Bovine serum albumin loaded poly(lactide-co-glycolide) microspheres : the influence of polymer purity on particle characteristics

AbstractTo study the influence of polymer purity on microsphere characteristics, bovine serum albumin (BSA) loaded biodegradable microspheres were prepared by spray drying using two samples of poly(lactide-co-glycolide), PLG, (50:50, mwt = 35 and 69kDa). Polymer properties were varied by m-lactide and glycolide addition or by ultrafiltration. While the effective drug loading was not affected by polymer purity, Tg was decreased with increasing 'monomer and oligomer content. The removal of these low molecular weight substances by ultrafiltration led to a narrower molecular weight distribution compared to the untreated PLG. Concerning the polymer with the higher molecular weight, microsphere morphology was also strongly affected by polymer composition. In contrast to the non-modified PLG, monomer addition yielded particles with a much smoother surface structure. Moreover, in vitro cytotoxicity of the micro-spheres prepared from the polymer pretreated by ultrafiltration was significantly reduced, whereas mono...