Preparation of antibacterial cotton wound dressing by green synthesis silver nanoparticles using mullein leaves extract

Abstract

Silver nanoparticles (AgNPs) were synthesized by a bio-reduction method using an aqueous extract of mullein leaves (Verbascum thapsus L.) functioning as reducing as well as a stabilizing agent. Various synthesis parameters such as reaction time, temperature and concentration of the extract were also studied for the synthesis of AgNPs. The so prepared AgNPs were characterized by various techniques including UV-Vis spectroscopy, X-ray diffraction, scanning electron microscopy (equipped with energy dispersive analysis of X-rays), and transmission electron microscopy. The electron microscopy images suggest the formation of polydispersed spherical AgNPs with average particle size of about 20 nm. The kinetic analysis revealed that the rate of bio-reduction of silver ions was very slow for initial 1h; however, later the reduction was fast as the development of characteristic color of AgNPs was completed within 5 hrs. This observation was concomitant with the appearance of the surface plasmon absorbance peak at ~ 430 nm. Further, these nanoparticles were used for the treatment of wound dressings by the exhaustion method. The so developed wound dressings showed good antibacterial activity against a gram positive bacterial strain Staphylococcus aureus.