Constructing Multifunctional Microenvironment On Cardiovascular Scaffold Surface Based On Micro-nanostructure And Surface Chemistry And Studying Its Biocompatibility

Interventional therapy,the most important clinical treatment for cardiovascular disease,has achieved remarkable efficacy.However,some clinical problems,such as late stent thrombosis and in-stent restenosis still exist.Rresearch has shown that the main causes of these problems are due to the morphology impairment and funcation change of endothelial cells?ECs?that lead to inflammation,coagulation and proliferation.The healthy vascular endothelium plays a vital role in regulation of vessel homeostasis and patency through production and secretion of a range of active substances.Nitric oxide?NO?,one of the most important mediators of endothelial cells,has multiple functions,such as anticoagulation,anti-proliferation of smooth muscle cells?SMCs?and inhibition of inflammation.As the important signaling molecule in the cardiovascular system,it plays a significant role in regulating the physiological functions of the cardiovascular system and maintaining the normal function of the vascular endothelium.In addition,micro-nano physical signal and biochemical signal exist in a complex microenvironment with extracellular matrix?ECM?as the main component,which regulates adhesion,orientation,proliferation and migration of cells.Therefore,the strategy to construct an ideal scaffold surface with functions of anticoagulation and inhibition of neointimal hyperplasia is to promote the repair and regeneration of healthy and functional endothelium,thereby achieving re-endothelialization of the stent surface and vascular remodeling.This study aims to construct a multifunctional surface that combines physical induction and surface chemical induction by simulating the morphology of designed ECM.It is based on the"contact-induced"response of the cell to the topology and the response to biochemical signals to promote endothelial cell function repair,regulate the growth behavior of SMCs and platelets,and achieve long-term effective cure.In this study,biocompatibility studies were performed from both microscale and nanoscale aspects combined with chemical factors.Herein,we first studied the comprehensive effects of dopamine-mediated NO on platelets,?ECs?,SMCs,competitive growth of ECs and SMCs,and the re-endothelialization from the micron scale.A layer of titanium dioxide film was deposited on the patterned surface of the micro-groove?1?m×1?m?by RF magnetron sputtering.The polydopamine-mediated selenocystamine?SeCA?was immobilized onto the surface of micro-patterned titanium dioxide material via the strong coordination of phenol hydroxyl group with Ti based on the self-polymerization of dopamine and the function of Michael addition and Schiff base reaction with the amino groups,thereby constructing a multi-functional surface combined the micro-scale morphological clues with biochemical cues.Furthermore,the effects of microgrooves and the chemical composition on cell growth behavior were investigated.Scanning electron microscopy?SEM?results showed that the microgrooves were successfully prepared on the surface of the material.Atomic force microscopy?AFM?,water contact angle and zeta potential were performed measure the surface morphology,hydrophobicity and potential change of the material before and after modification respectively.The chemical elemental composition of X-ray photoelectron spectroscopy?XPS?demonstrated the successful preparation of PDA/SeCA coatings.The cytocompatibility evaluation of ECs,SMCs and competitive adhesion assays demonstrated that micron-scale modified materials could efficiently regulate cell growth orientation and promote ECs adhesion and proliferation while inhibite the adhesion and proliferation behavior of SMCs.The results of cadherin and actin staining of ECs showed that the morphology of substrate was the determining factors of cell alignment and elongation.The ability of PDA/SeCA modified samples to catalyze the release of NO was examined by a nitric oxide analyzer.And a significant increase in the cGMP concentration of platelet further confirmed the capacity.Besides,the results of platelet adhesion and activation experiments further indicated that the micropatterned modified surface with nitric oxide inhibited platelet adhesion,aggregation and activation,which had excellent anticoagulation activity.Next,we studied the comprehensive effects of NO and integrin ligand REDV on blood compatibility and ECs growth behavior at the nanoscale.The multifunctional surface which combined nanoscale morphological cues and biochemical cues was formed by constructing?RADA?₄-REDV,?RADA?₄-U and?RADA?₄-REDV@?RADA?₄-U peptide nanofiber coatings on the surface of 316L SS via the self-assembly properties.And then the effects of chemical composition of the surface of nanofibers on cell growth behavior and blood compatibility were studied.The SEM results showed that nanofibers were successfully prepared on the surface of the material.The water contact angle was measured to evaluate the hydrophilicity of the surface of the material before and after modification.Combined mass spectrometry?MS?with Fourier transform infrared spectroscopy?FTIR?,the successful preparation of self-assembled nanofiber coating was through self-assembly technique was proved.Adhesion,proliferation and migration experiments of ECs demonstrated that the?RADA?₄-REDV peptide coating specifically recognized ECs with good cytocompatibility and when the?RADA?₄-REDV polypeptide content was 20%,its proliferation and migration rate was optimaized.The results of nitric oxide rate analysis indicated that the NO-catalyzed release rate of?RADA?₄-U was positively correlated with its content,and the further grafting?RADA?₄-REDV on the surface was not affected the rate.The semi-iex-vivo circulating animal experiments verified that the self-assembled peptide nanofiber coatings especially for the?RADA?₄-REDV@?RADA?₄-U nanofiber coating had excellent anticoagulant properties and good potential for maintaining blood flow.In summary,this study designed the cardiovascular materials based on the micro/nano scale for surface chemical modification combing physical induction and chemical induction to promote endothelial cell adhesion,inhibit platelet adhesion and activation,it provided a new strategic and theoretical support for the further research on bionic cardiovascular stents.Besides,if the microgrooves and nanofibers can be reasonably combined,a higher level of biomimetic cell microenvironment can be produced under certain conditions.