Construction And Performance Evaluation Of PEG-CS Coating Loaded With Sodium Tanshinone ⅡA Sulfonate For Vascular Graft

The vasculature is vital to human body.Healthy vascular system is essential to the function of organs and tissues.Impairment of vascular function and vascular disease caused by chronic and congenital diseases are quite common in clinic.Medications and interventions may lead to endothelial detachment and re-injury of the vessel wall.Autologous vascular grafts are the gold-standard for surgical treatment,but their availability is limited and suffer from trauma.Artificial vascular grafts provide alternatives.However,the implantation of small diameter prosthetic grafts often causes acute thrombosis,intimal hyperplasia and long-term wall calcification,which reduce long-term patency.Therefore,the ideal artificial vascular graft requires a rational structural design and appropriate surface modification to promote in situ endothelialization and anticoagulation in revascularization.In this project,by combining natural and synthetic materials,we herein constructed a functional surface coating of chitosan（CS）-polyethylene glycol（PEG）conjugates loaded with sodium tanshinone IIA sulfonate（STS）.This coating was applied to the surface of electrospun poly（lactic acid-caprolactone）（PLCL）nanofibers.The antithrombotic properties and capacity in promoting rapid regeneration of the endothelial layer of the coating was evaluated with the following details and results.（1）Three PEG-CS copolymers with three PEG grafting degrees（5%,10% and15%）were synthesized and made into 5% PEG-CS,10% PEG-CS and 15% PEG-CS coatings using dopamine as a bridge on a custom-made coating machine.The hydrophobicity,mechanical properties,cytotoxicity,and anti-platelet adhesion of coatings of different copolymers were investigated.The results of Fourier transform infrared spectroscopy and nuclear magnetic resonance hydrogen spectroscopy showed that the chemical structures of the copolymers were as expected,with grafting ratios of4.4%,7.9%,and 12%,respectively.Water contact angle test showed that the intervention of the coating significantly improved the hydrophilicity of nanofiber membranes in a PEG-CS grafting concentration dependent manner.Increased concentration of PEG-CS gave improved hydrophilicity.Uniaxial tensile tests showed that the PEG-CS coated electrospun PLCL membranes have good tensile properties.In vitro assessment of platelet adhesion showed that the PEG-CS coating significantly reduced platelet adhesion compared with the uncoated PLCL membrane and higher concentration of PEG-CS showed greater anti-adhesion capacity.In addition,the cytocompatibility assay showed that the 15% PEG-CS coating was more favorable to the adhesion and proliferation of endothelial cells.（2）To improve the rapid endothelialization and anticoagulation of the coating,the cytocompatibility and hemocompatibility of different STS coatings（STS-0.01;STS-0.05;STS-0.1）were evaluated by adding different mass fractions（0.01%;0.05%;0.1%）of sodium tanshinone IIA sulfonate to 15% PEG-CS solution by electrostatic action.Follow-up hemocompatibility results showed that the coating decreased hemolysis,increased anti-platelet adhesion activation,and increased plasma prothrombin time（PT）and activated partial thromboplastin time（APTT）as the concentration of tanshinone IIA sulfonate increased.Moreover,the cytocompatibility assay results showed that the addition of tanshinone IIA sodium sulfonate promoted the growth of endothelial cells,with the most obvious STS-0.01.Therefore,the in vitro characterization results can tentatively determine that STS-0.01 has some potential in promoting endothelialization and inhibiting thrombosis.（3）To further evaluate the in vivo biocompatibility of the coatings,PLCL nanofibrous membranes and STS-0.01 coatings were implanted subcutaneously in rats,and samples were taken at weeks 1,2 and 4,and the sections were histologically analyzed by H＆E staining and Masson’s trichrome staining.H＆E and Masson’s trichrome staining of the surrounding tissues showed a mild inflammatory response in STS-0.01 coatings,and after 4 weeks the results showed a large amount of host cell migration and collagen deposition inside the PLCL nanofibrous membrane,while the STS-0.01 coating showed almost no cell migration to the coating.This indicates that the coating has good stability and slow degradation ability.In summary,the STS-0.01 coating prepared in this study has suitable structural stability,hemocompatibility,and biocompatibility and shows potential for luminal layer coating of vascular grafts.