Ta-doped multifunctional bioactive nanostructured films

Ta-doped multifunctional bioactive nanostructured films (MuBiNaFs) were deposited by DC magnetron sputtering or ion implantation assisted magnetron sputtering of composite (Ti,Ta)C + Ca3(PO4)2 and (Ti,Ta)C + CaO targets produced by self-propagating high-temperature synthesis method. The films were characterized in terms of their structure, elemental and phase composition using X-ray diffraction, transmission electron microscopy, X-ray photoelectron, Raman, and IR spectroscopy. The films deposited in an Ar atmosphere consisted of (Ti,Ta)C, TixOy, and CaO phases in an amorphous matrix with P–O, C–O, and O–H bonding. In the films deposited in a gaseous mixture of Ar + 14%N2, apart from the (Ti,Ta)(C,N), TixOy, and CaO phases, the indication of diamond-like carbon, bcc Ta and traces of P–O bonding were observed. The MuBiNaFs demonstrated high hardness in the range of 38–44  GPa, Young's modulus 310–350  GPa, high percentage of elastic recovery 70–75%, low friction coefficient down to 0.17–0.25 (both in air and under physiological solution) and two orders of magnitude lower wear rate compared with Ti substrate. Ti ion implantation of growing films was shown to be an effective instrument to decrease their high internal stress. Static water contact angle measurements indicated hydrophilic nature of film surfaces. The electrochemical tests demonstrated that the Ta-doped films had positive values of corrosion potential with low current density. In vitro studies showed that cultured IAR-2 epitheliocytes and MC3T3-E1 osteoblastic cells were well spread on the surface of films and their actin cytoskeleton was well organized. Osteoblastic cells had a high rate of proliferation on all examined films and expressed alkaline phosphatase activity, an early-stage differentiation marker. The MuBiNaF revealed a high level of biocompatibility and biostability at experiments in vivo.