Cytotoxic and antibacterial activities of biologically synthesized gold nanoparticles assisted by Micrococcus yunnanensis strain J2

In the present study the capability of Micrococcus yunnanensis J2 (isolated from Sarcheshme mine soil samples and identified by 16S rDNA sequencing) for biosynthesis of gold nanoparticles (Au NPs) was evaluated. The produced biogenic Au NPs were characterized using UV-visible spectroscopy, transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction spectroscopy (XRD), thermal gravimetric analysis (TGA), and Fourier transform infrared spectroscopy (FTIR) methods. The related TEM and SEM images of biogenic Au NPs indicated spherical shaped and well dispersed nanostructures with the average particle size of 53.8 nm. Zeta potential analysis of as-synthesized Au NPs showed a peak at -17.6 +/- 1.8 mV. The XRD profile of the biogenic Au NPs contained five peaks positioned at 2. of 38.2 degrees, 45.8 degrees, 63.7 degrees, 77.6 degrees, and 82.1 degrees due to (111), (200), (220), (311), and (222) lattice planes, respectively, which clearly indicated the crystalline structure of the obtained Au NPs. Cytotoxic activity of biologically synthesized Au NPs (assisted by MTT-based colorimetric assay) revealed IC50 (mu g/mL) of 73.6 +/- 1.9, 85.6 +/- 2.9, 63.5 +/- 2.1, 65.2 +/- 1.9, 105.3 +/- 1.7, and 88.4 +/- 2.1 against six cancer cell lines of U87, HT1080, PC12, Caco2, MCF7, and A549, respectively. However, two normal cells of 3T3 and Vero inhibited by 85% in the presence of 500 mu g/mL of the biogenic Au NPs. Evaluation of antibacterial effect of the produced Au NPs and Au3+ ions against three Gram-positive and four Gram-negative bacterial strains exhibited lower inhibitory activity of Au NPs compared to that of Au3+ ions.