Phytogenic Synthesis and Characterization of Silver Metallic/Bimetallic Nanoparticles Using Beta vulgaris L. Extract and Assessments of Their Potential Biological Activities

Featured Application: The specific application of this work lies in the new avenue synthesis of nanomedicines—particularly Ag-mNPs, AgSeO₂-bmNPs, and Ag-TiO₂-bmNPs—using eco-friendly methods. These nanoparticles have shown significant potential as they can be used for potent antioxidant and antibacterial activities. The use of Beta vulgaris extract for the bio-reduction process adds to the environmentally sustainable aspect of the research. Furthermore, the antioxidant activity of the nanoparticles supports their potential medical applications beyond antibacterial therapy. Additionally, the study paves the way for future research into utilizing nature-inspired approaches for green and effective medical advancements. The synthesis of novel nanomedicines through eco-friendly protocols has been applied on a large scale with the prediction of discovering alternate therapies. The current work attained phytogenic synthesis of Ag-mNPs, AgSeO₂-bmNPs, and Ag-TiO₂-bmNPs through bio-reduction using an aqueous extract of Beta vulgaris (red beetroot). The phytochemical profile of the eco-friendly synthesized metallic/bimetallic nanoparticles was studied. The optical properties of nano-solutions were studied via UV-visible spectroscopy. The Fourier-transform infrared spectroscopy (FT-IR) spectral analyses revealed that stretching vibrations at wavenumbers 3303.81–3327.81 cm⁻¹ attributed to phenolic hydroxyl groups documented shifts in the values in this range owing to proton dissociation through the bio-reduction of the metal ions. The surface morphology and the charge of the nanoparticles were investigated using a Transmission Electron Microscope (TEM) and zeta potential analyses. The prepared nano-solutions showed lower antioxidant activity (1,1-Diphenyl-2-picrylhydrazyl (DPPH^•) and phosphomolybdate assays) than the plant extract. These results together with phytochemical analyses support the participation of the reactive species (phenolic contents) in the bio-reduction of the metal ions in the solutions through the formation of metallic/bimetallic nanoparticles. Ag-mNPs, AgSeO₂-bmNPs, and Ag-TiO₂-bmNPs showed antibacterial potentiality. AgSeO₂-bmNPs were superior with inhibitory zone diameters of 34.7, 37.7, 11.7, and 32.7 mm against Enterococcus faecalis, Staphylococcus aureus, Escherichia coli, and Salmonella enterica, respectively. Applying the Methylthiazole Tetrazolium (MTT) assay, the Ag-TiO₂ bmNPs revealed potent cytotoxicity against the HePG2 tumor cell line (IC₅₀ = 18.18 ± 1.5 µg/mL), while Ag-SeO₂ bmNPs revealed the most potent cytotoxicity against the MCF-7 cell line (IC₅₀ = 17.92 ± 1.4 µg/mL).