Phototoxicity of the fluorescent membrane dyes PKH2 and PKH26 on the human hematopoietic KG1a progenitor cell line.
BACKGROUND
The phototoxic effects of the well-known fluorescent membrane dyes PKH2 and PKH26 have been unknown, although their use in cell tracking experiments has increased dramatically. To eliminate the phototoxicity-induced alteration in cell function and morphology, it is essential to examine the suspicious phototoxicity of these dyes.


METHODS
Chemical and phototoxic effects of PKH dyes on the human hematopoietic KG1a cell line were examined. To minimize phototoxicity in long-term cell tracking experiments lasting up to 18 h with a fluorescence microscope system, time-lapse monitoring with different time intervals and exposure times was introduced.


RESULTS
There were no significant effects of the two PKH dyes on cell viability and growth when using dye concentrations up to 5 microM. However, when stained cells were exposed to excitation light, cell viability decreased dramatically, showing the phototoxicity of the PKH dyes. More than 60% of cells stained with 5 microM PKH26 died after 5 min of continuous light exposure. The phototoxic effect was more extensive in cells stained with higher concentrations of the dyes.


CONCLUSIONS
We present guidelines for the optimal use of these dyes by using a defined hardware configuration.
Oh
D J
DJ
Department of Bioengineering, University of California at San Diego, La Jolla, California 92093-0412, USA.
Lee
G M
GM
Francis
K
K
Palsson
B O
BO
D002455:Cell Division / Q000187:drug effects; D002462:Cell Membrane / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D005456:Fluorescent Dyes / Q000633:toxicity*; D006412:Hematopoietic Stem Cells / Q000187:drug effects*; D006801:Humans; D008027:Light; D008856:Microscopy, Fluorescence; D009930:Organic Chemicals; D012815:Signal Processing, Computer-Assisted; D013997:Time Factors; D014407:Tumor Cells, Cultured
D005456:Fluorescent Dyes; D009930:Organic Chemicals; C070080:PKH 26; C067882:PKH2-GL