Abstract
Green chemistry is generating an increasing amount of interest for the synthesis of metal nanoparticles due to the cost-effectiveness and eco-friendly nature of the plants. The green approach of nanoparticle synthesis is a better substitute for the chemical and physical methods since there is no involvement of toxic chemicals. The objective of the present research was the synthesis of silver nanoparticles (AgNPs) using bark extract of the medicinal plant Holarrhena pubescens Wall ex G. Don ( HP) and evaluating their antibacterial and antibiofilm properties against clinical isolates of P. aeruginosa. The HP-AgNPs were characterized by ultraviolet-visible spectroscopy, Fourier transform infra red, atomic force microscopy, and transmission electron microscopy (TEM). The synthesized HP-AgNPs were spherical in shape, and the average particle size as analyzed by TEM was 13.15 nm. The antibacterial potential of HP-AgNPs was evaluated by determining MIC (minimum inhibitory concentration) and MBC (minimum bactericidal concentration). The MIC was found to be in the range of 20-25 mu g/ml. Further, the interaction of AgNPs with imipenem-resistant P. aeruginosa was analyzed by TEM. The rupturing of the cell membrane and cell wall was seen at the lethal concentration, and the nanoparticles entered the cell from the several sites that caused great damage to the cell which eventually led to cell death. The antibiofilm properties of HP-AgNPs against imipenem-resistant P. aeruginosa were demonstrated by CLSM (confocal laser scanning microscopy) using propidium iodide and ConA-FITC dye. CLSM images clearly show that as the concentration of HP-AgNPs increased, the number of biofilm-forming cells decreased due to the cell death. It was also observed that AgNPs inhibit or restrict the colonization and halts the formation of biofilm. The result obtained suggested that green-synthesized HP-AgNPs have great antibacterial and antibiofilm potential and could be used as an alternative agent to treat the infection caused by imipenem-resistant P. aeruginosa.