Actinomycetes mediated microwave-assisted synthesis of nanoselenium and its biological activities

Abstract Selenium nanoparticles (SeNPs), an essential trace element are known to be nontoxic with excellent biocompatibility and bioavailability among other selenium compounds. Considering the potential benefits as well as toxic effects of the SeNPs regarding dosage, it is important to evaluate the biomedical efficacy of the functional SeNPs with great care. The current investigation involves the synthesis of SeNPs using culture supernatant of Nocardia concava through microwave-assisted synthesis method. The formation of SeNPs was confirmed by UV-Visible spectroscopy at 570 nm. The XRD spectrum confirmed the monoclinic crystalline phase of the synthesized SeNPs. FTIR spectra depicted the possible functional groups such as hydroxyl and hydrocarbon groups involved in the reduction. EDX micrographs showed strong Se signals at 2 KeV regions. The zeta potential of the synthesized SeNPs was found to be 6.5 mV which confirms good stability in water. SEM micrograph confirmed the spherical nature of the SeNPs. Good antimicrobial efficacy was reported for Xanthomonas campestris MTCC 2286 and Vibrio harveyi MTCC 7954 with a MIC of 1.625 µg/ml and 3.25 µg/ml concentration respectively. Also, they showed strong antioxidant activity in the DPPH assay (IC50 = 31.26 µg/ml) and ABTS assay (IC50 = 35.7 µg/ml). Remarkable cytotoxic activity was observed against MDAMB 231 and U87MG cancer cells with an IC50 value of 119 µg/ml and 65.8 µg/ml respectively whereas, mild toxicity was observed in the case of HT-29 cell lines. This is the first report on the synthesis of SeNPs from Nocardia concava and specifically by a microwave-assisted method. Synthesized SeNPs displayed unique properties that can be used in diverse biomedical applications. Graphical Abstract