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  • 1
    Electronic Resource
    Electronic Resource
    Effect of Size and Serum Proteins on Transfection Efficiency of Poly ((2-dimethylamino)ethyl Methacrylate)-Plasmid Nanoparticles (1996)
    Springer
    Pharmaceutical research 13 (1996), S. 1038-1042 
    Details
    ISSN: 1573-904X
    Keywords: DNA ; plasmid ; gene therapy ; transfection ; β-galactosidase ; poly(2-dimethylamino)ethyl methacrylate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. The aim of this study was to gain insight into the relation between the physical characteristics of particles formed by a plasmid and a synthetic cationic polymer (poly(2-dimethylamino)ethyl methacrylate, PDMAEMA) and their transfection efficiency. Methods. The PDMAEMA-plasmid particles were characterized by dynamic light scattering (size) and electrophoretic mobility measurements (charge). The transfection efficiency was evaluated in cell culture (COS-7 cells) using a pCMV-lacZ plasmid coding for β-galactosidase as a reporter gene. Results. It was shown that the optimal transfection efficiency was found at a PDMAEMA-plasmid ratio of 3 (w/w), yielding stable and rather homogeneous particles (diameter 0.15 µm) with a narrow size distribution and a slightly positive charge. Particles prepared at lower weight ratios, showed a reduced transfection efficiency and were unstable in time as demonstrated by DLS measurements. Like other cationic polymers, PDMAEMA is slightly cytotoxic. This activity was partially masked by complexing the polymer with DNA. Interestingly, the transfection efficiency of the particles was not affected by the presence of serum proteins. Conclusions. PDMAEMA is an interesting vector for the design of in vivo and ex vivo gene transfection systems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1016054623543
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  • 2
    Electronic Resource
    Electronic Resource
    Freeze-Drying of Poly((2-dimethylamino)ethyl Methacrylate)-Based Gene Delivery Systems (1997)
    Springer
    Pharmaceutical research 14 (1997), S. 1838-1841 
    Details
    ISSN: 1573-904X
    Keywords: plasmid ; poly(2-dimethylamino)ethyl methacrylate ; freeze-drying ; gene therapy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1012164804441
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  • 3
    Electronic Resource
    Electronic Resource
    Long Term Stability of Poly((2-dimethylamino)ethyl Methacrylate)-Based Gene Delivery Systems (1999)
    Springer
    Pharmaceutical research 16 (1999), S. 1417-1423 
    Details
    ISSN: 1573-904X
    Keywords: plasmid ; poly(2-dimethylamino)ethyl methacrylate ; freeze-drying ; long-term stability ; gene therapy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. To study the stability of polymer-plasmid complexes (polyplexes) both as an aqueous dispersion and in their lyophilized form. Methods. The characteristics of the polyplexes (size, charge and transfection potential) were monitored at different temperatures. Moreover, we studied possible changes in the secondary and tertiary structure of the plasmid by agarose gel electrophoresis and by CD spectroscopy to gain insight into the mechanism of polyplex degradation. Results. The polyplexes preserved almost their full transfection potential after aging in an aqueous solution of 20 mM Hepes (pH 7.4) containing 10% sucrose at 4 and 20°C for 10 months. On the other hand, the polyplexes aged at 40°C were rather unstable and lost their transfection capability with a half-life of around 2 months. During storage, conformational changes in the secondary and tertiary structure of DNA were observed. When naked plasmid DNA was aged at 40°C as an aqueous solution and complexed with polymer just before the transfection experiment, a slower drop in its transfection capability was observed. The freeze-dried polyplexes using sucrose as lyoprotectant almost fully retained their transfection efficiency, even when aged at 40°C for 10 months. Conclusions. This study provides information about polyplex stability in aqueous dispersions on storage and demonstrates that freeze-drying is an excellent method to ensure long term stability.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018907310472
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  • 4
    Electronic Resource
    Electronic Resource
    Controlled Release of Liposomes from Biodegradable Dextran Microspheres: A Novel Delivery Concept (2000)
    Springer
    Pharmaceutical research 17 (2000), S. 664-669 
    Details
    ISSN: 1573-904X
    Keywords: controlled release ; liposomes ; hydrogel ; dextran ; microspheres
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. To design liposome-loaded microspheres, which release theliposomes in a time-controlled manner and in intact form. Methods. Liposomes were encapsulated in biodegradabledextran-based microspheres, which were prepared using an aqueous two phasesystem consisting of poly(ethylene glycol) and methacrylated dextran.The effects of liposome size and membrane fluidity, microsphere watercontent, degree of methacrylate substitution, and type of dextranderivative used, on encapsulation efficiency, release, and integrity of theliposomes were investigated. Results. Liposomes were entrapped in dextran-based microspheresquantitatively and with full preservation of their integrity. Liposomeswith a low, as well as with a high membrane fluidity, were releasedfrom the microspheres in their intact form and with preservation oftheir size. Release kinetics depended only on the degradation rate ofthe microspheres. For rapidly degrading systems, pulsed release wasobserved and the time after which the pulse occurred (from 5 until 25days) could be tailored by the gel characteristics such as initial watercontent, degree of methacrylate substitution, and type of hydrolyticallysensitive spacer present in the cross-links. This delay time was notdependent on the size of the liposomes in the range studied(0.1–0.2 μm). Microspheres which degraded more slowly showed, after a certaindelay time, sustained release of the liposomes extended up to 100 days. Conclusions. A novel drug delivery concept based on the encapsulationof liposomes in biodegradable dextran-based microspheres wasdesigned. The system released the liposomes in intact form in acontrolled way after a prolonged period of time.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1007526114744
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  • 5
    Electronic Resource
    Electronic Resource
    Protein Instability in Poly(Lactic-co-Glycolic Acid) Microparticles (2000)
    Springer
    Pharmaceutical research 17 (2000), S. 1159-1167 
    Details
    ISSN: 1573-904X
    Keywords: controlled release ; microparticles ; PLGA ; protein stability ; stabilization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract In this review the current knowledge of protein degradation during preparation, storage and release from poly(lactic-co-glycolic acid) (PLGA) microparticles is described, as well as stabilization approaches. Although we have focussed on PLGA microparticles, the degradation processes and mechanisms described here are valid for many other polymeric release systems. Optimized process conditions as well as stabilizing excipients need to be used to counteract several stress factors that compromise the integrity of protein structure during preparation, storage, and release. The use of various stabilization approaches has rendered some success in increasing protein stability, but, still, full preservation of the native protein structure remains a major challenge in the formulation of protein-loaded PLGA microparticles.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1026498209874
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  • 6
    Electronic Resource
    Electronic Resource
    Association and Dissociation Characteristics of Polymer/DNA Complexes Used for Gene Delivery (1999)
    Springer
    Pharmaceutical research 16 (1999), S. 1534-1541 
    Details
    ISSN: 1573-904X
    Keywords: gene delivery ; poly(L-lysine) ; DNA interaction ; plasmid ; p(DMAEMA)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. The DNA association/dissociation properties of water-soluble cationic methacrylate polymers with closely related structures (poly(2-dimethylamino)ethyl methacrylate) [p(DMAEMA)], poly(2-(trimethylamino)ethyl methacrylate chloride) [p(TMAEMA)]) and the frequently used transfectant poly(L-lysine) were studied to gain a better insight into their transfection characteristics. Methods. Association of DNA with different polymers and dissociation of the complexes, achieved by adding an excess of anionic polymers or salt, were studied by using spectroscopic techniques (fluorescence, circular dichroism (CD)), agarose gel electrophoresis and an enzymatic assay (DNase I treatment). The transfection efficiency of the polyplexes was evaluated in tissue culture with OVCAR-3 cells. Results. Plasmid DNA complexed with either poly(L-lysine) or p(DMAEMA) was protected against digestion by DNase I. Fluorescence and CD spectroscopy as well as gel electrophoresis revealed that p(DMAEMA) with a relatively high molecular weight and poly(L-lysine) have similar DNA association/dissociation characteristics. Therefore, differences in transfection potential of the polyplexes cannot be ascribed to differences in binding characteristics, but are probably caused by other factors. As compared with the other polymers, p(TMAEMA) has a high affinity for DNA as was concluded from the observation that poly(aspartic acid) was unable to fully dissociate complexes containing this polymer. This fact might very well explain the low transfection efficiency of these polyplexes. p(DMAEM A) with a relatively low molecular weight probably has a low affinity for DNA, which might explain both the formation of DNA aggregates Ψ-DNA) and the low transfection potential obtained when using this polymer. Conclusions. DNA association/dissociation studies shed light on the preferred characteristics of polymeric transfectants.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1015096302720
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  • 7
    Electronic Resource
    Electronic Resource
    Cationic Polymer Based Gene Delivery Systems (2000)
    Springer
    Pharmaceutical research 17 (2000), S. 113-126 
    Details
    ISSN: 1573-904X
    Keywords: cationic polymers ; polycations ; DNA plasmid ; non-viral gene therapy ; gene carriers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Gene transfer to humans requires carriers for the plasmid DNA which canefficiently and safely carrythe gene into the nucleus of the desired cells. A series of chemically differentcationic polymers arecurrently being investigated for these purposes. Although many cationic polymersindeed condense DNAspontaneously, which is a requirement for gene transfer in most types of cells,the physicochemical andbiopharmaceutical behavior of the current generation of polyplexes severelylimits an efficient genetransfer in vitro and especially in vivo. This papersummarizes recent physicochemical and biologicalinformation on polyplexes and aims to provide new insights with respect to thistype of gene deliverysystem. Firstly, the chemical structure of frequently studied cationic polymersis represented. Secondly,the parameters influencing condensation of DNA by cationic polymers aredescribed. Thirdly, the surfaceproperties, solubility, aggregration behavior, degradation and dissociation ofpolyplexes are considered.The review ends by describing the in vitro and in vivo genetransfection behavior of polyplexes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1007548826495
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  • 8
    Electronic Resource
    Electronic Resource
    The Preparation of Dextran Microspheres in an All-Aqueous System: Effect of the Formulation Parameters on Particle Characteristics (1998)
    Springer
    Pharmaceutical research 15 (1998), S. 557-561 
    Details
    ISSN: 1573-904X
    Keywords: aqueous two phase system ; phase diagram ; microsphere preparation ; dextran ; hydrogel ; poly(ethylene glycol)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. The purpose of this study was to investigate the effect of the formulation parameters on the characteristics of dextran-based microspheres, prepared in an all-aqueous system. Methods. Dextran microspheres were formed by polymerization of methacryloyl groups attached to dextran (dexMA), emulsified in an aqueous poly(ethylene glycol) (PEG) solution. DexMA/PEG/water phase diagrams were established. Results. The binodals in the phase diagrams shifted to higher concentrations of dextran and PEG with decreasing molecular weight of both polymers, and with increasing degree of MA substitution. The volume-number mean diameter of the microspheres, varied between 2.5 and 20 μm. For a given formulation, the particle size was independent of the PEG/dexMA volume ratio 〉 40 and increased for volume ratios 〈 40. Furthermore, larger particles were obtained with decreasing viscosity of the continuous phase and increasing viscosity of the discontinuous phase. Conclusions. Particle characteristics of dextran microspheres prepared in an all-aqueous system, among which the size and initial water content, can be tailored by adjusting the formulation parameters.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1011925709873
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  • 9
    Electronic Resource
    Electronic Resource
    Synthesis and characterization of poly-L-lysine with controlled low molecular weight (1997)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 198 (1997), S. 3893-3906 
    Details
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: N-Carboxy-(N∊-benzyloxycarbonyl)-L-lysine anhydride (Z-L-lysine NCA) was polymerized in dimethylformamide with triethylamine, diethylamine or hexylamine as initiator, at varying molar ratios of NCA to initiator (M/I ratio). After removal of the protecting Z-group the resulting poly-L-lysine was characterized with 1H NMR and MALDI TOF MS. Both diethylamine- and hexylamine-initiated polymerization yielded poly-L-lysine in which the initiators were incorporated at the carboxylic end of the polymer. This indicates that the NCA polymerization occurred exclusively via nucleophilic attack of the initiator on the monomer. On the other, hand, when triethylamine was used as the initiator, poly-L-lysine was obtained in which no triethylamine-derived end group could be detected by MS. These polymer chains are most likely end-capped with an N-acyl-2,5-dioxopiperazine group at the carboxylic end of the polymer. Incorporation of diethylamine and hexylamine allowed determination of the degree of polymerization (DP) of the obtained polymers by 1H NMR. The DP depended linearly on the M/I ratio, for both diethylamine and hexylamine, with higher DPs for the diethylamine-initiated poly-L-lysine at equal M/I ratio.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1997.021981211
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  • 10
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    Self-Assembling Peptide Epitopes as Novel Platform for Anticancer Vaccination (2017)
    American Chemical Society
    Details
    Publication Date: 2017-01-27
    Print ISSN: 1543-8384
    Electronic ISSN: 1543-8392
    Topics: Chemistry and Pharmacology
    Published by American Chemical Society
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