Influence of Photosensitizer Solvent on the Mechanisms of Photoactivated Killing of Enterococcus faecalis

Abstract

This study evaluated the mechanisms involved and the influence of photosensitizer solvent in the killing of Enterococcus faecalis using photodynamic therapy (PDT). Enterococcus faecalis cells incubated with 100 microm methylene blue dissolved in water and in MIX (a mixture of glycerol:ethanol:water) were irradiated with 664 nm diode laser (63.69 J cm(-2)). The effect of PDT on the viability of bacteria, and the functional integrity of cell wall, chromosomal DNA and membrane proteins were analyzed. The bactericidal action of PDT was significantly higher when a MIX-based photosensitizer solvent was used (P<0.001). Fluorimetric and fluorescence microscopy-based analysis showed the functional impairment of E. faecalis cell wall which was significantly higher when a MIX-based photosensitizer solvent was used (P<0.001). PDT with MIX-based photosensitizer solvent showed extensive damage to chromosomal DNA. However, both PDT conditions showed similar trend in the degradation of membrane proteins, although cross-linked proteins were evident only in PDT conducted with MIX-based photosensitizer solvent. The findings from our study showed that PDT destroyed the functional integrity of cell wall, DNA and membrane proteins of E. faecalis. The degrees of damage on these targets were influenced by the photosensitizer solvent used during PDT.

Photodynamic Therapy (Part 1: Applications in Dentistry)

“…[24][25][26][27][28] The combination of conventional endodontic therapy and PDT has been shown as an effective approach in reducing bacterial load in vitro and in vivo models. 4,[28][29][30][31][32] In comparison with the conventional hypochlorite irrigation it is certain that PDT has shown promising results. 32 PDT has shown to be effective against Grampositive 33,34 as well as Gram-negative endodontic pathogens.…”

Bioactive Chitosan Nanoparticles and Photodynamic Therapy Inhibit Collagen Degradation In Vitro

“…As an example, the application of PDT using methylene blue as a PS against E. faecalis, has been shown to functionally impair the cell wall, damage chromosomal DNA, and degrade membrane proteins (72). PDT also has been reported to break single, as well as double-stranded DNA, resulting in the disappearance of the plasmid super-coiled fraction often associated with antibiotic resistance (73,74).…”

“…Photodynamic therapy (PDT) uses a specific wavelength of light to activate a light compatible nontoxic dye known as a photosensitizer (PS (68)(69)(70)(71)(72). As an example, the application of PDT using methylene blue as a PS against E. faecalis, has been shown to functionally impair the cell wall, damage chromosomal DNA, and degrade membrane proteins (72).…”

Antimicrobial Effects of Laser-assisted Photodynamic Therapy in Pediatric Endodontic Treatment: A New Clinical Horizon

“…However, most of the studies have been done in vitro [7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23] and on permanent teeth and very few in vivo 24,25 with only one study till date being done on deciduous teeth. 26 In the present 'in vivo' study we used naturally infected teeth, as they contain a much broader spectrum of pathogens with deeper penetration into the tubules compared to any 'in vitro' system.…”