Research On The Preparation Of Shellac Coatings And Its Material Properties And Biocompatibility

It is well know that venous thromboembolism has become the third major cardiovasccular disease,and its morbidity and mortality are increasing day by day.In addition to common anticoagulation and thrombolytic therapy,inferior vena cava filter placement has also been widely used in the treatment of venous thromboembolism.Patients who have an inferior vena cava filter implanted should remove the filter in time after getting out of the risk period to avoid complicationssuch as displacement,breakage,and perforation.However,the currently widely used retrievable inferior vena cava filter has problems such as adhesion between the support rod and the intima and thrombosis,which results in a low recovery rate.Therefore,surface modification of the inferior vena cava filter surface is an effective means to solve the adhesion between the top of the filter support rod and the inner membrane,which can improve the recovery rate of temporary filters.Shellac is a kind of natural polymer with good biocompatibility,non-toxic and edible properties.In addition,it is approved by the FDA for use in food and pharmaceutical applications.Shellac has many excellent properties and is popular in drug delivery system;it has a certain application prospect as a coating material in the study of surface modification of medical devices.In this paper,a series of shellac coatings were prepared by spin coating,and shellac coatings with different thickness were obtained by adjusting the preparation concentration of shellac solution(10 mg/m L,25 mg/m L,50 mg/m L),and the surface morphology,surface composition,surface wettability,roughness and long-term stability of the coatings were characterized.The cytocompatibility of endothelial cells,smooth muscle cells and macrophages was investigated by culture on a series of shellac coating surfaces and coating extracts.The blood compatibility of shellac coating was investigated by platelet adhesion and activation,static whole blood test,hemolysis test and clotting time test.The antibacterial properties of shellac coating were investigated by plate counting method.The biocompatibility of the coating was further explored through the rat subcutaneous implantation experiment and the rat abdominal aortic silk implantation experiment.T The research results showed that a series of shellac coatings prepared by spin coating have moderate hydrophilicity and good adhesion to the substrate and the coating thickness is positively correlated with the concentration of shellac prepared.XPS and FTIR results show that the bonding state and functional groups of the shellac coating will not change significantly with the thickness of the coating.After the shellac coating was soaked in PBS(37°C)for one month,its chemical functional groups did not change significantly,and there was no large-area peeling and failure of the coating.The coating layer was broken by hydrolysis and the ester bond was broken and the molecular weight was reduced.The results of the activity and proliferation behavior of endothelial cells and smooth muscle cells,and the expression of inflammatory factors in macrophages indicated that SH25(thickness about 300nm),SH50(thickness about 500nm)and their extracts can significantly inhibit the activity and proliferation of endothelial cells and smooth muscle cells.In addition,the results of macrophages showed that shellac coating(SH25,SH50)have a certain anti-inflammatory effect and can promote the secretion of anti-inflammatory factors by macrophages.The results of platelet adhesion,static whole blood and hemolysis rate showed that shellac coating can reduce the number of platelets adhered on the surface of samples,SH50 has the most significant effect on inhibiting platelet adhesion and prolong the clotting time,the hemolysis rate of shellac coating samples with different thicknesses is less than 5%.The antibacterial result showed that the antibacterial effect of shellac coating is closely related to its thickness.The experimental results of subcutaneous implantation in rats showed that shellac coating had no effect on reducing inflammation.The results of SD rat vascular filament grafting experiments showed that shellac coating can reduce the proliferation thickness of surrounding new tissues.In summary,shellac coating can significantly inhibit the activity and proliferation behavior of endothelial cells and smooth muscle cells.Meanwhile,shellac coating can inhibit platelet adhesion and activation without causing hemolysis and prolonging clotting time.The most important thing is that after being implanted in the body,it can reduce the proliferation thickness of the surrounding new tissue.This thesis is beneficial to the follow-up study of shellac drug-loaded coatings,and provides a certain theoretical basis for the application of shellac coatings in inferior vena cava filters.