Study On Surface Chemical Modification And Biocompatibility Of PTFE Membrane

Polytetrafluoroethylene(PTFE)is one of the most commonly used polymers in biomedical applications and is widely used in artificial blood vessels.After decades of clinical proof,PTFE performs well in large-diameter vascular grafts.However,due to its surface chemically inert,it is prone to thrombosis and intimal hyperplasia as a small-diameter vascular graft(<6 mm),resulting in a very low long-term patency rate.Improving the biocompatibility of the PTFE surface and establishing biomolecule coatings are the key to solving this problem.However,due to the natural characteristics of PTFE,how to improve the surface activity of PTFE and graft biomolecules is a challenge.Therefore,it is necessary to modify the surface of PTFE.The surface modification of PTFE can change the surface chemical structure,improve the surface biological activity,and realize the grafting of biomolecules.In this study,the surface of PTFE was chemically modified to gradually form a surface chemical structure with hydroxyl group and amino group as the main functional groups on the surface of PTFE,so as to provide active sites for different biomolecular grafting while improving biocompatibility.Meanwhile,the biocompatibility of modified PTFE and the expression of biomolecules were further studied.The main work is as follows:Firstly,the PTFE surface was reduced by benzoin to form an unsaturated carbon layer on the surface,and then the hydroxy-rich PTFE film was obtained by borohydride oxidation.The results showed that the content of oxygen element on the surface of oxidized PTFE reached 23.2%.Surface water contact Angle decreased from 133±4° of PTFE to 93±4°,and the surface hydrophilicity increased.At the same time,compared with the common modification methods of PTFE,this modification method reduces the introduction of impurities compared with the traditional chemical modification method,and is more efficient compared with the plasma modification method,which proves that this modification method can effectively improve the biocompatibility indicated by PTFE.Secondly,the anticoagulant chondroitin sulfate was grafted onto the surface of the hydroxyl-rich PTFE membrane using 3-aminopropyltriethoxysilane(APTES).The results showed that uniform ammoniated PTFE surface could be obtained by APTES reaction with hydroxyl group,and chondroitin sulfate could be grafted by EDC/NHS system.This APTES modification method can form uniform amino structure on the surface of PTFE and graft chondroitin sulfate simply and efficiently.The content of oxygen element on the surface of PTFE sample grafted with chondroitin sulfate reached 29.54%,with the highest roughness of 74 nm,and the water contact Angle decreased to 33±3°,which was conducive to cell adhesion.Finally,the cell compatibility and anticoagulation ability of the modified PTFE surface were characterized.The results showed that the cell compatibility of hydroxylated PTFE surface was improved and the adhesion of endothelial cells was promoted compared with that of pure PTFE.The biocompatibility of PTFE grafted with chondroitin sulfate is not only very good,which can promote the adhesion and proliferation of endothelial cells,but also inhibit the adhesion of platelets and inhibit thrombosis,showing the characteristics of high cell adhesion and low platelet adsorption.