Phototransformation of hematoporphyrin in aqueous solution: Anomalous behavior at low oxygen concentration
Contribuinte(s) |
UNIVERSIDADE DE SÃO PAULO |
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Data(s) |
20/10/2012
20/10/2012
2009
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Resumo |
The photoactivation of a photosensitizer is the initial step in photodynamic therapy (PDT) where photochemical reactions result in the production of reactive oxygen species and eventually cell death. In addition to oxidizing biomolecules, some of these photochemical reactions lead to photosensitizer degradation at a rate dependent on the oxygen concentration among other factors. We investigated photodegradation of Photogem A (R) (28 mu M), a hematoporphyrin derivative, at different oxygen concentrations (9.4 to 625.0 mu M) in aqueous solution. The degradation was monitored by fluorescence spectroscopy. The degradation rate (M/s) increases as the oxygen concentration increases when the molar ratio of oxygen to PhotogemA (R) is greater than 1. At lower oxygen concentrations (< 25 mu M) an inversion of this behavior was observed. The data do not fit a simple kinetic model of first-order dependence on oxygen concentration. This inversion of the degradation rate at low oxygen concentration has not previously been demonstrated and highlights the relationship between photosensitizer and oxygen concentrations in determining the photobleaching mechanism(s). The findings demonstrate that current models for photobleaching are insufficient to explain completely the effects at low oxygen concentration. Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) CEPID FAPESP Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) CAPES Canadian Cancer Society/NCIC Canadian Cancer Society/NCIC |
Identificador |
LASER PHYSICS, v.19, n.6, p.1263-1271, 2009 1054-660X http://producao.usp.br/handle/BDPI/29696 10.1134/S1054660X09060140 |
Idioma(s) |
eng |
Publicador |
MAIK NAUKA/INTERPERIODICA/SPRINGER |
Relação |
Laser Physics |
Direitos |
restrictedAccess Copyright MAIK NAUKA/INTERPERIODICA/SPRINGER |
Palavras-Chave | #PHOTODYNAMIC THERAPY #SINGLET OXYGEN #PHOTOSENSITIZER FLUORESCENCE #DOSIMETRY #PHOTOFRIN(R) #PHOTOGEM(R) #CELLS #PHOTOPRODUCTS #CYTOTOXICITY #DERIVATIVES #Optics #Physics, Applied |
Tipo |
article original article publishedVersion |