TIME-RESOLVED FLUORESCENCE SPECTROSCOPY OF A HEMATOPORPHYRIN DERIVATIVE USED FOR PHOTODYNAMIC THERAPY OF CANCER

Photodynamic therapy (PDT) is a treatment modality for malignancies th at, uses the accumulation of a photosensitizer in tumor tissue and a s ubsequent 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 we re determined at different concentrations with time-resolved fluoresce nce spectroscopy. Photosan-3 showed a concentration dependent fluoresc ence 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 respect ively. These findings confirm results of former studies on other HPD t hat aggregates and dimers are probably more responsible for the photod ynamic effect than monomers.