Study On Surface Modification And Biocompatibility Of Poly(Lactic Acid)

For coronary atherosclerotic heart disease,coronary stent implantation is still one of the most effective treatment methods.Coronary stents have developed to the fourth revolution-bioabsorbable vascular stents.Poly(lactic acid)(PLA)bioabsorbable vascular stents have become a hot research topic nowadays.The ideal PLA bioabsorbable vascular stent should be hydrolyzed and absorbed by the body after remodeling the patency and function of the blood vessel in the lesion.However,the stent still faces the problems of early thrombosis and restenosis during the treatment process,and the nature of PLA itself cannot make the problem.has been solved.Therefore,for the PLA surface that is in direct contact with vascular endothelial cells and blood,the improvement of cell compatibility and the customization of anticoagulant function are particularly important.In this paper,the surface modification method is used to modify the surface of polylactic acid by light-activated chlorine dioxide free radical oxidation technology.Based on the idea of chemical grafting,the biological macromolecule chondroitin sulfate is covalently grafted on the surface of PLA,and the grafting is investigated.The biocompatibility of the PLA surface of chondroitin sulfate enables the customization of the functions of the PLA surface to prevent blood clotting and promote endothelial cell adhesion.The main research contents are as follows:First of all,the PLA surface was oxidized by light-activated chlorine dioxide radical oxidation technology,while verifying its feasibility,a single factor experiment was used to obtain the best reaction conditions.The results show that:the light-activated chlorine dioxide radical oxidation technology can be successfully applied to the PLA surface,the optimal oxidation reaction time is 10min,and the reaction temperature is 90?.After oxidation,the content of O,C-O and C=O on the PLA surface has been increased,at the same time,the contact angle has been reduced,and the hydrophilicity has been improved.Especially under the optimal reaction conditions,the content of O,C-O and C=O on the PLA surface after oxidation reached 34.03%,26.17%and 17.28%,which increased by 10.74%,8.24% and 5.19%,respectively,compared with the original PLA.It reaches 62.5°,which is 28.7%lower than PLA as it is.Secondly,using the condensation reaction between the amino group and the carboxyl group,through the intermediate diaminopolyethylene glycol,the amino group is introduced on the surface of the PLA rich in carboxyl groups,and the chondroitin sulfate,which has the ability of anticoagulant and promoting cell adhesion,is connected through the amino group.Branch to the PLA surface.The results show that the carboxyl groups on the surface of PLA are reactive after oxidation,and can react with the amino group at one end of diamino polyethylene glycol(NH₂-PEG-NH₂)in the EDC/NHS reaction system to form an amide bond,and then graft chondroitin sulfate(CS)through the amino group at the other end.The surface S of PLA grafted with CS reached 1.07%,the surface roughness was improved to 88.2 nm,and the hydrophilicity reached 61°.Compared with PLA as it is,the hydrophilicity is improved.Finally,the biocompatibility of the PLA surface before and after the modification was characterized,including the recalcification whole blood coagulation test,the platelet adhesion test and the in vitro culture test of endothelial cells.The results show that:compared with the original PLA,the carboxylated modified PLA surface cell compatibility has been improved,but the number of platelet adhesion has been increased at the same time,which is not conducive to anti-thrombosis.The PLA grafted with CS showed the best anticoagulant and anti-platelet adhesion and activation abilities.At the same time,compared with the original PLA,the cytocompatibility has been greatly improved.This study aims to solve the early thrombosis of PLA vascular stents.Formation and low cell compatibility provide new modified ideas.