Effect of red dyes on blue light phototoxicity against VSC producing bacteria in an experimental oral biofilm

Antimicrobial photodynamic therapy with Bixa orellana extract and blue LED in the reduction of halitosis-A randomized, controlled clinical trial

BACKGROUND

This study aimed to evaluate the reduction of halitosis when using antimicrobial photodynamic therapy (aPDT) with Bixa orellana extract and blue light-emitting diode (LED).

METHODS

Forty-four UNINOVE students or employees with a diagnosis of sulfide (H2S) ≥ 112 ppb in gas chromatography were selected. The patients were randomly divided in groups: Group 1 (n = 15): aPDT with annatto and LED; Group 2 (n = 14): tongue scraping; Group 3 (n = 15): tongue scraping and aPDT. For aPDT, a wasBixa orellana extract used in a concentration of 20 % w/v (Fórmula e Ação®, São Paulo, Brazil) on the tongue for 2 min, associated with a blue-violet LED (Valo Cordless Ultradent® Products, Inc., South Jordan, UT, USA) (395-480 nm). Six points were irradiated on the back of the tongue, at wavelength 395-480 nm for 20 s, energy of 9.6 J and radiant energy of 6.37 J/cm² per point. The results were compared before, immediately after treatment and 7 days after. The Friedman test was used for the intragroup analysis and the Kruskal Wallis test for the intergroup analysis.

RESULTS

In all groups, there was a difference between baseline and the value immediately after the treatment. In Groups 1 and 3, there was no difference between the baseline and the 7 days control.

CONCLUSION

There was an immediate reduction of halitosis, but the reduction was not maintained after 7days.

Antimicrobial Photodynamic Inactivation Mediated by Rose Bengal and Erythrosine Is Effective in the Control of Food-Related Bacteria in Planktonic and Biofilm States

The thermal and chemical-based methods applied for microbial control in the food industry are not always environmentally friendly and may change the nutritional and organoleptic characteristics of the final products. Moreover, the efficacy of sanitizing agents may be reduced when microbial cells are enclosed in biofilms. The objective of this study was to investigate the effect of photodynamic inactivation, using two xanthene dyes (rose bengal and erythrosine) as photosensitizing agents and green LED as a light source, against Staphylococcus aureus, Listeria innocua, Enterococcus hirae and Escherichia coli in both planktonic and biofilm states. Both photosensitizing agents were able to control planktonic cells of all bacteria tested. The treatments altered the physicochemical properties of cells surface and also induced potassium leakage, indicating damage of cell membranes. Although higher concentrations of the photosensitizing agents (ranging from 0.01 to 50.0 μmol/L) were needed to be applied, the culturability of biofilm cells was reduced to undetectable levels. This finding was confirmed by the live/dead staining, where propidium iodide-labeled bacteria numbers reached up to 100%. The overall results demonstrated that photoinactivation by rose bengal and erythrosine may be a powerful candidate for the control of planktonic cells and biofilms in the food sector.