Relation between surface activity and antibacterial activity of amine-fluorides

Amine-fluoride molecules consist of two functional groups - the organic amine, which is a surface active agent and the fluoride ion. Both ions are known to have antibacterial properties. Studies have suggested that there is a positive correlation between the antibacterial properties and the surface activity of various organic amines. The purpose of our study was to determine the antibacterial activity of the two functional groups of amine-fluoride molecules and its relationship to their surface activity. In this study, minimal inhibitory/bacteriocidic concentration (MIC/MBC) were determined for Streptococcus sobrinus 6715 at a range of pH between 5 and 7. Surface activity measurements were conducted using a surface tensiometer. Amine-fluorides were found to have similar MIC values to that of chlorhexidine digluconate at all tested pH values, thus showing high antibacterial activity against Streptococcus sobrinus 6715. The MIC values of amine-fluorides and amine-chlorides are similar, and are about 100 times lower than the MIC value of NaF. No synergistic effect was found between the fluoride and the organic amine. No correlation was found between the antibacterial properties and the surface activity of amine-fluorides. Therefore, we conclude that the antibacterial activity of amine-fluorides derives mainly from the cationic nature of the organic amine, and not from its properties as a surface active agent.