To evaluate antimicrobial property of silver nanoparticles against MRSA we determined the minimum inhibitory concentration (MIC). To determine MIC different volumes of synthesized silver nanoparticles (5, 10, 15, 20, 25, 30, 35, 40, 45 and 50 μL) and MRSA culture (maintained selleck inhibitor at 106 CFU/ml) were added in to lactose broth medium and was incubated at 37 °C for 18 h. The MIC was determined by measuring the optical density at 625 nm. The synergistic effect of silver nanoparticles with antibiotics has proven to be
beneficial17 this effect against MRSA was determined by disk diffusion method. To assess the synergistic effect, each standard antibiotic disk was impregnated with 30 μL of freshly prepared silver nanoparticles, and then these disks was used in antibacterial activity assays. A number Akt inhibitor of approaches are available for the synthesis of silver nanoparticles, e.g., chemical synthesis, radiation-assisted synthesis, electrochemical sonication and biological synthesis.18 Among these methods, biological synthesis are not only a good way to fabricate benign nano materials, but also reduce the use of substances hazardous to human health and the environment. Non toxic biological synthesis of silver nanoparticles using 5 days old biomass of Aspergillus flavus in 9 h was reported by Vigneshwaran et al 9 Similarly Binupriya et al synthesized silver nanoparticles using 3 days old R. stolonifer biomass within 72 h. 10 In this study, we synthesized
silver nanoparticles
in 20 min using S. coelicolor pigment (actinorhodin) by photo-irradiation method. Compared with the above biological methods our synthesis is rapid. Moreover, it is a bio-based synthesis so; it is advantageous over other methods, in being non toxic. To best of our knowledge this is the first report on synthesis of silver nanoparticles using S. coelicolor pigment by photo-irradiation. The actinorhodin produced by S. coelicolor was used for the synthesis of silver nanoparticles ( Fig. 1b). For the synthesis, 15 ml AgNO3 (10−3 M) solution was treated with 1 ml actinorhodin and the solution was exposed to sun light. A color change from colorless to brown Sclareol took place within a few minutes indicating the formation of silver nanoparticles. The solution mixture also kept in dark (used as control). No change in color was observed indicating no synthesis of silver nanoparticles. The synthesis of silver nanoparticles was preliminary confirmed by color change caused due to surface plasmon resonance of silver nanoparticles in the visible region.19 The absorbance intensity of the brown color increased steadily as a function of reaction time. The absorption maximum between 400 and 450 nm (Fig. 2a) clearly indicates the formation of silver nanoparticles. The crystalline nature of the synthesized nanoparticles was analyzed by X-ray diffraction. Fig. 2b shows a representative pattern of the synthesized nanoparticles after the reduction of AgNO3.