Deposition and characterization of hydroxyapatite coatings with incorporation of graphene oxide

Full text: Biomaterials of natural or synthetic origin can be used in total or partial replacement of damaged living tissues. Hydroxyapatite (Ca₅(OH)(PO₄)₃), an example of calcium phosphate ceramics, is similar to the mineral phase present in our bones and teeth. Hydroxyapatite coatings have shown great deal of success because of bioactive and osteoconductive properties that induce bone growth. However, as ceramic material, it is a fragile and failure susceptible. In order to improve mechanical properties a second phase can be used (carbon nanotubes, talc, etc.). In this work, we propose to perform and analyze the incorporation of graphene oxide to hydroxyapatite coatings. Our aim is the improvement of hydroxyapatite mechanical properties maintaining its biocompatibility. The hydroxyapatite coatings with incorporation of graphene oxide has been investigated through scanning electron microscopy, energy dispersive spectroscopy, potentiodynamic polarization, x-ray diffraction, Raman spectroscopy, wear and biocompatibility tests. Several parameters were evaluated in the electrodeposition process of hydroxyapatite films. By means of scanning electron microscopy we observed that films deposited for 1 hour at -5 volts potential with pulse frequency at 0.2 Hz presented the most compact morphology and uniformity. Energy dispersive spectra measurements reveals that hydroxyapatite formation in the ratio Ca/P = 2.7. Hydroxyapatite phases and calcium oxide (CaO) were identified by means of X-ray diffraction. Potentiodynamic polarization curves indicate that hydroxyapatite films (electrodeposited during 1 hour), at a potential of -5 volts with pulse frequency at 0.2 Hz increases the titanium corrosion resistance. Our results also show that graphene oxide incorporation increases the wear resistance without important decrease in biocompatibility. We also observed that corrosion resistances of composite coatings are slightly better than that presented by bare titanium. (author)