Inorganic Nanoparticles for Near-infrared-II Fluorescence Imaging

Fluorescence imaging is widely used to image cells or small animals due to its high temporal and spatial resolution. Because conventional fluorescence imaging uses visible light, the penetration depth of light within the tissue is low, phototoxicity may occur due to visible light, and the detection sensitivity is lowered due to interference by background autofluorescence. In order to overcome this limitation, long-wavelength light should be used, and fluorescence imaging using near-infrared-I (NIR-I) in the region of 700 similar to 900 nm has been developed. To further improve imaging quality, researchers are interested in using a longer wavelength light, near-infrared-II (NIR-II) ranging from 1000 to 1700 nm. In the NIR-II region, light scattering is further minimized, and the penetration depth of light in the tissue is improved up to about 10 mm, and autofluorescence of the tissue is reduced, enabling high sensitivity and resolution fluorescence imaging. In this review, among various NIR-II fluorescence imaging probes, inorganic nanoparticle-based probes with excellent photostability and easily tunable emission wavelength were described, focusing on single-walled carbon nanotubes, quantum dots, and lanthanide nanoparticles.

Automated summary

Fluorescence imaging is widely used in cell and small animal imaging due to its high temporal and spatial resolution. However, conventional fluorescence imaging using visible light has limitations such as low penetration depth, phototoxicity, and interference from background autofluorescence. To overcome these limitations, fluorescence imaging using near-infrared-I (NIR-I) and near-infrared-II (NIR-II) light has been developed. NIR-II imaging offers advantages of reduced light scattering, improved penetration depth, and reduced autofluorescence. Inorganic nanoparticle-based probes, including single-walled carbon nanotubes, quantum dots, and lanthanide nanoparticles, have been explored for NIR-II fluorescence imaging due to their excellent photostability and tunable emission wavelength.