Time-resolved fluorescence spectroscopy of a hematoporphyrin derivative used for photodynamic therapy of cancer

Photodynamic therapy (PDT) is a treatment modality for malignancies that, uses the accumulation of a photosensitizer in tumor tissue and a subsequent laser light irradiation to selectively destroy tumor cells. Usually PDT is carried out with a hematoporphyrin derivative (HPD) as photosensitizer. Fluorescence characteristics of the HPD Photosan-3 were determined at different concentrations with time-resolved fluorescence spectroscopy. Photosan-3 showed a concentration dependent fluorescence with one fluorescence decay time below a concentration of 10 mu g/ml, two or three decay times at 50 and 100 mu g/ml Photosan-3 respectively. These findings confirm results of former studies on other HPD that aggregates and dimers are probably more responsible for the photodynamic effect than monomers.