Biocompatibility study of nanocomposite titanium boron nitride (TiBN) thin films for orthopedic implant applications

Thin films of Titanium Boron Nitride (TiBN) were sputtered onto SS 316 L substrates and were characterized for their microstructure and biocompatibility. The X-ray diffraction (XRD) showed reflections of TiN and an absence of boron containing phases. High resolution transmission electron microscopy (HRTEM) mapping, ion scattering spectroscopy (ISS), and X-ray photoelectron spectroscopy (XPS) determined the presence of boron. The mechanical properties of the thin films were characterized by both nanoindentation and block on ring wear tester which indicated a hardness of 13 GPa and a friction coefficient of 0.27, respectively. The biocompatibility screening of the thin films was performed via hemocompatibility studies, cytotoxicity assay, mineralization assay and monitoring its bioactivity in SBF. The results revealed non-cytotoxic and non-thrombogenic nature of the sputtered TiBN thin films. In addition, mineralization studies demonstrated the ability of thin films to facilitate calcium mineralization by MC3T3-E1 cells. The corrosion behavior of the TiBN coated specimen was monitored electrochemically by impedance spectroscopy and potentiodynamic polarization techniques. A positive shift in Ecorr value and a higher R et value compared to uncoated control indicated the protection of the underlying metal by the sputtered films.