| Magnesium alloys have the advantages of good biodegradability,biosafety,and comprehensive mechanical properties,which can avoid the clinical stents problems that hinder ciliary movement,restenosis,and secondary surgical at the present stage,and become the first choice for biodegradable tracheal stent materials.However,the rapid corrosion rate of magnesium alloys limites clinical applications.The surface coatings can protect magnesium alloys and promote cell adhesion,growth,and proliferation.They have important research value and application prospect.In this paper,Mg-Zn-Y-Nd alloy,developed by our own laboratory,was selected as matrix material.HACC/GPTMS hybrid coating,GPTMS/PLLA composite coating,and MAO/PLLA composite coating were prepared.The surface morphology and corrosion resistance were analyzed by SEM,EDS,XRD,FTIR,NPFLEX 3D surface measurement system,RST5200F,and contact angle machine.The cytocompatibility of the MAO/PLLA composite coating was evaluated.The results showed that the pH value of the GPTMS solution had a significant effect on the coatings,which morphology became integritied with the pH value increased.The coating?s uniformity became the best when the pH value was 11.Compared with the Mg matrix,its corrosion current density decreased from 1.06×10-5A/cm2 to 3.19×10-6 A/cm2.The silane coating was suitable for being applied as a surface pretreatment coating.MAO treatment time had a significant effect on the surface morphology of Mg matrix.The size and quantity of the pores and cracks on the surfaces were increased as the processing time increased from 1 min to 7 min.The average surface roughness?Ra?value of MAO coatings was also increased.The corrosion current density of MAO coating formed by 3 min treatment was 2.10×10-6A/cm2,which was one order of magnitude lower than that of Mg matrix.Combined with the surface morphology and properties,3 min was considered as the best parameter.The HACC/GPTMS hybrid coating was prepared on the silane-pretreated coating.The corrosion current density did not decrease obviously,due to the hygroscopicity of HACC,which could accelerate the expansion of the coating and separate from the silane pretreatment coating.As the interfacial bonding of the layers,the GPTMS/PLLA coatings required further exploration.The PLLA coatings,dipped on the MAO coatings,could overlay the micro cracks and pores.The MAO/PLLA composite coating greatly improved the corrosion resistance of Mg matrix,with the corrosion current density decreased to 8.77×10-8 A/cm2,3 and 2 orders of magnitude lower than that of the Mg matrix and MAO sample,separately.The cell toxicity indicated that toxicity grade of MAO/PLLA composite coating was level 0,showed no cytotoxicity.The cell viability at 24 h,48 h,and 72 h,were more than 100%and the cells showed a typical paving stone mosaic arrangement on the surface,and indicated the MAO/PLLA coating had well cytocompatibility.Although the silane-pretreated coating was uniformity,the HACC/GPTMS hybrid coating and PLLA composite coating had poor combination.The MAO/PLLA coating had good corrosion resistance and cytocompatibility,which can be used as a good surface modification material for magnesium alloy tracheal stent. |
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