Previous Illumination of a Water Soluble Chlorine
Photosensitizer Increases Its Cytotoxicity¹

J. C. Correa^a, V. S. Bagnato^b, H. Imasato^a, and J. R. Perussi^a, *

^a Instituto de Química de São Carlos, Universidade de São Paulo—Av. Trabalhador saocarlense,
400–13566-590, São Carlos, SP, Brazil

^b Instituto de Física de São Carlos, Universidade de São Paulo—Av. Trabalhador saocarlense,
400–13566-590, São Carlos, SP, Brazil

*e-mail: janice@iqsc.usp.br

Received August 11, 2011; in final form, February 6, 2012; published online August 1, 2012

Abstract—Photodithazine (PDZ) is an N-methyl-D-glucosamine derivative of chlorine e6 that is water soluble
and has an intense absorption in the range of 650–680 nm. PDZ photobleaching and photoproduct formation
were induced by illumination with laser at two wavelengths: 514 nm (ion argon laser) as well as in 630nm (dye
laser). The time constants of PDZ photobleaching were: 18 min for 630 nm irradiation and 50min for 514 nm
irradiation, suggesting that degradation after irradiation with red light is faster than with green light. Photoprod-
ucts formation was evidenced by the appearance of a new absorption band at 668 nm with slight broaden of the
Soret band, suggesting that there was no break of the macrocycle. The cytotoxicity of the photodegradated PDZ
was investigated and showed to be lower in the dark and higher than non irradiated PDZ. These results may
have important clinical implications for PDT such as the possibility to use the previously irradiated PDZ just
before clinical application in order to get increased efficiency.

DOI: 10.1134/S1054660X12090034

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