Screening of cyanobacterial strains for the selenium nanoparticles synthesis and their anti-oxidant activity

Selenium (Se) is a crucial trace element required by all living organisms and its deficiency as well as excess is known to cause many diseases. Se substitutes when consumed in higher concentration cause toxicity. Therefore, research is now being focused to overcome the adverse effects of high Se doses. One possible way is to use them in form of Selenium nanoparticles (SeNPs). However, SeNPs synthesized through physical and chemical methods also show toxicity. Biologically synthesized SeNPs due to their lesser toxicity emerged as an alternative. Like plants, bacteria and other organisms, cyanobacterial extracts also have the ability to reduce the metal ions into nanoparticles due to the presence of many reducing biomolecules. The present study envisages screening of 20 cyanobacterial extracts for SeNPs synthesis based on time taken and particle size. The obtained synthesis time was in between two to five days and the range of SeNPs size was in between 11.8 to 60 nm. Synthesized SeNPs were characterized by UV-Vis spectroscopy, Scanning electron microscopy and Energy dispersive X-ray spectroscopy (EDX). Further, the anti-oxidant activities of best five cyanobacterial strains (Anabaena variabilis NCCU-441, Arthrospira indica SOSA-4, Gloeocapsa gelatinosa NCCU-430, Oscillatoria sp. NCCU-369, Phormidium sp. NCCU-104) were tested by the DPPH and SOR scavenging assays. The SeNPs synthesized by Arthrospira indica SOSA-4 showed the best anti-oxidant activity with IC50 = 81.67 +/- 0.77 mu g/ml (SOR) and 73.94 +/- 1.53 mu g/ml (DPPH).