Investigating the selective distribution of Streptococcus mitis biofilm by titanium dioxide and graphene oxide-based nanocomposite

Streptococcus mitis is a foundational oral colonizer that drives biofilm formation, exhibiting both protective and pathogenic characteristics depending on its growth state. To overcome antibiotic tolerance, researchers are actively developing non-bactericidal biofilm dispersion therapies that break down biofilm architecture without killing the bacteria. Maintaining the viability of these commensal strains is critical; eradicating them destabilizes the oral microbiome and invites severe secondary infections by cariogenic pathogens. In this study, a TiO 2 @GO nanocomposite was synthesized via a sol-gel assisted hydrothermal method. For the first time, this nanocomposite is applied to eradicate biofilms of the pioneer oral colonizer S. mitis through a non-lethal, interface-masking approach. The anti-biofilm activity of TiO 2 @GO nanocomposite was evaluated against oral S. mitis isolates using a crystal violet microtiter plate assay and further assessed on sterilized human tooth surfaces by field emission scanning electron microscopy. TiO 2 @GO significantly reduced biofilm formation compared with TiO 2 or graphene oxide alone, achieving up to 89% inhibition on polystyrene surfaces after 8 h and approximately 70% reduction on human teeth after 24 h of incubation. FE-SEM analysis confirmed disruption of dense biofilm architecture and extracellular matrix on treated tooth surfaces, while bacterial cells retained normal morphology, indicating limited impact on planktonic growth at optimized concentrations. This demonstrates that TiO 2 @GO nanocomposite operates via surface masking without exerting non-selective bactericidal pressure on the surrounding microbiota. These findings demonstrate that TiO 2 @GO nanocomposite can effectively inhibit S. mitis biofilm formation through a surface-active mechanism and support further exploration of nanocomposite-based approaches for targeted oral biofilm control.