Sol-gel deposition of hydroxyapatite coatings on porous titanium for biomedical applications

The stress shielding and the poor osseointegration in titanium implants are still problems to be resolved. In this context, this work proposes a balanced solution. Titanium samples were fabricated, with a porosity of 100–200 μm of pore size employing space-holder technique (50 vol% NHHCO, 800 MPa at 1250 °C during 2 h under high vacuum conditions), obtaining a good equilibrium between stiffness and mechanical resistance. The porous titanium substrates were coated with hydroxyapatite, obtained by sol-gel technique: immersion, dried at 80 °C and heat treatment at 450 °C during 5 h under vacuum conditions. Phases, surface morphology and interfacial microstructure of the transverse section were analyzed by Micro-Computed Tomography, SEM and confocal laser, as well as the infiltration capability of the coating into the metallic substrate pores. The FTIR and XRD showed the crystallinity of the phases and the chemical composition homogeneity of the coating. The size and interconnected pores obtained allow the infiltration of hydroxyapatite (HA), possible bone ingrowth and osseointegration. The scratch resistance of the coating corroborated a good adherence to the porous metallic substrate. The coated titanium samples have a biomechanical and biofunctional equilibrium, as well as a potential use in biomedical applications (partial substitution of bone tissue).This work was supported by the Junta de Andalucía-FEDER (Spain) through the Project Ref. P12-TEP-1401 and by the Spanish Ministry of Economy and Competitiveness under the Grant No. MAT2015-71284-P. The authors would also like to thank the Technician, J. Pinto, for assistance in the scratch tests.Peer Reviewe