Synthesis of antimicrobial surfaces bearing graphene oxide particles on additively manufactured titanium implants

Implant associated infections are one of the main reasons for implant failure in total joint arthroplasty. The cause is due to bacteria that adhere to surfaces forming a biofilm. Biofilm formation is an irreversible situation which requires excessive hospitalization and medical treatment with antibiotics, however bacteria have been proven highly resistant to antibiotics. Self-defending implants that can incorporate nanoparticles (NPs) onto their surface are proven to be effective towards the prevention of biofilm formation. NPs acting as antimicrobial agents are being researched for the synthesis of antimicrobial coatings, one of the most promising of them so far has been proven to be silver NPs (AgNPs). Graphene based materials are being suggested as a promising antibacterial agent as well. This study aims to investigate the incorporation of graphene oxide (GO) on the surface of additively manufactured porous Ti-6Al-4V implants produced by selective laser melting (SLM). Plasma Electrolytic Oxidation (PEO) was used to create layers bearing GO on the surface of porous Ti-6Al-4V implants. For this purpose, Ca and P containing electrolytes were used, bearing different concentrations of GO. In addition, layers bearing mixture of GO + AgNPs were also synthesized. Solid implants of similar Ti composition were tested for comparison reasons with the SLM surfaces. The implants were characterized in terms of surface morphology by Scanning electron microscopy (SEM), chemical composition by Energy dispersive x-ray spectroscopy (EDS), phase composition by X-ray diffraction (XRD) and Raman spectroscopy. Thereafter, they were evaluated towards their antibacterial activity against methicillin resistant staphylococcus aureus (MRSA). Furthermore, the surfaces bearing GO and GO + AgNPs were also tested for their reactive oxygen species (ROS) formation potency. Results showed the incorporation of GO flakes on the surface of SLM and solid implants which was identified by SEM and EDS. The implants oxidized in the GO + AgNPs electrolyte displayed GO flakes and AgNPs on their surfaces as well. The antibacterial testing revealed the formation of inhibition zone on the implants bearing GO + AgNPs. The ROS study revealed the generation of radicals developed by the SLM surfaces bearing GO and GO + AgNPs as well.