Pyrazole-substituted Near-infrared Cyanine Dyes Exhibit pH-dependent Fluorescence Lifetime Properties

Near‐infrared heptamethine cyanine dye is functionalized with pyrazole derivatives at the meso‐position to induce pH‐dependent photophysical properties. The presence of pyrazole unsubstituted at 1N‐position is essential to induce pH‐dependent fluorescence intensity and lifetime changes in these dyes...

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Bibliographic Details
Published in:Photochemistry and photobiology 2013-03, Vol.89 (2), p.326-331
Main Authors: Lee, Hyeran, Berezin, Mikhail Y., Tang, Rui, Zhegalova, Natalia, Achilefu, Samuel
Format: Article
Language:English
Subjects:
Acidity
Carbocyanines - chemistry
Dimethyl Sulfoxide
Electron transfer
Electrons
Fluorescence
Fluorescent Dyes - chemistry
Hydrogen-Ion Concentration
Indocyanine Green - analogs & derivatives
Indocyanine Green - chemistry
Organic chemistry
Photochemistry
Physical properties
Pyrazoles - chemistry
Spectrometry, Fluorescence
Spectroscopy, Near-Infrared
Spectrum analysis
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Summary:Near‐infrared heptamethine cyanine dye is functionalized with pyrazole derivatives at the meso‐position to induce pH‐dependent photophysical properties. The presence of pyrazole unsubstituted at 1N‐position is essential to induce pH‐dependent fluorescence intensity and lifetime changes in these dyes. Replacement of meso‐chloro group of cyanine dye IR820 with 1N‐unsubstituted pyrazole resulted in the pH‐dependent fluorescence lifetime changes from 0.93 ns in neutral media to 1.27 ns in acidic media in DMSO. Time‐resolved emission spectra (TRES) revealed that at lower pH, the pyrazole consists of fluorophores with two distinct lifetimes, which cor‐responds to pH‐sensitive and non‐pH‐sensitive species. In contrast, 1N‐substituted pyrazoles do not exhibit pH response, suggesting excited state electron transfer as the mechanism of pH‐dependent fluorescence lifetime sensitivity for this class of compounds. Pyrazole meso‐substituted heptamethine cyanine dye showed pH‐dependent fluorescence lifetime change within physiological useful range. This novel fluorescent probe is a good candidate for in vivo diagnostics using fluorescence lifetime imaging method.
ISSN:0031-8655
1751-1097
DOI:10.1111/php.12009