Multifunctional Ti–(Ca,Zr)–(C,N,O,P) films for load-bearing implants

Abstract

Films of Ti–Ca–P–C–O–(N), Ti–Ca–C–O–(N) and Ti–Zr–C–O–(N) were deposited by DC magnetron sputtering or ion implantation-assisted magnetron sputtering of composite targets TiC 0.5+10%Ca 10(PO 4) 6(OH) 2, TiC 0.5+20%(CaO+TiO 2) and TiC 0.5+10%ZrO 2 in an Ar atmosphere or reactively in a gaseous mixture of Ar+14%N 2. The microstructure, elemental and phase composition of films were studied by means of X-ray diffraction, transmission electron microscopy, scanning force microscopy, X-ray photoelectron spectroscopy and energy-dispersive X-ray spectroscopy. The films were characterized in terms of their hardness, Young's modulus, elastic recovery, adhesion strength, and friction and wear both in air and under physiological solution. Particular attention was paid to the analysis of deformation and fracture for various film/substrate systems during scratch testing. The biocompatibility of the films was evaluated by both in vitro and in vivo experiments. In vitro studies involved the investigation of adhesion, spreading, and proliferation of MC3T3-E1 osteoblasts and IAR-2 epithelial cells, morphometric analysis, actin cytoskeleton, focal contacts staining, alkaline phosphatase activity and von Kossa staining of osteoblastic culture. Cell culture experiments demonstrated an increase of osteoblastic proliferation on Ca- and P-incorporated films. In vivo studies were fulfilled by subcutaneous implantation of Teflon plates coated with the tested films in mice and analysis of the population of adherent cells on their surfaces. The results obtained show that multicomponent nanostructured Ti–(Ca, Zr)–(C, N, O, P) films possess a combination of high hardness, wear resistance and adhesion strength, reduced Young's modulus, low friction coefficient and high biocompatibility.