Spectral properties of stilbazolium merocyanines – potential sensitizers in photodynamic therapy and diagnosis: Part II. Merocyanines in resting and stimulated lymphocytes

Three stilbazolium merocyanines, selected on the basis of their investigations in model systems in part I of this work [J. Photochem. Photobiol., A: Chem. 163 (2004) 127], were introduced into resting and phytohemagglutinin-stimulated lymphocytes. All these merocyanines in solution exhibit high yield of generation of very photochemically active triplet states, but are characterized by different yields of fluorescence emission. The PHA-stimulated lymphocytes were the model of tumor cells. The fluorescence emission and fluorescence excitation spectra are more sensitive to small changes in the cell material than absorption spectra. The course of the photodynamic reactions in stained and unstained cells were established. ficiency of triplet states generation of the dyes incorporated into stimulated cells has been evaluated using time-resolved photothermal spectroscopy. As follows from the photographs of stained cancerous cells taken by means fluorescence microscope, merocyanines are located predominantly in cell membranes. The spectral properties of the dye-sensitizes in solutions and in the cells can differ therefore the selection of proper sensitizers for medical applications made on the ground of the investigation of dye molecules in simple artificial model systems is only preliminary. The selected dyes have to be further investigated after introducing them into resting and PHA-stimulated lymphocytes. It has been shown that the dyes exhibiting high yields of triplet state generation in the stimulated cells usually are also efficient sensitizers of photodynamic reactions. The exceptions are the dyes undergoing fast photobleaching in the cells.