Photodynamic inactivation of cultured bladder tumor cells: a preliminary study of the effects of porphyrin aggregation.

This study was designed to determine the influence, if any, of intracellular porphyrin aggregation upon in vitro photosensitivity. HpD uptake conditions were manipulated in such a way as to yield three experimental groups, each containing equal levels of cellular porphyrins but having different porphyrin aggregation status. Aggregation status was determined through comparison of the spectral properties of intact cells. Subsequent exposure to red light resulted in a family of survival curves which generally corresponded to cellular HpD fluorescence yields and optical densities (indicators of aggregation status). These data suggest that porphyrin aggregation within the cell may be partially responsible for the observed differential photosensitivity following various uptake conditions.