Bacterial Nanocellulose Functionalized with Graphite and Niobium Pentoxide: Limited Antimicrobial Effects and Preserved Cytocompatibility

Chronic wounds remain locked in persistent inflammation with high microbial burden, demanding dressings that suppress infection without sacrificing biocompatibility. Bacterial nanocellulose (BNC) is an attractive matrix due to its biocompatibility, nanofibrillar architecture, and moisture retention, but it lacks antimicrobial activity. Here, we engineer BNC membranes post-functionalized with functionalized graphite (f-Gr; predominantly graphitic with residual surface groups) and/or niobium pentoxide (Nb₂O₅), and evaluate four groups: BNC (matrix control), BNC/Nb₂O₅, BNC/f-Gr, and BNC/f-Gr/Nb₂O₅. Physicochemical analyses (Raman and Voigt fitting, FTIR-ATR, XRD, and SEM) confirm a graphitic carbon phase and physical incorporation of the modifiers into the BNC network, with a noticeable shift in the hydration/polarity profile-more evident in the presence of f-Gr. In standardized microbiological assays, BNC/f-Gr promoted a moderate, contact-dependent reduction in bacterial proliferation, particularly against <i>Staphylococcus aureus</i>, whereas BNC/Nb₂O₅ behaved similarly to pristine BNC under the tested conditions. The combined f-Gr/Nb₂O₅ formulation showed an intermediate antimicrobial response, with no clear synergy beyond f-Gr alone. Cytotoxicity assays indicated cytocompatibility for BNC, BNC/f-Gr, and BNC/Nb₂O₅; the combined group displayed a slight reduction that remained within acceptable limits. Overall, BNC/f-Gr emerges as the most promising antimicrobial dressing, while Nb₂O₅ did not significantly enhance antimicrobial performance under the tested conditions and warrants further optimization regarding loading and distribution.