Biocompatibility Of Nanometer Silver Plating On Steel Surface

Over the last century, one of the most amazing achievements made in the field of coronary heart disease therapy is the percutaneous coronary intervention(PCI) alongside with its derivative technologies, which have successfully reduced the mortality rate. In the last decade, sustainable progress has been made in China’s intervention therapy. Specifically, the technology becomes more and more reliable and mature. Mortality related to intervention therapy are declining. However, PCI isn’t flawless. The technology itself has unresolved problems. In-stent thrombosis(IST)and in-stent restenosis(ISR) are main complications of PCI and the incidence of them are still high. Though the exact mechanism of these complications are complex, generally its occurrence is tightly associated with factors such as supporting platform, coating substrate of drug-eluting stent, the compatibility of the biologically active drugs and certain operations in the procedure. Supporting material, hydrophobicity and lipophobicity of the coating substrate can significantly impact on the compatibility of the supporting platform. So far, the researches on 316 L stainless steel nano modified material are scarce. Particularly, the research regarding histocompatibility and hemocompatibility is extremely scarce. To the best of our knowledge, there is no research about the effect of hydrophobicity and lipophobicity of the material or the effect of changing the property of 316 stainless steel in animal model experiments. Therefore, we conducted experiments for testing histocompatibility and hemocompatibility of nano modified layer, which is prepared by chemical deposition of Ag on the 316 L stainless material. Moreover, the property of inducing IST and ISR of coronary stent made of 316 L stainless steel was evaluated in animal model experiments. The data derived from these experiments can predict the further research about the surface modification of coronary stents.This research prepared the nano modified layer on the surface of 316 L stainless steel by chemical deposition of Ag. And the experiment material was submerged into the whole fluorine silane solution. We used scanning electron microscope and infrared spectrum test to prove the modification is successful. The silver particle with different diameter(90-130nm) and depositing time was tested to make sure their contact angle are within 130°-143°.The oleophobic contact angle of 316 L stainless steel was improved from 00 to 620-720. Then we test the histocompatibility and hemocompatibility of the modified 316 L stainless steel according to the GB/T 16886.5-2003 criteria. Among all the tests, it was found that 1600 s group has the best albumin adhesion ability. But there are no significant different of fibrin adhesion ability among all the groups. Both 800 s and 1600 s is superior to the bare 316 L stainless steel in anticoagulation test and histocompatibility test. And 1600 s goup has the least platelet adhesion on the steel surface.In vivo test, the coronary stents made by modified stainless were implanted into the targeted vessels. Intravascular unltrasound(IVUS) were also employed to evaluate endothelization and ISR. By comparing the pathological sections, we were able to examine certain properties of the experimental materials such as incidence of in stent thrombosis. The results indicated that 1 month after implanted the modified stainless stents there are no increase of incidence of in stent thrombosis. 800 s 2000s and 4000 s groups have advantages over 316 L stainless steel in terms of intima thickness and area(p<0.05), but there are no significant different between 1600 s and 316 L stainless steel in terms of intima area. 800 s 1600s 2000 s also have advantages over 316 L stainless steel in terms of medium thickness and area(p<0.05). In terms of lumen area 800 s 1600s 2000 s are all bigger than 316 L stainless steel. And there are no significant different between 800 s 1600s 2000 s and 316 L stainless steel groups.Accordingly, we drew the following conclusions. Preparing the surface of 316 L stainless steel by depositing nano silver modified layer and submerging into the fluorinated silane can improve its contact angel and compatibility. And the coronary stent made by this material can prevent subacute IST, and reduce the incidence of ISR.