Anaphoretical/oxidative approach to the in-situ synthesis of adherent hydroxyapatite/titanium oxide composite coatings on titanium

Abstract

In-situ synthesis of HAp/TiO2 coating on titanium was performed via anaphoretic deposition of HAp and simultaneous anodization of Ti to produce highly adherent and strengthened composite coating. The prepared coatings were characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray difraction and electron dispersive spectroscopy. HAp on anodized titanium was prepared at constant voltage of 60 V and deposition time of 45 s, which provided uniform and adherent HAp/TiO2 composite coating on Ti. Since smaller size of HAp crystals within highly porous coating structures is of improved binding ability to various biomolecules, our coating is expected to be of excellent coverage and compactness. The obtained coating can be good candidate for bone implants due to reduced brittleness and improved adhesion.

Relationship between the properties of an interlayer formed by in situ Ti anodization and anaphoretically deposited hydroxyapatite

“…It is attractive for its low weight, fatigue resistance, corrosion resistance, having superior room and elevated temperature mechanical properties. [1][2][3][4] As one of the valve metals (others being Al, Ta, Nb, V, Hf and W), titanium is protected by a thin oxide layer which spontaneously forms on its surface when exposed to air or other oxygen-containing environments. This 2-to 5-nm thick oxide passive layer is responsible for the corrosion resistance of titanium and its alloys.…”

“…5 HAp is the main mineral in bones with the Ca/P mole ratio of 1.67 in stoichiometric hydroxyapatite (Ca 10 (PO 4 ) 6 (OH) 2 ). 4 The HAp-coated titanium was shown to have excellent corrosion resistance and good biocompatibility. 20 HAp is of porous structure and sufficient bioactivity for its partial resorption leading to successful replacement of natural bone cells.…”

“…It is widely used in medical applications, including tissue engineering, drug delivery and bone tissue repair, owing to ability to create strong chemical bonds with bones. 4,21 The main problem in altering titanium surface by ceramic coatings is large difference in properties of the hydroxyapatite and titanium substrate. The coating adhesion to the substrate remains a major problem due to different mechanical properties.…”

“…The coating adhesion to the substrate remains a major problem due to different mechanical properties. 4 Literature review showed that most of the papers did not address adhesion problem. [22][23][24][25][26] Poor coating adhesion appeared in the form of delamin-ation, poor mechanical properties, poor connections between ceramics and metals and long-term failures due to weak adhesion to the metal substrate and dissolution once they have been implanted.…”

“…[22][23][24][25][26] Poor coating adhesion appeared in the form of delamin-ation, poor mechanical properties, poor connections between ceramics and metals and long-term failures due to weak adhesion to the metal substrate and dissolution once they have been implanted. 4,5 Solutions to this problem were partially found in the surface modification methods of the substrate, such as anodization, sandblasting, electrophoretic deposition of HAp coatings or chemical treatment of the surface to improve adhesion. 27,28 With electrodeposition, HAp coatings of complex structures can be obtained, with easily controlled thickness at low temperature.…”