Green Synthesis of Copper Nanoparticles from Kiwi Peel: Antibacterial Properties and the Role of MexY Gene Expression in Pseudomonas aeruginosa Efflux Pumps.

This study presents an eco-friendly and cost-effective method for synthesizing copper oxide nanoparticles (CuO-NPs) using kiwi peel waste (KPW) via a room-temperature ultrasound-assisted cavitation process. The green synthesis approach highlights the sustainable reuse of agro-waste while offering a promising route for producing biologically active nanomaterials. The resulting CuO-NPs were thoroughly characterized using UV-Visible spectroscopy (UV-Vis), atomic force microscopy (AFM), Fourier-transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), and transmission electron microscopy (TEM). The UV-Vis spectrum revealed a characteristic absorption peak at 305 nm, confirming nanoparticle formation. XRD analysis indicated the presence of copper, oxygen, and carbon, while morphological analysis showed predominantly spherical to cuboidal nanoparticles with sizes ranging from approximately 51 nm to 62 nm. Functionally, the biosynthesized CuO-NPs exhibited potent antibacterial activity, with a minimum inhibitory concentration (MIC) of 250 µg/mL against both Gram-positive and Gram-negative bacteria. Furthermore, treatment with CuO-NPs led to a significant downregulation of the MexY efflux pump gene in Pseudomonas aeruginosa, as revealed by real-time PCR analysis. This gene suppression is associated with reduced biofilm formation, indicating that the nanoparticles can effectively disrupt bacterial resistance mechanisms. The study demonstrates that green-synthesized CuO-NPs not only possess strong antibacterial and anti-biofilm properties but also effectively inhibit MexY gene expression in multidrug-resistant bacteria. These findings underline their potential application as alternative antimicrobial agents in biomedical and environmental settings.