Biosynthesis of selenium nanoparticles by using the green microalga chlamydomonas reinhardtii

Selenium nanoparticles (SeNPs) have attracted tremendous attention of material scientist owing to their high biological activity and low toxicity. Amorphous selenium nanoparticles have demonstrated unique photoelectric, semiconducting and anti-cancer properties. The present study depicts the bioproduction of SeNPs using resources of the unicellular, green microalga Chlamydomonas reinhardtii (CR) via an easy, single-step process. This was done either using the whole living cultures of CR or the harvested supernatant. This microalga was grown for 3 weeks in Bold's Basal Medium (BBM), incubated at ~23 °C with a photoperiod of 16 h light / 8 h dark. To evaluate the feasibility of Se-NPs production by CR, three precursors of selenium were introduced to the flasks at a final concentration of 10-2 M: selenium tetrachloride (SeCl4), selenous acid (H2SeO3) and sodium selenite (Na2SeO3). Most notorious results were obtained using selenous acid (H2SeO3). This was confirmed by the change in color from green to orange-red, the presence of an absorption band ~500-600 nm using UV-Vis spectroscopy and the presence of spherical NPs with an average diameter of 66 nm, using transmission electron microscopy (TEM). Moreover, this process resulted to be light-dependent.