Applications of photothermic methods in photodynamic therapy investigations

The applications of steady state photoacoustic and time resolved photothermal methods are carried out in our laboratory. Based on these methods, the selection of optimal sensitizers for photodynamic therapy and photodynamic diagnosis of cancer were described. Additionally, in order to establish the fate of absorbed energy, the absorption and fluorescence spectra were measured. All spectra were measure using natural and/or linearly polarized light because of polarized spectroscopy delivers information about the sample structures. Spectral and photochemical properties of selected sensitizers (merocyanines, porphyrines and phthalocyanines) were investigated. All dyes were first investigated in model systems (fluid solutions or rigid matrix) and later incorporated into resting or stimulated cells as well as into cancer cells delivered from cell lines. Stimulated cells could serve as models of malignant tissue and the properties of these cells at various procedures of stimulation were compared. It was shown that steady state photoacoustic, which is less perturbed by scattering than absorption, is very useful in the establishment of the efficiency of sensitizer incorporation into cells whereas a time resolved photothermal method (laser induced optoacoustic spectroscopy) enabled the establishment of a yield of dye triplet states generation. The triplet states are very active in photochemical reactions. Therefore, on the basis of their yield, it is possible to predict the efficiency of light induced lesions of malignant cells