Sustainable Ag–Cu bimetallic nanozymes derived from Juglans regia husk exhibit multifunctional catalytic, antimicrobial, and antioxidant activities

The rapid emergence of multidrug-resistant microorganisms, oxidative stress, and heavy metal pollution necessitates the development of sustainable and efficient therapeutic agents. Nanozymes, as enzyme-mimicking nanomaterials, offer high stability and tunable catalytic activity. In this study, we report a rapid, green, and cost-effective strategy for synthesizing multifunctional Ag-Cu alloy-like nanozymes using the aqueous extract of the green husk of Juglans regia (walnut), an abundant agricultural byproduct. Comprehensive physicochemical characterization confirmed the formation of spherical, crystalline Ag-Cu nanozymes with a uniform elemental distribution and an average core size of ~ 17 nm. The phytochemicals from the extract served as both producing and capping agents, ensuring colloidal stability and enhancing catalytic efficiency. The synthesized nanozymes exhibited robust peroxidase- and oxidase-like activities with favorable kinetic parameters. The nanozymes demonstrated optical stability, which serves as a key indicator of their structural integrity. Beyond their catalytic performance, the Ag-Cu nanozymes displayed broad-spectrum antimicrobial efficacy against Gram-positive and Gram-negative bacteria, including multidrug-resistant microorganism strains, as well as significant antifungal activity against Candida albicans and mature biofilms. The antioxidant capacity of the nanozymes was also evaluated, revealing radical scavenging activity attributed to surface-bound biomolecules and the intrinsic redox properties of the bimetallic core. The enhanced biological and catalytic performance of the Ag-Cu nanozymes, compared to monometallic counterparts, suggests a synergistic effect arising from their alloy-like structure and nanoscale dimensions. This work highlights the potential of transforming agricultural waste into high-performance nanozymes with promising applications in biomedicine, environmental remediation, and catalysis.