Evaluation of the Antibacterial and Anti-Biofilm Activity of Chitosan-Arginine Nanoparticles and Sodium Fluoride against <i>Streptococcus</i> <i>mutans</i>.

Dental caries is among the most prevalent chronic diseases. It arises from bacterial biofilm formation on tooth surfaces due to metabolic activity. <i>Streptococcus</i> <i>mutans</i> (<i>S</i>. <i>mutans</i>) is a key pathogen implicated in the development of dental caries. As bacterial resistance to conventional treatments increases, there is a growing interest in using novel compounds that possess antibacterial and antibiofilm properties. This study evaluated the effect of chitosan-arginine nanoparticles (CS-Arg NPs) and sodium fluoride (NaF) on inhibiting <i>S</i>. <i>mutans</i>' growth. After synthesizing CS-Arg NPs, their size, morphology, and chemical structure were evaluated. The broth microdilution method determined the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of CS-Arg NPs and NaF. The combined antibacterial and antibiofilm effect of CS-Arg NPs and NaF was assessed using the checkerboard method. The CS-Arg NPs had an average size of 269.9 nm with a zeta potential of +38.3 mV. The MIC of <i>S</i>. <i>mutans</i> for CS-Arg NPs and NaF was 312 µg/mL and 625 µg/mL, respectively, and the MBC for these NPs and NaF was 625 µg/mL and 2500 µg/mL, respectively. The fractional inhibitory concentration index (FICI) of the combination of CS-Arg NPs and NaF showed an additive effect (FICI = 1). The inhibitory effect of different concentrations of CS-Arg NPs and NaF, alone or in combination, on biofilm formation in the studied strain ranged from approximately 12% to 81%. This study demonstrated that CS-Arg NPs have antibacterial and antibiofilm properties against <i>S</i>. <i>mutans</i>, and their combination with NaF can enhance these antibacterial effects. These findings suggest that CS-Arg NPs and NaF, as a novel combination, could effectively develop oral hygiene products.