Photophysical and photosensitizing properties of selected cyanines.

The present work has been carried out to obtain detailed information about the photophysical and photobiological properties of selected cyanines, in view of their possible use as photosensitizing agents. All the cyanines studied by us except CY-IV (3,3'-diethyl-4,4'-oxacarbocyanine), expressed an accelerated photobleaching in aqueous medium, a poor generation of singlet oxygen, and a relative weak photosensitizing activity towards albumin. On the cellular level, all cyanines exhibited a significant phototoxicity towards Balb/c 3T3 cells, upon irradiation with a total fluence of 30 J/cm(2). CY-III (3,3'-diethylcarbothiocayanine iodide) and CY-II (1,1'-diethyl-4,4'-carbocyanine iodide) appear to be promising photosensitizers, in spite of previous reports on the inefficiency of the former cyanine, and the rapid photobleaching of the latter compound.