Preparation and biocompatibility evaluation of absorbable internal fixed PLLA material

Abstract

Objective To evaluate the properties and biocompatibility of the pedicle screw-rod system made by absorbable Poly L-Lactic Acid (PLLA) material. Methods Using L-lactic acid as raw material, we adopted ring-opening polymerization method to make appropriate viscosity-average molecular weight PLLA for compression molding and preparation of the screw-rod system of the pedicle of vertebral arch. To analyze the degradation characteristics in vitro through detection of related physical properties and changes of pH value, we co-cultured PLLA extracts and osteoblasts to observe the influence of PLLA to osteoblasts proliferation and apoptosis by MTT method and PI/hochest method, determine the contents of alkaline phosphatase to the influence on the differentiation of osteoblasts, to test allergy and acute systemic toxicity, and compatibility of PLLA internal fixation material with animal tissues. Results There was no remarkable influence of PLLA on proliferation, apoptosis, and osteogenic differentiation of the co-cultured Mc3T3-E1 osteoblasts of mice. No cytotoxicity had been found in vitro. After treated with PLLA in mice, the growth was normal without causing death or systemic toxicity. In vivo implantation experiments, it showed no inflammatory tissue and purulent secretion. Conclusions PLLA absorbable material has good biocompatibility and no cytotoxicity. It meets the requirements of primary detection and preclinics in biosafety as a substitute for traditional metal material with broad prospects. Key words: L- polylactic acid; Biodegradable material; Biocompatibility; Rats