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  • 1
    Electronic Resource
    Electronic Resource
    Poly(L-lactic acid)/Pluronic blends: characterization of phase separation behavior, degradation, and morphology and use as protein-releasing matrixes (1992)
    s.l. : American Chemical Society
    Macromolecules 25 (1992), S. 116-122 
    Details
    ISSN: 1520-5835
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ma00027a019
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  • 2
    Electronic Resource
    Electronic Resource
    Sodium chloride-induced phase transition in nonionic poly(N-isopropylacrylamide) gel (1993)
    s.l. : American Chemical Society
    Macromolecules 26 (1993), S. 5045-5048 
    Details
    ISSN: 1520-5835
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ma00071a010
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  • 3
    Electronic Resource
    Electronic Resource
    Immobilized Biocatalysts in Reversible Hydrogels (1990)
    Oxford, UK : Blackwell Publishing Ltd
    Annals of the New York Academy of Sciences 613 (1990), S. 0 
    Details
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1749-6632.1990.tb18227.x
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  • 4
    Electronic Resource
    Electronic Resource
    Biodegradable Nanoparticles Containing Doxorubicin-PLGA Conjugate for Sustained Release (1999)
    Springer
    Pharmaceutical research 16 (1999), S. 1114-1118 
    Details
    ISSN: 1573-904X
    Keywords: poly(lactic-co-glycolic acid) ; doxorubicin ; conjugation ; nanoparticles ; sustained release
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. Doxorubicin was chemically conjugated to a terminal end group of poly(D,L-lactic-co-glycolic acid) [PLGA] and the doxorubicin-PLGA conjugate was formulated into nanoparticles to sustain the release of doxorubicin. Methods. A hydroxyl terminal group of PLGA was activated by p-nitrophenyl chloroformate and reacted with a primary amine group of doxorubicin for conjugation. The conjugates were fabricated into ca. 300 nm size nanoparticles by a spontaneous emulsion-solvent diffusion method. The amount of released doxorubicin and its PLGA oligomer conjugates was quantitated as a function of time. The cytotoxicity of the released species was determined using a HepG2 cell line. Results. Loading efficiency and loading percentage of doxorubicin-PLGA conjugate within the nanoparticles were 96.6% and 3.45 (w/w) %, respectively while those for unconjugated doxorubicin were 6.7% and 0.26 (w/w) %, respectively. Both formulation parameters increased dramatically due to the hydrophobically modified doxorubicin by the conjugation of PLGA. The nanoparticles consisting of the conjugate exhibited sustained release over 25 days, whereas those containing unconjugated free doxorubicin showed rapid doxorubicin release in 5 days. A mixture of doxorubicin and its PLGA oligomer conjugates released from the nanoparticles had comparable IC50 value in a HepG2 cell line compared to that of free doxorubicin. Sustained drug release was attributed to the chemical degradation of conjugated PLGA backbone, which permitted water solubilization and subsequent release of doxorubicin conjugated PLGA oligomers into the medium. Conclusions. The conjugation approach of doxorubicin to PLGA was potentially useful for nanoparticle formulations that require high drug loading and sustained release. The doxorubicin-PLGA oligomer conjugate released in the medium demonstrated a slightly lower cytotoxic activity than free doxorubicin in a HepG2 cell line.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018908421434
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  • 5
    Electronic Resource
    Electronic Resource
    Preparation of large, uniform size temperature-sensitive hydrogel beads (1992)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 30 (1992), S. 505-507 
    Details
    ISSN: 0887-624X
    Keywords: hydrogel ; beads ; poly(N-isopropylacrylamide) ; LCST ; Ca-alginate ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1992.080300318
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  • 6
    Electronic Resource
    Electronic Resource
    Controlled Protein Release from Polyethyleneimine-Coated Poly(L-lactic Acid)/Pluronic Blend Matrices (1992)
    Springer
    Pharmaceutical research 9 (1992), S. 37-39 
    Details
    ISSN: 1573-904X
    Keywords: protein release ; poly(L-lactic acid) ; polyethyleneimine ; coating ; burst effect
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Protein release from degradable polymer matrices, composed of poly(L-lactic acid) and its blends with Pluronic surfactant, was investigated with and without the aqueous coating of an adsorptive water-soluble polymer, polyethyleneimine (PEI). PEI is a highly branched cationic polymer containing primary, secondary, and tertiary amino groups in its backbone. The treatment of PEI for PLA/Pluronic blend films exhibited a remarkable decrease in the “burst” release of protein at an initial stage and a significant extension in the protein release period. Protein release profiles could be controlled by varying PEI treatment time and its concentration. Our results suggest that PEI diffuses into the polymer matrices and crosslinks protein molecules by ionic interactions. Such a PEI–protein network near the surface region of matrix may act as a diffusional barrier for further release of protein molecules.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018971525301
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  • 7
    Electronic Resource
    Electronic Resource
    Immobilization of Arthrobacter simplex in a thermally reversible hydrogel: Effect of temperature cycling on steroid conversion (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 35 (1990), S. 152-159 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Arthrobacter simplex cells, which convert the steroid hydrocortisone to prednisolone, have been entrapped in a thermally reversible hydrogel. Such hydrogels exhibit a lower critical solution temperature (LCST) wherein the gel shrinks and deswells when it is warmed through its LCST, and then reversibly expands and reswells when it is cooled below the LCST. The immobilized cell-hydrogel system has been thermally cycled between two temperatures, each below the LCST. The upper temperature was selected to be just below the LCST, where the gel deswells but does not collapse, as it does at the LCST. The thermal cycling acts like a “hydraulic pump” which enhances mass transfer of the substrate (hydrocortisone) in and the product (prednisolone) out of the gel, thereby increasing steroid conversion dramatically relative to isothermal operation at either the upper or lower temperature. The increased conversion can also be due in part to reduced product inhibition. Mass transfer resistance and product inhibition are among the most serious problems in immobilized biocatalyst technology and thermal cycling of LCST hydrogels is both a novel and useful approach to minimizing these problems.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260350207
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  • 8
    Electronic Resource
    Electronic Resource
    Thermally induced core-shell type hydrogel beads having interpenetrating polymer network (IPN) structure (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Rapid Communications 19 (1998), S. 167-172 
    Details
    ISSN: 1022-1336
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Monodisperse hydrogel beads composed of calcium alginate and crosslinked polyNIPAAm (N-isopropylacrylamide) were synthesized based on a simultaneous interpenetrating network process. With increasing the temperature above the phase transition temperature of polyNIPAAm, a core-shell type of hydrogel beads was developed; polyNIPAAm-enriched core region and Ca-alginate-enriched outer shell layer were observed. The thermally reversible formation of the core-shell double structure in the IPN hydrogel beads was applied for the temperature modulated drug release using indomethacin as a model drug.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Controlled release of proteins from poly(L-lactic acid) coated polyisobutylcyanoacrylate microcapsules (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 52 (1994), S. 1797-1807 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Poly(L-lactic acid)-coated polyisobutylcyanoacrylate microcapsules containing protein molecules were prepared by a single-step procedure based on either a double-emulsion-solvent evaporation method or a spray-drying method. First, an aqueous protein solution was emulsified in an organic phase of methylene chloride containing a wall-forming monomer (isobutylcyanoacrylate), various kinds of poly(L-lactic acid), and a surfactant. An immediate polymerization process of isobutylcyanoacrylate takes place at the W/O interface upon contact with hydroxide ion in the aqueous phase, leading to the formation of a polyisobutylcyanoacrylate wall around the aqueous droplets. This W/O emulsion was reemulsified in an aqueous solution to promote the solvent removal and, consequently, the precipitation of poly(L-lactic acid) onto polyisobutylcyanoacrylate microcapsules or was spraydried to directly deposit the poly(L-lactic acid) on the wall. Three proteins, bovine serum albumin, horseradish peroxidase, and tetanus toxoid, were encapsulated in these poly(L-lactic acid)-coated polyisobutylcyanoacrylate microcapsules, and then their release profiles were examined in vitro as a function of molecular weight of poly(L-lactic acid) and its copolymers with glycolic acid. These formulations exhibited a low “burst” effect at initial incubation stages and released the proteins for extended periods of time. Subcutaneous injections of the tetanus toxoid-loaded microparticles into rats showed that the time course of immunization (antibody titer) can be controlled by the type of polymer matrices used. © 1994 John Wiley & Sons, Inc.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1994.070521214
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  • 10
    Electronic Resource
    Electronic Resource
    Synthesis and characterization of pH- and/or temperature-sensitive hydrogels (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 46 (1992), S. 659-671 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A series of pH-sensitive hydrogels that exhibit volume phase transition phenomena have been synthesized in aqueous solution and characterized with respect to their dynamic swelling behaviors. Positively charged hydrogels were prepared by copolymerizing varying ratios of N-isopropylacrylamide and NN′-dimethylaminopropylmethacrylamide. The hydrogels based on a temperature-sensitive hydrogel demonstrate a large change of equilibrium swelling in response to small variations of pH and/or temperature. These hydrogels exhibit different lower critical solution temperature (LCST) ranges depending on the environmental pH values. Below their LCST, they exhibit small and broad pH sensitivities normally observed in most hydrophilic polyelectrolyte gels, but above their LCST, they exhibit sharp pH dependent phase transition behaviors. The pH-dependent phase transition is strongly affected by temperature, while the temperature-dependent transition is, in turn, largely influenced by the pH. As the temperature is raised, the transitional degree of gel swelling change becomes sharper and larger, and the phase transition pH value shifts to a lower pH. It was also found that swelling is faster than deswelling for these cationic hydrogels, which suggests the existence of a water diffusion barrier during the deswelling. The swelling kinetics of initially dry and glassy gels were strongly dependent on both the pH value and temperature.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1992.070460413
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