Effect of the Combinatorial use of Naringin and Silver Nanoparticles on Enterococcus Faecalis

This study aims to evaluate the antibacterial activity of naringin and its aglycone derivatives, alone and combined with silver nanoparticles (AgNPs), against E. faecalis, focusing on bacterial morphology and virulence gene expression.

The antimicrobial activities of naringin and its derivatives were evaluated through the minimal inhibitory concentration (MIC), minimal bactericidal concentration (MBC), and checkerboard assays, while an ex vivo human tooth model tested irrigation efficacy. Gene expression was analyzed via qPCR, and bacterial morphology changes were examined using scanning electron microscopy.

Naringin and its derivatives inhibited 50% of E. faecalis growth at concentrations above 21,500 μg/mL. Combining naringin with AgNPs did not boost antimicrobial activity but disrupted typical bacterial pairing and increased bacterial aggregation. Notably, this is the first study to report that antimicrobial concentrations of naringin and its derivatives upregulate genes associated with stress protection and biofilm formation in E. faecalis.

The idea of combining natural flavonoids with AgNPs for infection control during endodontic procedures is promising for reducing tissue damage. However, the findings suggest that simply mixing these compounds does not guarantee better antibacterial effects and may even hinder them. Study Limitations include difficulties in evaluating biofilm-specific effects and solubility challenges with naringin, highlighting the need for further optimization.

Naringin may increase E. faecalis tolerance to stress, weakening the antibacterial impact of AgNPs when combined. Its role in biofilm development requires more research to understand and harness its potential in dental antimicrobial strategies fully.