Biocompatibility Of TiO₂Nanotubes Modified By Human Smooth Muscle Cell-Derived Extracellular Matrix

Titanium has been studied for applications of implants because of its excellent mechanical properties, corrosion resistance and biocompatibility. Recent studies have already shown that nano-and micro-topography can promote adhesion, differentiation and proliferation of cells and stimulate cells to secret more extracellular matrix (ECM). Extracellular matrix contains a variety of active factors that can improve cells adhesion, growth and reproduction. Combining TiO2nanotubes with ECM derived from cells on the biomaterial surface has great potential and value in biomedical modification and application areas.Titanium dioxide (TiO2) nanotubes on titanium substrates were prepared by anodization. Scanning electron microscopy (SEM) micrographs showed that TiO2nanotubes were self-assembled, vertically and highly ordered growth on the Ti substrate. X-ray diffraction (XRD) results confirmed that these TiO2nanotubes were the mixture of anatase and rutile phases. The measurement of water contact angle revealed that the surface with TiO2nanotubes was hydrophilic. Compared to the flat Ti, the growth and viability of human umbilical vein endothelial cell (HUVEC) are prohibited, but those of HUASMC on30nm TiO2nanotubes are normal.The ECM secreted from HUASMC is in situ deposited onto the30nm TiO2nanotubes Immunofluorescence staining test revealed that almost all the cell components were removed after decelluarization. It also proved that the ECM components, including fibronectin (FN), laminin (LN) and type IV collagen (IV-COL) were presented on the ECM-covered TiO2nanotubes surfaces. SEM and atomic force microscopy (AFM) further exhibited the ECM secreted from HUASMC is a well-formed interconnected network of fibrin on TiO2nanotubes. Diffuse reflectance fourier infrared spectroscopy (FTIR) proved the existence of amide I and amide II band and X-ray photoelectron spectroscopy (XPS) indicated the existence of N element in the ECM modified TiO2nanotubes surfaces, which came from the proteins’existence in the ECM. The TiO2nanotubes surface was a highly hydrophilic surface and its water contact angle (WCA) was below10°. The WCA of30nm-ECM was81°, which suggested that the ECM deposition can significantly change the hydrophilicity.HUVECs and HUASMCs in vitro tests showed that compared to on a flat Ti, endothelial cells arranged closely and had little burr-like protrusions on the ECM-covered TiO2nanotubes surface. The results of Cell Counting Kit-8test demonstrated that ECs cultured on the ECM-covered TiO2nanotubes surfaces proliferated faster than those on the unmodified TiO2nanotubes surfaces at1day,3day and5day.Thus, this study may provide an ideal method to biological modify surface of titanium implants.