NIR dyes for bioimaging applications

Abstract

Summary of recent advances Fluorescent dyes based on small organic molecules that function in the near infra red (NIR) region are of great current interest in chemical biology. They allow for imaging with minimal autofluorescence from biological samples, reduced light scattering and high tissue penetration. Herein, examples of ongoing NIR fluorophore design strategies as well as their properties and anticipated applications relevant to the bioimaging are presented.

<italic>In vivo</italic> testing of a prototype system providing simultaneous white light and near infrared autofluorescence image acquisition for detection of bladder cancer

“…Interestingly, the NIR is considered to be part of the spectrum in which there is relatively little native tissue absorption and autofluorescence, which has helped generate a large interest in developing contrast agents that fluoresce in the NIR for biological imaging. 23 The ability for the system to qualitatively generate a NIR fluorescent signal that corresponds with presence of visible tumor reflects the high sensitivity that this combination of excitation and fluorescence wavelengths allow, without the loss of signal that would typically be associated by absorption of excitation light by heme.…”

“…Such NIR contrast agents are in the process of being developed. 23 The convenience of not needing to switch imaging modes during surgery increases the potential utility of including fluorescence imaging as a surgical tool in a way that has not yet been realized and increases the flexibility of the instrument to use in a wide variety of endoscopic applications. In addition, the use of relatively long wavelength excitation light increases the probe depth compared to what is possible using UV or blue light for fluorophore excitation.…”

Facile synthesis of β-lactoglobulin capped Ag2S quantum dots for in vivo imaging in the second near-infrared biological window

“…As a result, NIR-II fluorescence imaging can allow deep penetration into biological tissues with excellent imaging fidelity, sensitivity and resolution. [5][6][7] Over the past few years, considerable efforts have been devoted to develop high-quality NIR-II emitters including single-walled carbon nanotubes (SWNTs), [8][9][10] quantum dots (QDs), [11][12][13][14][15][16][17] rare-earth-doped nanoparticles (NPs), [18][19][20] and polymeric fluorophores. 21,22 Among them, the no toxic heavy metal-containing Ag2S QDs have become one of the most intensively studied NIR-II emitters.…”

2-{(E)-2-[(3E)-2-Chloro-3-{(2E)-2-[1,1-dimethyl-3-(3-phenylpropyl)-1,3-dihydro-2H-benzo[e]indol-2-ylidene]-ethylidene}cyclohex-1-en-1-yl]ethenyl}-1,1-dimethyl-3-(3-phenylpropyl)-1H-benzo[e]indolium Iodide

“…Cyanine dyes are an interesting class of fluorescent compounds that are defined by two terminal heterocyclic nitrogen containing rings that have a delocalized monocation across a polymethine bridge, as compound 4 shown in Scheme 1 [1][2][3][4][5]. The synthetic preparation of these chromophores allows for diverse modifications at various locations to finely tune the binding properties to biomolecules or to modify for achieving very specific wavelengths [6,7].…”