Synthesis and antibacterial activities of novel polymerizable Gemini quaternary ammonium monomers

Abstract

In order to get durable antibacterial polymer materials, two series of novel polymerizable Gemini quaternary ammonium salts (QAS) were synthesized via a facile approach. The first series of monomers which have a completely symmetrical structure contain two unsaturated double bonds that allow it to polymerize as cross-linker. The second series of monomers are asymmetric Gemini QAS and contain only one polymerizable double bond. All the QAS monomers were characterized by 1H NMR and IR spectra. The six kinds of QAS monomers were bonded to dental restoration resin system. To evaluate the bactericidal activity of these compounds against Escherichia coli and Staphylococcus aureus (S. aureus), the minimum inhibitory concentration (MIC) and the minimum bactericidal concentration were tested by using broth dilution test. Among the six monomers, four compounds were found to have MIC values (for S. aureus) less than 10 μg/mL. The asymmetric Gemini QAS which have a long alkyl chain length of 12 carbons on the nitrogen showed stronger antibacterial activity than other monomers. The inhibitory effect of polymeric resins incorporated with QAS against the growth of S. aureus was determined by counting the number of viable cells. The result showed that the antibacterial activities of cured resins were increased as the concentration of QAS monomers increased.