Characterization of Effective Parameters on the Synthesized Gold Nanoparticles and Investigating their Antimicrobial Activities Using Aqueous Extract of Hibiscus sabdariffa L.

Background: During the last decade research have been focussed on developing simple, clean, non-toxic, cost effective and ecofriendly protocols for synthesis of nanoparticles. Objective: The current study aim to characterization and biosynthesis of gold nano particles (Au NPs) using calyx aqueous extract of Hibiscus sabdariffa L. and study of their antimicrobial activity. Methods: Gold nano particles (AuNPs) were biosynthesized by using HAuCl4.3H2O and the calyx aqueous extract of Hibiscus sabdariffa L. In order to gain the best AuNPs with a uniform shape and size, parameters affecting on synthesis such as: volume of plant extract, pH of the reaction, concentration of HAuCl4.3H2O solution, time of reaction were investigated and optimized by UV-Vis spectrophotometry. Moreover, transmission electron microscopy (TEM) and X-ray diffraction (XRD) were used for further characterization of the nanoparticles. Finally, the antibacterial properties of gold nanoparticles were evaluated by disc diffusion method. Results: The results of transmission electron image identified the formation of spherical nanoparticles with a size range of 5-10nm. A sharp peak with a maximum absorbance of 570nm was observed which is the characteristic wavelength of gold nanoparticles. The highest inhibition were obtained with the gold nanoparticles against Hafnia alvei bacteria. Conclusion: In this study, the gold nanoparticles synthesized by calyx aqueous extract of H. sabdariffa L. and they have relatively good antibacterial activity against Gram-negative bacteria