Notwithstanding the prominent advantages of hydroxiapatite (HAp) coatings obtained by HVOF thermal spray process for biomedical applications these coatings are intrinsically brittleas well as low adherence to metallic surfaces[1]. Therefore, other compunds as Al2O3, ZrO2[2], SiO2 or TiO2[3] have been proposed as bond coats (BC) with HAp coatings. Among these alternatives, TiO2 enhances adherence, mechanical properties of the HAp top-coat[5] and displays better biocompatible properties than other oxides[4]. The present work reports the analysis on the cell viability of an optimized TiO2 BC on stainless steel substrate deposited by high velocity oxy-fuel (HVOF). In the thermal HVOF porcess two steps were completed to optimize TiO2 BC. The first one is focused on the study of this first stages deposition, where the first splats are formed. The second step deals with theTiO2 coating build up process in terms of microstructure, roughness and thickness. The selection of the thermal spray conditions for TiO2 splats and coatings analysis were carried out trought the Design of Experiment (DoE) method using the MiniTab® software. Thereafter, a multiple response optimization in the DoE was applied. Finallly, these results were used as optimization criteria to fabricate BC coatings to analyze cell viability.Osteoblast cells were cultured on the BC surface and it viability was measured by MTS (3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium) essay. In this test the presence of MTS formazan, which is related with cell viability in terms of mitochondrial activity, was measured spectrophotometrically (e.g. 490nm line) in cell cultured plates. The cell spreading characteristics, a sign that the TiO2 is a bioactive material that allows cell growth and proliferation were qualitatively evaluated as a function of time (24, 72 and 120 h[6]) by scanning electron microscopy (SEM). It was found that the TiO2 BC coating allows a significant cell viability.The results were used as criteria to determine the influence of the HVOF parameters in the deposition of TiO2 BC on a stainless steel substrate on the osteoblast cell viability.
Consejo Nacional de Ciencia y Tecnología CONACyT; MEXTRAUMA; LIDTRA and CENAPROT teams (National Laboratories for advanced coatings and thermal spray from Cinvestav)
References:
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[5] M. Gaona-Latorre, Recubrimientos biocompatibles obtenidos por proyección térmica y estudio in vitro de la función osteoblástica, Memoria Doctoral, Universitat de Barcelona. 2007
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