Recent Advances in Near‐Infrared‐II Fluorescence Imaging for Deep‐Tissue Molecular Analysis and Cancer Diagnosis

Abstract

Fluorescence imaging with high sensitivity and minimal invasiveness has received tremendous attention, which can accomplish visualized monitoring and evaluation of cancer progression. Compared with the conventional first near‐infrared (NIR‐I) optical window (650–950 nm), fluorescence imaging in the second NIR optical window (NIR‐II, 950–1700 nm) exhibits deeper tissue penetration capability and higher temporal‐spatial resolution with lower background interference for achieving deep‐tissue in vivo imaging and real‐time monitoring of cancer development. Encouraged by the significant preponderances, a variety of multifunctional NIR‐II fluorophores have been designed and fabricated for sensitively imaging biomarkers in vivo and visualizing the treatment procedure of cancers. In this review, the differences between NIR‐I and NIR‐II fluorescence imaging are briefly introduced, especially the advantages of NIR‐II fluorescence imaging for the real‐time visualization of tumors in vivo and cancer diagnosis. An important focus is to summarize the NIR‐II fluorescence imaging for deep‐tissue biomarker analysis in vivo and tumor tissue visualization, and a brief introduction of NIR‐II fluorescence imaging‐guided cancer therapy is also presented. Finally, the significant challenges and reasonable prospects of NIR‐II fluorescence imaging for cancer diagnosis in clinical applications are outlined.

Recent advances in activatable NIR-II organic fluorophores for biomedical applications

“…3 There is no doubt that fluorophores play important roles here in NIR-II imaging. To date, various types of fluorescent probes in the NIR-II region have been developed for biomedical research, 4 including carbon nanotubes, 5 quantum dots, 6 lanthanide-doped nanoparticles 7 and organic fluorescent probes. 8 Among them, organic fluorophores are the superior alternatives because of their easy processability, tunable optical performances and also favorable biocompatibility.…”

Origins of near-infrared-II emission tail and fluorescence enhancement of albumin-chaperoned cyanine dyes from a multiscale computational study

“…26 Up to now, however, the emission spectra of NIR-I dyes have been rarely studied in the NIR-II region, and to the best of our knowledge, the origin of NIR-II tail emission has never been systematically investigated. Various possible mechanisms including the vibration effect, [27][28][29][30][31] twisted intramolecular charge transfer (TICT), 14,17,[32][33][34] aggregation-induced emission, [35][36][37] etc. were proposed and thus have brought new puzzles for understanding the phenomenon of such a weak red-shifted tail.…”

Recent progress of second near-infrared (NIR-II) fluorescence microscopy in bioimaging

“…Then, through collecting, splitting, filtering, and focusing the emitting light path, the excited fluorescence signal enters the photodetector to complete the photoelectric conversion. This is followed by signal amplification, analysis, and processing, to finally obtain the image ( Meng et al, 2022 ). As a promising imaging method, fluorescence imaging has the advantages of high temporal and spatial resolution and few side effects, which cannot be achieved by in vitro imaging at the cell and tissue level.…”