Biosynthesis of silver nanoparticles by the cell-free extracts of Mariannaea sp. HJ and their antimicrobial characteristics research

Abstract:

[Objective] Due to their unique antibacterial activity, silver nanoparticles (AgNPs) have attracted great attention recently. And it is said that AgNPs are extensively antibacterial agents which have strong inhibition and toxic effects on dozens of pathogenic microorganisms. Compared with traditional synthetic methods, biosynthesis way has the advantages of mild reaction conditions and environmental-friendliness and is becoming a hot research topic. [Methods] In this study, we have used the cell-free extracts of fungal Mariannaea sp. HJ to synthesize AgNPs. The conditions for synthesis and the antibacterial activity were also investigated. [Results] Study has shown that the cell-free extracts of 350 mg/L, AgNO₃ 5 mmol/L and pH 7.0 were the optimal synthesis conditions for this reaction. Transmission Electron Microscope (TEM) images showed that the as-synthesized AgNPs were mainly spherical and pseudo spherical with good dispersibility. Diffraction of x-rays (XRD) analysis indicated that the crystal structure of AgNPs were face-centered cubic. The Fourier Transform Infrared Spectrometer (FTIR) analysis results suggested that the hydroxyl, carboxyl and other functional groups in the extracts might have played a functional role in the reduction or stabilization process. Besides, it has been verified that the AgNPs synthesized under the optimal experimental conditions had good antibacterial activity against both Gram-negative bacteria Escherichia coli BL21 and Gram-positive bacteria Arthrobacter sp. W1. [Conclusion] In brief, the cell-free extracts of Mariannaea sp. HJ could greenly synthesize spherical AgNPs with uniform size and good dispersion. The synthesized AgNPs might have potential research value in antibacterial advances.