The Antibacterial Efficacy of a Novel CPC-Clay Toothpaste

Objectives: To demonstrate the antibacterial effect and mode of action of a novel Cetylpyridinium Chloride Clay (CPC-Clay) complex alone and in a toothpaste formulation versus active CPC using Confocal Laser Scanning Microscopy (CLSM) and Transmission Electron Microscopy (TEM).
Methods: 0.05% CPC, 1.5% CPC-clay, and a calcium carbonate, sodium lauryl sulphate (SLS) based toothpaste containing 1.5% CPC-clay were tested. The experimental agents were applied to 2 day old Streptococcus sanguinis (strain ATCC 10556) biofilms for 5 minutes (n=3). Biofilms were subsequently stained with the Filmtracer™ LIVE/DEAD® Biofilm Viability Kit and visualised using CLSM (LSM 700, Zeiss, Germany). Image analysis was used to calculate the percentage of live and dead bacteria. TEM (JEOL 1200CX2) was used to image bacteria in a biofilm after application of CPC and CPC-clay to evaluate the mode of action.
Results: CLSM images showed that the majority of bacteria (84±6%) were alive in the negative control (no treatment). For all of the test samples, more than 85% bacteria were killed. Analysis showed no significant difference in the antibacterial effect between CPC (93.8±5%), CPC-Clay (91.4± 6.1%) and CPC-Clay in a calcium carbonate, SLS toothpaste (95.6±6.5%).
TEM images of bacterial cells treated with CPC and CPC-clay showed ruptured cell membranes, suggesting the same mode of action, i.e. bacterial cell death via binding of CPC to the negatively charged surface of the bacterial cell membrane, altering and rupturing it, resulting in loss of cytoplasmic material.
Conclusions: CLSM imaging demonstrated that there was no significant difference in antibacterial efficacy for the test treatments. The combination of CPC-clay has no impact on the efficacy of CPC overcoming the incompatibility of CPC with SLS. Additionally, TEM imaging confirms that the antibacterial mode of action of CPC and CPC-clay is equivalent through bacterial cell membrane rupture.