Photodegradation of photodynamic therapy agents in aqueous TiO2 suspensions

Abstract

The presence of emergent pollutants in waters and wastewaters are an issue of increasing concern due to the risk they pose to human and environmental health. Cancer Photodynamic Therapy photosensitizers and their metabolites and photodegradation products are pharmaceutical substances that after treatment will be eliminated from the human body and will eventually reach water bodies. Porphyrins are well established PDT sensitizers and cyanine dyes are promising candidates for the same use. In that way it is important to know how those compounds degrade once they reach water bodies and to find efficient treatment methodologies in case they are persistent. In this paper the simulated solar light photodegradation of a porphyrin (Zinctetraphenylporphyrin) and of a cyanine dye (3,3́-diethylindocarbocyanine iodide) in water was investigated, in the absence and in the presence of the most used photocatalyst for semiconductor photocatalysis: Titanium dioxide (TiO2). We observed that the porphyrin (1x10-3M) did not undergo photodegradation in the absence of photocatalyst and that in its presence the photodegradation process was strongly promoted (60% photodegradation reached after 1 hour of irradiation with 0,01g of TiO2). The cyanine dye (1x10-3M) suffered a photodegradation of about 20% even in the absence of TiO2 and reached 100% photodegradation in its presence. © 2013 WIT Press.