Biogenic nanoselenium synthesis, its antimicrobial, antioxidant activity and toxicity

Biogenic selenium nanoparticles (SeNPs) were synthesised using the herbal extract of Triphala, and the authors assessed their antimicrobial and antioxidant activity and toxicity. Synthesised nanoparticles were confirmed through ultraviolet–visible spectroscopy and were characterised using X-ray diffraction spectroscopy. The structure, size and crystal density were evaluated through transmission electron microscopy, and the compounds responsible for the synthesis and stabilisation of SeNPs were identified using Fourier transform infrared spectroscopy. Antimicrobial activity was assessed against Streptococcus mutans, Staphylococcus aureus, Enterococcus faecalis and Candida albicans using agar diffusion, and the 2,2-diphenyl-2-picrylhydrazyl hydrate assay was used to evaluate the nanoparticles’ antioxidant potential. The toxicity of SeNPs was tested on brine shrimps. Spectrophotometry (415 nm), infrared spectroscopy (C–O, N=O, C=O) and diffraction analysis (mil-101 face-centred cubic) confirmed the synthesis of crystalline nanoparticles, and transmission electron microscopy revealed smooth spherical nanoparticles (13.5 nm). The nanoparticles exhibited a significant antimicrobial activity against S. mutans, S. aureus, E. faecalis and C. albicans and an excellent antioxidant potential in a dose-dependent manner (93% inhibition/50-µl concentration). The 100-µl concentration was as effective as commercial antimicrobials, approximately 1/10 of their concentration, and exhibited a minimal toxicity (LC₅₀ for brine shrimp at 48 h was 2 mg/10 ml). Triphala-augmented biogenic SeNPs are cost-effective, eco-friendly and efficient. They show a great potential as oral antimicrobial agents with superior biocompatibility and antioxidant properties.