| At present,magnesium alloy materials for cardiovascular stent have great potential in mechanical properties and biodegradability.However,the rapid degradation rate in the body leads to the premature failure of the stent and the limited biological properties of the surface restrict the clinical application of the magnesium alloy material.In order to improve the performance of magnesium alloy and the possibility of clinical application of magnesium alloy,in this paper,the dopamine and hyaluronic acid coatings with excellent biocompatibility were selected to modify the surface of the vascular scaffold Mg-2Zn-0.46Y-0.5Nd base after alkali heat treatment.First,a layer of dopamine was deposit on the surface of the magnesium alloy after alkali heat treatment.Four different molecular weights of hyaluronic acid(HA)were immobilized on the polydopamine(PDA)coating(HA:Mw =4×103,1×105,5×105,l×106 g/mol,PDA-HA,labeled PDA/HA-1,PDA/HA-2,PDA/HA-3,PDA/HA-4,respectively).In this study,the surface morphology was observed by SEM and the coating composition was analyzed by EDS.The surface roughness of the coating was measured by AFM,and the contact angle of the water was used to assist the analysis of the effect of the coating on cell activity.Electrochemical experiments and immersion experiments were used to evaluate the protective effect of the coating on the substrate.In vitro tests,blood compatibility was evaluated by observing whole blood adhesion,measuring the hemolysis rate and fibrinogen denaturation rate of different coatings,and the cytocompatibility was evaluated by the influence of different implants on the growth of target cells.Finally,in vivo experiments were carried out.The implants of different coatings were implanted into the rat celiac artery for one month,and the tissues containing the implants were subjected to HE staining to comprehensively evaluate the biocompatibility of different implants.SEM and EDS test results show that the PDA-HA coating was successfully prepared on magnesium alloy.The difference of surface roughness and water contact angle of different coatings indirectly indicates the influence of the coating on the alloy matrix.The surface roughness was reduced after the HA coating fixed,and the hydrophilicity of the surface improved by the deposition of PDA.The immersion weight loss experiment and electrochemical polarization showed that HA with a molecular weight of 1×105 g/mol further delayed the corrosion of the magnesium alloy.The blood test results showed that the fixation of HA improved the blood compatibility of the PDA coating to some extent.In cell experiments,PDA/HA-2 had been shown to play a more effective role in promoting endothelial cells growth,inhibiting proliferating smooth muscle cells and inflammatory macrophages.At the same time,the results of in vitro blood experiments and cell experiments revealed that the PDA/HA-2 coating improved the blood compatibility and cytocompatibility of the alloy surface initially.In vivo experiments,it was found that there was no excessive tissue proliferation on the surface of the PDA/HA-2 implant.After measurement,the neointimal thickness of the PDA/HA-2 implant was only 48?m,and the lumen loss rate was only 0.18%,indicating that the PDA/HA-2 coating played a more significant role in anti-proliferative,anti-inflammatory and rapid endothelialization,which was consistent with the results of in vitro experiments.In summary,the PDA/HA-2 coating with a HA molecular weight of 1x105 g/mol exhibited better overall performance.By preparing the PDA/HA-2 functionalized coating on the surface of Mg-Zn-Y-Nd,the possibility of clinical use of the vascular stent magnesium alloy material can be further improved. |
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