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

During the last decade research have been focussed on developing simple, clean, non-toxic, cost effective and ecofriendly protocols for synthesis of nanoparticles.
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.
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.
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.
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.