Molecular design strategies for near-infrared ratiometric fluorescent probes based on the unique spectral properties of aminocyanines.
In spite of the wide availability of various near-infrared (NIR) fluorophores as labeling reagents, there are few functional NIR fluorescent probes for which change in the absorption and/or fluorescence spectra upon specific reaction with biomolecules is seen. The widely used photoinduced electron-transfer mechanism is unsuitable for NIR fluorophores, such as tricarbocyanines, because their long excitation wavelength results in a small singlet excitation energy. We have reported the unique spectral properties of amine-substituted tricarbocyanines, which were utilized to develop two design strategies. One approach was based on control of the absorption wavelength by using the difference in electron-donating ability before and after a specific reaction with a biomolecule, and the other approach was based on control of the fluorescence intensity by modulating the Förster resonance energy-transfer efficiency through a change in the overlap integral that arises from the change in absorption under acidic conditions. These strategies were validated by obtaining tricarbocyanine-based ratiometric NIR fluorescent probes for esterase and for pH level.
Kiyose
Kazuki
K
Graduate School of Pharmaceutical Sciences, The University of Tokyo, 7-3-1, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.
Aizawa
Sakiko
S
Sasaki
Eita
E
Kojima
Hirotatsu
H
Hanaoka
Kenjiro
K
Terai
Takuya
T
Urano
Yasuteru
Y
Nagano
Tetsuo
T
D002232:Carbocyanines / Q000737:chemistry*; D004950:Esterases / Q000378:metabolism; D005456:Fluorescent Dyes / Q000138:chemical synthesis / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D015394:Molecular Structure; D019265:Spectroscopy, Near-Infrared
D002232:Carbocyanines; D005456:Fluorescent Dyes; D004950:Esterases