Interaction of biosynthesized gold nanoparticles with genomic DNA isolated from E. coli and S. aureus

In the present study we have synthesized gold nanoparticles by using the broth of Citrus limon. The process is eco friendly, simple and cost effective. We expect that the natural citric acid present in the fruit is responsible for synthesis of gold nanoparticles. A simple reaction mechanism has been proposed based on the results obtained from FTIR. The synthesized nanoparticles have been characterized using UV- Visible spectrophotometer, FESEM, Bio TEM and XRD. The time taken for synthesis is around 4 hours. The nanoparticles are found to be stable even after 3 months of storage under refrigerated condition. Particles are well dispersed and in the size range of 40-70 nm. Optimization study has also been done under different pH and varying concentration of gold nanoparticles. A pH of 4 with 1 mM gold salt is found to be optimum for synthesis of gold nanoparticles by this route. Particles synthesized under the above condition were taken to find their interaction with isolated genomic DNA of E. coli and S. aureus. Visual observation by running the agarose gel electrophoresis confirmed the binding of nanoparticles to the isolated DNA of both the organisms. Bio TEM images also showed the slight increase in size of the particles as well as severe aggregation following attachment with the isolated genomic DNA. In case of E. coli, the attachment is seen to be influenced by increasing concentration of nanoparticles (1.6-8.0 μg/ml) as well as increasing time of incubation (5-25 mins).