Developing alkaline titanate surfaces for medical applications

Improving the surface of medical implants by plasma spraying of a hydroxyapatite coating can be of critical importance to their longevity and the patient's convalescence. However, residual stresses, cracking, undesired crystallisation and delamination of the coating compromise the implants lifetime. A promising alternative surface application is an alkali-chemical treatment to generate bioactive surfaces, such as sodium and calcium titanate and their derivatives. Such surfaces obviate the need for high temperatures and resulting micro-crack formation and potentially improve the bioactive and bone integration properties through their nanoporous structures. Also, metallic ions such as silver, gallium and copper can be substituted into the titanate structure with the potential to reduce or eliminate the infections. This review examines the formation and mechanisms of bioactive/antibacterial alkaline titanate surfaces, their successes and limitations, and explores the future development of implant interfaces via multifunctional titanate surfaces on Ti-based alloys and on alternative substrate materials.