Biofabrication of Selenium Nanoparticles Using Marine Streptomyces sp. and Assessment of Its Antibacterial, Antibiofilm, Antioxidant, and In Vivo Cytotoxic Potential

In recent days, there is increasing demand for the benign production of selenium nanoparticles (SeNPs) over synthetic methods. Hence in this present study SeNPs were synthesized using the cultural supernatant of marine actinobacterium Streptomyces sp. MA4. The UV spectral analysis of synthesized SeNPs showed a characteristic peak at 290 nm. The HR-SEM analysis confirmed that the synthesized SeNPs were spherical in shape with the average diameter of 50–70 nm and EDX analysis proved that selenium exists as the major constituent of SeNPs. FTIR analysis evidenced the occurrence of peptides, amides, and aldehydes as capping and reducing agents. The synthesized SeNPs is shown to possess broad spectrum antibacterial activity against tested bacteria with the maximum zone of inhibition of 31.3 ± 0.4 mm against Pseudomonas aeruginosa. The MIC and MBC of SeNPs against P. aeruginosa were found to be 128 µg/100 µl. In the anti-biofilm assay, it was also found that biofilm formation by P. aeruginosa was inhibited by SeNPs at the concentration higher than 25 µg/ml. The antioxidant activity against DPPH free radical increases with increasing concentrations of SeNPs. Further in vivo cytotoxicity of SeNPs was tested by brine shrimp larvicidal assay that showed low toxicity with LC50 168.5 µg/ml.