Antibacterial activity and cytotoxicity of two novel cross-linking antibacterial monomers on oral pathogens

The antibacterial activity and cytotoxicity of two novel cross-linking antibacterial monomers, 2-methacryloxylethyl dodecyl methyl ammonium bromide (MAE-DB) and 2-methacryloxylethyl hexadecyl methyl ammonium bromide (MAE-HB) were tested in this study.

The minimum inhibitory concentration (MIC) and the minimum bactericidal concentration (MBC) of unpolymerized MAE-DB and MAE-HB against eight strains of oral bacteria were tested using a broth dilution test. Time-kill determinations were performed to examine the kinetics of unpolymerized MAE-DB and MAE-HB against Streptococcus mutans UA159 and Streptococcus sanguinis ATCC6715. Bacterial morphology was observed using a field emission scanning electron microscope (Fe-SEM). The cytotoxicity of unpolymerized two new monomers and Bis-GMA on the human gingival fibroblast cell line H2620 was assessed using a methyl thiazolyl tetrazolium assay.

Unpolymerized MAE-DB and MAE-HB showed strong bactericidal activity against oral bacteria. The MBC value of MAE-DB ranged from 12.2 to 24.4μg/ml and the MBC value of MAE-HB ranged from 6.2 to 48.8μg/ml. Time-kill determinations indicated that unpolymerized MAE-DB and MAE-HB had rapid killing effects against S. mutans UA159 and S. sanguinis ATCC6715 at the concentration of 4× MBC. The Fe-SEM observation showed that MAE-DB and MAE-HB could disturb the integrity of bacteria and cause lysis of bacterial cells. The median lethal concentration values on human gingival fibroblast for both monomers were between 10 and 20μg/ml, and greater than that of Bis-GMA.

Unpolymerized MAE-DB and MAE-HB monomers had strong bactericidal activity against eight strains of oral bacteria. Their cytotoxicities were less than that of Bis-GMA.