Electrophoretic deposition of graphene oxide reinforced hydroxyapatite on the tantalum substrate for bone implant applications: In vitro corrosion and bio-tribological behavior

Tantalum (Ta) is used in dental implantology due to its high biocompatibility and potential clinical applications. Ta has low bone regeneration and low abrasion resistance, which can lead to inflammatory reactions in biological environments. In the present study, the graphene oxide/hydroxyapatite (GO/HA) composite on the Ta substrate was coated using the electrophoretic deposition technique. The deposition process was conducted at a constant voltage of 30 V at two deposition times of 5 and 10 min. Confocal Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD) confirmed GO in the GO/HA composite coating layer. The roughness of samples increased from 35 +/- 3 nm for the GO/HA-coated Ta (at 10 min) to 120 +/- 4 nm for the uncoated Ta. After coating Ta with the GO/HA at deposition time of 10 min, nanoindentation curve shifted to the left and maximum depth decreased due to an 18-fold increase in the hardness of coated sample in comparison to the uncoated Ta. The GO/HA composite coating improved the bio-tribological behavior, the resistance to plastic deformation, and fracture toughness of Ta substrate. The stiffness of GO/HA-coated Ta (at 10 min) was 8-fold higher than that of the uncoated Ta. Additionally, the friction coefficient of GO/HA-coated Ta (0.3) was lower than the uncoated Ta (0.43). The GO/HA-coated Ta (at 10 min) showed significantly higher corrosion current density (18.6 +/- 1.2 vs 4.97 +/- 0.23 mu A/cm(2)) compared to the uncoated Ta. The results of antibacterial activity test indicated that the presence of GO in the GO/HA coating decreased the viability of Escherichia coli and Staphylococcus aureus cells on the surface of Ta. Due to higher surface roughness and wettability of the GO/HA-coated Ta compared to the uncoated Ta, the proliferation and viability of MG-63 cells on the surface of GO/HA-coated Ta significantly increased. Our findings demonstrated that the GO/HA composite coating can enhance the lifetime of Ta based dental and orthopedic implants.