Antimicrobial and cytotoxic evaluation of biosurfactant-coated copper nanoparticles: A study on selected endodontic pathogens

BACKGROUND: Endodontic infections caused by pathogens such as Escherichia coli, Staphylococcus aureus, Streptococcus oralis, and Enterococcus spp. pose significant challenges due to biofilm formation and resistance to conventional treatments. Copper nanoparticles (CuNPs) exhibit promising antimicrobial properties, and coating them with biosurfactants may enhance stability while reducing cytotoxicity. OBJECTIVES: The aim of the study was to synthesize and characterize CuNPs stabilized with biosurfactants derived from Achromobacter xylosoxidans and Pseudomonas aeruginosa, and to evaluate their antimicrobial efficacy and cytotoxicity. MATERIAL AND METHODS: Copper nanoparticles were synthesized using a chemical reduction method and coated with biosurfactants to prevent oxidation and aggregation. The nanoparticles were characterized using Fourier transform infrared spectroscopy (FTIR), ultraviolet-visible (UV-Vis) spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy-dispersive X-ray spectroscopy (EDX). Antimicrobial activity against E. coli, S. aureus, S. oralis, and Enterococcus spp. was evaluated using the well diffusion method and the minimum inhibitory concentration (MIC). Cytotoxicity was assessed using an MTT assay on L929 fibroblast cell lines. RESULTS: Characterization confirmed the formation of spherical CuNPs with sizes ranging from 90 nm to 100 nm. Both CuO+P5C and CuO+P11 nanoparticles demonstrated potent antimicrobial activity against all tested pathogens, with a MIC value of 125 μg/mL. Cytotoxicity results showed minimal toxicity, with nearly 78-80% cell viability maintained at concentrations of up to 100 μg/mL, indicating excellent biocompatibility. CONCLUSIONS: Biosurfactant-coated CuNPs represent a stable, eco-friendly and effective antimicrobial alternative for addressing persistent endodontic infections. Further in vivo studies and extended cytotoxicity evaluations are needed to confirm their clinical application.