Molecular Design Strategies for Near‐Infrared Ratiometric Fluorescent Probes Based on the Unique Spectral Properties of Aminocyanines

Abstract

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.

Combining Aminocyanine Dyes with Polyamide Dendrons: A Promising Strategy for Imaging in the Near‐Infrared Region

“…These features are in agreement with previous reports on aminocyanine dyes and result from an intramolecular charge transfer (ICT). [24,28] The maximum absorption of the dyes is highly solvent dependent (Table 1). However, contrary to the reported aminocyanine dyes with alkyl or phenyl termini, the solvatochromism of the new [a] The absorption spectra were recorded at 25 8C and e is expressed in m À1 cm À1 at the maximum of the highest peak.…”

“…9 (26), e) dendron dyeÀPEGÀA C H T U N G T R E N N U N G (COOtBu) 9 (28), and f) dendron dyeÀPEGÀ(N 3 ) 9 (30) in different solvents (blue = PBS, green = DMSO, orange = DMF, red = EtOH, and black = MeOH). All spectra were taken at concentrations of 1 10 À5 m at 25 8C.…”

Recent Development of Chemosensors Based on Cyanine Platforms

“…97 Therefore, many cyanine chemosensors based on PET suffer from high background fluorescence. On the contrary, ICT exhibits a promising strategy to develop cyanine-based chemosensors, because ICTinvolved cyanine sensors always display ratiometric response to analytes, which is more reliable for quantitative detection.…”

Silicon-substituted xanthene dyes and their applications in bioimaging

“…For example, PeT-based quenching of tricarbocyanine dye IR-768 derivatives requires benzene moieties with a much higher HOMO energy level compared to TokyoGreen, a major core for PeT-based fluorescence probes. 29,30 Therefore, it is a considerable challenge to control far-red to NIR fluorescence by means of the PeT mechanism. It is noteworthy that SiR650 achieves NIR absorption owing to its low-lying LUMO energy level arising from σ*-π* conjugation, resulting in a larger reduction potential (E red = -0.62 V) than that of NIR cyanine dye IC5 (E red = -0.88 V).…”