Comparative degradation study of biodegradable microspheres of poly(DL-lactide-co-glycolide) with poly(ethyleneglycol) derivates

The biodegradable polymers of poly(DL-lactide-co-glycolide) (PLGA) and poly (ethyleneglycol) (PEG) have come into use in the last few years for the con trol of the release of drugs. The incorporation of units of PEG produce an increased in nu iota nu o half life of the microparticles. The methoxylatio n of the PEG allows a control of the microparticles. The methoxylation of t he PEG allows a control of the polymerization reaction by blocking one of t he reactive terminals. An important aspect to be studied is the degradation of these polymers. The objective was centred on comparing the degradation that microspheres made of PLGA and PLGA-PEG (also with derivate methoxylate d PEG). Degradation of the microspheres was studied at 37 degrees C and neu tral pH. Samples were taken at different times to determine the size distri butions, the mean diameter, the molecular weight and the structural composi tion of the polymer. The fastest decrease in Mw is observed in the case of PLGA microspheres. The PLGA-PEG microspheres show a significant size increa se (from 24.6 to 90 mu m) due to a swelling process. Any appreciable change s in Tg values were observed during the assay (30 days).