Particulate retrieval of hydrolytically degraded poly(lactide-co-glycolide) polymers

This article describes a technique for the retrieval of polymeric particulate debris following advanced hydrolytic in vitro degradation of a biodegradable polymer and presents the results of the subsequent particle analysis. Granular 80/20 poly(L-lactide-co-glycolide) (PLG) was degraded in distilled, deionized water in Pyrextrade mark test tubes at 80 degrees C for 6 weeks. Subsequently, a density gradient was created by layering isopropanol over the water, followed by a 48-h incubation. Two opaque layers formed in the PLG tubes, which were removed and filtered through 0.2-micrometer polycarbonate membrane filters. In addition, Fourier transform IR spectroscopy (FTIR) was performed to confirm the presence of polymer in the removed layers. The filters were gold sputter coated, and scanning electron microscopy (SEM) images were made. FTIR analysis confirmed that the removed material was PLG. SEM images of the extracts from the upper (lowest density) opaque layer showed a fine, powderlike substance and globular structures of 500-750 nm. The SEM images of the lower (highest density) opaque layer showed particles with a crystalline-like morphology ranging in size from 4 to 30 micrometer. Particulate PLG debris generated with the described technique can be useful for further studies of its biological role in complications associated with poly(alpha-hydroxy)ester implants. This study shows the presence of very persistent nano- and microparticles in the degradation pathway of PLG.