A comparative study of irradiation systems for photoinactivation of microorganisms

Abstract

Estudou-se a construção de sistemas de LED aplicados a processos de fotosensitização. Visando à obtenção de dispositivos mais eficientes avaliou-se a aplicação de LED de alta potência (HPLED), que apresenta maior fluxo fotônico, tendendo a excitar uma maior fração de moléculas. Foram descritos detalhes de construção de 3 diferentes sistemas de irradiação completamente distintos (lâmpada halógena filtrada, LED convencional, HPLED), utilizando azul de metileno como fotosensitizador. A comparação entre a eficiência de cada equipamento foi realizada através da cinética de fotooxidação de 1,3-Diphenylisobenzofuran e inativação de Staphylococcus aureus. A emissão de luz de cada equipamento, sobreposta à absorção do fotosensitizador, também se mostrou um importante parâmetro na estimativa da eficiência dos equipamentos. Foi observada uma inibição bacteriana superior a 99% para concentrações de 5 × 10 -6 mol dm -3 de fotosensitizador, no sistema que emprega HPLED. Os equipamentos baseados em LED, apresentaram resultados satisfatórios além de baixo custo e simples montagem.The construction of LED systems applied to photosensitization processes was studied. Aiming to obtain more efficient devices it was evaluated the use of high intensity LED (HPLED), that present greater photonic flux, tending to excite a greater fraction of molecules. Construction details for 3 different irradiation systems were described (filtered halogen bulbs, conventional LED, HPLED), using methylene blue as a photosensitizer. A comparison between the efficiency of the equipments was carried out through the kinetics of photooxidation of 1,3-Diphenylisobenzofuran and Staphylococcus aureus photoinactivation. The overlap between the light emited from each equipment and the photosensitizer absorption, was also an important parameter in estimating the efficiency of the equipment. Bacterial inhibition higher than 99% for concentrations of 5 × 10 -6 mol dm -3 of the photosensitizer was observed, in the system that uses HPLED. The equipments based on LED showed satisfactory results, besides their low cost and simple to assembling. Keywords: high power LED, Staphylococcus aureus, methylene blue, irradiation systems IntroductionPhotodynamic Inactivation (PDI) 1 or Photodynamic Antimicrobial Chemotherapy (PACT) 2 is the name of a process, derived from Photodynamic Therapy, that causes the death of microorganisms under the action of visible light and a specific drug, also called photosensitizer. 3 The electronic excitation of the photosensitizer in the presence of oxygen implies in the generation of a large number of reactive oxygen species (ROS), as for example, singlet oxygen, 4,5 in a process known as photosensitization.Since 1976, the oxidative action of singlet oxygen and other ROS on tumor cells has been reported in the medical and scientific communities. 5,6 Around the world, several research results have been published on the use of photosensitization to fight diseases caused by fungi, viruses, bacteria and yeasts. 3,5,[7][8][9][10][11] Among the photos...

Photodynamic inactivation of Escherichia coli with cationic ammonium Zn(ii) phthalocyanines

“…The amount of energy required to excite the PS is an important factor in the process of the photosensitization of bacteria. 5,29,30 The most appropriate light sources are those displaying emission peaks close to the absorption maxima of the PS. 31 All Pc tested in this work have Q-bands within the red region of the visible spectrum (Fig.…”

Photoinactivation of Planktonic and Biofilm Forms of Escherichia coli through the Action of Cationic Zinc(II) Phthalocyanines

“…Our results are consistent with observed higher reductions in the viability of the planktonic Staphylococcus aureus and Pseudomonas aeruginosa than in the corresponding biofilms. [45][46][47] In biofilms, cells are embedded in an extracellular polymeric matrix and the chemical composition of the matrix as well as the charge or hydrophobicity, may either favour or impair the binding of PS to the cells. [19] In the case of E. coli biofilms, the extracellular matrix seems to act more like a barrier to PS making biofilm cells less susceptible to photosensitization.…”

Antimicrobial Biophotonic Treatment of Ampicillin-Resistant Pseudomonas aeruginosa with Hypericin and Ampicillin Cotreatment Followed by Orange Light

“…In the case of light treatment, the light-emitting diode (LED) source was convenient for application in the APDT system because of its easy universal handling features. The main advantages of using an LED are resistance, durability, wavelength selectivity, low heat emission, and lower cost than other conventional light sources [18,44]. albicans at 37 °C in SB broth.…”