Concentration-dependent effects of modified triple antibiotic paste on human periodontal ligament stem cells and antibacterial efficacy: an in vitro study

Intracanal medication is critical for regenerative endodontic procedures (REPs). The purpose of this study was to examine the effects of modified triple antibiotic paste (mTAP) on the migration, proliferation, and osteogenic/cementogenic differentiation of human periodontal ligament stem cells (hPDLSCs) as well as its antibacterial effectiveness against Enterococcus faecalis (E. faecalis). hPDLSCs were treated with mTAP across various concentration gradients. hPDLSCs were treated with mTAP across concentration gradients. Cell Counting Kit-8, wound-healing assay, alizarin red staining, real-time quantitative polymerase chain reaction, and western blot were used to evaluate cell functions. The antibacterial efficacy was evaluated using microdilution assays and static biofilm models. The results demonstrated concentration-dependent effects on hPDLSCs functionality. At low and medium concentrations (3.9, 15.6, and 62.5 μg/mL), mTAP had no significant effect or slightly promoted hPDLSCs migration and proliferation, whereas high concentrations (≥ 250.0 μg/mL) inhibited these functions. With increasing mTAP concentration, mineralized nodule formation and osteogenic differentiation expression first increased and then decreased, whereas cementoblastic differentiation expression gradually increased. Against E. faecalis, mTAP exhibited a minimum inhibitory concentration (MIC) of 1 μg/mL and a minimum bactericidal concentration (MBC) of 128 μg/mL. mTAP inhibited 76.33 ± 0.89% early-stage biofilm formation at 32 μg/mL and eradicated ≥ 72.53 ± 1.15% 14-day mature biofilms at concentrations ≥ 125 μg/mL. Balancing biocompatibility and antibacterial efficacy, the optimal concentration range of mTAP during REPs was 128-250 μg/mL, which provides a robust basis for the future clinical application and formulation of safe and effective intracanal medications.