In vitro degradation of a novel poly(lactide-co-glycolide) 75/25 foam

Macroporous poly(lactide-co-glycolide) PLGA 75/25 foams were prepared for application in bone tissue engineering. Their in vitro degradation behaviour was followed over a 30 week period at 37 degrees C and at one of three pHs: (1) pH 5.0, which mimics the acidic environment produced by activated macrophages, (2) pH 7.4, which reproduces normal physiological conditions and (3) an intermediate pH 6.4. The degradation of the PLGA 75/25 foams was studied by measuring changes in mass, molecular weight and morphology. The degradation profile of foams maintained at pH 5.0, 6.4 and 7.4 was similar until week 16, after which foams maintained at pH 6.4 and 7.4 had comparable degradation patterns whereas foams maintained at pH 5.0 degraded faster. For example, mass loss was less than 3% for foams maintained at all three pHs until week 16; however, by week 30, foams maintained at pH 6.4 and 7.4 had lost 30% of their mass whereas foams maintained at pH 5.0 had lost 90% of their mass. Foams maintained at pH 6.4 and 7.4 showed a similar constant decrease in molecular weight over the entire degradation study. Foams maintained at pH 5.0 had a similar rate of molecular weight loss as those maintained at pH 6.4 and 7.4 until week 16, after which the rate of molecular weight loss of foams maintained at pH 5.0 was accelerated. The morphology of the foams maintained at pH 6.4 and 7.4 was unchanged for 25 weeks. Foams maintained at pH 5.0 collapsed after week 18. Thus the PLGA 75/25 foams, described herein, maintained their 3-D morphology at physiological pH for over 6 months, which is an important feature for tissue engineering applications.