Green synthesis of silver nanoparticles using Moringa oleifera and its efficacy against gram-negative bacteria targeting quorum sensing and biofilms

Abstract

AbstractGram-negative pathogenic bacteria are the leading cause of high morbidity and mortality in humans globally. The majority of such pathogens has gained the status of multidrug resistance and requires the development of new anti-pathogenic agent. Moringa oleifera is a widely distributed and quickly proliferating medicinal plant, making it an easy source for extracting bioactive components. It is rich in bioactive compounds which can act as stabilizing and reducing agents during the synthesis of silver nanoparticles. It is well-recognized for its several medical benefits, including antibacterial action. As a result, it is an excellent option for synthesizing AgNPs with improved antibacterial characteristics. Considering the above properties, less explored Moringa oleifera was used for the green synthesis of nanoparticles. Targeting biofilms and virulence factors of Gram-negative bacteria by green synthesized metal nanoparticles is an alternative approach to combat antimicrobial resistance. Silver nanoparticles (MO-AgNPs) synthesized using Moringa oleifera leaf (MOL) extract were characterized using Ultraviolet–visible spectroscopy (UV–vis spectroscopy), Fourier-transform infrared spectroscopy (FTIR), Scanning electron microscopy-energy dispersive X-ray analysis (SEM–EDX), Transmission Electron Microscopy (TEM), and X-Ray Diffraction analysis (XRD). The absorption spectra of silver nanoparticles showed a band of absorption near 440 nm, associated with spherical silver nanoparticles. At sub-minimum inhibitory concentrations (sub-MICs), the MO-AgNPs inhibit the Quorum Sensing-mediated virulence factors and biofilm formation against three Gram-negative bacteria (Escherichia fergusonii, Serratia marcescens, and Chromobacterium violaceum). QS-mediated virulence factors in test bacteria were reduced by 80.67% (violacein), prodigiosin production (77.45%), exoprotease activity (76.02%), and swarming motility (86.5%). MO-AgNPs also demonstrated broad-spectrum antibiofilm activity against test bacteria, ranging from 77.95 to 82.4% inhibition. Microscopic analysis of biofilms showed significant structural change and inhibition. Our results demonstrate appreciable in vitro activity of MO-AgNPs against the selected pathogens, which could be used as an alternative therapeutic agent for treating infection caused by drug-resistant bacteria and preventing biofilm development by bacteria on medical devices and other surfaces. Graphical abstract