Surface Modification And Characterization Of Organization And Performance Of NiTi Alloy Left Atrial Appendage Occlusion Device

Percutaneous left atrial appendage occlusion is an effective physical therapy method for the patients with atresia and atrial fibrillation.Due to its safety in operation with a minimal invasive,a strong drug adaptability and a flexible operation,it becomes one of hot research spots.It is well documented that an excellent surface quality can effectively improve the biocompatibility and corrosion resistance.Thus,in the present thesis,the NiTi alloy left atrial appendage occlusion device was taken as the research object,and the surface of the device was polished by the electrochemical polishing method in an anhydrous sulfuric acid methanol system,and then heat treated,and finally chemical passivation treated.The effects of the surface modification processes on the hydrophilicity,corrosion resistance and biocompatibility of NiTi alloy left atrial appendage occlusion device.The main research contents and results are as follows:(1)The surface modification processes of the NiTi alloy left atrial appendage occlusion device were investigated.It found that the polish voltage is key factor for the surface flatness the device,and the polishing time has an importance impact on the weight loss of the device during the chemical polishing treatment.By chemical polishing under voltage of 21V± 2V at-20?.,we can obtain the high quality surface with a low weight loss of the device.Through annealing treatment at 500 ? for 10 min,,the finish austenite transition temperature(Af)of the device can be effectively controlled in the range of 21?±3?.The chemical passivation processes were optimized,in which,the device is passivated in the concentrated nitric acid solution at 40 ? for 30 min.By surface modifications mentioned above,the local corrosion issue caused by the complex shape of left atrial appendage occlusion device can be avoided.(2)The surface microstructure,hydrophilicity and corrosion resistance of the device after the surface treatments were characterized and evaluated.It is found that,after the electrochemical polishing(EP),a very thin film of TiO2 oxide layer is formed on the surface of the device,which is mainly in an adsorbed oxygen structure,and the surface is smooth with few defects.After electrochemical polishing + heat treatment + chemical passivation surface modification(HCP),the thickness of TiO2 oxide layer mainly in a lattice oxygen structure,smoothly.The surface modifications improve the surface hydrophilicity of the device,and the device exhibits an excellent corrosion resistance with a breakdown voltage over 1500 mv.(3)The biocompatibility of NiTi alloy left atrial appendage occlusion device was evaluated by animal biopsy.During the animal experiment,by imaging and pathological anatomical analyses,one can see that the NiTi alloy left atrial appendage system can transport,position,release and withdrawal smoothly in the vascular lumen and atrium of the live laboratory animals.One experimental animal died immediately after the operation due to the atrial perforation and massive pericardial tamponade.For other 9 cases,no adverse symptoms and death was found in the 28 days and 180 days follow-up period,but in the 2 cases,the animals appeared the symptom of the mild residual shunt angiography after 180 days.Moreover,during the animal observation period,no corrosion and structural damage were found.The device exhibits a good tissue biocompatibility,andt the endothelial cells can grow closely on the surface of the device.