Biofilm modulatory response of arginine-fluoride varnish on multi-species biofilm

Abstract

Objectives: To examine the biofilm modulatory effect of arginine (Arg)-fluoride (F) varnish on multi-species biofilms. Methods: Experimental varnishes were prepared by incorporating L-Arg (1, 2, and 4%) in 5% NaF varnish, which served as the control. Multi-species biofilms comprising Streptococcus mutans, Streptococcus sanguinis and Streptococcus gordonii were grown on hydroxyapatite (HA) discs and treated with the Arg and F released from the experimental and control groups. The HA discs with treated biofilms were examined for biofilm composition. The biofilm thickness and live/dead counts were investigated using confocal microscopic imaging, while biofilm polysaccharides, proteins, and extracellular DNA (eDNA) were assessed spectrophotometrically. Bacterial composition in biofilms was analysed using viability real-time quantitative polymerase chain reaction (qPCR). The relative gene expression (RGE) was determined for gtfB, SMU.150, nlmD, arcA, and sagP. Results: Both the 2 and 4% Arg-NaF groups reduced biofilm thickness, with the 4% Arg-NaF group showing a significantly greater proportion of dead bacteria, followed by 1 and 2% Arg-NaF (p < 0.001). All Arg-NaF groups significantly reduced the carbohydrate content of the biofilm, while the 4% Arg-NaF-treated biofilms demonstrated higher concentration of eDNA and proteins compared to the control NaF (p < 0.001). Expression of gtfB, SMU.150, and nlmD were significantly downregulated in 4% Arg-NaF-treated biofilms; while 2% Arg-NaF enhanced the expression of arcA. Both 2% Arg-NaF and 4% Arg-NaF significantly increased the expression of sagP. Conclusion: The incorporation of L-arginine (2%/4%) enhances the biofilm modulatory effect of 5% NaF varnish through released Arg and F. Clinical significance: The study results indicate that Arg-F varnish (at 2%/4% w/v. Arg) has the potential to modulate cariogenic biofilms in high-risk individuals.