Bioresponsive fluorescent probes active in the second near‐infrared window

Abstract

Emerging stimuli-responsive composite probes active in the second nearinfrared window (NIR-II, 1000-1700 nm) hold vast potential for improving in vivo imaging performance with minimized noise interference. The interactions among external irradiation, shell species, and the emissive core are key factors in the design of smart structures. The external irradiation provides energy for shell species and the emissive core to generate intense NIR-II fluorescence signals, while the energy transfer process hinders NIR-II emission in the inner structure of smart composite probes. However, if pathophysiological stimuli interrupt the above processes, then NIR-II fluorescence signals are recovered. This review covers NIR-II imaging based on diverse smart composite NIR-II fluorescent probes responding to various biological stimuli, including ONOO − , overexpressed reactive sulfur species, abnormally expressed enzymes, and abnormal levels of physiological metabolites. Finally, to appreciate these advances, the challenges and perspectives of stimuliresponsive composite NIR-II probes are highlighted.

NIR-II fluorescence imaging without intended excitation light

“…Meanwhile, active-targeting NIR-II probes need to be developed to improve tumor imaging contrast. 33 Introducing a polyethylene glycol moiety into the optical probes or developing renal-clearable optical agents can improve the uptake of probes in the liver. 34,35 Furthermore, improvements in the imaging equipment, such as equipping it with longer wavelength LED excitation light, are needed to achieve deeper penetration.…”

Development of Polymethine Dyes for NIR‐II Fluorescence Imaging and Therapy

“…In the presence of H 2 S, the absorption of the heptamethine polymethine cyanine at 808 nm decreased, resulting in the recovery of NIR‐II emission from the nanoparticles. [ 178 ]…”

Development of a Novel HER2-Targeted Peptide Probe for Dual-Modal Imaging of Tumors

“…Biomedical optical imaging has emerged as a powerful tool to be used in pre-clinical research, clinical diagnosis, and intraoperative detection of tumors. − Several HER2-targeted fluorescent probes that emit light in the visible (400–700 nm) and near-infrared window one region [near-infrared window one region I (NIR-I), 700–1000 nm] have been developed for imaging HER2-positive tumors and show promise for cancer detection . Recently, near-infrared window II region (NIR-II, 1000–1700 nm) imaging has demonstrated many advantages such as minimal autofluorescence, low light scattering, increased imaging sensitivity, and tissue penetration depth over the traditional visible and NIR-I imaging techniques, and it provides a promising, non-invasive, and real-time imaging technique for monitoring diseases in vivo .…”