Minocycline hydrochloride loaded on titanium by graphene oxide: an excellent antibacterial platform with the synergistic effect of contact-killing and release-killing.

Titanium and its alloys have been widely used in orthopedic and dental implants because of their excellent properties. However, implant failures still occur due to implant-associated bacterial infections. Therefore, proper surface modification of titanium and its alloys is necessary. In this work, commercial pure titanium plates were modified with graphene oxide (GO) which was used to load minocycline hydrochloride. Gram-positive Staphylococcus aureus (S. aureus) and Streptococcus mutans (S. mutans) and Gram-negative Escherichia coli (E. coli) were used to investigate the antibacterial activity of the samples. Human gingival fibroblast (HGF) cells were applied to assess the cytocompatibility of the various samples. To investigate cell adhesion and cell surface coverage in the presence of bacteria, the coculture of HGF cells and S. aureus was performed. The results indicated that the GO-modified titanium surface could inhibit the growth of the bacteria which had direct contact with GO, while it could not affect the bacteria without direct contact of GO. Minocycline hydrochloride on the GO-modified titanium surface (M@GO-Ti) showed a slow release behavior and exhibited excellent antibacterial activity with the synergistic effect of contact-killing and release-killing by GO and minocycline hydrochloride, respectively. In the coculture process with the presence of S. aureus, HGF cells on M@GO-Ti demonstrated the best cell viability and cell surface coverage among all the samples.