Biosynthesis and characterization of Serratia marcescens derived silver nanoparticles: Investigating its antibacterial, anti-biofilm potency and molecular docking analysis with biofilm-associated proteins

Abstract

The catastrophe of surging antibiotic resistance makes it obligatory to develop potent alternative antibacterial agents that could exhibit their action through novel approaches. Over the past few years, a shift in the ideologies has been witnessed towards synthesizing metal nanoparticles as a non-toxic formulation, the output of which could be employed to meet diverse biomedical functions. This work reports a green method of biosynthesis of silver nanoparticles (AgNPs) using the growth supernatant of Serratia marcescens as the reductant and capping agent. Though these nanoparticles are anticipated to act by varying molecular routes, their minuscule particle size is what facilitates and helps delineate its prodigious properties. The visuals from scanning electron microscopy revealed small dispersed spherical-shaped AgNPs sized between 14.7-20.8 nm. Elemental analysis through EDX ascertained the presence of Ag in good amount along with other elements contributed by the bacterial extract. The FTIR result confirmed the presence of various chemical moieties and/or biomolecules decorated on the surface of AgNPs. The S. marcescens-derived AgNPs presented excellent antibacterial activity at minimum inhibitory concentration (MIC) values ranging between 8-96 μg/mL against Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, Chromobacterium violaceum, Kocuria sp. and Micrococcus luteus. Besides, a significant biofilm inhibition was observed at sub-MIC levels against P. aeruginosa, S. aureus and C. violaceum. The bactericidal action of AgNPs and thereby reduction in cell population was confirmed through CFU assay and fluorescence imaging. Furthermore, molecular docking analysis done for evaluating the molecular interaction of Ag with the active site of biofilm-associated proteins of those bacteria showed effective binding of Ag to designated amino acids, thereby hinting its plausible utilization as a futuristic antimicrobial armamentarium. The entire process of biosynthesis is environmentally compatible and in future, these AgNPs could emerge as a promising alternative candidate to conventional antibiotics.