Research On Biodegradable Coronary Stents

Nowadays,Cardio-vascular diseases come out with the characteristic of high-risks, widespread,which became the "human's primary killer",this kind of diseases cost more and more expenses year by year.The metal stents which had been popularly used in the intravascular stent show excellent clinical results.However it had been challenged by some defects like the long-term safety and developing new kind of stents with better biocompatibility to improve the therapy is a hotspot in this field.In the paper,the mechanic property,,the biocompatibility and the intro degradability of the PLLA with molecular weight of 400,000 and its composite modified by Chitosan were investigated.To find out that whether Chitosan can remedy the efficacy of PLLA and which one was the reasonable biodegradable(bio-absorbable) materials for a biodegradable stent.CAD software Solidworks was introduced to design an explorasive model,referring to different kinds of metallic stents and the mechanic property of PLLA or modified PLLA,Meanwhile,this model was evaluated by Finite element analysis method.And then the materials with better performance were applied in manufacturing laser-cut seamless tubes.The radial force of this kind of tubes was tested by a mechanic tester.Common microscope was used to analyze the processing accuracy and the depth under different laser-cutting rate.The best laser-cutting rate was found out and applied in cutting the seamless tubes into biodegradable coronary stents with high consistency to the design model.At the same time,infrared(IR) spectroscopy was used to analyze the effect of manufacture method.Finally,automatic coagulation analyzer,SEM and AFM were used to find out whether the biodegradable stents meet the clinical requirement.The results show that modified PLLA is superior to pure PLLA in preparing biodegradable coronary stents.The mechanical property testing shows that the seamless PLLA tubes perform excellent radial strength,which indicates that the mechanical properties of biodegradable stents made of these tubes was supposed to be excellent.PLLA and its composites were first used in preparing seamless tubes as antecedency of laser-cut biodegradable coronary stents in china.Finite element analyses of the biodegradable coronary stent model indicate the explorative design basically meets the requirement of reasonable and applicable stents.There is not such kind of research yet in domestic.Optimum laser-cuttting parameters of CO₂ laser was cauculated based on experiential formula,within it,biodegradable coronary stents,especially those with complex structure would be manufacutured from seamless tubes quickly by laser microprocessing with high consistency to the design model.The processing efficiency of the CO₂ laser demonstrated in experiential formula by us will play an important guiding role in manufacturing biodegradable stents by laser-processing.Our stents that ascribed to laser-cutted,slotted tube stent are proved to be biodegradable, self-expandable and good biocompatible,basically reach the international level on the aspest of manufacturing procedures and design.On the whole,a rapid designed,immediately refined and normalized process route was set up in the paper.Finally,further reaserach is prospected,aiming at developing biodegradable stents that meet the cilincial requirement.