Immobilization of silver nanoparticles with gum of Moringa oleifera for effective antibacterial activities against human disease-causing bacterial species

Abstract

The misuse of antibiotics generates resistant bacterial strains that are extremely dangerous and pose a serious threat to global health systems. This global issue needs a rapid and urgent alternative to control the growth of resistant strains. In this study, a novel strategy was adopted to suppress the growth of resistant pathogens. Here, an immobilization approach was applied using silver nanoparticles (AgNPs) and gum of medicinally important Moringa oleifera. In many studies, the gum and AgNPs alone have proven antibacterial activities. Here, the differential concentrations of AgNPs were immobilized with gum of M. oleifera to investigate its potential against highly resistant pathogens. Immobilization is a powerful technique that is commonly used in pharmaceutics for controlled reactivity and emulsification. The immobilized AgNPs displayed promising activities against highly resistant B. subtilis (23.6mm, 50 µL:200 µL), E. coli (19.3; 75 µL:200 µL), K. pneumoniae (22 mm; 200 µL:200 µL), P. mirabilis (16.3 mm; 100 µL:200 µL), P. aeruginosa (22 mm; 175 µL:200 µL) and S. typhi (19.3; 25 µL: 200 µL) than either AgNPs alone or gum. The immobilized AgNPs released the positive sliver ions and the positively charged nanoparticles (NPs) are attracted by the negatively charged bacterial cells. After attachment and permeation to bacterial cell, the immobilized NPs altering the cell membrane permeability, protein denaturation, causing oxidative stress, deactivating enzymes, generating ROS, DNA damage and changing gene expression level. It has been mechanistically considered that the immobilized AgNPs can kill bacteria by damaging their cell membranes, dephosphorylate tyrosine residues during their signal transduction pathways, cell apoptosis, rupture the organelles and inhibiting the cell division and finally lead to cell death. This study has a potential to be adopted by pharmaceutical industries as highly effective antibacterial alternatives to synthetic drugs.