In the present study, selenium nanoparticles were biologically synthesized by non-pathogenic, economic and easy to handle bacterium Ralstonia eutropha. The selenium oxo anion was reduced to selenium nanoparticles in the presence of the bacterium. The bacterium was grown aerobically in the reaction mixture. An extracellular, stable, uniform, spherical selenium nanoparticle was biosynthesized. The TEM analysis revealed that the biosynthesized selenium nanoparticles were spherical in shape with size range of 40-120 nm. XRD and SAED analysis showed that nanocrystalline selenium of pure hexagonal phase was synthesized. The formation of actinomorphic trigonal selenium nanorods was also observed. A mechanism of biosynthesis of selenium nanoparticles by R. eutropha was proposed. The biosynthesized selenium nanoparticles were investigated for their antimicrobial activity against potential pathogens. Selenium nanoparticles showed excellent antimicrobial activity. The 100, 100, 250 and 100 µg/ml selenium nanoparticles were found to inhibit 99 % growth of Pseudomonas aeruginosa, Staphylococcus aureus, Escherichia coli and Streptococcus pyogenes, respectively. Similarly, the 500 µg/ml of selenium nanoparticles was found to inhibit the growth of pathogenic fungi Aspergillus clavatus. The antimicrobial efficacy of selenium nanoparticle was comparable with commercially available antibiotic drug Ampicillin.

No abstract

No abstract

SARS-CoV-2, the causative agent of COVID-19, has imposed a major public health threat, which needs effective therapeutics and vaccination strategies. Several potential candidate vaccines being rapidly developed are in clinical evaluation. Considering the crucial role of SARS-CoV-2 spike (S) glycoprotein in virus attachment, entry, and induction of neutralizing antibodies, S protein is being widely used as a target for vaccine development. Based on advances in techniques for vaccine design, inactivated, live-vectored, nucleic acid, and recombinant COVID-19 vaccines are being developed and tested for their efficacy. Phase3 clinical trials are underway or will soon begin for several of these vaccines. Assuming that clinical efficacy is shown for one or more vaccines, safety is a major aspect to be considered before deploying such vaccines to the public. The current review focuses on the recent advances in recombinant COVID-19 vaccine research and development and associated issues.

Tetragonal SnO 2 nanoparticles (15−40 nm) were synthesized according to a green biological synthesis technique using Gram-negative bacteria Erwinia herbicola followed by an annealing treatment over 425 K. The SnO 2 nanoparticles were characterized by dynamic light scattering (DLS), transmission electron microscopy (TEM), X-ray diffraction spectroscopy (XRD), and scanning electron microscopy with energy dispersive X-ray (SEM-EDX). The zeta potential of biosynthesized SnO 2 nanoparticles was 7.53 mV. A biosynthesis mechanism for SnO 2 nanoparticles was also proposed. In the biosynthesis, the bacterial protein and biomolecules served as the template for reduction and stabilization of SnO 2 nanoparticles. These biomolecules also helped in controlling SnO 2 nanoparticle size and aggregation. The SnO 2 nanoparticles exhibited excellent photocatalytic activity for photodegradation of organic dyes such as methylene blue, methyl orange, and erichrome black T. Approximately 93.3, 97.8, and 94.0% degradations of methylene blue, erichrome black T, and methyl orange were observed with biosynthesized SnO 2 nanoparticles in the photocatalytic degradation process, respectively.