Hongjie Hu

Antibacterial activity and increased bone marrow stem cell functions of Zn-incorporated TiO2 coatings on titanium

In this work, zinc was incorporated into TiO2 coatings on titanium by plasma electrolytic oxidation to obtain the implant with good bacterial inhibition ability and bone-formability. The porous and nanostructured Zn-incorporated TiO2 coatings are built up from pores smaller than 5 μm and grains 20-100 nm in size, in which the element Zn exists as ZnO. The results obtained from the antibacterial studies suggest that the Zn-incorporated TiO2 coatings can greatly inhibit the growth of both Staphylococcus aureus and Escherichia coli, and the ability to inhibit bacteria can be improved by increasing the Zn content in the coatings. Moreover, the in vitro cytocompatibility evaluation demonstrates that the adhesion, proliferation and differentiation of rat bone marrow stem cells (bMSC) on Zn-incorporated coatings are significantly enhanced compared with Zn-free coating and commercially pure Ti plate, and no cytotoxicity appeared on any of the Zn-incorporated TiO2 coatings. Moreover, bMSC express higher level of alkaline phosphatase activity on Zn-incorporated TiO2 coatings and are induced to differentiate into osteoblast cells. The better antibacterial activity, cytocompatibility and the capability to promote bMSC osteogenic differentiation of Zn-incorporated TiO2 coatings may be attributed to the fact that Zn ions can be slowly and constantly released from the coatings. In conclusion, innovative Zn-incorporated TiO2 coatings on titanium with excellent antibacterial activity and biocompatibility are promising candidates for orthopedic and dental implants.

Osteoblast-like cell adhesion on porous silicon-incorporated TiO2 coating prepared by micro-arc oxidation

Silicon-incorporated TiO(2) coating (Si-TiO(2) ) was prepared on titanium (Ti) by micro-arc oxidation (MAO) technique in the Ca, P, Si-containing electrolyte. The surface topography, phase, and element composition of the coatings were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and energy-dispersive X-ray spectrometry (EDS), respectively. Osteoblast-like MC3T3-E1 cells were cultured on the surface of the coatings to evaluate their adhesion behavior. The obtained results showed that Si element was successfully incorporated into the porous TiO(2) coating, which did not alter apparently the surface topography and phase composition of the coating. The adhesion of the MC3T3-E1 cells on Si-incorporated TiO(2) coating was significantly enhanced compared with the Si-free TiO(2) coating and pure Ti plates. In addition, the enhanced cell adhesion may at least partly be mediated by integrin β1-FAK signal transduction pathway. The present work suggests that the Si-TiO(2) coating is worth further consideration for orthopedic implant applications.

Enhanced apatite-forming ability and cytocompatibility of porous and nanostructured TiO2/CaSiO3 coating on titanium.

To improve the bioactivity and cytocompatibility of biomedical titanium dioxide coating, many efforts have been made to modify its surface composition and topography. Meanwhile, CaSiO(3) was commonly investigated as coating material on titanium implants for fast fixation and firm implant-bone attachment due to its demonstrated bioactivity and osteointegration. In this work, gradient TiO(2)/CaSiO(3) coating on titanium was prepared by a two-step procedure, in which porous and nanostructured TiO(2) coating on titanium was prepared by plasma electrolytic oxidation in advance, and then needle and flake-like CaSiO(3) nanocrystals were deposited on the TiO(2) coating surface by electron beam evaporation. In view of the potential clinical applications, apatite-forming ability of the TiO(2)/CaSiO(3) coating was evaluated by simulated body fluid (SBF) immersion tests, and MG63 cells were cultured on the surface of the coating to investigate its cytocompatibility. The results show that deposition of CaSiO(3) significantly enhanced the apatite-forming ability of nanostructured TiO(2) coating in SBF. Meanwhile, the MG63 cells on TiO(2)/CaSiO(3) coating show higher proliferation rate and vitality than that on TiO(2) coating. In conclusion, the porous and nanostructured TiO(2)/CaSiO(3) coating on titanium substrate with good apatite-forming ability and cytocompatibility is a potential candidate for bone tissue engineering and implant coating.

Enhanced Performance of Osteoblasts by Silicon Incorporated Porous TiO2 Coating

Silicon (Si) incorporated porous TiO 2 coating (Si-TiO 2 ) prepared on titanium (Ti) by micro-arc oxidation (MAO) technique was demonstrated to be cytocompatible in previous studies. In view of the potential clinical applications, a detailed in vitro study of the biological activity of Si-TiO 2 coating, in terms of osteoblast (MC3T3-E1 cells) morphology, proliferation, differentiation and mineralization was performed. Immunofluo-rescent staining indicated that cells seeded on the Si-TiO2 coating showed improved adhesion with developing mature cytoskeletons, which contained numerous distinct and well-defined actin stress fibers in the cell membranes compared with those on the TiO 2 coating and Ti plate. Results from proliferation assay showed that the proliferation rate of cells seeded on the Si-TiO 2 coating was significantly faster than that on the TiO 2 coating and Ti plate. Furthermore, the analysis of osteogenic gene expression demonstrated that the Si-TiO 2 coating stimulated the expression of osteoblast-related genes and promoted differentiation and mineralization of MC3T3-E1 cells. In addition, the Si-TiO 2 coating differentially regulated Wnt signaling pathway by up-regulating the expression of low-density lipoprotein (LDL) receptor-related protein 5 (Lrp5), and down-regulating the expression of Dickkopf-1 (Dkkl). All together, these results indicate that the investigated titanium with Si-TiO 2 coating is biocompatible and a good candidate material used as implants.

Preparation and formation mechanism of porous and nanostructured TiO 2 /BCP coatings on titanium

Porous and nanostructured TiO2/biphasic calcium phosphate (BCP) composite coatings were prepared on titanium by plasma electrolytic oxidation (PEO). The phase composition, microstructure, thickness and surface roughness of the coatings were characterized. Their formation mechanism were also discussed. The results reveal that the TiO2/BCP composite coatings mainly consist of anatase, rutile, β-tricalcium phosphate and hydroxyapatite. The surface of the coatings is porous, rough and nanostructrued with grain diameter of 50–100 nm. A two-step electro-migration mode was proposed to explain the ion migration in electrolyte. The granules consisted of amorphous calcium phosphate compound and the ions in electrolyte were brought onto the coating surface by stirring and electro-migration roles during PEO process, sintered by plasma arc produced locally high temperature surrounding the anode, which accelerated its crystallization. Thus is thought to be the possible mechanism for the TiO2/BCP composite coatings formation.