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  • 1
    ISSN: 1573-904X
    Keywords: supercritical extraction ; SEDS ; poly (d,l-lactide-co-glycolide) ; poly caprolactone ; biodegradable microparticles ; poly (L-lactide) ; poly (DL-lactide)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. We have evaluated a new process, involving solution-enhanced dispersion by supercritical fluids (SEDS), for the production of polymeric microparticles. Methods. The biodegradable polymers, Poly (DL-lactide-co-glycolide) : copolymer composition 50:50 (DL-PLG), Poly (L-lactide) (L-PLA), Poly (DL-lactide) (DL-PLA) and Polycaprolactone (PCL), were used for preparation of microparticles using SEDS. Solutions of the polymers in organic solvents were dispersed and sprayed with supercritical CO2. Extraction of the organic solvents resulted in the formation of solid microparticles. The amounts of highly toxic solvents such as dichloromethane (MC) were reduced in the process. Results. Microparticles were obtained from all polymers. The mean particle size and shape varied with the polymer used. The morphology of the particles was strongly affected by the choice of polymer solvent. Discrete spherical microparticles of DL-PLG were produced with a mean volumetric diameter of 130 μm. The microparticles of the L-PLA were almost spherical, and their size increased from 0.5 to 5 μm as the density of supercritical CO2 decreased. PCL formed microparticles with diameters of 30−210 μm and showed a strong tendency to form films at high pressure. Conclusions. The SEDS process appears a promising method for production of microparticles from biodegradable polymers without the use of toxic solvents.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Pharmaceutical research 14 (1997), S. 1556-1562 
    ISSN: 1573-904X
    Keywords: poly (d,l-lactide-co-glycolide) ; biodegradable microspheres ; lysozyme ; entrapment ; enzyme ; activity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. The purpose of this study was to investigate the process of preparing microspheres for maximising entrapment efficiency (EE) and retained biological activity (RBA) of peptides and proteins. Methods. A controlled-release formulation based on poly(d,l-lactide-co-glycolide) was designed and produced using a small-scale double emulsion method. These PLG microspheres contained a model peptide, lysozyme. The retained bioactivity of the incorporated lysozyme was determined by bacterial assay. The size distributions and the morphology of the microspheres were characterized. Results. The RBA and EE improved when the PLG concentration in the organic phase of the emulsion was increased. A high lysozyme concentration in the inner water phase of the emulsion resulted in decreased EE and an increase in the proportion of fragmented particles. The RBA of lysozyme in the microspheres varied between 30 and 80% with changes to the process. Conclusions. The study shows that the RBA of lysozyme in PLG microspheres is strongly dependent on the experimental conditions for preparing the microspheres. Measurement of the EE alone, without the RBA is insufficient to evaluate the efficacy of the designed delivery system.
    Type of Medium: Electronic Resource
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