Photomodification of ALA-induced protoporphyrin IX in cells in vitro

Giedre Streckyte; Kristian Berg; Johan Moan

doi:10.1117/12.199173

12 January 1995 Photomodification of ALA-induced protoporphyrin IX in cells in vitro

Giedre Streckyte, Kristian Berg, Johan Moan

Proceedings Volume 2325, Photodynamic Therapy of Cancer II; (1995) https://doi.org/10.1117/12.199173
Event: International Symposium on Biomedical Optics Europe '94, 1994, Lille, France

Abstract

Cells of the line WiDr were incubated with media containing different concentrations of (delta) -aminolevulinic acid (ALA) and the amount of the produced protoporphyrin (Pp) IX was evaluated by means of steady-state fluorescence. The photomodification process of ALA- induced Pp IX was investigated by measuring spectroscopic properties of cells suspensions incubated with 0.2 mM and 1 mM of ALA. Light exposure of cells containing Pp IX resulted in a decrease of fluorescence intensities at 635 and 705 nm ((lambda) _exc equals 413 nm) due to photobleaching and in an increase of fluorescence intensity at around 670 nm due to the formation of a photoproduct. These spectral changes arise from photochemical reactions resulting in the formation of photoprotoporphyrin and destruction of porphyrin ring. The fluorescence kinetics indicate that for ALA-induced Pp IX in cells the ring opening reaction prevails the photoprotoporphyrin formation. Singlet oxygen may be involved in both processes since the photobleaching is slowed down on bubbling N₂ through the samples and photoprotoporphyrin formation is slightly faster in suspensions in phosphate buffered saline (PBS) made of D₂O compared with suspensions in PBS made of H₂O.

Citation Download Citation

Giedre Streckyte, Kristian Berg, and Johan Moan "Photomodification of ALA-induced protoporphyrin IX in cells in vitro", Proc. SPIE 2325, Photodynamic Therapy of Cancer II, (12 January 1995); https://doi.org/10.1117/12.199173

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