Eco-friendly biosynthesis of manganese oxide-silver bimetallic nanoparticles using Cucumis melo peel extract: characterization, antioxidant, antimicrobial, and antiviral activities

Abstract The employment of plant extracts for green production of bimetallic nanoparticles (BNPs) has gotten significant consideration because of its cheap, ecological, single–step, and easily scalable procedures. This methodology enables the manufacture of biocompatible nanoparticles (NPs) with improved activity. In this study, an environmentally friendly approach was utilized to biosynthesize manganese oxide–silver BNPs (MnO–Ag BNPs) using Cucumis melo ( C. melo ) peel extract (CPE), which served as the source of the required reducing and stabilizing materials. Several spectroscopic analytical methods, including ultraviolet–visible (UV–vis) spectroscopy, Fourier transform infrared (FTIR) spectroscopy, energy–dispersive X–ray (EDX) spectroscopy, X–ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM), were applied for careful confirmation and characterization of successful MnO–Ag BNPs assembly. This work introduces a novel green route employing CPE for MnO–Ag BNPs synthesis, providing distinct phytochemical efficiency and multifunctional bioactivity compared with previously reported plant–based systems. The biosynthesized MnO–Ag BNPs bacterial inhibitory capability as well as free radical scavenging effect were evaluated. Also, human kidney normal epithelial–derived cells (Vero cell line CCL–81) was employed for assessment of the cytotoxic outcome of MnO–Ag BNPs at various concentrations. Regarding the elemental composition, the manganese (Mn) and Ag contents were detected by the UV–vis, XRD, and EDX studies with consequent validation of MnO–Ag BNPs biosynthesis. The range of the assessed BNPs size was 2 to 10 nm with average diameter of 5.8 ± 1.7 nm and an average area of 22.7 nm 2 . Analysis based on EDX technique revealed the presence of Mn and Ag metals with 23.7–46.6% of the atomic percentages and 32.2–28.0% of the weight percentages, respectively. The biosynthesized NPs showed strong free radical scavenging, achieving 85–90% inhibition at higher concentrations. The cytotoxic activity findings indicated no significant harmful effects, at concentration range of 31.25–250 µg/mL, on Vero cell line. Additionally, the viability of the tested cell line infected with herpes simplex virus type–1 (HSV–1) significantly increased from 43% (untreated) to 78–99% when treated with 125 µg/mL MnO–Ag BNPs and acyclovir, respectively. Moreover, the inhibition rates achieved against the tested virus were 73% for MnO–Ag BNPs and 99% for acyclovir. These outcomes highlight the potential of MnO–Ag BNPs as promising candidates for biomedical and antiviral applications. Graphical abstract