Fluorescence Imaging In Vivo at Wavelengths beyond 1500 nm

Abstract

Compared to imaging in the visible and near-infrared regions below 900 nm, imaging in the second near-infrared window (NIR-II, 1000-1700 nm) is a promising method for deep-tissue high-resolution optical imaging in vivo mainly owing to the reduced scattering of photons traversing through biological tissues. Herein, semiconducting single-walled carbon nanotubes with large diameters were used for in vivo fluorescence imaging in the long-wavelength NIR region (1500-1700 nm, NIR-IIb). With this imaging agent, 3-4 μm wide capillary blood vessels at a depth of about 3 mm could be resolved. Meanwhile, the blood-flow speeds in multiple individual vessels could be mapped simultaneously. Furthermore, NIR-IIb tumor imaging of a live mouse was explored. NIR-IIb imaging can be generalized to a wide range of fluorophores emitting at up to 1700 nm for high-performance in vivo optical imaging.

Continuous injection synthesis of indium arsenide quantum dots emissive in the short-wavelength infrared

“…The tradeoff between increased resolution and decreased imaging speed at longer imaging wavelength stresses the need for fluorescent emitters with high QYs and tunable emission linewidths that maximize the ratio of emitted photons per given spectral region. Our new generation of CSS QDs achieves a 2–3 order of magnitude increase in QY compared with commonly employed SWIR-emissive CNTs212 across the entire sensitivity range of modern SWIR cameras while exhibiting narrow emission linewidths. As a result, CSS QDs not only facilitate multiplexed fluorescence imaging, but also enhance imaging speed for high-resolution imaging at long imaging wavelengths through improved particle quality and the resulting enhancement in QY.…”

“…With QYs of 16% at the red edge of the sensitivity range of SWIR cameras, our probes are more than six times brighter than previously published InAs-based QD systems and further maintain high QYs in aqueous media after phase transfer. Ultimately, we demonstrate how our SWIR fluorophores exhibit a 2–3 order of magnitude higher QY than CNTs212 across the entire sensitivity range of SWIR cameras and demonstrate their use in non-invasive through-skull fluorescence imaging in mice. The improved material properties position our InAs CSS QDs as the material of choice for SWIR fluorescence imaging and suggest possible use in other applications such as SWIR LEDs, photovoltaics, photodetectors and photon upconversion devices15161718.…”

“…While much recent SWIR imaging has focused on carbon nanotubes (CNTs)21112, the low QYs (<0.1%) and broad emission profiles of as-synthesized CNT ensembles have rendered imaging in narrow spectral windows and multiplexed imaging applications challenging. In contrast to other SWIR QDs, such as PbS or Ag 2 S, InAs QDs can exhibit higher QYs and probe stability after transfer from the organic phase to aqueous media513.…”

Traumatic Brain Injury Imaging in the Second Near‐Infrared Window with a Molecular Fluorophore

“…[10a–e, 11] We recently reported that epifluorescence imaging in the NIR-IIa window (1,300–1,400 nm) and NIR-IIb window (1,500–1,700nm) afforded an imaging depth of 2–3 mm (compared to ~ 0.2 mm imaging depth in NIR-I) in the brain of mice capable of sub-10 microns and sub-5 microns cerebrovascular imaging resolutions, respectively. [12] This was further aided with the capability of video rate dynamic imaging to follow vascular hemodynamics. [12] Thus far, carbon nanotubes and inorganic nanoparticles are the most commonly used NIR-II fluorescent agents for in vivo imaging with the caveat of slow excretion of nanomaterials from the body and side effects concerns.…”

Near-Infrared to Visible Upconversion Emission Induced Photopolymerization: Polystyrene Shell Coated NaYF₄ Nanoparticles for Fluorescence Bioimaging and Nanothermometry

“…Especially, over-1000-nm (OTN-) NIR fluorescence imaging has attracted much attention because NIR light in this region can penetrate the body more deeply than the commonly used first biological window (NIR-I: 700-900 nm) region [5][6][7][8][9][10]. The OTN-NIR region is also called the second (NIR-II or NIR-IIa: 1000-1350 nm) and third (NIR-III or NIR-IIb: 1550-1850 nm) biological windows [11].…”