Use of visible light‐based photodynamic therapy to bacterial photoinactivation

Abstract

The main focus of this laboratory exercise was to investigate the photodynamic therapy (PDT) acting over Streptococcus mutans. A handheld photopolymerizer and a classical photosensitizer (Rose Bengal) were used to induce photodynamic response. In this way, a suspension of S. mutans was treated with different concentrations of Rose Bengal (0 -10 mol/liter), irradiated with a light (400 -600 nm) for 20 s, and then cell viability was evaluated. It was observed that the light (per se) is not toxic, and in the dark, Rose Bengal is toxic only to the cells tested at concentrations above 5.0 mol/liter. Under light exposure, concentrations of Rose Bengal above 0.5 mol/liter killed all S. mutans. Therefore, for the purpose of our work, the photoactivation of Rose Bengal using the handheld photopolymerizer was efficient in bacteria inactivation.

Produção científica sobre estratégias didáticas utilizadas no ensino de Bioquímica: uma revisão sistemática

“…As atividades experimentais foram predominantes (32,5%), o que revela uma preocupação por parte dos docentes em inserir e divulgar as atividades práticas realizadas em suas disciplinas. Foi observado que as aulas desenvolvidas no laboratório envolviam atividades de rotina [30], desenvolvimento de kits de análise [32], aplicação de práticas antigas [35], construção de tabelas e gráficos [12], trabalhos em grupo [17], discussão [12], e tinham por objetivo desenvolver algumas habilidades como relacionar http://dx.doi.org/10.16923/reb.v14i3.630…”

Photodynamic Therapy with Rose Bengal Induces GroEL Expression inStreptococcus mutans

“…This solution was filter sterilized (0.22 mm) and stored at À208C. An odontologic resin photopolymerizer (HHP) from Dabi Atlante SA (Ribeirã o Preto, SP, Brazil) was used as a light source with the following characteristics: 350-500 mJ/cm 2 of light emitted at a wavelength range of 400-500 nm, as described by Paulino et al 30,31 Strain and bacterial culture…”

“…Then 15 mL of the stock was inoculated in ''Falcon tubes'' (15 mL) containing 4 mL of previously autoclaved TSB medium. The number of colonies forming units per milliliter (CFU/mL) was estimated by measuring the suspension turbidity with a spectrophotometer and verified by using CFU/mL counts on TSA after anaerobic growth at 378C for 36 h. 30,31 Photosensibilization of S. mutans by rose bengal and stress procedure S. mutans was grown as described and diluted in TSB medium to get 10 3 CFU/mL. This bacterial suspension (200 mL) was preincubated with 0.1 mmol/L RB for 10 min and then photoirradiated with HHP (at a 11-cm distance from the light source), with gentle stirring.…”

“…32 It was found that RB, at ideal concentrations and associated with the use of light, promotes cellular death of the S. mutans bacteria without causing damage to the fibroblast cells. 30,31 Previous work of Dahl et al 33 reported a comparison of PDT effects (by using a tungsten lamp) and RB (5 mmol/L), resulting in death of gram-positive species about 200 times more quickly (99% inactivation) than with gram-negative species. Also, Goulart et al 34 showed the use of odontologic resin photopolymerizer and RB (0.1 mmol/L), resulting in death of Aggregatibacter actinomycetemcomitans, in both planktonic and biofilm cultures, not causing damage to fibroblast cells under the same conditions.…”

“…27,28 Rose bengal (RB) has been shown to be a good singlet oxygen producer when used as a model photosensitizer agent, presenting a light absorption in the range of 500 nm region. [29][30][31] Preclinic studies with other dyes have already demonstrated that, in adequate doses of drug and light, it can be safely used to treat skin disorders. 32 It was found that RB, at ideal concentrations and associated with the use of light, promotes cellular death of the S. mutans bacteria without causing damage to the fibroblast cells.…”