In vitro antimicrobial and in vivo wound healing effect of actinobacterially synthesised nanoparticles of silver, gold and their alloy

The therapeutic use of metal and alloy nanoparticles is claimed to have reduced side effects and enhanced curative activity as compared to its ionic counterpart. With this view, the present study focused on the synthesis of silver (Ag), gold (Au) and silver/gold (Ag/Au) nanoparticles (NPs) by using actinobacterial metabolites as a reducing agent for enhanced in vitro antimicrobial and in vivo wound healing activities. Physico-chemical parameters of the synthesised nanoparticles were systematically assessed by using Xray based spectroscopic, zeta potential, dynamic light scattering (DLS), atomic and electron microscopic analysis. The average sizes of the AgNPs, AuNPs and Ag/AuNPs were found to be 30.5 nm, 14.5 nm and 41.5 nm respectively. The synthesized AgNPs and Ag/AuNPs showed better antibacterial activity on Gram negative bacterial pathogens (Escherichia coli, Pseudomonas aeruginosa and Aeromonas hydrophila) than Gram positive bacterial pathogens. A Minimum Inhibitory Concentration (MIC) value of 6.25 mu g ml(-1) was observed for E. coli, P. aeruginosa and Candida albicans. AgNP and Ag/AuNP based ointments of about 10% concentration heal (100%) the excision wound within 19 and 21 days in contrast with standard ointment. Further, the complete healing process was evaluated by histopathological analysis, and estimation of tensile strength, inflammatory cytokines (IL-6, TNF alpha, IL-10) and collagen constituents (hexosamine, hydroxyproline and hyaluronic acid). Metal and alloy nanoparticle use may provide a new and effective therapeutic direction for achieving development of novel antimicrobial drugs and scarless wound healing in clinical practice.