Gingerol-functionalized zinc oxide nanoparticles enhance antimicrobial and antibiofilm activities against two types of multidrug-resistant pathogenic bacteria

The rapid increase in antibiotic resistance among major bacterial pathogens, such as Pseudomonas aeruginosa and Staphylococcus aureus , has emerged as a significant global health challenge. In this study, a Gingerol-functionalized zinc oxide nanoparticle formulation (ZnO NPs@Gingerol) was synthesized and characterized, and their antimicrobial performance against these two clinically important bacteria was assessed. Successful ZnO NPs@Gingerol formation was confirmed through multiple analytical techniques, including FTIR, XRD, EDX, and TEM analysis. Antimicrobial evaluation against P. aeruginosa and S. aureus was conducted using standardized disc diffusion and broth microdilution methods. Additionally, their antibiofilm potential was investigated through microplate assay, along with analysis of their effect on the transcription of biofilm associated genes. Structural analysis showed that the synthesized ZnO NPs@Gingerol possessed a quasi-hexagonal morphology, uniform dispersion, and low aggregation, with an approximate particle size of 10 nm. The nanocomposite exhibited enhanced antibacterial activity, with minimum inhibitory concentration (MIC) values ranging from 128–256 µg/mL against P. aeruginosa and 256–512 µg/mL against S. aureus , representing a four-fold improvement compared with free Gingerol. Furthermore, it inhibited biofilm formation by 60–75%, reduced viable bacterial counts in established biofilms by 2.55–3.2 log 10 CFU/mL ( P < 0.001) and downregulated the expression of biofilm-associated genes by more than 58% in P. aeruginosa and 62% in S. aureus ( P < 0.001). Checkerboard assays demonstrated synergistic interactions between ZnO NPs@Gingerol and both gentamicin and ciprofloxacin, with fractional inhibitory concentration index (FICI) values ranging from 0.19–0.37 and 0.125–0.19, respectively ( P < 0.05). Cytotoxicity evaluation using NIH-3T3 fibroblasts maintained > 85% viability at 200 µg/mL. Collectively, these findings suggest that ZnO NPs@Gingerol is a promising adjunctive antimicrobial strategy for the treatment of multidrug-resistant planktonic and biofilm-associated infections caused by P. aeruginosa and S. aureus .