In vitro evaluation of the antimicrobial and cytotoxic properties of oral rinse solutions with different compositions

The aim of this study is to compare in vitro antimicrobial effects of oral rinse solutions containing chlorhexidine (CHX), propolis (P), the metal–organic framework (ZIF-8), and a deep eutectic solvent (DES) against S. mutans and L. acidophilus, which play key roles in caries formation, as well as to evaluate their cytotoxic effects on human gingival fibroblast cells (HGF-1). Five different solutions were formulated and characterized using FTIR, SEM, EDX, XRD, and TGA analyses. Antimicrobial activity was evaluated using the broth microdilution method, and cytotoxicity was assessed with the MTT assay. The obtained data were analyzed with a ANOVA, Tukey HSD and Mann–Whitney U tests. CHX was found to be the strongest antimicrobial agent, showing the lowest minimum inhibitory concentration and minimum bactericidal concentration values against both S. mutans and L. acidophilus. Propolis demonstrated limited antibacterial activity against S. mutans but showed more pronounced inhibition of L. acidophilus. ZIF-8 alone exhibited moderate antibacterial activity, but when combined with Propolis (ZIF-8-P), it provided higher efficacy at lower concentrations. In terms of cell viability, propolis showed the highest biocompatibility, while CHX exhibited moderate cytotoxicity. ZIF-8-P-DES formulation showed the highest cytotoxicity on cells, followed by ZIF-8-P and ZIF-8. Although CHX remains the gold standard in efficacy, its cytotoxicity may limit its clinical use. ZIF-8-based formulations modified with propolis have clinical potential in balancing efficacy and safety, and they stand out as candidates that may overcome the limitations of CHX. Keywords: Antimicrobial, Chlorhexidine, Deep Eutectic Solvent, Propolis, ZIF-8