Recent Progress in NIR-II Contrast Agent for Biological Imaging

Abstract

Fluorescence imaging technology has gradually become a new and promising tool for in vivo visualization detection. Because it can provide real-time sub-cellular resolution imaging results, it can be widely used in the field of biological detection and medical detection and treatment. However, due to the limited imaging depth (1-2 mm) and self-fluorescence background of tissue emitted in the visible region (400-700 nm), it fails to reveal biological complexity in deep tissues. The traditional near infrared wavelength (NIR-I, 650-950 nm) is considered as the first biological window, because it reduces the NIR absorption and scattering from blood and water in organisms. NIR fluorescence bioimaging's penetration is larger than that of visible light. In fact, NIR-I fluorescence bioimaging is still interfered by tissue autofluorescence (background noise), and the existence of photon scattering, which limits the depth of tissue penetration. Recent experimental and simulation results show that the signal-to-noise ratio (SNR) of bioimaging can be significantly improved at the second region near infrared (NIR-II, 1,000-1,700 nm), also known as the second biological window. NIR-II bioimaging is able to explore deep-tissues information in the range of centimeter, and to obtain micron-level resolution at the millimeter depth, which surpass the performance of NIR-I fluorescence imaging. The key of fluorescence bioimaging is to achieve highly selective imaging thanks to the functional/targeting contrast agent (probe). However, the progress of NIR-II probes is very limited. To date, there are a few reports about NIR-II fluorescence probes, such as carbon nanotubes, Ag 2 S quantum dots, and organic small molecular dyes. In this paper, we surveyed the development of NIR-II imaging contrast agents and their application in cancer imaging, medical detection, vascular bioimaging, and cancer diagnosis. In addition, the hotspots and challenges of NIR-II bioimaging are discussed. It is expected that our findings will lay a foundation for further theoretical research and practical application of NIR-II bioimaging, as well as the inspiration of new ideas in this field.Keywords: fluorescence imaging technology, the second region near infrared (NIR-II), biological imaging, contrast agents, biomedical applications Frontiers in Bioengineering and Biotechnology | www.frontiersin.org

Ultrafast photochemistry produces superbright short-wave infrared dots for low-dose in vivo imaging

“…In this spectral range, the absorption and scattering coefficients of biological tissues are reduced to a minimum, allowing high-contrast, high-resolution in vivo imaging at large (>1 cm) tissue depths 9 . NIR-II fluorescent materials have changed the game in preclinical imaging 10,11 , enabling high-resolution anatomical imaging 12,13 , tumor detection 14,15 , biosensing 16 , brain vasculature mapping 17,18 , image-guided genome editing 19 and surgery 20,21 , and dynamic tracking of metabolic processes 22 . NIR-II-emitting Ag 2 S nanocrystals do not contain highly toxic heavy metal ions, unlike other nanoprobes operating in this spectral range, minimizing biocompatibility concerns and making them one of the most promising systems among all currently reported NIR-II fluorophores 23,24 .…”

A Paper-Based Near-Infrared Optical Biosensor for Quantitative Detection of Protease Activity Using Peptide-Encapsulated SWCNTs

“…The detector itself, in many cases, could be a simple complementary metal oxide semiconductor (CMOS) camera—sometimes one that is integrated into a smartphone [ 22 , 23 ], thus significantly reducing the device cost. Optical biosensors that emit signals in the near-infrared (NIR) region are of particular interest in the biomedical field, as NIR wavelengths are less absorbed and scattered in biological tissues compared to visible wavelengths [ 24 ].…”

Shortwave Infrared-Emitting Theranostics for Breast Cancer Therapy Response Monitoring

“…Optical imaging provides excellent sensitivity, with the ability to image at molecular resolution ( Wang et al, 2015 ). However, in vivo optical imaging is limited due to a shallow millimeter-scale depth of penetration and tissue autofluorescence in the visible spectrum (λ = 400–700 nm) ( Cao et al, 2019 ). Previously, we have addressed this shortcoming of optical imaging through the use of rare earth (Re)-doped ceramic nanoprobes that emit shortwave infrared (SWIR) light (λ = 1000–1700 nm) following excitation by a 980 nm source ( Naczynski et al, 2010 ).…”

“…Previously, we have addressed this shortcoming of optical imaging through the use of rare earth (Re)-doped ceramic nanoprobes that emit shortwave infrared (SWIR) light (λ = 1000–1700 nm) following excitation by a 980 nm source ( Naczynski et al, 2010 ). SWIR, also referred to as the second optical window of near infrared light (NIR-II), can penetrate deeper into tissue because of lower absorbance than visible light ( Cao et al, 2019 ). Furthermore, reduced scattering and autofluorescence compared to both visible and NIR-I wavelengths (λ = 700–1000 nm) results in significantly improved signal-to-noise ratios without a loss of spatial resolution ( Cao et al, 2019 ).…”

“…SWIR, also referred to as the second optical window of near infrared light (NIR-II), can penetrate deeper into tissue because of lower absorbance than visible light ( Cao et al, 2019 ). Furthermore, reduced scattering and autofluorescence compared to both visible and NIR-I wavelengths (λ = 700–1000 nm) results in significantly improved signal-to-noise ratios without a loss of spatial resolution ( Cao et al, 2019 ). Naczynski et al designed a biocompatible formulation of Re-doped ceramic nanoprobes through encapsulation in human serum albumin to generate rare earth albumin nanocomposites (ReANCs) and subsequently established these as novel diagnostic agents in tumor surveillance ( Naczynski et al, 2013 ).…”