Microwave Synthesis And Characterization Of Chitosan-graft-poly(L-lactide) With Low Temperature Under Normal Pressure

Nowadays, chitosan (CS) and polylactide (PLA) are widely used in the field of biomaterials. To improve the slow degradation rate of CS and biocompatibility of PLA, make up for native material and synthetic material's deficiencies, we synthesized the chitosan-graft-poly (L-lactide) copolymer (CS-g-PLLA). Under microwave irradiation we prepared PLLA which exhibited high purity, good crystallinity and satisfactory mechanical performance, then to make the biomaterials' biocompatibility more better, we firstly used porcine pancreatic lipase (PPL) as the catalyst, which completily asepsis, to get the CS-g-PLLA. We can operate with much lower temperature than ever before and under ordinary pressure. The copolymer was synthesized under different reaction time, temperature, reagent mole ratio and different kinds and dosages of catalyst. The copolymers were characterized by FTIR, ¹³C-NMR, DSC, TG and X-RD, and used weight method to get the grafting percentage. The copolymers' grafting percentage can be controled by change of the feeding molar ratio of L-lactide and chitosan. The results of these spectra showed that the product was CS-g-PLLA copolymer; the crystallinity of raw CS was destroyed and the products' thermal stability descented after the copolymerization. And the grafting percentage of the products can be controled.The results of vitro degradation test by lysozyme in PBS indicated that the copolymers had a higher weight loss in PBS than that of pure CS, and degradation rate increased with the increasing the feeding molar of L-LA, so we can adjust the degradation velocity of the products and PH value by change of the feeding molar ratio of L-lactide and chitosan, which can reduce acidity of the degradation product of the pure PLLA. Cell culture of vitro was assessed using the MTT assay, the results show that in vitro the copolymers' biocompatibility is more better than PLLA, and the PPL catalysis system's cell viabilitys was much better than the tin octoate catalysis systerm. So using the PPL as the catalyst maybe a really good method to synthesis the biomaterials because of it is non-cytotoxicity and totally harmless to human. The results of hemolysis test indicated that the copolymers consistent with the standard of the hemolysis test's requirement, and the PPL system is the best.