Antibacterial effects and mechanisms of graphene oxide loaded on TiO₂-nanotube-modified ti: an in vitro study

Peri-implant inflammation is an important factor affecting the success rate of dental implants. Improving the antibacterial performance of implants is an effective method to prevent and treat peri-implant inflammation.

In this study, Graphene oxide (GO) was loaded onto Titanium (Ti) dioxide nanotubes (TNT) to produce a material with good antibacterial effects and biocompatibility. TNT was prepared through anodization, and GO-loaded TNT-modified Ti (TNT-GO) was synthesized through electrodeposition. The materials were characterized using scanning electron microscopy (SEM), Raman spectroscopy, X-ray diffraction (XRD), and atomic force microscopy (AFM). Standard plate counting assay, methyl thiazolyl tetrazolium (MTT) assay, and fluorescence staining were used to assess the antibacterial effects of the samples. Bacterial morphology observations were conducted to explore the antibacterial mechanisms via SEM, transmission electron microscopy (TEM), reactive oxygen species (ROS) assay, and lactate dehydrogenase (LDH) cytotoxicity assay. Cell proliferation and morphological observations of the materials were performed to test the biocompatibility of TNT-GO.

The characteristic peaks of graphene oxide on TNT-GO were detected by Raman spectra. The results of contact angle test and AFM show that TNT-GO had the greatest hydrophilicity and the largest surface roughness. When P. gingivalis was cultured on the sample surfaces, the TNT-GO demonstrated the lowest bacterial adhesion, with significantly disrupted bacterial morphology. Specifically, the bacterial cells exhibited collapsed and ruptured cell membranes, leakage of intracellular contents, reduced membrane density, and phospholipid extraction. The TNT-GO group also showed the highest release of LDH extracellularly and the greatest ROS generation. The results of CCK-8 show that there was no significant difference between TNT-GO group and Ti group. The results of adherent cells morphology observation show that human gingival fibroblasts on TNT-GO group were in fusiformis and irregular triangle shapes while human gingival fibroblasts on TNT group and Ti group were in round shapes.

The TNT-GO had good biocompatibility and a good antibacterial effect on Porphyromonas gingivalis. It can inhibit bacteria-derived soft tissue infections and bone resorption and may be a very promising implant material.