The effect of surface treatment on the surface texture and contact angle of electrochemically deposited hydroxyapatite coating and on its interaction with bone-forming cells

This work demonstrates the effects of both surface preparation and surface post-treatment by exposure to electron beam on the surface texture, contact angle and the interaction with bone-forming cells of electrochemically deposited hydroxyapatite (HAp) coating. Both the surface texture and the contact angle of the ground titanium substrate changed as a result of either heat treatment following soaking in NaOH solution or soaking in H2O2 solution. Consequently, the shape of the current transients during potentiostatic deposition of HAp changed, and the resulting coatings exhibited different surface textures and contact angles. The developed interfacial area ratio Sdr and the core fluid retention index Sci were found more reliable than the mean roughness Ra and the root-mean-square roughness Zrms in correlating the adhesion of the coating to the metal substrate and the cellular response with surface texture. The NaOH pretreatment provided the highest surface area and induced the highest cell attachment, even though the H2O2 treatment provided the highest hydrophilicity to the metal substrate. Electrodeposition at pH 6 was found preferable compared to electrodeposition at pH 4.2. The ability to modify the cellular response by exposure to unique electron-beam surface treatment was demonstrated. The very high hydrophilicity of the as-deposited HAp coating enhanced its bioactivity.