Enzymatic degradation of stereocopolymers derived from L-, DL- and meso-lactides

Three stereocopolymers, namely PLA(50)-rac, PLA(50)-mes, and PLA(62.5), wer e synthesized by ring opening polymerization of race-mic-lactide (or DL-lac tide), meso-lactide, and a mixture of 25/75 L/DL-lactides, respectively. Th e enzymatic degradation of these PLA polymers was investigated at 37 degree s C in a pH=8.6 Tris-HCl buffer solution in the presence of proteinase K. D egradation of PLA(50)-mes was found to be much faster than that of PLA(50)- rac, PLA(62.5) degrading at an intermediate rate. It was assumed that prote inase K preferentially degrades L-L, L-D and D-L bonds as opposed to D-D on es. On the other hand, the much higher water uptake ratio of PLA(50)-mes as compared to those of PLA(50)-rac and PLA62.5 could have facilitated the en zymatic attack in the former case. (C) 1999 Elsevier Science Ltd. All right s reserved.