Abstract
Elemental selenium nanoparticles (SeNPs) are useful in medicine, environmental remediation and in material science. Biosynthesized SeNPs (BioSeNPs) by bacteria are cheap, eco-friendly and have a lower cytotoxicity in comparison with chemically synthesized ones. Organic matters were found to cap on the surface of BioSeNPs, but the functions were still not entirely clear. The purified BioSeNPs were coated in a thick layer of organic substrates observed by transmission electron microscopy (TEM). Fourier Transform Infrared (FT-IR) and quantitative detection of the coating agents showed that one gram of purified BioSeNPs bound 1069 mg proteins, 23 mg carbohydrates and only very limited amounts of lipids. Proteomics of BioSeNPs showed more than 800 proteins bound to BioSeNPs. Proteins enriched in charged amino acids are the major factor thought to govern the formation process and stabilization of BioSeNPs in bacteria. In view of the results reported here, a schematic model for the molecular mechanism of BioSeNPs formation in bacteria is proposed. These findings are helpful for the artificial green synthesis of stable SeNPs under specific condition and guiding the surface modification of SeNPs for medicine application.
Highlights
Selenium (Se) is an essential trace element in humans and many microorganisms with a broad utility in biological systems[1]
selenium nanoparticles (SeNPs) occurred in most cells when the Se (IV) concentration was elevated to 10 mM as shown by transmission electron microscopy (TEM) (Fig. 1D and E) and X-ray spectroscopy (EDX) (Fig. 1F and G)
It was interesting that most of the intracellular SeNPs were in proximity of the cell border whereas only a few SeNPs were located inside the cytoplasm (Fig. 1E)
Summary
Selenium (Se) is an essential trace element in humans and many microorganisms with a broad utility in biological systems[1]. It is of great significance to better understand the processes leading to the formation and stabilization of BioSeNPs in bacteria. This would be helpful for mass green production on an industrial scale and guiding surface modification of SeNPs for medicine application. BioSeNPs were extracted and their colloidal properties were analyzed quantitively to understand the factors governing the formation and stabilization of BioSeNPs. BioSeNPs were extracted and their colloidal properties were analyzed quantitively to understand the factors governing the formation and stabilization of BioSeNPs It suggests that intracellular organic matter especially on proteins are the capping agents and affect the surface charge of the BioSeNPs and its stability and non-specified functional but charged amino acid enriched proteins control the formation and stabilization of the selenium nanoparticles
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