Abstract
Bacteriogenic synthesis of metal nanoparticles is ecofriendly and greatly influenced by physico-chemical reaction parameters with respect to shape and size. Thus, present work aimed to synthesize and optimization of bacteriogenic gold nanoparticles (AuNPs) and study their antioxidant activity. Acinetobacter sp. cells were able to synthesize AuNPs, when challenged with tetra-chloroauric acid (HAuCl4). By physicochemical optimization, maximum synthesis was obtained with 72 h old culture using 2.1 × 109 CFU/ml cell density. Whereas, pH-7 is suitable for AuNPs synthesis. HAuCl4 concentration (0.5 mM) enhanced the formation of monodispersed and spherical nanoparticles (15 ± 10 nm). At 37°C temperature, Acinetobacter sp. released nanoparticles in supernatant. From characterization, AuNPs were found to be crystalline in nature with negative surface charge. AuNPs showed up to 86% different radical scavenging ability, exhibiting antioxidant activity. In conclusion, spherical AuNPs can be synthesized using Acinetobacter sp. through physicochemical optimization. This is the first report of antioxidant activity exhibited by monodispersed bacteriogenic AuNPs synthesized using Acinetobacter sp.
Highlights
Biological methods of synthesis of nanoparticles are ecofriendly with easy scale up processes (Makarov et al, 2014)
All isolates of Acinetobacter spp. screened for synthesis of AuNPs, showed positive result when cell suspension was challenged with 1 mM HAuCl4 (Figure 1)
Acinetobacter spp. isolated from rhizosphere are known to synthesize silver and platinum nanoparticles (Gaidhani et al, 2013; Singh et al, 2013). This is the first report on synthesis of AuNPs using biomass Acinetobacter spp., having plant growth promoting properties, isolated from wheat rhizosphere soil (Sachdev et al, 2010)
Summary
Biological methods of synthesis of nanoparticles are ecofriendly with easy scale up processes (Makarov et al, 2014). Acinetobacter spp. are isolated from sewage have ability to synthesize polyhedral gold nanoparticles on optimization of physiochemical parameters (Wadhwani et al, 2014). DPPH Scavenging Assay Synthesized nanoparticles were separated from cells by sonication and centrifuged at 6,000 rpm for 5 min to get rid of cell residues. The experiment was performed in triplicate and value is expressed as mean ± s.d. H2O2 Scavenging Assay In this assay different concentrations of 1.5 ml AuNPs (25– 150 μg/ml) was first mixed with 0.25 ml ammonium ferrous sulfate (1 mM). H2O2 Scavenging Assay In this assay different concentrations of 1.5 ml AuNPs (25– 150 μg/ml) was first mixed with 0.25 ml ammonium ferrous sulfate (1 mM) To this mixture, 0.0625 ml of 5 mM H2O2 solution was added and incubated for 5 min in dark at RT.
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