Commercial graphene oxides show distinct suitability for silver-nanocomposite formation and antibiofilm activity and...

Graphene oxide (GO)-silver nanocomposites are promising antimicrobial coatings for medical devices, yet differences among commercial GO sources can strongly affect synthesis and biological behavior. In this study, four commercial GO samples (B1-B4) were systematically evaluated as precursors for GO with silver nanocomposites (GOAg), focusing on physicochemical properties, antibacterial activity against Staphylococcus aureus and Pseudomonas aeruginosa, biofilm inhibition, and cytocompatibility with L929 fibroblasts. Sample B3 most closely matched the reference B4, whereas B1 showed marked deviations, lacking typical D and G Raman bands and oxygenated functional groups, as confirmed by XPS and FTIR analyses. The synthesized composites, particularly 3-BAg and 4-BAg, exhibited antimicrobial performance comparable to or exceeding that of isolated silver nanoparticles (99%, 92%, and 23% against S. aureus in the fifth dilution, respectively). These samples retained antibiofilm activity up to the third dilution, with 97% for 3-Bag and 98% for 4-Bag, corresponding to 39.06 µg·mL⁻¹ of GO and 52.5 µg·mL⁻¹ of Ag. This enhanced effect is attributed to the GO framework, which promotes uniform nanoparticle dispersion, limits silver aggregation, and increases the effective contact area with bacterial cells. Combined antimicrobial, antibiofilm, and cytotoxicity assessments showed that 3-BAg and 4-BAg achieved the lowest MIC and MBC values while preserving acceptable fibroblast viability. Overall, immobilizing silver on GO sheets improves ionic availability, stability, and bacterial interaction, while reducing cytotoxicity.