Synthesis and properties of malic acid-containing functional polymers

Poly-L-lactides containing beta-alkyl alpha-malate-units were prepared by r ing-opening copolymerizations of L-lactide with 3-(s)-[(benzyloxycarbonyl)m ethyl]- (BMD) and 3-(s)-[(dodecyloxycarbonyl)methyl]-1,4-dioxane-2,5-diones (DMD). The solution-cast films of these copolymers were alkali-treated to form a carboxyl-functionalized surface on which cell-binding Arg-Gly-Asp tr ipeptide (RGD) was immobilized with dicyclohexylcarbodiimide as coupling ag ent. For the copolymer of L-lactide and BMD the benzyl groups were removed by catalytic hydrogenolysis to obtain a fully carboxyl-functionalized copol ymer (PLGM), and RGD was immobilized on the surface of its cast film. All t he RGD-immobilized films thus prepared exhibited improved cell attachment c ompared with the original films. The cell attachment increased with increas ing amount of immobilized RGD, which depended on the composition of the alp ha-malate units in the copolymer. The RGD-immobilized PLGM films were degra ded rapidly during the cell culture, while the RGD-immobilized films of the beta-alkyl alpha-malate-containing polymers survived the cell culture with little degradation. The rate of hydrolysis increased with increasing conte nt of alpha-malate units for both series, depending on the structure of the protecting groups of the beta-carboxyl. These results suggest that the RGD -immobilized polymers could be a new class of functional bioresorbable poly mer having improved cell-attachment and adjustable hydrolysis rate. (C) 199 9 Elsevier Science B.V. All rights reserved.