In vitro degradation of poly(lactic-co-glycolic) acid block copolymers

We have investigated the in vitro degradation of poly(lactic-co-glycolic) acid copolymer with a lactic to glycolic ratio of 65/35. The degradation studies were performed on solvent-cast films of controlled thickness and shape. The samples were then incubated at 37 °C in phosphate buffered saline solution. The degradation was followed using potentiometry, light microscopy, gravimetry and gel permeation chromatography. Water was found to diffuse inside the film as soon as the sample was placed in the degradation media. A surface layer and wrinkles formed while degradation through chain scission took place in the bulk of the film. After 10 days, this led to the creation of a vesicle where liquid low molecular weight oligomers were trapped inside a thin film of high molecular weight polymer. This thin film acted as a membrane allowing only low molecular weight compounds to diffuse out of the film. © 2007 Materials Research Society.