Krzysztof Wiktorowicz

Yield of intersystem (singlet-triplet) crossing in phthalocyanines evaluated on the basis of a time in resolved photothermal method

The yields of triplet state formation for seven various phthalocyanines (Pc) unsubstituted by metal and substituted by Mg, Zn, Cu and Al in dimethyl-sulfoxide (DMSO) solutions were compared on the basis of time resolved photothermal measurements. The sample with atmospheric oxygen and bubbled by nitrogen were investigated. Absorption, fluorescence, and steady state photoacoustic spectra (PAS) of the same samples were also measured. The yields of triplet state formation for most of metal substituted dyes were higher than for investigated metal-free dyes. The triplets for various dyes were differently quenched by oxygen. The possibility of the application of investigated dyes in photodynamic therapy and diagnosis was discussed.

Spectral properties of stilbazolium merocyanines – potential sensitizers in photodynamic therapy and diagnosis: Part I. Merocyanines in model systems

Abstract Spectral and photochemical properties of seven stilbazolium merocyanines of different chain length and side groups attached, dissolved in ethanol or methanol solutions as well as in polyvinyl alcohol water solutions and films, were investigated. The absorption, fluorescence emission and fluorescence excitation spectra as well as steady state photoacoustic and laser induced optoacoustic spectroscopy signals were measured. Triplet states are, because of their slow decay time, usually very effective in photochemical reaction; therefore dyes with efficient triplet states generation are suitable for destruction of illuminated diseased cells. The laser induced optoacoustic measurements were used to evaluate the efficiency of generation and decay times of dye triplet states. The quenching of the dye triplet state by oxygen was also studied. The results show that properties of merocyanines and their interactions with macromolecules depend strongly on the type of side groups attached. The dyes with NO 2 groups attached exhibit low yield of fluorescence therefore they could be useful rather in photodynamic therapy (PDT) than for diagnostic purposes. Some of the merocyanines investigated exhibit high yields of triplet state generation and, therefore, should be effective in photodynamic reactions. Further investigations will be carried out with the same dyes on healthy and diseased cells in order to show whether it is possible, on the grounds of spectral and photochemical properties of dye molecules in simple model systems, to predict the efficiencies of the dye incorporation into cells and the yield of photodynamic reactions.

Incorporation of Dye in Resting and Stimulated Leukocytes

Methods of investigating the incorporation efficiency of dye molecules into leukocytes and other cells are reviewed. The application of polarized light spectroscopy into the establishment of changes in the structure of biological membranes due to cell stimulation is reported. Results obtained by polarized light absorption, fluorescence, delayed luminescence and photoacoustic spectra and flow cytometry applications are described. The incorporation of two types of dyes: stilbazolium merocyanines and porphyrins are discussed on the basis of the authors’ results.

The phthalocyanines applications in photodynamic therapy investigated by time-resolved and steady-state photothermal methods

The time-resolved photothermal methods are used in order to establish the yield of intersystem (singlet-triplet) crossing of dyes that are candidates for the application in photodynamic therapy. It is known that molecules with long living triplet state cause efficient photosensitization by direct interaction with the cells or by singlet oxygen generation.

Selection of proper sensitizers for photodynamic therapy on the basis of time-resolved and steady-state photothermal study

The possibility of application of natural photosynthetic pigments and their derivatives in photodynamic therapy and photodynamic diagnosis has been investigated. The triplet states of dyes are highly photochemically active, therefore, the dyes exhibiting high efficiency of triplet states generation are usually efficient photosensitizers in photodynamic therapy. Generation of triplet states has been estimated by means of the laser induced optoacoustic spectroscopy. The type of the photoreaction was established by comparing the yield of triplet generation with and without the oxygen presence. The intersystem crossing transition from excited singlet state S1 to triplet state T1 is competing with fluorescence emission, therefore, the dyes with efficient triplet generation usually are not suitable for diagnosis which requires a high yield of fluorescence. The chlorophyll-like pigments of prospective applications in medicine have been studied. Preliminary selection of dye-sensitizers has been made on the basis of investigation of the same dyes in model systems (solutions) and their complexes with macromolecules. The final study has been performed for resting (healthy) and stimulated (cancerous cells models) lymphocytes. Of course, the properties of sensitizers in cells and in models are not the same, but the measurements have enabled a selection (from a set of similar molecules) of the most promising dyes, tested later in the cells. The results obtained for chlorophyll-like pigments are compared with those obtained for the synthetic dyes (porphyrins, stilbazolium merocyanines and phthalocyanines) earlier investigated in our laboratory and with literature data.