Evaluation of the antimicrobial activity of chitosan- and curcumin-capped copper oxide nanostructures against multi-drug-resistant microorganisms†

The emergence of multi-drug-resistant microorganisms presents a serious threat to infection control, for which new antimicrobial strategies are urgently needed. Herein, the antimicrobial activities of copper oxide nanoparticles capped with curcumin (Cur-CuO NPs) and copper oxide nanoparticles capped with chitosan (CS-CuO NPs) were investigated. They were prepared via the co-precipitation method. A total of 180 clinical ICU patients were found to have 70% Gram-negative and 30% Gram-positive isolates. Antimicrobial susceptibility testing indicated resistance of these isolates to 14 among the 21 tested antibiotics. Physicochemical properties of the curcumin-capped (Cur-CuO NPs) and chitosan-capped (CS-CuO NPs) copper oxide nanoparticles were identified using UV-vis spectroscopy, transmission electron microscopy (TEM), dynamic light scattering (DLS), zeta-potential (ζ), and Fourier transform infrared (FT-IR) spectroscopy. Cur-CuO- and CS-CuO-NPs exhibited potent antimicrobial efficacy, wherein CS-CuO NPs were found to possess a lower minimum inhibitory concentration (MIC) (3.9–15.6 μg mL⁻¹) than Cur-CuO NPs (14.5–31.2 μg mL⁻¹). Biocompatibility assay showed that Cur-CuO NPs were safer with an IC₅₀ dose of 74.17 μg mL⁻¹ than CS-CuO NPs with an IC₅₀ dose of 41.01 μg mL⁻¹. Results revealed that the Cur-CuO- and CS-CuO-NPs have the potential to be safely used as effective antimicrobial agents in clinical applications at low concentrations (6.25–12.5 μg mL⁻¹).