Antimicrobial action of photoactivated C-Phycocyanin against Enterococcus faecalis biofilms: Attenuation of quorum-sensing system.

Abstract

The limitations of conventional chemo-mechanic therapy in endodontic have given rise to introduce and develop photoactivated disinfection (PAD) as an adjunctive treatment. The objective of this ex vivo study was to evaluate the effects of PAD using C-Phycocyanin, as a natural photosensitizer, on biological activities and expression of quorum-sensing system gene fsrB of Enterococcus faecalis. A total of 52 extracted single-rooted human premolar teeth were divided into five groups (n = 10) and were incubated with E. faecalis for biofilm formation, and they were treated according to following groups; A. C-PC only; B. Diode laser only (at wavelengths of 635 nm); C. PAD (C-PC plus diode laser); and D. Sodium hypochlorite (NaOCl). E. Control group (not treatment). Two remaining teeth were used to confirm E. faecalis biofilm formation in the root canal system by scanning electron microscopic. The effects of each treatment were measured on viability and expression level of fsrB gene of E. faecalis using microbial cell viability and quantitative real-time PCR assays, respectively. Additionally, intracellular reactive oxygen species (ROS) production was measured using 2',7'-dichlorfluorescein-diacetate (DCFH-DA) fluorescent probe. The C-PC alone and C-PC-PAD reduced the culture viability of E. faecalis by 38.1% and 89.45%, respectively (both; P < 0.05). According to the Bonferroni post hoc test, a significant difference in the reduction of E. faecalis count was observed between C-PC-PAD and other groups (P < 0.05), except the NaOCl group (P > 0.05). As well as, photoexcited C-PC in PAD could increase (3.8- fold) the intracellular ROS production in E. faecalis compared to the control group (P < 0.05). C-PC-PAD at sub-significant inhibitory concentration and NaOCl at sub-lethal dose could significantly decrease the expression levels of fsrB by 10.8- and 11.4-fold, respectively. Our data support that C-PC alone and C-PC-PAD can serve as a potent irrigation solution and a disinfection method, respectively for microbial reduction and promising adjunct therapy in endodontic infection treatment against E. faecalis with clinical applications for infection control in endodontics.