Influence of naringenin on the biofilm formation of Streptococcus mutans

Objectives: To evaluate the effect of naringenin on the biofilm formation of Streptococcus mutans (S. mutans), and to investigate its mechanisms of action and biological toxicity. Methods: Minimum inhibitory concentrations, growth curves, and biofilm inhibition rates of naringenin were determined to assess its antimicrobial effect on S. mutans. The morphology of S. mutans and the structure of biofilm were observed by FESEM and CLSM. Bacterial aggregation, bacterial surface hydrophobicity, and real-time PCR for gtfB, gtfC, comD, comE, and luxS mRNA expression were assessed to preliminarily investigate the mechanisms of action. MTT test using human dental pulp cells (HDPCs) was also performed to investigate cytotoxicity. Results: The S.mutans growth curves, FESEM, CLSM showed that both 100 and 200 mu g/mL of naringenin obviously inhibited S. mutans growth and biofilm formation, increased S. mutans surface hydrophobicity, reduced bacterial aggregation, and downregulated the mRNA expression of gtfB, gtfC, comD, comE, and luxS. However, naringenin at 200 mu g/mL slightly decreased the growths of HDPCs compared with 100 mu g/mL. Conclusion: Naringenin at 100 and 200 mu g/mL suppressed the second (bacterial adhesion) and third stages (biofilm maturation) of S. mutans biofilm formation. Clinical significance: Naringenin is promising for dental clinic promotion to prevent the biofilm formation of S. mutans, serving as a safe anti-caries agent at an appropriate concentration.