Influence of light intensity and irradiation mode on methylene blue, chlorin-e6 and curcumin-mediated photodynamic therapy against Enterococcus faecalis

Author(s)

Sampaio, Lais Simoes ; de Annunzio, Sarah Raquel ; de Freitas, Laura Marise ; Dantas, Livia Oliveira ; de Boni, Leonardo ; Donatoni, Maria Carolina ; de Oliveira, Kleber Thiago ; Fontana, Carla Raquel

• Document type: Journal article
• Source: Photodiagnosis and Photodynamic Therapy; v. 31, p. 13-pg., 2020-09-01.

Abstract

This study aimed to evaluate the effect of the continuous irradiation with low intensity (continuous mode) and fractioned irradiation with high intensity (fractionated mode), keeping the same dose of light by using Light Emitting Diode (LEDs) with wavelength emission centered at 450 and at 660 nm, using methylene blue (MB), chlorin-e6 (Ce-6) and curcumin (CUR) as photosensitizers (PSs) against planktonic phase of E. faecalis. Cell viability was assessed by counting colonies forming per mL (CFU/mL), and the quantification of reactive species was performed by fluorescence with the photodegradation rate evaluated by measurements of absorbance of PSs at different times. The results revealed that MB-mediated PDT was efficient to achieve total microbial load reduction in both irradiation modes, but in fractional mode it was possible to use a lower light dose. Using Ce-6, a total bacterial reduction was observed when fractional light was used, but at the same light dose, there was no reduction in the continuous irradiation mode. CUR-mediated PDT under continuous irradiation mode promoted the total microbial load reduction. However, for fractional mode, a higher concentration of CUR was required to completely reduce E. faecalis cell viability. Our results suggest that the biological response to PDT is variable depending on the irradiation mode and on the photosensitizer. Therefore, these studies indicate that the irradiation mode, intensity and the specific PSs should be taken into account for the development of clinical protocols for PDT. (AU)

• FAPESP's process: 18/23015-7 - Antimicrobial photodynamic therapy by continuous and switched mode irradiation against Enterococcus faecalis and Cutibacterium acnes
• Grantee: Carla Raquel Fontana
• Support Opportunities: Regular Research Grants
• FAPESP's process: 18/00106-7 - Photocatalyzed Reactions by using porphyrins and continuous flow conditions: Arylations of heterocycles and activated olefins.
• Grantee: Kleber Thiago de Oliveira
• Support Opportunities: Regular Research Grants
• FAPESP's process: 13/07276-1 - CEPOF - Optics and Photonic Research Center
• Grantee: Vanderlei Salvador Bagnato
• Support Opportunities: Research Grants - Research, Innovation and Dissemination Centers - RIDC
• FAPESP's process: 18/09088-1 - Assessment of photodynamic therapy against polymicrobial acne biofilms: a preclinical study
• Grantee: Sarah Raquel de Annunzio
• Support Opportunities: Scholarships in Brazil - Doctorate