Selenium Nanoparticles: Green Synthesis and Exploitation

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. Selenium as selenite and selenate is toxic in comparison to selenium nanoparticles (SeNPs), which have no toxicity. SeNPs can be synthesized by physical, chemical, and biological methods. The bio-synthesized SeNPs are red-colored, stable structures. Different microorganisms like plants, bacteria, cyanobacteria, fungus, etc., have been used to synthesize SeNPs due to the presence of many reducing biomolecules. Parameters that govern their synthesis are reaction time, temperature, pH, and reactant concentration. Microbial synthesis of SeNPs is a two-step reduction process from SeO4−2 to SeO3−2and then to insoluble elemental selenium (Se0). These reactions are catalyzed by selenate and selenite reductases. SeNPs act as potent antioxidant, antibacterial, anti-inflammatory, chemopreventive, and chemotherapeutic agents. Conjugation of SeNPs with antibiotics enhances their anticancer efficacy. SeNPs also have applications in nanobiosensors and environmental remediation.