Time-resolved fluorescence polarization microspectroscopy of photosensitizers in a single living cell

Different types of photosensitizers used in photodynamic therapy (PDT) differ by mechanism of penetration into the cell, their localization, and aggregational properties. On the other hand, all these factors determine the efficiency of photodamage. That is why the experimental equipment which permits the direct non-destructive observation of the processes of accumulation of photosensitizers in living cell is of great interest. The effective combination of fluorescence microscope, time-correlated single photon counting registration system, and computer-controlled polarization device is developed. The dynamics of hematoporphyrin accumulation in different sites of single living cell was measured. The main role of porphyrin- lipid interaction in aggregation of hematoporphyrin in plasma and nuclear membranes was shown. The experiments with phthalocyanines and ether-bonded porphyrin-chlorin dimers are on the way.