Influence of particle size and dissolution conditions on the degradation properties of polylactide-co-glycolide particles

Polymer degradation usually plays a crucial role in drug release from susta ined release polyester systems, therefore in order to elucidate the mechani sm governing release, it appears essential to analyse the in vitro degradat ion behaviour of these devices. In this study the influence of processing c onditions, particle characteristics and release media temperature on the de gradation of PLGA spherical particles were examined. It was found that a li near relationship between the degradation rate and particle size existed, w ith the larger particles degrading fastest. In smaller particles degradatio n products formed within the particle can diffuse easily to the surface whi le in larger particles degradation products have a longer path to the surfa ce of the particle during which autocatalytic degradation of the remaining polymer material can occur. The influence of release media temperature on t he degradation of PLGA particles was also examined. At lower incubation tem peratures PLGA microparticles showed an induction period after which polyme r degradation proceeded. The rate of polymer degradation was found to incre ase with increasing incubation temperature. The polymer erosion profile was fitted to the Prout-Tompkins equation and the rate constants were used to determine the activation energy of PLGA hydrolysis. (C) 2000 Elsevier Scien ce Ltd. All rights reserved.