%0 Generic %A Hasegawa, Guilherme K. F. %A Morais, Josmaria Lopes de %A Soares, Marlene %A Freitas, Adriane M. de %D 2018 %T Photodynamic inactivation of Escherichia coli by methylene blue and malachite green under red LED light %U https://scielo.figshare.com/articles/dataset/Photodynamic_inactivation_of_Escherichia_coli_by_methylene_blue_and_malachite_green_under_red_LED_light/7519508 %R 10.6084/m9.figshare.7519508.v1 %2 https://scielo.figshare.com/ndownloader/files/13985027 %2 https://scielo.figshare.com/ndownloader/files/13985030 %2 https://scielo.figshare.com/ndownloader/files/13985033 %2 https://scielo.figshare.com/ndownloader/files/13985039 %K bacteria, cationic dye %K photodynamic therapy %K water disinfection %X

This study assessed the effectiveness of methylene blue (MB) and malachite green (MG) on photodynamic inactivation (PDI) of Escherichia coli. The photosensitizers methylene blue (1000 (mol L-1) and malachite green (250 (mol L-1) were activated with a red light-emitting diode (LED) lamp ((max = 636 nm). Bacterial suspensions containing 106 CFU mL-1 were irradiated for 5, 10 and 15 minutes (energy density = 119.9 J cm-2, 223.9 J cm-2 and 335.8 J cm-2, respectively). The following experimental conditions were performed for each photosensitizer: no light irradiation or photosensitizer, irradiation only, photosensitizer only or irradiation in the presence of a photosensitizer. Next, serial dilutions were prepared and seeded onto PCA medium for the determination of the number of colony-forming units per milliliter (CFU mL-1). The results were subjected to analysis of variance (ANOVA) and Tukey test (P<0.05). Photodynamic inactivation using MB and MG was effective in reducing the number of E. coli. Malachite green (250 µmol L-1) photosensitization was able to achieve reductions of over 89% in the viable counts after 15 min of irradiation and methylene blue (1000 µmol L-1), at the same conditions of irradiation, showed a rate growth inhibition of 94.6%. The red LED light used has proven to be effective in the photosensitizing dyes and proved a good alternative to conventional light sources such as laser.

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