Biogenic Selenium Nanoparticles from Coleus amboinicus and Solanum trilobatum Extracts: Synthesis, Characterization and Comparative Biomedical Applications

Green synthesis of selenium nanoparticles (SeNPs) using plants offers ecofriendly means to produce biocompatible and bioactive nanomaterials for medicinal purposes. Coleus amboinicus and Solanum trilobatum species have significant phytochemical properties, but their efficacy for the synthesis of SeNPs has not been compared. In the current study, aqueous extracts of these plants were used to reduce sodium selenite to produce SeNPs. Several characterization techniques, including UV–Vis spectroscopy, FTIR, XRD and SEM, were used for characterization of the synthesized nanoparticles. DPPH assay was used to determine antioxidant activity of the SeNPs and MIC and MBC assays were performed to assess antibacterial activity of the SeNPs against clinical Staphylococcus aureus strains. Excellent crystalline and spherical nanoparticles with average sizes ranging from 70 to 100 nm were obtained from both extracts. The FTIR technique indicated that various functional groups of the plant extracts contributed to nanoparticle stabilization. At a concentration of 100 µg/mL, C-SeNPs displayed greater DPPH scavenging capability, around 81%, in comparison to S-SeNPs, which showed around 77%. On the other hand, S-SeNPs exhibited a higher antibacterial activity against S. aureus strains due to larger inhibition zones as well as better MIC and MBC results than C-SeNPs. This is evidence of the significant role that phytochemicals play in the biological activity of SeNPs. Thus, while C-SeNPs were able to achieve better antioxidant performance, S-SeNPs showed stronger antibacterial properties.