Antibacterial properties of graphene oxide and montmorillonite against Porphyromonas gingivalis

Clinical antibacterial agents for periodontitis are frequently limited by bacterial resistance, insufficient targeting, and disturbances to the normal oral flora. Two-dimensional nanomaterials have attracted extensive attention in oral antibacterial research owing to their unique physicochemical properties and promising antibacterial activity. As typical monolayer two-dimensional nanomaterials, Graphene oxide (GO) and Montmorillonite (MMT) exhibit favorable biocompatibility and antibacterial potential. This study aimed to investigate the antibacterial effects of GO and MMT against P. gingivalis , and thereby provide experimental and theoretical support for the development of novel antibacterial materials for periodontitis treatment. GO dispersion was prepared using a modified Hummers method, and MMT dispersion was prepared via liquid-phase ion exchange, followed by material characterization. HPDLFs were extracted and cultured, and the cytotoxicity of the materials was assessed using the CCK-8 assay. The effects of the materials on the metabolic activity of P. gingivalis planktonic bacteria were evaluated using an MTT reduction assay and bacterial growth curve analysis. The preventive and disruptive effects of the materials on P. gingivalis biofilm were analyzed using crystal violet staining and MTT assay. SEM was employed to observe the microscopic morphology and adhesion of bacteria. One-way ANOVA was used for intergroup comparisons, with p < 0.05 considered statistically significant. The as-prepared GO and MMT were both confirmed as single-layer two-dimensional nanomaterials. The safe concentrations of GO and MMT for human periodontal ligament fibroblasts were determined to be 80 μg/mL and 612.5 μg/mL, respectively. GO exhibited concentration-dependent antibacterial activity against planktonic bacteria. At 80 μg/mL, bacterial metabolic activity was reduced to only 7.87% of the control group ( p < 0.05), whereas MMT at its safe concentration showed no significant antibacterial effect ( p > 0.05). Moreover, GO significantly inhibited biofilm formation. The MBICs of GO and MMT were 20 μg/mL and 76.5 μg/mL, respectively, both in a concentration-dependent manner, and the trend of biofilm activity was consistent with that of biofilm biomass. Notably, the combination of GO with MBIC-level MMT effectively decreased the effective dosage of GO. The antibacterial efficacy of 40 μg/mL GO combined with MMT was equivalent to that of 80 μg/mL GO alone. SEM observations suggested that GO appeared to induce bacterial lysis and structural disruption, while MMT mainly attenuated bacterial adhesion to the surface. At safe biocompatible concentrations, GO exhibited concentration-dependent antibacterial activity against P. gingivalis in both planktonic and biofilm forms, and its inhibitory effect was accompanied by observable disruption of bacterial structural integrity. In contrast, MMT showed no direct bactericidal activity yet significantly reduced bacterial adhesion to the material surface to decrease biofilm formation. Notably, MMT enhanced the antibacterial efficacy of GO; their combination also effectively lowered the required effective concentration of GO to suppress P. gingivalis .