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  • 1
    ISSN: 1573-904X
    Keywords: hydrogels ; site-specific ; drug delivery ; chitosan ; poly-(ethylene oxide)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. The purpose of this study was to develop novel drug delivery systems with pH-sensitive swelling and drug release properties for localized antibiotic delivery in the stomach. Methods. The drug delivery systems were synthesized by crosslinking chitosan and poly(ethylene oxide) (PEO) in a blend to form semi-interpenetrating polymer network (semi-IPN). Scanning electron microscopy was used to compare the surface and bulk morphology of the freeze-dried and air-dried chitosan-PEO semi-IPN. The hydrogels were allowed to swell and release the antibiotics—amoxicillin and metronidazole—in enzyme-free simulated gastric fluid (SGF, pH 1.2) and simulated intestinal fluid (SIF, pH 7.2) at 37°C. Results. Freeze-dried chitosan-PEO semi-IPN with a porous matrix had swollen extensively as compared to the air-dried hydrogel. The swelling ratio of freeze-dried and air-dried chitosan-PEO semi-IPN after 1 h in SGF was 16.1 and 2.30, respectively. More than 65% of the entrapped amoxicillin and 59% of metronidazole were released from the freeze-dried chitosan-PEO semi-IPN after 2 h in SGF. Conclusions. The results of this study suggest that freeze-dried chitosan-PEO semi-IPN could be useful for localized delivery of antibiotics in the acidic environment of the gastric fluid.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 52 (1994), S. 539-544 
    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: We have examined the adsorption of poly(ethylene oxide)/ poly(propylene oxide)/poly(ethylene oxide) (PEO/PPO/PEO) triblock copolymers (Pluronics™) on dimethyldichlorosilane-treated glass (DDS-glass). The surface concentration of 125I-labeled Pluronic F-68(76/30/76) reached a maximum of 0.3 μg/cm2 when the bulk concentration in the adsorption solution was 3.0 mg/mL. Above 5.0 mg/ml, the surface Pluronic F-68 concentration started to decrease and reached 0.17 μg/cm2 when the bulk concentration for adsorption was 10 mg/mL. The surface concentration of Pluronic F-108 (129/56/129), on the other hand, increased to 4.0 μg/cm2 at the same bulk concentration. Fluroscence spectroscopic studies using pyrene suggested that the Pluronic F-68 molecules self-associated at the bulk concentration of 5.0 mg/mL and above. Because the aggregates are expected to expose the hydrophilic PEO segments to water, they may have lower affinity to DDS-glass. Aggregation of Pluronic F-68 also decreases the number of individual Pluronic molecules for adsorption. Pyrene fluorescence in Pluronic F-108 solution, however, suggests that Pluronic F-108 molecules do not form aggregates. It appears that the high surface concentrations of Pluronic F-108 may result from the preferential adsorption of individual molecules in multilayers. This explains the high effectiveness of Pluronic F-108 in preventing protein adsorption and platelet adhesion when adsorbed on to be hydrophobic surface. © 1994 John Wiley & Sons, Inc.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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