Preliminary evaluation of a lemongrass-based nanoparticle gel for antibacterial control of Enterococcus faecalis: an in vitro study

Abstract

Background: The search for biocompatible antimicrobial agents in endodontics has driven interest in phytotherapeutic compounds, including Cymbopogon citratus (lemongrass). This study aimed to perform a preliminary evaluation of the antibacterial potential of a lemongrass-based nanoparticle gel against Enterococcus faecalis.

Materials and methods: Lemongrass leaves were collected, authenticated, and processed using different extraction methods. The most effective extract was selected for green synthesis of silver nanoparticles and incorporated into a 1% hydroxyethyl cellulose gel. Antibacterial activity against E. faecalis (ATCC 29212) was assessed by colony-forming unit (CFU/mL) quantification, agar well diffusion, and minimum inhibitory concentration (MIC) determination using resazurin. A 2.5% sodium hypochlorite (NaOCl) gel and 2% chlorhexidine (CHX) digluconate gel were used as positive controls, and a vehicle gel served as the negative control. Data were analyzed using Student’s t-test and the Wilcoxon test (α = 0.05).

Results: The nanoparticulate lemongrass gel demonstrated significantly greater antibacterial activity than the non-nanoparticulated extract (p < 0.05), showing higher CFU/mL reduction and larger inhibition zones. The nanoparticle formulation maintained inhibitory activity at lower concentrations (MIC 50%) compared with the natural extract. Antibacterial performance of the nanoparticulate gel was comparable to CHX and superior to NaOCl in CFU reduction, while inhibition zones were similar to both controls.

Conclusions: Nanoparticle incorporation significantly enhances the antibacterial efficacy of C. citratus against E. faecalis. The lemongrass-based nanoparticulate gel represents a promising alternative for use as a chemical auxiliary substance in endodontic treatment.