Formation of hydroxyapatite coating using novel chemo-biomimetic method.

A novel chemo-biomimetic method was developed to deposit hydroxyapatite (HA), simulating the porous nano-scale structure and chemical composition of natural bone. Electrochemical activation in NaOH solution, a prerequisite process to heterogeneously nucleate hydroxyapatite in this investigation, creates nano-scale porous structure on the surface of Ti6Al4V alloy. XPS analysis confirmed that the surface of activated Ti6Al4V substrate converted to TiO2 during activation, existing in the form of hydrated TiO2. Benefiting from the biocompatible top-layer of hydrated TiO2 and the favorable alkaline surface chemistry created through the electrochemical activation, the HA coating nucleates heterogeneously and grows continuously on the activated substrate resembling the nano-scale porous bone-like structure. The coating was characterized using XRD, SEM/FESEM/EDX, TEM and FTIR, and was confirmed as pure hydroxyapatite. A coating thickness of 50 microm was achieved, which is preferable and acceptable for medical implant application to promote bone ingrowth, thus enhancing fixation and biocompatibility of implant surface.