ANTIBIOFILM ACTIVITY OF GREEN SYNTHESIZED SILVER NANOPARTICLES OF MENTHA PIPERITA L. (PEPPERMINT) AGAINST ESCHERICHIA COLI

Abstract

Background: Biofilm formation by Escherichia coli contributes to persistent bacterial infections and reduced antimicrobial effectiveness. Green-synthesized silver nanoparticles (AgNPs) have emerged as promising antimicrobial agents because of their potential antibacterial and antibiofilm properties. This study aimed to investigate the antibiofilm activity of green-synthesized silver nanoparticles using Mentha piperita L. (peppermint) against biofilm-forming E. coli.

Methods: Clinically isolated E. coli strains were obtained from the Microbiology and Biotechnology Research Laboratory, Abasyn University, Peshawar, Pakistan. Aqueous extracts of peppermint were prepared and used for the green synthesis of silver nanoparticles. The synthesized AgNPs were characterized using ultraviolet-visible (UV-Vis) spectroscopy, Fourier-transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). Biofilm formation was assessed using the tube adherence method, while the antibiofilm activity of AgNPs was evaluated quantitatively using the microtiter plate assay. Percentage biofilm inhibition was calculated by comparing the optical density of treated samples with that of untreated controls.

Results: UV-Vis spectroscopy demonstrated characteristic absorption peaks within the range of 350–460 nm, indicating the formation of silver nanoparticles. FTIR analysis identified several functional groups, including an O–H stretching band at 3298.2 cm⁻¹, suggesting the involvement of plant-derived phytochemicals in nanoparticle stabilization. SEM analysis revealed predominantly spherical and rounded nanoparticles with an approximate average diameter of 40 nm. The synthesized AgNPs demonstrated an antibiofilm inhibition of 65.33% against E. coli, indicating substantial inhibition of biofilm formation under the experimental conditions.

Conclusion: Green-synthesized silver nanoparticles using Mentha piperita demonstrated promising in vitro antibiofilm activity against E. coli. The findings highlight the potential of peppermint-mediated AgNPs as an alternative plant-based approach for controlling bacterial biofilms. Further studies involving different bacterial isolates, concentration-dependent assessments, toxicity evaluation, and in vivo investigations are recommended to establish their therapeutic potential.