Nanoparticulates for Antibiofilm Treatment and Effect of Aging on Its Antibacterial Activity

Introduction: Issues pertaining to the effective elimination of bacterial biofilm and disruption of biofilm structure still remains in endodontic disinfection. Nanoparticulates such as chitosan (CS-np) and zinc oxide (ZnO-np) are known to possess significant antibacterial properties. This study aimed to test (1) the efficacy of CS-np and ZnO-np in disinfecting and disrupting biofilm bacteria and (2) the long-term efficacy of these nanoparticulates following aging. Methods: Enterococcus faecalis (ATCC & OG1RF) in planktonic and biofilm forms were treated with different concentrations of CS-np and ZnO-np. The treated bacteria were quantified by using microbiologic methods. The biofilm viability and structure after nanoparticulate treatment were assessed by using confocal laser scanning microscopy. The effect of aging by using sterile saliva and phosphate-buffered saline on the antibacterial properties of the nanoparticulates was also determined. Results: The rate of bacterial killing by the nanoparticulates depended on the concentration and time of interaction. Total elimination of planktonic bacteria was observed in contrast to the biofilm bacteria, which survived even after 72 hours. The confocal microscopy images showed predominantly dead bacterial cells and significant reduction in the thickness of biofilm (P<.01) after nanoparticulate treatment in both groups. Both CS-np and ZnO-np were found to retain their antibacterial properties after aging for 90 days. Conclusions: The present study highlighted the efficacy of the nanoparticulates to reduce biofilm bacteria, disrupt biofilm structure, and retain the antibacterial property even after aging. CS-np and ZnO-np present a potential approach in biofilm disinfection. (J Endod 2010;36:1030-1035)