Chitosan-capped CuO nanoparticles: a comprehensive, comparative study of their broad-spectrum antibacterial efficacy

Antibacterial efficacy of chitosan-capped copper oxide nanoparticles (CuO–CS NPs) was evaluated against the Gram-negative bacteria (E. coli) and Gram-positive bacteria (B. subtilis). Comparative antibacterial activity evaluation was performed for CuO–CS NPs, nano Cu(OH)_2, nano silver, CuO, and CuSO₄.5H₂O salt. Miles and Misra method and the spread plate CFU count method were used to enumerate cell counts for antibacterial activity evaluation. The spread plate colony forming unit (CFU) count method is preferable because of its reliability and accuracy. The minimum bactericidal concentration (MBC) of CuO–CS NPs were determined to be 2 µg/ml for E. coli and 12.5 µg/ml for B. subtilis. The values were comparable to those obtained for AgNPs. Moreover, in kinetic study these NPs showed the ability to decontaminate 2 × 10⁵ CFU/ml of E. coli within 2 h at a concentration of 10 μg/ml and 3 × 10⁵ CFU/ml of B. subtilis within 4 h at a concentration of 20 μg/ml. The potential application of synthesized CuO-CS NPS as an effective antibacterial nanocoating on fabrics was also demonstrated by using both qualitative and quantitative test methods.