Effects of curcumin-mediated antimicrobial photodynamic therapy associated to different chelators against Enterococcus faecalis biofilms

•Curcumin with chelators showed being beneficial to reduce viable bacteria.•Chelators can contribute relatively to the reduction of the vitality of biofilms.•Curcumin-mediated aPDT can have harmful effects against microorganisms.•The action of aPDT on biofilms is related to a strain-dependent condition. The aim of this study was to evaluate curcumin-mediated antimicrobial photodynamic therapy (aPDT) action combined or not with ethylenediaminetetraacetic acid (EDTA) and hydroxyethylidene bisphosphonate (HEBP) on Enterococcus faecalis biofilms. Enterococcus faecalis biofilms were grown on dentin bovine discs in brain heart infusion (BHI) medium with 1% glucose, in aerobic conditions at 37°C for 7 days. Then, they were randomly distributed to one of experimental conditions, as follows: control, 75 J.cm−2 LED, 600 μmol.L−1 curcumin, 17% EDTA, 18% HEBP, 600 μmol.L−1 curcumin plus 75 J.cm−2 LED, 600 μmol.L−1 curcumin plus 17% EDTA, 600 μmol.L−1 curcumin plus 18% HEBP, 600 μmol.L−1 curcumin plus 17% EDTA and 75 J.cm−2 LED or 600 μmol.L−1 curcumin plus 18% HEBP and 75 J.cm−2 LED. The viability of microorganisms and the vitality of biofilms were determined by colony forming unit counts and confocal scanning laser microscopy (CSLM), respectively. Statistical analysis was conducted by Kruskal Wallis and Dunn's post-hoc tests (α = 0.05). The results showed that all combinations of aPDT with chelators significantly reduced the viability of microbial cells and the vitality of biofilms in comparison to control, even when considering deeper layers of biofilms. The combination of curcumin with EDTA and HEBP similarly improved the effect of aPDT on E. faecalis biofilms.