Enhanced antimicrobial activity of silver nanoparticles-Lonicera Japonica Thunb combo

Silver metals have long been known to possess antimicrobial properties. Recently, even the nanoparticle version of silver (AgNPs) has also been established as antimicrobials. In this study AgNPs were combined with extracts of the medicinal plant Chinese honeysuckle, Lonicera japonica Thunb. The antimicrobial activity of the AgNPs-herb was tested against pathogenic Escherichia coli CMCC44113. Using different AgNPs or herb (honeysuckle water extract or HWE) ratios in the presence of a fixed concentration of E. coli CMCC44113, potencies were found to be proportional with concentrations. The antimicrobial activities of AgNPs-HWE combo were significant enhanced, when compared with solely AgNPs or HWE. Thus, atomic force microscopic and propidium monoazide-PCR were used to probe the damages caused by AgNPs-HWE combo on the cell morphology and cell membrane integrity of E. coli. The mechanism of AgNPs-HWE combo against E. coli may attribute to AgNPs leads to cell wall lysis and damages cell membrane integrity, and thus increases the penetration of HWE into the bacterium, which results in more serious damage to bacterial cells. These findings indicated that AgNPs-herb was more potent than the AgNPs alone and holds promise for the development of nanoparticle enhanced herbal pharmaceuticals.