8 Red and Near-IR Fluorescent Two-Photon Absorption Dyes
293
(Mao et al. 2017a). The newly designed TPA dye, 21, which is composed of the aminesubstituted benzocoumarin chromophore as the red-emissive TPA unit, reacts with
NO, resulting in the corresponding N-nitroso derivative, 22, together with enhanced
red light emission at 613 nm and a two-photon action cross section of 54 GM (at
830 nm) (Fig. 8.9). This system can be applied to monitoring NO in ischemia–reperfusion injuries in mice kidneys by two-photon fluorescence microscopy. A similar
strategy of NO detection is used in silicon–rhodamine-based TPA dye 23 (Mao et al.
2017b). This dye provides very weak fluorescence emission at 672 nm with a twophoton action cross section of 0.14 GM. After the reaction with NO, a significant
emission enhancement of 440-fold was achieved to produce product 24, which has
a large two-photon action cross section of 62 GM (Fig. 8.9). This dye can be used to
monitor NO in the development of tumors in a xenograft mouse model.
A TPA fluorescence probe for H 2 S detection was reported by Fan and Peng group
(Sun et al. 2013). A donor–acceptor dicyanomethylene-benzopyran dye 25, which
had a terminal azide group, is nonfluorescent due to PET quenching. When the
dye was treated with sodium hydrogen sulfide as the H 2 S precursor, the resulting
dye, 26, which had a terminal amino group, provided a 65-fold turn-on response
of fluorescence because of the inhibition of the PET effect (Fig. 8.10). The farred fluorescence can be detected upon two-photon excitation. This probe can be
developed for tracking H 2 S in living mice using two-photon fluorescence microscopy.
The dicyanomethylene-benzopyran chromophore was also developed for cysteine
detection as reported by Dong’s group (Wang et al. 2016). The donor–acceptor dye
27 displays fluorescence enhancement of near-IR light (702 nm) with an up to 35fold increase after the addition of cysteine (Fig. 8.10). This cysteine recognition
can be developed for live-cell imaging. The fluorescence detection of SO 2 in brain
tissues and zebrafishes was reported by Lin’s group (Ma et al. 2017). Imaging was
based on a ratiometric fluorescence change from red light emission at 645 nm to blue
emission at 450 nm, which is based on the Michael addition reaction of coumarin–
benzopyrylium-conjugated TPA dye 29 with SO 2 (Fig. 8.10). Three-dimensional
fluorescence imaging of SO 2 in living brain tissue of mice can be performed at a
depth of 80 μm. Endogenous CO imaging by a two-photon technique was reported
by Lin’s group (Liu et al. 2017). Nile Red-based Pd complex 31 has a significantly
weak fluorescent at 660 nm with a fluorescence quantum yield of 0.0047 because
of the strong quenching effect of Pd. When dye 31 reacts with CO molecule, the
released free dye, 32, becomes fluorescent. In the presence of 100 equivalents of
CO, the far-red fluorescence is increased by 60-fold (Fig. 8.10). This CO response
system enables the monitoring of CO in both zebrafish embryos and living mice by
two-photon near-IR light excitation at 760 nm.
An efficient TPA in the second near-IR region was reported by Kawamata and
Konishi’s group (Niko et al. 2015). A pyrene-based acceptor–π–acceptor dye, 33,
exhibited bright red light emission at 650 nm and had an efficient two-photon action
cross section of 304 GM at 1050 nm (Fig. 8.11). In this TPA, a femtosecond fiber laser
was developed as an inexpensive excitation source in the second near-IR region. This
attractive TPA system can be applied for mitochondria imaging in Hek293 cells. The
styrylpyridine-salt-based TPA dye, 34, was reported by Yu and He’s group (Guo et al.
293
(Mao et al. 2017a). The newly designed TPA dye, 21, which is composed of the aminesubstituted benzocoumarin chromophore as the red-emissive TPA unit, reacts with
NO, resulting in the corresponding N-nitroso derivative, 22, together with enhanced
red light emission at 613 nm and a two-photon action cross section of 54 GM (at
830 nm) (Fig. 8.9). This system can be applied to monitoring NO in ischemia–reperfusion injuries in mice kidneys by two-photon fluorescence microscopy. A similar
strategy of NO detection is used in silicon–rhodamine-based TPA dye 23 (Mao et al.
2017b). This dye provides very weak fluorescence emission at 672 nm with a twophoton action cross section of 0.14 GM. After the reaction with NO, a significant
emission enhancement of 440-fold was achieved to produce product 24, which has
a large two-photon action cross section of 62 GM (Fig. 8.9). This dye can be used to
monitor NO in the development of tumors in a xenograft mouse model.
A TPA fluorescence probe for H 2 S detection was reported by Fan and Peng group
(Sun et al. 2013). A donor–acceptor dicyanomethylene-benzopyran dye 25, which
had a terminal azide group, is nonfluorescent due to PET quenching. When the
dye was treated with sodium hydrogen sulfide as the H 2 S precursor, the resulting
dye, 26, which had a terminal amino group, provided a 65-fold turn-on response
of fluorescence because of the inhibition of the PET effect (Fig. 8.10). The farred fluorescence can be detected upon two-photon excitation. This probe can be
developed for tracking H 2 S in living mice using two-photon fluorescence microscopy.
The dicyanomethylene-benzopyran chromophore was also developed for cysteine
detection as reported by Dong’s group (Wang et al. 2016). The donor–acceptor dye
27 displays fluorescence enhancement of near-IR light (702 nm) with an up to 35fold increase after the addition of cysteine (Fig. 8.10). This cysteine recognition
can be developed for live-cell imaging. The fluorescence detection of SO 2 in brain
tissues and zebrafishes was reported by Lin’s group (Ma et al. 2017). Imaging was
based on a ratiometric fluorescence change from red light emission at 645 nm to blue
emission at 450 nm, which is based on the Michael addition reaction of coumarin–
benzopyrylium-conjugated TPA dye 29 with SO 2 (Fig. 8.10). Three-dimensional
fluorescence imaging of SO 2 in living brain tissue of mice can be performed at a
depth of 80 μm. Endogenous CO imaging by a two-photon technique was reported
by Lin’s group (Liu et al. 2017). Nile Red-based Pd complex 31 has a significantly
weak fluorescent at 660 nm with a fluorescence quantum yield of 0.0047 because
of the strong quenching effect of Pd. When dye 31 reacts with CO molecule, the
released free dye, 32, becomes fluorescent. In the presence of 100 equivalents of
CO, the far-red fluorescence is increased by 60-fold (Fig. 8.10). This CO response
system enables the monitoring of CO in both zebrafish embryos and living mice by
two-photon near-IR light excitation at 760 nm.
An efficient TPA in the second near-IR region was reported by Kawamata and
Konishi’s group (Niko et al. 2015). A pyrene-based acceptor–π–acceptor dye, 33,
exhibited bright red light emission at 650 nm and had an efficient two-photon action
cross section of 304 GM at 1050 nm (Fig. 8.11). In this TPA, a femtosecond fiber laser
was developed as an inexpensive excitation source in the second near-IR region. This
attractive TPA system can be applied for mitochondria imaging in Hek293 cells. The
styrylpyridine-salt-based TPA dye, 34, was reported by Yu and He’s group (Guo et al.