Haemo- and cytocompatibility of bioresorbable homo- and copolymers prepared from 1,3-trimethylene carbonate, lactides, and epsilon-caprolactone.

A series of bioresorbable polymers were prepared by ring-opening polymerization of L-lactide (LLA), DL-lactide (DLLA), epsilon-caprolactone (CL) and 1,3-trimethylene carbonate (TMC), using low toxic zinc lactate as catalyst. The various PLLA, PTMC, PCL homopolymers, and PLLA-TMC, PDLLA-TMC, PCL-TMC copolymers with 50/50 molar ratios were characterized by using analytical techniques such as proton nuclear magnetic resonance, gel permeation chromatography, tensiometer, and differential scanning calorimetry. The haemo- and cyto-compatibility were investigated in order to evaluate the potential of the polymers as coating material in drug eluting stents. Haemolysis tests show that all the homo- and copolymers present very low haemolytic ratios, indicating good haemolytic properties. Adhesion and activation of platelets were observed on the surface of PLLA, PCL, PLLA-TMC, and PDLLA-TMC films, while less platelets and lower activation were found on PTMC. The most interesting results were obtained with PCL-TMC which exhibited the lowest degree of activation with few adhered platelets, in agreement with its outstanding anticoagulant properties. Both indirect and direct cytocompatibility studies were performed on the polymers. The relative growth ratio data obtained from the liquid extracts during the 6-day cell culture period indicate that all the polymers present very low cytotoxicity. Microscopic observations demonstrate adhesion, spreading and proliferation of human umbilical vein endothelial cells ECV304. Therefore, it is concluded that these bioresorbable polymers, in particular PCL-TMC, are promising candidate materials as drug loading coating material in drug eluting stents.