Preparation And Evaluation Of Composite Coatings Based On TiO₂ Nanorods And ECM

Surface modification on metal implants to enhance their integration with the host bone is a crucial research in the field of bone repair.Using micro/nano structure or adding bioactive substances,to build suitable surface microenvironment for cell/tissue growth,is an effective mean to promote the formation of surface bone tissue and bone integration.TiO2 nanorods.have been widely studied because of their good cellular responses.Meanwhile,the extracellular matrix(ECM),as an ideal tissue engineering material,can not only provide cells with supportive sites,but also provide the biological information needed for the growth of cells.However,there are few researches on how to effectively combine them and exert synergistic effects.In this dissertation,TiO2 nanorods and ECM were effectively combined to obtain TiO2 nanorods/ECM composite coatings,and further carrying the bioactive element Ca to obtain Ca2+chelated ECM/TiO2 nanorod composite coatings.Cell spread,adhesion,proliferation,differentiation and mineralization were evaluated.The mechanism of the composite coatings in promoting osteoblast differentiation was discussed.This article has got two major findings as following:1.TiO2 nanorods/ECM composite coatingsAfter culturing MC3T3-E1 cells on TiO2 nanorods with high density,followed by repeated freezing and thawing,we successfully prepared TiO2 nanorods/ECM composite coatings.A series of TiO2 nanorods/ECM composite coatings with different degree of combination were obtained by cell culture cycles.ECMs derived from MC3T3-E1 cells can be effectively immobilized on TiO2 nanorods.The active ingredients of ECM are retained,and the composite coatings are still rich in three-dimensional structure.Composite coatings can not only provide cells with support sites,but also provide the necessary biological information for the growth of cells.They can obviously promote the adhesion and proliferation of stem cells.The coating with less ECM showed more excellent promotion effect in initial adhesion and early osteogenic differentiation.The one with medium ECM is more conducive to promoting the late osteogenic differentiation.The synergistic effect of TiO2 nanorods and extracellular matrix makes the composite coating have more excellent osteogenic properties.2.Ca2+ chelated ECM/TiO2 nanorods composite coatingsWe prepared Ca2+ chelated ECM/TiO2 nanorods composite coatings by culturing cell sheets on TiO2 nanorods and then soaking in CaCl2 solution.Three kinds of composite coatings with low,medium and high Ca2+ doping were obtained by adjusting the concentration of CaCl2 solution.The surface of the obtained composite coatings were uniformly loaded with abundant ECM.Ca2+ was effectively incorporated and chelated with the extracellular matrix via a coordination bond.The concentration of Ca2+ in the sample had little effect on the initial adhesion of the cells,but the low concentration of Ca2+ favored cell proliferation.The 0.5M group showed more excellent performance in the early stage of cell differentiation,but in the later stage,the 2.0M group was more prominent.Generally speaking,higher concentration of Ca2+ is more conducive to promote the differentiation of stem cells into osteoblasts.Compared with the non-doped composite coatings,they are better in promoting new bone formation.