Comparative analysis of metal nanoparticles synthesized from Hibiscus rosa-sinesis and their antibacterial activity estimation against nine pathogenic bacteria

Abstract

Objective: This study demonstrates a simple, cost-effective protocol for biosynthesis of stable silver nanoparticles (AgNPs) and gold nanoparticles (AuNPs) from Hibiscus rosa-sinesis and their comparison by applying antibacterial activities against nine pathogenic bacterial species. Methods: AgNPs and AuNPs were biosynthesized from H. rosa-sinesis. The antibacterial activities of biosynthesized AgNPs (bio-AgNPs) and biosynthesized AuNPs (bio-AuNPs) were evaluated against 9 pathogenic bacterial species Pseudomonas aeruginosa, Bacillus subtilis, Micrococcus luteus, Staphylococcus aureus, Staphylococcus epidermidis, Enterobacter aerogenes, Escherichia coli, Streptococcus pneumoniae, Aeromonas hydrophila by the agar disc diffusion method. Results: Biological synthesized AgNP/AuNPs were characterized by an ultraviolet-visible (UV-Vis) spectrophotometer, Fourier transform infrared spectroscopy (FTIR), and transmission electron microscopy (TEM). The existence of silver and gold ions in the extracts was conformed (primary confirmation) through UV-Vis and the maximum plasmon peak was observed at 402 and 530 nm of bio-AgNPs and bio-AuNPs, respectively. Bio-AgNPs were obtained in 13.01-28.14 nm size range, whereas bio-AuNPs were in 6.32-18.19 nm size range after analysis of TEM images. The results of FTIR spectra indicate that the bio-AuNPs were bound to amine groups and bio-AgNPs to carboxylate ion groups. The antibacterial activities of AgNP/AuNP, the zone of inhibition significantly increased with the increases of concentrations of bio-AgNPs in all pathogenic bacterial species except in the case of S. epidermidis at 50%, Streptococcus aerogenes and A. hydrophila at 70%, whereas in the case of bio-AuNPs antibacterial activities were displayed only against B. subtilis at 20% and 100% concentration. Conclusion: This study suggests that AgNPs exhibits outstanding antibacterial activity against pathogenic bacteria as compared to AuNPs synthesized from H. rosa-sinensis leaf extract and insights to their potential applicability as an alternative antibacterial agent in microbial and human health system to reduce the resistance ability of pathogenic bacteria.