Title : Biosurfactant conjugated and functionalized silver nanoparticles with enhanced antimicrobial and antibiofilm efficacy: A mechanistic approach
Abstract:
Background
Green synthesis has gained significant attention as a sustainable and environmentally friendly approach for the fabrication of metal oxide nanoparticles. However, a major limitation of plant-mediated synthesis of silver nanoparticles (AgNPs) is the requirement for additional capping or stabilizing agents to ensure long-term stability and functionality. Biosurfactants, amphipathic compounds produced by microbes, have gained significant attention due to their eco-friendly, biodegradable, and surface-active properties.
Methods
In this study, we optimized the synthesis of AgNPs utilizing Mangifera indica leaf extract, which demonstrated potent antibacterial activity. Notably, these nanoparticles also exhibited anti-biofilm properties without the need for an external stabilizing agent, a crucial aspect of their potential application. In addition, native Bacillus sp. was isolated from Sapindus spp. and screened for biosurfactant production. Further we conjugated these silver nanoparticles with biosurfactant in a synergetic process, which substantially enhanced the stability of nanoparticles.
Significant Findings
High-resolution transmission electron microscopy (HR-TEM) analysis revealed that the synthesized AgNPs exhibited quasi-spherical and cubical morphologies, with particle sizes ranging from 10 to 70 nm. These findings were in agreement with dynamic light scattering (DLS) measurements, which reported an average particle size of 60.02 nm, corroborating with the field-emission scanning electron microscopy (FE-SEM) data. Additionally, a high negative zeta potential value indicated strong colloidal stability of the synthesized nanoparticles. X-ray diffraction (XRD) analysis confirmed the crystalline nature of the cubic AgNPs, with characteristic diffraction peaks corresponding to the (111) and (200) planes. The antibacterial and anti-biofilm activities of the AgNPs were evaluated against multiple bacterial strains, including Bacillus subtilis, Salmonella typhi, Staphylococcus aureus, and Escherichia coli. Notably, biofilm inhibition ranged from 60–85% against E. coli and 64–80% against B. subtilis. Further, we purified our biosurfactant and characterized the biosurfactant conjugated AgNPs (Bs-AgNPs) by DLS, Zeta potential and XRD. We also studied the anti-biofilm, antibacterial and antifungal activity of Bs-AgNPs. These findings strongly suggest that the synthesized biomolecule “Bs-AgNPs” have promising potential as novel antimicrobial agents, paving the way for future applications in biomedical and environmental fields.
Keywords: Nanotechnology; green synthesis; NMR; Silver nanoparticle (AgNPs); HR-TEM; antibacterial study; DLS; XRD; Zeta potential; Biosurfactant.
