Cell-free supernatant-assisted biogenic silver nanoparticles enhance the antibacterial efficacy of communicating bacterial pathogens

The use of nanoparticles (NPs) as an alternative to the current generation of conventional antibiotics has exploded in the research community in recent years, as evidence of the superiority of NPs over antibiotics in the treatment of pathogens has been steadily presented. However, therapy with NPs may result in the removal of both multidrug-resistant (MDR) pathogens and commensal bacteria due to the broad-spectrum activity of NPs and the non-specificity of target bacteria. Therefore, the fabrication of MDR-pathogen-targeting NPs is necessary. In this study, biogenic silver nanoparticles (Bio-AgNPs) were synthesized using bacterial cell-free supernatant from three communicating gram-negative bacteria. The size, physical features, and morphology of the AgNPs were characterized by dynamic light scattering (an average size of 158–168 nm), X-ray diffraction (co-ordinate patterns), and transmission electron microscopy (spherical structure). The antibacterial activity of the Bio-AgNPs as minimum inhibitory concentration values was obtained between 0.8 and > 6.4 μg mL⁻¹ for bacterial strains. Mechanistic studies of Bio-AgNPs have revealed that biofilm inhibition, protein leakage, hyperproduction of reactive oxygen species, and physical cell damage are plausible mechanisms underlying the activity of Bio-AgNPs against gram-negative pathogens. Overall, the Bio-AgNPs synthesized in this study may bolster the potential use of Bio-AgNPs as a stand-in for traditional antibiotics, and offer potential specificity against bacterial targets.

Graphical abstract