Hydroxyapatite-biomolecule coatings onto titanium surfaces

To date, surface structuring of metallic implants for use in load bearing bone implantation focuses on the coating of their surface with hydroxyapatite (HA) through plasma spraying. Despite the inherent disadvantages of this method, research on alternative coating techniques has been slow to yield suitable results, mostly due to the lack of surface tailoring for efficient osseointegration coupled with inefficient coating adhesion to the implant surface. Through the presented work we provide a new route for the formation of nanostructured functional coatings of HA onto titanium implant surfaces employing amino acids to not only potentially induce osteogenic cell activity, but to aid the attachment of HA onto the titanium surface. Briefly, crystalline, partially carbonated HA nanoparticles were synthesised through a novel sol–gel route employing CaCl2 and Na2HPO4 as precursors and l-arginine or l-lysine to facilitate nanoparticle formation and gellation and to control the viscosity of the slurries. The grafted amino acids were in turn used to attach the HA coating through covalent interactions between the amino acid carboxyl end groups and the TiOH groups on the titanium surface. The composites were characterised by SEM, TEM, powder XRD, FT-IR, scratch and roughness testing. Samples were also treated in an SBF solution to observe their bioactivity.