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Figure 1. Linker part of the chemical structure of the chromophore (the optically active part of the voltage-sensitive dye) which shifts spectral sensitivity to near-infrared range. The complete chromophore and more details can
be found in Matiukas et al., 2006 (See Publications).
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In close collaboration with Dr. L.Loew‘s group we have
developed new potentiometric indicators for cardiac optical mapping. These
membrane voltage sensitive styryl dyes have excitation wavelengths ranging
above 700 nm and emission spectra extending to 900 nm. They provide excellent
optical action potentials in all typical cardiac tissues (mouse, rat, guinea
pig, pig). The voltage sensitivities of these new potentiometric indicators
(7-20% in a variety of species) are as good as those of the widely used ANEP
series of probes.
Near-infrared (NIR) dyes have better depth penetration in
cardiac tissue because NIR light is significantly less scattered and absorbed
than light of shorter wavelength.
Consequently, NIR dyes provide advantages for optical mapping of thick
cardiac tissues. Some modes of optical
mapping (such as transillumination when light source and photodetector face
opposite sides of tissue) significantly benefit from using NIR dyes.
Possible use of inexpensive excitation sources such as red
LED, red laser diodes (see Fig. 2), and HeNe lasers (at 633 nm) is a great
advantage.
The new dyes have excitation and emission spectra that are
well separated from the blood absorption maximum (~580 nm), better than for any
other known voltage-sensitive dyes. This allows us to effectively use them in
optically mapping blood perfused tissues (see Fig. 3, excitation at 650nm,
voltage-sensitive fluorescence at >715nm).
Finally, due to molecular engineering of the chromophore the
new dyes provide a wide range of dye washout time constants (50-5000 s). This
allows tailoring dye loading and washout to the specific application.
The latest generation of near-infrared voltage-sensitive dyes, with further improved major characteristics, is patent pending.
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