| With the economic development and social progress,the incidence of cardiovascular disease is getting higher and higher worldwide,and interventional therapy has become the main treatment method.The advent of vascular stents replaced percutaneous transluminal angioplasty,and Occupies a major position in cardiology,and opens up a new world of treatment for cardiovascular diseases.Nitinol alloys have advantages in many metals due to their unique shape memory function,good biocompatibility and superelasticity,as well as low density and corrosion resistance.The material stands out and becomes the first choice for the manufacture of cardiovascular stents.However,nickel contained in nickel-titanium alloys is a toxic element,which can cause allergic reactions in the body,cause cell distortion,and even cause cancer.Cardiovascular stents have better surface properties and biocompatibility,and they need to be surface modified.Studies have shown that the electrolytic polishing process has high processing efficiency,simple operation,and can process parts with complex shapes that are difficult to machine by mechanical polishing.The oxide film formed on the surface of the polished material can enhance corrosion resistance and prevent the penetration of nickel elements from cardiovascular stents.Therefore,in this paper,the surface modification of the stent was performed by electrolytic polishing process,and the biocompatibility of the stent before and after polishing was studied.First,we use a self-designed electrolytic polishing device to electrolytically polish a nickel-titanium cardiovascular stent.The volume ratio used during the test was The 1:17perchloric acid-glacial acetic acid polishing liquid system uses triethanolamine and absolute ethanol concentrations of 9 g/l and 100 ml/l as additives,and the best polishing is obtained by orthogonal test and single factor test.The combination of process parameters is:current density 1.15 A/cm~2,inter-electrode distance 15 mm,polishing temperature 25℃,polishing time 90 s.According to the above order,the influence degree of the four factors on the surface roughness Ra value decreases in turn.After the test,the surface of the bracket is detected by a white light interferometer.Roughness,multiple samples are selected as test points for each sample to ensure the accuracy of the test.The minimum surface roughness Ra value was 53.8nm.Then,the changes in the biocompatibility of the cardiovascular stent before and after polishing were compared and analyzed,including corrosion resistance,hydrophobicity,nickel ion release,etc.The surface morphology of the stent was observed with a white light interferometer and a scanning electron microscope.The scaffold was placed in Hank’s artificial simulated body fluid and measured by static weight loss method and electrochemical corrosion test method;the hydrophilicity was measured by observing the contact angle formed by deionized water on the scaffold with an OCA15EC contact angle measuring instrument;the nickel ion The release property is measured by using a field emission inductively coupled plasma emission spectrometer to determine the concentration of nickel ions in the immersion solution of the stent,and the calculated nickel ion release content and release rate are carried out.Finally,through experimental and comparative studies,it is concluded that under the best polishing process parameters,the electrolytic polishing process effectively reduces the surface roughness Ra value of the stent,improves the corrosion resistance and hydrophilicity of the nickel-titanium cardiovascular stent,and greatly reduces The release amount of nickel ions has enhanced the blood compatibility of the stent and effectively improved its biocompatibility. |
