Increased antibacterial activity of silver nanoparticles synthesized from leaf extract of Isodon coetsa

Abstract

Application of nanotechnology for the synthesis of silver nanoparticles using plant extract can be a promising alternative to traditional chemical methods. Products of biological origin have less side effects, thus are safe for human health besides being cost-effective and pollution-free. Keeping in view this, the current work was designed for the environment- friendly production of silver nanoparticles (AgNPs) utilising Isodon coetsa acetone leaf extract. The effect of some important variables including incubation time, pH, AgNO3 concentration, temperature and volume of plant extract were examined for the optimum production of AgNPs. Synthesized nanoparticles were further characterized using atomic force microscopy (AFM), X-ray diffraction spectroscopy (XRD), and UV-visible absorption spectroscopy. In addition, the antibacterial potential of nanoparticles was also determined by agar-well diffusion method. The optimal conditions for synthesis of AgNPs achieved after 24 h of incubation at pH 9.0, 2mM AgNO3, 60°C temperature, and using 10% I. coetsa leaf extract. X-ray diffraction spectroscopy revealed that the size of the strongest peak for AgNPs was 9.5 nm, while atomic force microscopy confirmed their spherical shape with smooth surface without any pinholes or cracks. AgNPs showed excellent antibacterial action against Gram-positive and Gram-negative bacteria. The current study has contributed to the development of a simple and fast bioprocess for the synthesis of AgNPs of the appropriate size and form which also have increased antibacterial activity in comparison to crude extract. Therefore, the process of biogenically synthesised AgNPs from plants is a straightforward, commercially feasible, and environmentally benign approach that can be used in disease control while utilizing their important role as therapeutic agent for treating various ailments caused by pathogenic bacteria.