Novel green synthesis of silver nanoparticles using carotenoid extracted from Kocuria sp.: determination of antioxidant, antimicrobial, and anti-human breast cancer activities.

In recent decades, nanotechnology has emerged as a promising field with diverse medical applications. Silver nanoparticles (Ag NPs) exhibit several biological activities. The aim of the current study was to investigate antioxidant, antimicrobial, and anti-breast cancer properties of green-synthesized Ag NPs. To achieve this, Ag NPs were synthesized using Kocuria sp., and their successful formation and physicochemical properties were evaluated using UV-vis, FTIR, XRD, DLS, zeta potential analysis, SEM, and TEM. The antioxidant capacity of Ag NPs was evaluated using a DPPH scavenging assay. The antimicrobial effects of the Ag NPs were tested on two Gram-negative bacteria (Escherichia coli and Pseudomonas aeruginosa) and two Gram-positive bacteria (Bacillus subtilis and Staphylococcus aureus) using a 96-well plate. HUVEC, MCF7, and MDA-MB-231 cells were treated with varying concentrations of Ag NPs, and cell viability, migration, and apoptosis rates were assessed using MTT, scratch, and flow cytometry assays, respectively. Additionally, qPCR was performed to analyze the expression levels of some genes involved in apoptosis, such as caspases 3, 8, and 9. Characterization techniques confirmed the successful synthesis of pure crystalline structures and spherical Ag NPs. Antioxidant and antimicrobial assays demonstrated the significant antioxidant capacity of the Ag NPs and their antibacterial properties against all tested bacteria. Moreover, in vitro studies indicated that Ag NPs effectively inhibited cell proliferation, suppressed migration, and induced apoptosis, likely owing to the upregulation of caspase 3, 8, and 9 and BCL2 downregulation genes. Our findings suggest that green-synthesized Ag NPs using carotenoids extracted from Kocuria sp. might serve as promising antibacterial and anti-breast cancer agents; however, more in vitro and in vivo investigations are required to elucidate the therapeutic potential of Ag NPs.