Due to considerable impact on day-to-day life through superior functioning of energy, medicine, electronics, sensors and space industries young researchers are being attracted towards nanotechnology/biotechnology field. Selenium (Se) is acting as an essential element in most of the organism and beneficial nutrient in higher plants. Se nanostructures (NSs) i.e. nanospheres or particles (NPs) and nanowires (NWs) have unusual properties compared to their bulk counterparts. It has seven-fold lower toxicity than its other biologically utilizable materials. Several physical & chemical methods are being applied for the synthesis of Se NSs, but development of eco-friendly routes is of considerable importance towards biological applications. Recently microorganisms are being reported for the synthesis of Se NSs by reduction of oxyions in anaerobic and aerobic environments. This review briefly proposes the recent developments in the microbial synthesis, characterization, synthesis mechanism of Se NSs along with non-biological (solar, sensor, photocatalysis etc.) and biological (anticancer, antioxidant, antiprotozoal etc.) applications. Advantages of Se NSs synthesized using green approaches, over commonly used, are explored.

Presently most bacteria are becoming antibiotic resistant. Due to this there is a deficiency of potent antibiotics, therefore we have to preserve and improve the efficiency of existing antibiotics by mitigating the side effects. Enrofloxacin (EFX) is an important antimicrobial used in veterinary practice but it is known to exert immune suppression antioxidant stress. In the present study, we report on: (a) the biosynthesis of selenium nanoparticles (Se NPs), and (b) their protective effect in reducing adverse effects of EFX on broiler chicken. A potent bacterial strain, isolated from farm soil, has been identified as Pantoea agglomerans (GenBank: KU500622). It tolerates a high concentration of selenium dioxide (9 mM) and produces Se NPs under aerobic conditions. The obtained Se NPs are amorphous in structure and spherical in shape with sizes of less than 100 nm. The activity of cellular, humoral immune response and enzymatic and non-enzymatic antioxidants, has significantly been decreased as a result of EFX treatment. We investigated that Se NP supplementation greatly restores these values towards the control, and to even higher than those of the control. Adverse effects of EFX are prevented by simultaneous exposure to Se NPs (0.6 mg per kg of feed) in the diet of poultry chicken.

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A rapid synthesis of stable and smaller sized Se NPs was achieved in tryptic soya medium maintained at pH ∼9, temperature ∼50 °C, and a 9 mM Se oxyion concentration.

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