carbon paste electrode (CPE) with bis(1,10-phenanthroline)(1,10-phenanthroline-5,6-dione)nickel(II) hexafluorophosphate (BPPDNi) as new electro-catalyst and Pt:Co nanoparticle (Pt:CO-NPs) as highly conductive mediator. The analyses were performed at a scan rate of 10 mV/s and at a pH value of 7.4. The BPPDNi/Pt:CO-NPs/CPE showed a high sensitivity and good selectivity for electro-catalytic determination of glutathione (GSH) in nano-molar concentration range. In addition, the BPPDNi/Pt:CO-NPs/CPE was used for the determination of glutathione in the presence of doxorubicin (DOX) and tyrosine (Tyr) with three separated oxidation signals ~160 mV, ~385 mV and ~790 mV vs. Ag/AgCl/KCl〈sub〉sat〈/sub〉, respectively. The peak currents of the square wave voltammetric analyses were linearly dependent on glutathione, doxorubicin and tyrosine concentrations in the respective ranges of 0.001–450, 0.5–300 and 1.0–650 μM, with detection limits of 0.5 nM, 0.1 μM and 0.6 μM, respectively.〈/p〉 〈p〉 〈span〉 〈caption〉 〈strong〉Graphical abstract〈/strong〉 〈em〉 〈div〉The first analytical sensor for simultaneous determination of glutathione, doxorubicin and tyrosine.〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/604_2019_3598_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉A photoelectrochemical (PEC) method has been developed for sensitive detection of trypsin. It is based on the use of a composite consisting of MoS〈sub〉2〈/sub〉 nanosheets and TiO〈sub〉2〈/sub〉 nanorods (MoS〈sub〉2〈/sub〉-TiO〈sub〉2〈/sub〉). The material has a high specific surface area, superior electrical conductivity, excellent biocompatibility and good band gap matching. The composite was synthesized by a one-pot method using TiO〈sub〉2〈/sub〉 as a template. This results in a uniform distribution of the MoS〈sub〉2〈/sub〉 nanosheets (〈5 layers) in the composite. If the composite, placed on an indium tin oxide (ITO) electrode, is coupled to apoferritin, the photocurrent response decreases due to the insulating effect of the protein. Trypsin, in acting as an alkaline protease, decomposes the apoferritin. This results in the recovery of the PEC signal. Attractive features of this PEC method include (a) a superior PEC signal, (b) sensor stability, (c) simple operation, and (d) the lack of any additional modifications of the biosensor. This warrants high sensitivity, reproducibility, repeatability and practicality. The ITO sensor has a linear response in the 1 to 1000 ng·mL〈sup〉−1〈/sup〉 trypsin concentration range and a 0.82 ng·mL〈sup〉−1〈/sup〉 detection limit. The assay was applied to the determination of trypsin in spiked serum samples and gave satisfactory results.〈/p〉 〈p〉 〈span〉 〈caption〉 〈strong〉Graphical abstract〈/strong〉 〈em〉 〈div〉Schematic presentation of an indium tin oxide (ITO)/MoS〈sub〉2〈/sub〉-TiO〈sub〉2〈/sub〉 sensor for detecting trypsin. The PEC signal was decreased after immobilization of apoferritin (APO) on the modified ITO. Trypsin catalytically hydrolyzes APO specifically and induces the PEC signal to recover.〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/604_2019_3589_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉This study describes a universal fluorometric method for sensitive detection of analytes by using aptamers. It is based on the use of graphene oxide (GO) and cryonase-assisted signal amplification. GO is a strong quencher of FAM-labeled nucleic acid probes, while cryonase digests all types of nucleic acid probes. This makes the platform widely applicable to analytes for which the corresponding aptamers are available. Theophylline and ATP were chosen as model analytes. In the absence of targets, dye-labeled aptamers are in a flexible single strand state and adsorb on the GO. As a result, the probes are non-fluorescent due to the efficient quenching of dyes by GO. Upon the addition of a specific target, the aptamer/target complex desorbed from the GO surface and the probe becomes fluorescent. The released complex will immediately become a substrate for cryonase digestion and subsequently releasing the target to bind to another aptamer to initiate the next round of cleavage. This cyclic reaction will repeat again and again until all the related-probes are consumed and all fluorophores light up, resulting in significant fluorescent signal amplification. The detection limits are 47 nM for theophylline and 22.5 nM for ATP. This is much better than that of known methods. The assay requires only mix-and-measure steps that can be accomplished rapidly. In our perception, the detection scheme holds great promise for the design enzyme-aided amplification mechanisms for use in bioanalytical methods.〈/p〉 〈p〉 〈span〉 〈caption〉 〈strong〉Graphical abstract〈/strong〉 〈em〉 〈div〉A cryonase-assisted signal amplification (CASA) method has been developed by using graphene oxide (GO) conjugated with a fluorophore-labeled aptamer for fluorescence signal generation. It has a large scope because it may be applied to numerous analytes.〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/604_2019_3596_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉This article describes a method for highly selective preconcentration of Cd(II) via magnetic Mn〈sub〉2〈/sub〉O〈sub〉3〈/sub〉 coated by N,N′-bis(salicylidene)ethylenediamine (BSED). The metal oxide components were prepared via combining sol-gel and precipitation methods. Then, BSED was added as the third component of the composite. X-ray diffraction, scanning electron microscopy, transmission electron microscopy, alternating gradient force magnetometry, and Fourier transform infrared spectroscopy were applied to characterize the materials. BSED selectively forms a complex with Cd(II), and the sorbent can then be magnetically separated. The preconcentration conditions were optimized as pH value (4.0 ± 0.5), sorbent amount (30 mg), adsorption time (20 min), eluent 2 M HNO〈sub〉3〈/sub〉), eluent volume (1.5 mL) and desorption time (4 min). The quantification of Cd(II) was done by flame atomic absorption spectroscopy. The method has the following figures of merit: (a) a detection limit of 320 µg L〈sup〉−1〈/sup〉, (b) a relative standard deviation of 1.1%, (c) an enhancement factor of 36, (d) a preconcentration factor of 33, and (e) a linear dynamic range that extends from 10 to 120 μg L〈sup〉−1〈/sup〉. Other features include the use of safe reagents, fast and simple preparation, high selectivity and reliable analytical performance. The effects of potentially interfering ions were examined. The Dubinin–Radushkevich model and the pseudo second-order model are found to fit the adsorption behavior. The absorption is spontaneous and exothermic. The method was successfully applied to the determination of Cd(II) in (spiked) fruit samples.〈/p〉 〈p〉 〈span〉 〈caption〉 〈strong〉Graphical abstract〈/strong〉 〈em〉 〈div〉Schematic presentation of a nanocomposite (Fe〈sub〉3〈/sub〉O〈sub〉4〈/sub〉 – Mn〈sub〉2〈/sub〉O〈sub〉3〈/sub〉 – Schiff base) that was prepared from MnCl〈sub〉2〈/sub〉, H〈sub〉2〈/sub〉O〈sub〉2〈/sub〉, FeCl〈sub〉2〈/sub〉, FeCl〈sub〉3〈/sub〉, NH〈sub〉3〈/sub〉, salicylaldehyde, ethylenediamine and tetraethylammonium hydroxide for the magnetic solid phase extraction of cadmium at trace levels.〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/604_2019_3567_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉The one-pot synthesis of iron-doped carbon quantum dots (Fe-CQDs) for use as both magnetic resonance (MR) and fluorescent (dual-mode) imaging nanoprobes is described. Comprehensive characterizations of the material confirmed the successful doping of the CQDs with Fe(II) ions. The imaging probe has a longitudinal relaxivity of 3.92 mM〈sup〉−1〈/sup〉∙s〈sup〉−1〈/sup〉 and a low 〈em〉r〈/em〉〈sub〉2〈/sub〉/〈em〉r〈/em〉〈sub〉1〈/sub〉 ratio of 1.27, both of which are critical for 〈em〉T〈/em〉〈sub〉1〈/sub〉-weighted contrast agents. The maximum emission of Fe-CQDs locates at 450 nm under 375 nm excitation, which also can be applied to fluorescence imaging. Biotoxicity assessment showed good biocompatibility of the Fe-CQDs. The in-vitro experiments with A549 cells indicated that the Fe-CQDs are viable candidates as dual-mode (MR/fluorescence) imaging nanoprobes. For in-vivo experiments, they exhibit high contrast efficiency, thereby improving the positive contrast in 〈em〉T〈/em〉〈sub〉1〈/sub〉-weighted MR images. In-vivo time-dependent MRI of major organs showed that the Fe-CQDs undergo fast glomerular filtration and can evade immuno-absorption due to their ultra-small size and excellent biocompatibility.〈/p〉 〈p〉 〈span〉 〈caption〉 〈strong〉Graphical abstract〈/strong〉 〈em〉 〈div〉Schematic presentation of the synthesis of Fe-CQDs and applications to magnetic resonance and fluorescent dual-mode imaging.〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/604_2019_3593_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉A magnetic graphene-like molybdenum disulfide nanocomposite was prepared by liquid-phase exfoliation and hydrothermal synthesis. The morphology, structure, and magnetic behavior of the nanocomposite were characterized by X-ray diffraction, FTIR spectroscopy, thermogravimetric analysis, vibrating sample magnetometry, scanning electron microscopy and transmission electron microscopy. The nanocomposite was employed as a sorbent for magnetic solid-phase extraction (MSPE) of eight triazine and ten sulfonylurea herbicides from environmental water and corn samples. Specifically, this was studied with cyanazine, simetryn, atrazine, methoprotryne, ametryn, prometryn, terbutryn, dipropetryn, metsulfuron-methyl, sulfometuron-methyl, amidosulfuron, rimsulfuron, nicosulfuron, bensulfuron-methyl, halosulfuron-methyl, pyrazosulfuron-ethyl, chlorimuron-ethyl, and cyclosulfamuron. The parameters affecting extraction efficiency (sorbent amount, pH value of the sample, extraction and elution conditions) were studied and optimized. Following MSPE, the multi-residue herbicides were quantified by ultra-high performance liquid chromatography combined with ion trap mass spectrometry and electrospray ionization. The limits of detection range between 20 and 170 ng·L〈sup〉−1〈/sup〉. The extraction recoveries of eighteen herbicides from corn samples were in the range between of 64.7% and 103.1%, with RSDs of 〈17.6%.〈/p〉 〈p〉 〈span〉 〈caption〉 〈strong〉Graphical abstract〈/strong〉 〈em〉 〈div〉Schematic presentation of magnetic graphene-like MoS〈sub〉2〈/sub〉 nanocomposite as an absorbent for simultaneous preconcentration of eight triazine and ten sulfonylurea herbicides in corn and water prior to ultra-high performance liquid chromatography (UHPLC) with ion trap mass spectrometry detection.〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/604_2019_3536_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉A nanocomposite was prepared from β-cyclodextrin (β-CD) functionalized graphene oxide and magnetic nanoparticles (GO/Fe〈sub〉3〈/sub〉O〈sub〉4〈/sub〉/β-CD). In parallel, a polyamidoamine dendrimer conjugated to avidinylated alkaline phosphatase (PAMAM-avidin-ALP) was prepared and exploited as a signal amplification unit in a voltammetric immunoassay for 5-methylcytosine (5mC) in genomic DNA. The GO/Fe3O4/β-CD as a substrate material exhibited good solubility, electrical conductivity and large surface. This is beneficial for the further modification of antibodies (Ab) by host-guest interaction and amide bonds. By taking advantage of three-dimensional structure to capture avidin-ALP by amide linkages, PAMAM was used as a catalytic signal amplification element in this assay. Under the optimized condition and at a typical working potential of 0.94 V, the response to 5mC is linear in the 0.01–50 nM concentration range with a detection limit of 3.2 pM (at S/〈em〉N〈/em〉 = 3). The method is stable, selective and reproducible. It was applied to the determination of 5mC in genomic DNA of human tissue.〈/p〉 〈p〉 〈span〉 〈caption〉 〈strong〉Graphical abstract〈/strong〉 〈em〉 〈div〉An electrochemical immunoassay was constructed for 5-methylcytosine detection based on nanocomposite of graphene oxide, magnetite nanoparticles and β-cyclodextrin, and enzymatic signal amplification.〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/604_2019_3575_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉An electrochemical dopamine (DA) sensor has been fabricated by modifying a glassy carbon electrode (GCE) with ruthenium disulfide (RuS〈sub〉2〈/sub〉) nanoparticles (NPs). FESEM and TEM micrographs show the NPs to have an average size of ~45 nm. XRD, Raman and EDS, in turn, confirm the successful formation of cubic phased RuS〈sub〉2〈/sub〉 NPs. The modified GCE displays has attractive features of merit that include (a) an ultra-low detection limit (73.8 nM), (b) fast response time (〈 4 s), (c) a low oxidation potential (0.25 V vs. Ag|AgCl), (d) excellent reproducibility and stability, (e) an electrochemical sensitivity of 18.4 μA μM〈sup〉−1〈/sup〉 cm〈sup〉−2〈/sup〉 and 1.8 μA.μM〈sup〉−1〈/sup〉.cm〈sup〉−2〈/sup〉 in the linear ranges from 0.1–10 μM of DA (R〈sup〉2〈/sup〉 = 0.97) and 10–80 μM of DA (R〈sup〉2〈/sup〉 = 0.99), respectively. The sensor exhibits excellent specificity over potential interferents like ascorbic acid, glucose and uric acid. The superior performance of the sensor is attributed to its high electrical conductivity, large electro-active surface, and large numbers of exposed catalytically active sites resulting from the presence of unreacted sulfur atoms.〈/p〉 〈p〉 〈span〉 〈caption〉 〈strong〉Graphical abstract〈/strong〉 〈em〉 〈div〉A ruthenium disulfide modified electrochemical sensor material was obtained by single-step hydrothermal synthesis. Sensitive and highly selective detection of dopamine is demonstrated.〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/604_2019_3622_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉