Green Synthesis, Characterization, and Antimicrobial Activity of Silver Nanoparticles from Water-Soluble Fractions of Brazilian Kefir

Background: Nanotechnology offers innovative approaches to combat drug-resistant diseases. Silver nanoparticles (AgNPs) have emerged as potent antimicrobial agents in vitro and in vivo. Green synthesis methods, which leverage the bioactive components of the water-soluble fractions of Brazilian kefir (whole water-soluble fraction and smaller than 10 kDa fraction), provide sustainable alternatives to conventional nanoparticles production. However, despite the documented therapeutic benefits of kefir, its potential in nanomedicine remains underexplored. Results: The successful synthesis of silver nanoparticles using water-soluble fractions of kefir was confirmed by UV-Visible spectroscopy and Fourier-transform infrared analyses. The hydrodynamic radius of nanoparticles derived from the entire water-soluble fraction was 1300 nm, while those from the smaller than 10 kDa fraction displayed a radius of 400 nm. All synthesized AgNPs exhibited a zeta potential of -30 mV. The disk diffusion method demonstrated the antimicrobial efficacy of our AgNPs against a range of multidrug-resistant bacteria and Candida fungi (p<0.0001), with no observed toxicity on Drosophila melanogasteron a long-term treatment. Conclusion:This study highlights the potential of these AgNPs as effective antimicrobial agents, particularly against drug-resistant pathogens. Future research is needed to evaluate the minimum inhibitory concentrations of our AgNPs and enhance specificity through conjugation with other compounds. Additionally, further investigations into electron microscopy analysis and various applications, such as disinfectant solutions, wound healing, and antibiotic production, will advance the utilization of kefir-derived AgNPs in healthcare.