Quaternized chitosans bind onto preexisting biofilms and eradicate pre-attached microorganisms

. Bacterial and fungal biofilms were formed on poly(methyl methacrylate) (PMMA) films and then treated with TMC aqueous solutions. Zeta potential measurement suggested that TMC bonded onto the preexisting biofilms. Biofilm-binding kinetics was evaluated in UV studies using phenyl group-labeled TMC as model compounds, which revealed that quaternized chitosans bonded onto the preexisting biofilms rapidly. Colony-forming unit (CFU) determination and SEM, confocal laser scanning microscopy (CLSM) and fluorescence microscopy studies demonstrated that the bonded TMC had powerful biocidal activities to eradicate the pre-attached bacterial and fungal cells in the preexisting biofilms. The biocompatibility of the TMC samples with rat skin fibroblast cells was evaluated in the MTT assay.