Fluorescence imaging of Foscan and Foslip in the plasma membrane and in whole cells.
A fluorescence microscope equipped with a condenser for total internal reflection (TIR) illumination was combined with a pulsed laser diode and a time-gated image intensifying camera for fluorescence lifetime measurements of single cells. In particular, fluorescence patterns, decay kinetics, and lifetime images of the lipophilic photosensitizers Foscan and Foslip were studied in whole cells as well as in close vicinity to their plasma membranes. Fluorescence lifetimes of both photosensitizers in cultivated HeLa cells decreased from about 8 ns at an incubation time of 3 h to about 5 ns at an incubation time of 24 h. This seems to result from an increase in aggregation (or self-quenching) of the photosensitizers during incubation. Selective measurements within or in close proximity to the plasma membrane indicate that Foscan and Foslip are taken up by the cells in a similar way, but may be located in different cellular sites after an incubation time of 24 h. A combination of TIR and fluorescence lifetime imaging microscopy (FLIM), described for the first time, appears to be promising for understanding some key mechanisms of photodynamic therapy (PDT).
Hochschule Aalen, Anton-Huber-Straße 21, 73430 Aalen, Germany; Centre de Recherche en Automatique de Nancy, Nancy Université, CNRS, Centre Alexis Vautrin, Avenue de Bourgogne, 54511 Vandoeuvre les Nancy, France.
Henri-Pierre
HP
Lassalle
Hochschule Aalen, Anton-Huber-Straße 21, 73430 Aalen, Germany.
Michael
M
Wagner
Centre de Recherche en Automatique de Nancy, Nancy Université, CNRS, Centre Alexis Vautrin, Avenue de Bourgogne, 54511 Vandoeuvre les Nancy, France.
Lina
L
Bezdetnaya
Centre de Recherche en Automatique de Nancy, Nancy Université, CNRS, Centre Alexis Vautrin, Avenue de Bourgogne, 54511 Vandoeuvre les Nancy, France.
François
F
Guillemin
Hochschule Aalen, Anton-Huber-Straße 21, 73430 Aalen, Germany.
Herbert
H
Schneckenburger
D045744:Cell Line, Tumor; D002462:Cell Membrane / Q000737:chemistry*; D005453:Fluorescence; D006367:HeLa Cells; D006801:Humans; D008652:Mesoporphyrins / Q000032:analysis*; D008856:Microscopy, Fluorescence / Q000379:methods*; D017319:Photosensitizing Agents / Q000032:analysis*
D008652:Mesoporphyrins; D017319:Photosensitizing Agents; C072269:temoporfin