Luminescence Study of Singlet Oxygen Production by Meso-Tetraphenylporphine
The research in the field of the photodynamic therapy of cancer (PDT) is focused on a development of photosensitizers exhibiting high quantum yield of singlet oxygen production. Direct time-resolved spectroscopic observation of singlet oxygen phosphorescence can provide time constants of its population and depopulation as well as photosensitizer phosphorescence lifetime and relative quantum yields. In our contribution, a study of time and spectral resolved phosphorescence of singlet oxygen photosensitized by meso-tetraphenylporphine in acetone together with the photosensitizer phosphorescence is presented. Time constants of singlet oxygen population and depopulation were determined at wide range of photosensitizer concentrations. The time constant of singlet oxygen generation (0.28 ± 0.01) μs is slightly shorter then the lifetime of photosensitizer's triplet state (0.32 ± 0.01) μs. It is caused by lower ability of TPP aggregates to transfer excitation energy to oxygen. The lifetime of singlet oxygen (≈50 μs) decreases with increasing photosensitizer concentration. Therefore, the photosensitizer acts also as a quencher of oxygen singlet state, similarly to the effects observed in [A. A. Krasnovsky, P. Cheng, R. E. Blankenship, T. A. Moore, and D. Gust (1993). Photochem. Photobiol.57, 324–330; H. Küpper, R. Dědic, A. Svoboda, J. Hála, and P. M. H. Kroneck (2002). Biochim. Biophys. Acta Gen. Subj.1572, 107–113]. Moreover, the increasing concentraion of the photosensitizer causes a slight hypsochromic shift of the singlet oxygen luminescence maximum.
Unable to display preview. Download preview PDF.
- 3.C. A. Parker (1968). Photoluminescence of Solutions, Elsevier, New York.Google Scholar
- 4.A. A. Krasnovsky, S. Y. Egorov, O. V. Nasarova, E. I. Yartsev, and G. V. Ponomarev (1988). Photosensitised formation of singlet molecular oxygen in solutions of water soluble porphyrins. Direct luminescence measurement. Stud. Biophys. 124(2/3), 123-142.Google Scholar
- 5.H. Küpper, R. Dvědic, A. Svoboda, J. Hála, and P. M. H. Kroneck (2002). Kinetics and efficiency of excitation energy transfer from chlorophylls, their heavy metal-substituted derivatives, and pheophytins to singlet oxygen. Biochim. Biophys. Acta Gen. Subj. 1572, 107-113.Google Scholar