Zhiqian Lu

In vivo study on the histocompatibility and degradation behavior of biodegradable poly(trimethylene carbonate-co-D,L-lactide).

The aim of this study was to explore the in vivo behavior and histocompatibility of poly(trimethylene carbonate-co-D,L-lactide) (PDLLA/TMC) and its feasibility of manufacturing cardiovascular stents. Copolymers with 50/50 molar ratio were synthesized by ring-opening polymerization with TMC and D, L-LA, or TMC and L-LA. Poly(L-lactide) (PLLA) was synthesized as a control. The films of the three polymers were implanted into 144 Wistar rats. At different time points of implantation, polymer films were explanted for the evaluation of degradation characteristics and histocompatibility using size exclusion chromatography , nuclear magnetic resonance , environmental scanning electron microscope , and optical microscope. Results showed that there were differences in the percentage of mass loss, molecular weight, shape and appearance changes, and inflammation cell counts between different polymers. With the time extended, the films superficial structure transformed variously, which was rather obvious in the polymer of PDLLA/TMC. In addition, there were relatively lower inflammation cell counts in the PDLLA/TMC and poly(trimethylene carbonate-co-L-lactide) (PLLA/TMC) groups at different time points in comparison with those in the PLLA group. The differences were of statistical significance (P< 0.05) in the group of PDLLA/TMC vs. PLLA, and the group of PLLA/TMC vs. PLLA, but not within the PDLLA/TMC and PLLA/TMC groups (P> 0.05). These results suggested that the polymer of PDLLA/TMC (50/50) with favorable degradation performance and histocompatibility is fully biodegradable and suitable for manufacturing implanted cardiovascular stents.

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