ICMCTF2012 Session D1-1: Bioactive and Biocompatible Coatings and Surface Functionalization of Biomaterials

The long term clinical success of an orthopaedic implant is strongly related to bone formation at the biomaterial–tissue interface. Surface parameters that include topography and roughness influence this process of osseointegration. Electropolishing is a cost effective approach for surface treatment of metallic implant materials such as titanium alloys.

In this study, it is found that the electropolished surface enhances levels of bone formation. However, the mechanical property of the neo–bone remains unknown. In this study, we use nanoindentation with in–situ AFM imaging to identify and characterize the small features (such as calcospherulite) of the neo-bone. The measured Young’s modulus and hardness of the neo–bone formed on the electropolished surface is higher, which may indicate the formation of more mature bone. The length scale of the current tests (100nm) is commensurate with the dimensions at which individual cells interact with the extracellular environment. Therefore, understanding the mechanical properties of bone at this scale can reveal the likely role that substrate conformity plays in the control of cell behaviour.

A pure TiO₂ and three Al-TiO₂ composite nano thin films were prepared on glass, quartz and silicon substrates at Ar:O₂ gas ratio of 70:30 in sccm by reactive magnetron sputtering method. For pure TiO₂, titanium target was mounted on the magnetron connected to 200W DC power supply while for Al-TiO₂ composite film an additional aluminium target was connected to RF power supply of 15W, 30W and 45W in a dual magnetron co-sputtering unit. The crystallinity and phase of the films were determined by Grazing Incidence X-ray Diffraction where as the surface chemical composition was obtained by X-ray Photoelectron Spectroscope. It was found that aluminium was in the form of Al₂Ti_xO_2-x and so in the films and in surface it was weakly bonded with oxygen to form its oxides. The band gap was observed to increases as we increase the Al content in the films as compared to pure TiO₂ thin films as calculated from UV- Visible transmission spectra. The Scanning Electron Microscopic image revealed that Al-TiO₂ composite nano thin films displayed rough and flake-like morphology having less porosity with the increase in the Al content. Photoinduced hydrophilicity was examined with the help of OCA. The qualitative and quantitative bactericidal efficiency was observed through SEM image of the treated E.coli cells and optical density (OD) measurement respectively under UV irradiation. The better bactericidal efficiency was observed in the film with 30W of RF power to Al magnetron. The crystallinity, surface chemical composition, band gap in context of Al present in the films was discussed and correlated to bactericidal efficiency.