Trimethyl chitosan: Antibacterial activity on Enterococcus faecalis biofilm and cytocompatibility on human periodontal ligament fibroblasts cells.

Background/purpose: Effective disinfection of the root canal system remains a major challenge due to complex anatomy and the persistence of biofilm-forming bacteria such as Enterococcus faecalis. Trimethyl chitosan (TMC), a quaternized chitosan derivative, has shown promising antimicrobial properties but has not been extensively studied for endodontic use. This study aimed to evaluate the antibacterial and antibiofilm efficacy of TMC against E. faecalis and assess its cytocompatibility with human periodontal ligament fibroblasts (HPdLFs). Materials and methods: The E. faecalis biofilm formation in the presence of TMC and antibacterial activity of TMC against mature E. faecalis biofilms were evaluated using crystal violet staining, adenosine triphosphate assays, colony forming unit counting, scanning electron microscopy, and fluorescence microscopy. The expression of genes associated with E. faecalis biofilm formation, such as ace, esp, and gelE, was determined. Moreover, cytocompatibility of TMC with HPdLFs was assessed using a cell counting kit-8 assay. Results: TMC significantly inhibited biofilm formation by E. faecalis and in the mature E. faecalis biofilm, TMC interfered with the total biofilm biomass, reduced bacterial numbers, weakened the biofilm structure, and upregulated ace, esp, and gelE expression. Furthermore, a lower concentration of TMC maintained HPdLFs viability. Conclusion: This study highlights the potential of TMC as a novel irrigating material owing to its antibacterial and antibiofilm activities against E. faecalis and its cytocompatibility with HPdLFs.