Functional synergistic effects of graphene nanoribbons and surfactant stabilizers on inhibition of growth of biofilm-forming and biofilm non-forming bacteria

In this study, we investigated the antimicrobial properties of graphene nanoribbons (GNRs) synthesized via a bottom-up approach. Due to their tendency to aggregate in aqueous solutions, various surfactants were used as stabilizers. We examined the effects of GNRs in combination with commonly used surfactants-including the cationic CTAB, anionic TWEEN, and non-ionic TRITON-to evaluate their impact on GNR toxicity. A range of GNR-surfactant concentrations was tested against biofilm-forming (Escherichia coli MG1655 and Staphylococcus epidermidis DSM 20044) and non-biofilm-forming (E. coli TOP10 and S. epidermidis BH1) bacterial strains under short-term (acute) and long-term (continuous) exposure conditions. CTAB alone exhibited antibacterial effects, but a synergistic interaction between CTAB and GNRs was observed during continuous exposure, particularly against Gram-positive bacteria. The capability to form biofilms did not significantly contribute to bacterial resistance, except in E. coli MG1655, which survived at the highest concentrations of GNR-CTAB during short-term exposure. In contrast to GNR-CTAB, GNR-TWEEN, and GNR-TRITON suspensions showed no inhibitory effects on bacterial growth and, in some cases, even promoted bacterial growth. Microscopic analysis revealed bacterial cell aggregation exclusively in GNR-CTAB suspensions. These findings highlight the critical role of surfactant selection in modulating GNR toxicity and provide insights into optimizing GNRs as antibacterial agents or minimizing their environmental impact.