Journal
COLLOIDS AND SURFACES B-BIOINTERFACES
Volume 33, Issue 3-4, Pages 177-183Publisher
ELSEVIER SCIENCE BV
DOI: 10.1016/j.colsurfb.2003.10.003
Keywords
monomethoxypoly(ethylene glycol)-b-poly-D,L-lactide; biodegradable microspheres; bovine hemoglobin; stability; protein entrapment efficiency
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This study focused on the influences of solvent removal method and wall polymer composition on microspheres characteristics in W/O/W double emulsion procedure. Monomethoxypoly(ethylene glycol)-b-poly-D,L-lactide (PELA) microspheres containing bovine hemoglobin (BHb, a model protein) were prepared by four solvent removal methods, including solvent-evaporation at atmosphere, at reduced pressure, solvent-extraction and solvent-diffusion methods, where the last method used ethyl acetate (EA) as organic solvent and the others used methylene chloride (MC). The bio-activity of encapsulated BHb, encapsulation efficiency, particle size and surface morphology of microspheres were evaluated in relation to the influences of solvent removal method and PELA composition. BHb encapsulated by the W/O/W double emulsion-sol vent diffusion method with EA as organic solvent displayed a bio-activity near to that of native BHb. The efficiency of BHb entrapment achieved by this method was much higher than those by other methods (ca. 90% versus 30%). When using this process, the copolymers with MPEG 2000 block (molecular weight of PEG block: 2000 g/mol) yielded much higher efficiencies of BHb entrapment than those with MPEG 5000 block (90% versus 36%). Copolymer composition had less impact on microsphere size, but had a pronounced effect on surface morphology of microspheres. This study suggests that the W/O/W double emulsion-solvent diffusion method with EA as organic solvent is an effective process to prepare microspheres containing therapeutic proteins, and that the PELA copolymers containing MPEG 2000 block are promising wall material for biodegradable microsphere protein delivery system. (C) 2003 Elsevier B.V. All rights reserved.
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