Green synthesis, characterization and functional validation of bio-transformed selenium nanoparticles

Selenium, an essential micronutrient with potent anticancer and antioxidant properties, the inorganic form of selenium is highly toxic, while organic and elemental nanoforms are more bioavailable and less toxic and have gained attention owing to their dietary and clinical relevance. This study aims to optimize conditions for the biosynthesis and production of elemental selenium nanoparticles for selenium supplements using marine microalgae, Nannochloropsis oceanica CASA CC201. The 10 mM precursor solution treated with 1 % of the algal extract (10:1 ratio of precursor and algal extract, respectively) was shown to be the optimal concentration for synthesizing highly stable selenium nanoparticles with a size of 183 nm and a zeta potential of -38.5 mV. AFM and TEM analysis suggest that the spherical-shaped nanoparticles with smooth surfaces were polydispersely distributed. The nanoparticles are well characterized using various analytical and advanced techniques, including Raman spectroscopy and X-ray photoelectron spectroscopy. FT-IR analyses reveal the presence of microalgae proteins and peptides as stabilizing and fabricating agents of Se-NPs to further understand the mode of bioreduction. The synthesized elemental nanoform (Se⁰) has been validated for its biological functions, showing enhanced radical scavenging activity (74 % in a concentration-dependent manner). Subsequently, algal-mediated selenite reduction and nanoparticle synthesis is an eco-friendly, non-toxic, and sustainable method for the large-scale production of highly stable Se-NPs for niche applications as dietary and feed supplements.