Surface Modification Of Vascular Stent Materials And Interfacial Effects Between The Materials And Blood

Cardiovascular diseases(CVDs)are the main cause of death because of disease.Coronary heart disease is common,most threatening CVDs.The treatment of coronary heart disease concludes medication,coronary artery bypass surgery and percutaneous coronary intervention.Among them,percutaneous coronary intervention based on vascular stent has advantages of minor trauma and remarkable therapeutic effect.It has become the main treatment for coronary disease.The stenosis rate decreased significantly after stent implantation due to drug-eluting stent used.However,stent thrombosis and late restenosis still existed after stent implantation.Stent thrombosis and late restenosis were found at the interface between the stent and blood.The mechanism was very complex.The interaction between vascular stent and living organism always existed after stent implantation.The surface properties of stent materials affected the stability of stents,the type of protein adsorption and cell growth rate on stent surface,which determine the safety and effectiveness of stents in service.In this thesis,316L stainless steel was chosen as the research object.The corrosion resistance and blood compatibility were improved by surface modification.The effect of blood electrolyte on the stent materials was discussed.The interaction between the surface of stent materials and main components of blood was studied.The mechanism of corrosion resistance and blood compatibility improvement was reveled.A two step surface modification technique was proposed to prolong the long-term efficacy and safety of vascular stent.The main research work and results were given below.(1)The interface corrosion of vascular stent in blood environment was studied by static simulation in vitro.Uniform corrosion and local corrosion both exist in the chloride ions environment.The surface roughness,composition,wettability and corrosion resistance of the stent were changed by local corrosion.(2)Uniform and compact TiO2 thin films were prepared on the surface of vascular stent materials by magnetron sputtering method.The films can act as a"physical barrier" to inhibit the release of metal ions from stent materials.The corrosion resistance of stent materials was improved.The TiO2 thin film prepared by magnetron sputtering has wide band-gap,which can inhibit fibrinogen denaturation.The wide band-gap structure of films improved the anticoagulant performance of stent materials.However,the TiO2 film prepared by sputtering was hydrophobic,which affects the rapid growth of endothelial cells on the surface of the stent.(3)The process of TiO2 thin films prepared on stent materials by sol-gel method was studied.The microstructure and properties of TiO2 films doped with carbon nanotubes(CNTs)were discussed.The films prepared by sol-gel method not only have good corrosion resistance and anticoagulant properties,but also have hydrophilic properties,which can promote the rapid growth of endothelial cells.The inter facial interaction between the modified stent materials and the blood was investigated.The results showed that TiO2 film prepared by sol-gel method has good blood compatibility.The micro structure of TiO2 film was changed by CNTs doping.The corrosion resistance and blood compatibility of CNTs doped TiO2 films were further improved.(4)The "two step method" based "in situ surface passivation + film preparation"was used to improve the interfacial adhesion between the stent materials and the modified films.The surface composition and surface energy of the stent material were changed by in situ surface passivation.The interfacial adhesion between the modified film and the vascular stent material was improved.The increase of interfacial adhesion was helpful to improve the safety and effectiveness of the vascular stent in long-term service.In summary,this research is based on 316L staimless steel vascular stent material.The corrosion behavior of stent materials,blood compatibility and long-term stability of modified films were investigated.The research belongs to basic application research.The work can be used as reference for surface modification of stent materials.