Biodegradation of PLA/GA polymers: increasing complexity.

The degradation of aliphatic polyesters derived from lactic and glycolic acids (PLA/GA) depends on many factors. It has been found recently that the interior of large size devices degrades faster than the outer zone. A qualitative model has been proposed to account for this heterogeneous degradation. It is based on diffusion-reaction phenomena combined with the well-known autocatalytic effect of carboxylic chain ends. This contribution recalls the present understanding of the hydrolytic degradation of PLA/GA polymers and emphasizes its complexity on the basis of the influence of secondary factors such as the presence of a basic load, namely, gentamycin, in poly(lactic acid) matrices, and the presence of long stereoregular sequences in poly(DL-lactic acid) macromolecules.