Preparation Of Submicron-micron Roughness Gradient On Magnesium Alloy For Probing Morphological Influence On Vascular Cells Response

Magnesium alloys present a promising candidate for the nextgeneration vascular stent due to its favorable biocompatibility,mechanical properties and biodegradation.Although the occurrence of late in-stent restenosis can be obviated as magnesium-based stents completely degrade by the end of service,in-stent restenosis(ISR)remains a challenge in the early stage of stent implantation.In view of the drawbacks of commercial drug-eluting stents(DES),recently it becomes a more promising strategy of stent surface modification to promote the proliferation of vascular endothelial cells(ECs)and inhibit the proliferation of vascular smooth muscle cells(SMCs)in the early stage of stent implantation.Researches have shown that micro-nano scale surface topography of materials,in addition to surface chemistry,also specifically affects the response behaviors of vascular cells.However,so far there has been few systematic investigation on the influence of submicron scale topography,not to mention such study on degradable magnesium-based materials.Hence,in this study,a submicron/micron roughness gradient(Sa = 0.1-2.0?m)was prepared on the biomedical magnesium alloy Mg-Nd-Zn-Zr(JDBM)previously developed in our group,through a “down top” method of selective chemical etching with citric acid.Further surface chemical modification with fluorination conversion layer followed by polydopamine(PDA)nano-coating was designed to improve the corrosion-resistance and biocompatibility of the Mg substrates while not to interfere with the submicron/micron roughness.Employing the as-prepared surface roughness gradient,we have performed a systematic study of vascular ECs and SMCs behaviors in vitro,including cell adhesion,proliferation,spreading and function.Our study clearly revealed a synergistic effect of magnesium degradation microenvironment and submicron/micron surface topography on the response of vascular ECs and SMCs.Meanwhile,optimal surface roughness parameters with vascular endothelial cell/smooth muscle cell selectivity were efficiently screened by this gradient method.This study provides a novel promising method of surface topography engineering of magnesium-based vascular stents for achieving rapid endothelialization and reducing the rate of restenosis.