Tunable anti-biofilm activity of Zn-doped CuO nanoparticles: structural, morphological, and biological insights against Gram-positive and Gram-negative bacteria

Abstract

Biofilm-associated infections represent a major challenge in healthcare due to antibiotic resistance, driving the search for effective nano-antimicrobial agents. This study presents the synthesis of Zn-doped CuO nanoparticles (Cu_1−xZn_xO, 0 ≤ x ≤ 0.5) via an eco-friendly co-precipitation method and investigates their anti-adhesive efficacy against Gram-positive Staphylococcus epidermidis S61 and Gram-negative Pseudomonas aeruginosa 2629. Comprehensive characterization (XRD, SEM, AFM, FTIR, and EDX) revealed that Zn doping refined crystallite size, altered surface morphology, and enhanced specific surface area. The anti-biofilm assays demonstrated that Zn incorporation significantly improved anti-adhesive activity against S. epidermidis, with x = 0.2 achieving >73% inhibition at 500 µg mL⁻¹. In contrast, pure CuO was most effective against P. aeruginosa, indicating a strain-dependent response linked to bacterial cell-wall structure. The anti-adhesive mechanism is attributed to nanoparticle-surface interactions, ion release, and reactive oxygen species generation. These findings highlight the potential of compositionally tunable Zn-doped CuO nanoparticles as selective anti-biofilm agents for combating healthcare-associated infections.