Near Infrared (NIR) Fluorescent Dyes

Near Infrared (NIR) Fluorescent Dyes have emission maxima in the NIR range (650-1,700 nm) and offer several advantages over visible-range light dyes (400-700nm) such as deep tissue penetration, low tissue background autofluorescence and minimum phototoxicity for biological components due to the longer excitation wavelengths required. They are therefore an ideal choice for in vivo fluorescence imaging.

Literature (1)
Cat. No. Product Name / Activity
7373 FNIR-Tag, NHS
Near-infrared fluorescent dye for labeling of amines; supplied as NHS ester
7749 ICG-d7
Near-infrared (NIR) fluorescent dye; partially deuterated form of Indocyanine Green (Cat. No. 7510), suitable for in vivo imaging.
7510 Indocyanine green
Near-infrared fluorescent dye; suitable for in vivo imaging
7626 NIR Dye s775z, NHS
Near-infrared fluorescent dye

NIR Fluorescent Dyes have light absorption and emission in the near infrared range (650-1,700 nm), which includes the NIR-I (650-900 nm) and the NIR-II (also known as SWIR - shortwave infrared) (1,000-1,700 nm). NIR light offers several advantages over visible-range light (400-650 nm) in fluorescence imaging. It exhibits higher tissue penetration depths due to reduced absorption and scattering, as well as lower background autofluorescence (Figure 1), which together allow highly specific and sensitive detection. Due to the lower energy of longer wavelength light, NIR Fluorescent Dyes present low phototoxicity, making them an ideal tool for live-cell and in vivo imaging.

Effect of different light wavelengths on tissue penetration

Figure 1: Characteristics of light wavelengths that impact tissue penetration depths.

Adapted from Yuanyuan et al. (2020) Near-infrared fluorescence imaging in immunotherapy. Adv. Drug Deliv. Rev. 167, 121. PMID: 32579891

Key Benefits of NIR Fluorescent Dyes:

  • In vivo imaging with high sensitivity and resolution
  • Improved sensitivity when imaging in deep tissues
  • Low phototoxicity
  • Minimal background autofluorescence.

Featured Product: FNIR-Tag, NHS (Cat. No. 7373)

FNIR-Tag, NHS is an NIR cyanine-based fluorescent dye that has excellent properties for labeling antibodies with a high degree of labeling (DOL) and low aggregation. Provides improved signal-to-noise (S/N) and reduced liver uptake in vivo compared to existing NIR dyes. Supplied as an NHS ester for coupling to primary amine groups. For more information on conjugation, see our protocol: Conjugation Protocol for Amine Reactive Dyes.

Key features of FNIR-Tag, NHS:

  • Achieves a higher DOL with less aggregation than competitor products.
  • FNIR-Tag, NHS conjugates are significantly brighter than competitor conjugates in vitro and in vivo.

Application in vitro and in vivo for FNIR-Tag, NHS

Figures 2 (in vitro) and 3 (in vivo) demonstrate the improved brightness of FNIR-Tag, NHS versus a leading competitor dye.

Figures 7373-FNIR-Tag2

Optical Data for FNIR-Tag, NHS

FNIR-Tag-NHS Emission Color Near-IR
λabs 765 nm
λem 788 nm
Extinction Coefficient (ε) 200,000 M-1cm-1
Quantum Yield (φ) 0.099
Closest Laser Line 750 nm
Reactive Group NHS ester
Reactivity Primary amines
Correction factor 280 0.05

Figure 4: Spectral data for FNIR-Tag-NHS


Use of Indocyanine in Clinical Applications

NIR Fluorescent Dyes are powerful tools for in vivo fluorescence imaging in biomedical research and clinical applications.

NIR fluorescent dye structures consist mainly of phthalocyanine, BODIPYs, cyanine, and rhodamine analogs. Among these dyes, cyanine has attracted considerable interest. For example, Indocyanine green (ICG) (Cat. No. 7510), is one of the most widely used NIR fluorescent dyes for optical imaging. It is the main commercially available US Food and Drug Administration (FDA)-approved contrast agent. It is commonly used preclinically and clinically in NIR medical imaging applications for cancer detection, angiography, imaging of intestinal, biliary and lymphatic function, among other uses. ICG is also used in preclinical research for imaging of various animal model of disease.

Interestingly, ICG has a spectral peak wavelength ranging in the NIR-I (700-900 nm) region with a tail extending in the NIR-II (1,000-1,700 nm) region. Light with wavelengths in the NIR-II range exhibits lower absorption, background autofluorescence and scattering, and deeper tissue penetration than NIR-I. As a result, imaging of ICG in the NIR-II gives a better contrast, sensitivity, and resolution over NIR-I region. Given that no FDA-approved fluorophores have peak emission in the NIR-II, ICG off-peak detection in the NIR-II offers big advantages in biomedical imaging applications.

Literature for Near Infrared (NIR) Fluorescent Dyes

Tocris offers the following scientific literature for Near Infrared (NIR) Fluorescent Dyes to showcase our products. We invite you to request* your copy today!

*Please note that Tocris will only send literature to established scientific business / institute addresses.

Fluorescent Dyes and Probes Research Product Guide

Fluorescent Dyes and Probes Research Product Guide

This product guide provides a background to the use of Fluorescent Dyes and Probes, as well as a comprehensive list of our:

  • Fluorescent Dyes, including dyes for flow cytometry
  • Fluorescent Probes and Stains, including our new MitoBrilliantTM mitochondria stains
  • Tissue Clearing Kits and Reagents
  • Aptamer-based RNA Imaging Reagents
  • Fluorescent Probes for Imaging Bacteria
  • TSA VividTM Fluorophore Kits
  • TSA Reagents for Enhancing IHC, ICC & FISH Signals