Sustainable, scalable nanotechnology approach using filtrate from Raphanus sativus in combating multidrug-resistant pathogens and causing neglected tropical diseases

Introduction: The green synthesis of silver nanoparticles (AgNPs) provides a more eco-friendly approach over the conventional chemical procedures. In this study, a fast and sustainable methodology for the production of high-density AgNPs utilizing the aqueous root filtrate of Raphanus sativus is presented. Methods: AgNPs were prepared under room temperature conditions by optimizing the concentrations of NaOH, R. sativus filtrate, and AgNO₃. UV–Vis spectroscopy was employed for characterizing AgNPs. Antibacterial properties and mechanisms of action were assessed against multi-drug resistant, gram negative Escherichia coli KCCM 11234, and gram positive Staphylococcus aureus KCCM 11335. Results: Optimally formed monodispersed AgNPs were synthesized using 0.1 mL of 1 M solution of NaOH, 1 mL (20 mM) AgNO₃ solution, and subsequent addition of plant filtrate into a final volume of 10 mL. UV-visible analysis indicated the surface plasmon resonance peak to be 405 nm, confirming the classic nucleation and isotropic growth of spherical AgNPs. The AgNPs with concentrations ranging from 20 to 30 ppm permitted the partial recovery of the bacteria and the concentrations ranging from 50 to 100 ppm showed potent antibacterial activity against MDR bacteria. Discussion: The antibacterial mechanism involved disruption of membrane integrity and permeability, leakage of intracellular substances, and oxidative damage by reactive oxygen species, resulting in bacterial cell death.