ALBERT

Description: The rheological changes that occur during the chemical gelation of semidilute solutions of chitosan in the presence of the low-toxicity agent glyceraldehyde (GCA) are presented and discussed in detail. The entanglement concentration for chitosan solutions was found to be approximately 0.2 wt.% and the rheological experiments were carried out on 1 wt.% chitosan solutions with various amounts of GCA at different temperatures (25 °C and 40 °C) and pH values (4.8 and 5.8). High crosslinker concentration, as well as elevated temperature and pH close to the pKa value (pH ≈ 6.3–7) of chitosan are three parameters that all accelerate the gelation process. These conditions also promote a faster solid-like response of the gel-network in the post-gel region after long curing times. The mesh size of the gel-network after a very long (18 h) curing time was found to contract with increasing level of crosslinker addition and elevated temperature. The gelation of chitosan in the presence of other chemical crosslinker agents (glutaraldehyde and genipin) is discussed and a comparison with GCA is made. Small angle neutron scattering (SANS) results reveal structural changes between chitosan solutions, incipient gels, and mature gels.

Description: Marine polymer gels play a critical role in regulating ocean basin scale biogeochemical dynamics. This brief review introduces the crucial role of marine gels as a source of aerosol particles and cloud condensation nuclei (CCN) in cloud formation processes, emphasizing Arctic marine microgels. We review the gel’s composition and relation to aerosols, their emergent properties, and physico-chemical processes that explain their change in size spectra, specifically in relation to aerosols and CCN. Understanding organic aerosols and CCN in this context provides clear benefits to quantifying the role of marine nanogel/microgel in microphysical processes leading to cloud formation. This review emphasizes the DOC-marine gel/aerosolized gel-cloud link, critical to developing accurate climate models.

Description: Hydrogels are three-dimensional soft polymeric materials that can entrap huge amounts of water. They are widely attractive in the biomedicine area because of their outstanding applications such as biosensors, drug delivery vectors, or matrices for cell scaffolds. Generally, the low mechanical strength and fragile structure of the hydrogels limit their feasibility, but this is not the case. In this work, acrylic acid–agar hydrogels with excellent mechanical properties were synthesized using gamma radiation as a crosslinking promoter. The obtained hydrogels exhibited a water absorption capacity up to 6000% in weight without breaking and keeping their shape; additionally, they showed a noticeable adhesion to the skin. The synthesized materials were characterized by infrared spectroscopy (FTIR-ATR), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), scanning electron microscopy (SEM), and mechanical testing. Additionally, their water uptake capacity and critical pH were studied. Net(Agar/AAc) hydrogel exhibited a noticeable capacity to load silver nanoparticles (AgNPs), which endowed it with antimicrobial activity that was demonstrated when challenged against Escherichia coli and methicillin-resistant Staphylococcus aureus (MRSA) on in vitro conditions.

Description: This study states the preparation of novel ink with potential use for bone and cartilage tissue restoration. 3Dprint manufacturing allows customizing prostheses and complex morphologies of any traumatism. The quest for bioinks that increase the restoration rate based on printable polymers is a need. This study is focused on main steps, the synthesis of two bioceramic materials as WO3 and Na2Ti6O13, its integration into a biopolymeric-base matrix of Alginate and Gelatin to support the particles in a complete scaffold to trigger the potential nucleation of crystals of calcium phosphates, and its comparative study with independent systems of formulations with bioceramic particles as Al2O3, TiO2, and ZrO2. FT-IR and SEM studies result in hydroxyapatite’s potential nucleation, which can generate bone or cartilage tissue regeneration systems with low or null cytotoxicity. These composites were tested by cell culture techniques to assess their biocompatibility. Moreover, the reinforcement was compared individually by mechanical tests with higher results on synthesized materials Na2Ti6O13 with 35 kPa and WO3 with 63 kPa. Finally, the integration of these composite materials formulated by Alginate/Gelatin and bioceramic has been characterized as functional for further manufacturing with the aid of novel biofabrication techniques such as 3D printing.

Description: Carcinoembryonic antigen (CEA) is an important broad-spectrum tumor marker. For CEA detection, a novel type of metal–organic framework (MOF) was prepared by grafting CEA aptamer-incorporated DNA tetrahedral (TDN) nanostructures into PCN-222 (Fe)-based MOF (referred as CEAapt-TDN-MOF colloid nanorods). The synthesized CEAapt-TDN-MOF is a very stable detection system due to the vertex phosphorylated TDN structure at the interface, possessing a one-year shelf-life. Moreover, it exhibits a significant horseradish peroxidase mimicking activity due to the iron porphyrin ring, which leads to a colorimetric reaction upon binding toward antibody-captured CEA. Using this method, we successfully achieved the highly specific and ultra-sensitive detection of CEA with a limit of detection as low as 3.3 pg/mL. In addition, this method can detect and analyze the target proteins in clinical serum samples, effectively identify the difference between normal individuals and patients with colon cancer, and provide a new method for the clinical diagnosis of tumors, demonstrating a great application potential.

Description: Hydrogels are attractive biomaterials with favorable characteristics due to their water uptake capacity. However, hydrogel properties are determined by the cross-linking degree and nature, the tacticity, and the crystallinity of the polymer. These biomaterials can be sorted out according to the internal structure and by their response to external factors. In this case, the internal interaction can be reversible when the internal chains are led by physicochemical interactions. These physical hydrogels can be synthesized through several techniques such as crystallization, amphiphilic copolymers, charge interactions, hydrogen bonds, stereo-complexing, and protein interactions. In contrast, the internal interaction can be irreversible through covalent cross-linking. Synthesized hydrogels by chemical interactions present a high cross-linking density and are employed using graft copolymerization, reactive functional groups, and enzymatic methods. Moreover, specific smart hydrogels have also been denoted by their external response, pH, temperature, electric, light, and enzyme. This review deeply details the type of hydrogel, either the internal structure or the external response. Furthermore, we detail some of the main applications of these hydrogels in the biomedicine field, such as drug delivery systems, scaffolds for tissue engineering, actuators, biosensors, and many other applications.

Description: In recent years, the rising number of bone diseases which affect millions of people worldwide has led to an increased demand for materials with restoring and augmentation properties that can be used in therapies for bone pathologies. In this work, PMMA- MBG composite scaffolds containing ceria (0, 1, 3 mol%) were obtained by the phase separation method. The obtained composite scaffolds were characterized by X-ray diffraction, infrared spectroscopy, and scanning electron microscopy. UV–Vis measurement and EDX analysis confirmed the presence of cerium ions in the composite scaffolds. Evaluation of the in-vitro biocompatibility using MTT assay showed that composite scaffold containing 1 mol% of ceria presented higher viability than control cells (100%) for concentrations ranging between 5 and 50% after 96 h of incubation.

Description: Currently, macroporous hydrogels have been receiving attention in wastewater treatment due to their unique structures. As a natural polymer, alginate is used to remove cationic dyes due to its sustainable features such as abundance, low cost, processability, and being environmentally friendly. Herein, alginate/montmorillonite composite macroporous hydrogels (cryogels) with high porosity, mechanical elasticity, and high adsorption yield for methylene blue (MB) were generated by the one-step cryogelation technique. These cryogels were synthesized by adding montmorillonite into gel precursor, followed by chemical cross-linking employing carbodiimide chemistry in a frozen state. The as-prepared adsorbents were analyzed by FT-IR, SEM, gel fraction, swelling, uniaxial compression, and MB adsorption tests. The results indicated that alginate/montmorillonite cryogels exhibited high gelation yield (up to 80%), colossal water uptake capacity, elasticity, and effective dye adsorption capacity (93.7%). Maximum adsorption capacity against MB was 559.94 mg g−1 by linear regression of Langmuir model onto experimental data. The Pseudo-Second-Order model was fitted better onto kinetic data compared to the Pseudo-First-Order model. Improved porosity and mechanical elasticity yielding enhanced dye removal capacity make them highly potential alternative adsorbents compared to available alginate/montmorillonite materials for MB removal.

Description: The foams stabilized by nanoparticles (NPs), water-soluble polymers, and surfactants have potential application prospects in the development of new, environmentally friendly firefighting foams. In the present study, a gel foam containing a water-soluble polymer (xanthan gum, XG), hydrophilic silica NPs, hydrocarbon surfactant (SDS), and fluorocarbon surfactant (FS-50) were prepared. The surface activity, conductivity, viscosity, and foaming ability of foam dispersions were characterized. The gel foam stability under a radiation heat source and temperature distribution in the vertical foam layer were evaluated systematically. The results show that the addition of NPs and XG has a significant effect on the foaming ability, viscosity and foam thermal stability, but has a very subtle effect on the conductivity and surface activity. The foaming ability of the FS-50/SDS solution was enhanced by the addition of NPs, but decreased with increasing the XG concentration. The thermal stability of the foams stabilized by SDS/FS-50/NPs/XG increased with the addition of NPs and increasing XG concentration. Foam drainage and coarsening were significantly decelerated by the addition of NPs and XG. The slower foam drainage and coarsening are the main reason for the intensified foam thermal stability. The results obtained from this study can provide guidance for developing new firefighting foams.

Description: Many high-strength hydrogels have been developed in recent years; however, few of them are both tough and resilient, and their intrinsic paradoxical nature makes designing a gel with both high toughness and high resilience a great challenge. To address this problem, we introduced both N,N,N,N-pentamethyldiethylenetriamine (PA) and N,N-methylenebisacrylamide (MBA) into polyacrylamide hydrogel networks to construct an entangled network that contains chemically cross-linked chains and branched chains simultaneously. The entanglements of branched chains can act as a physical cross-linking point to uniformly disperse stress on molecular chains, and chemical cross-linking ensures the stability of the hydrogel network. The increase in the number and length of branched chains is able to achieve an enhancement in strength while the slip of the entangled polymer chains can effectively achieve energy dissipation and can improve the toughness of the gel. Moreover, the resultant hydrogels exhibit an excellent resilience (〉98%). Therefore, high toughness and resilience are achieved simultaneously. In addition, we also investigated the initiation mechanism of PA. This strategy creates a new way for the preparation of next-generation high toughness and high resilience hydrogel-based materials, which have promising applications in wearable, flexible strain/pressure sensors.