Activatable NIR-II organic fluorescent probes for bioimaging

Abstract

NIR-II imaging is developed rapidly for noninvasive deep tissue inspection with high spatio-temporal resolution, taking advantage of diminished autofluorescence and light attenuation. Activatable NIR‐II fluorescence probes are widely developed to report pathological changes with accurate targeting, among which organic fluorescent probes achieve significant progress. Furthermore, the activatable NIR‐II fluorescent probes exhibited appealing characteristics like tunable physicochemical and optical properties, easy processability, and excellent biocompatibility. In the present review, we highlight the advances of activatable NIR-II fluorescence probes in design, synthesis and applications for imaging pathological changes like reactive oxygen species (ROS), reactive nitrogen species (RNS), reactive sulfur species (RSS), pH, hypoxia, viscosity as well as abnormally expressed enzymes. This non-invasive optical imaging modality shows a promising prospect in targeting the pathological site and is envisioned for potential clinical translation.

Skin Cancer Pathobiology at a Glance: A Focus on Imaging Techniques and Their Potential for Improved Diagnosis and Surveillance in Clinical Cohorts

“…Other authors exploited a BODIPY fluorophore conjugated with a prodrug (e.g., doxorubicin and DOX) that exhibits a dose-dependent turn-on fluorescence response and cytotoxicity in lipopolysaccharide-induced proinflammatory M1 macrophages for the real-time monitoring of targeted therapies including prodrug activation and intracellular trafficking in different cancer models [ 198 ]. Finally, there were also several reports that presented the efficiency of superoxide anion (O 2 −)-activatable NIR chemiluminescent reporters (SPNRs) to detect O 2 − for real-time in vivo NIR imaging of drug-induced cancer immune activation [ 199 , 200 ]. This mechanism relies on the principle that cytotoxic T cells have higher endogenous O 2 − levels than cancer and normal cells and that SPNR may link the chemiluminescence signals with the O 2 − levels to depict the populations of activated cytotoxic T cells and helper cells during immunotherapy administration [ 193 ].…”

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

“…From a clinical perspective, the NIR fluorophore should have certain characteristics, including high safety, high stability, high quantum yield, low toxicity, minimal or no accumulation in non-target organs, and long emission wavelengths. A variety of NIR fluorophores have been developed for in vivo fluorescence imaging, including inorganic fluorophores (such as carbon nanotubes, quantum dots, lanthanide-doped nanoparticles) ( Zhong et al, 2017 ; Chen et al, 2018 ; Zhang et al, 2020 ; Qin et al, 2022a ; Teng et al, 2022 ) organic fluorophores (such as organic small molecules, polymers and activatable fluorescence probes) ( Antaris et al, 2016 ; Li et al, 2022b ; Zhang et al, 2022b ; Gao and Lei, 2022 ; Zhao et al, 2022 ) A variety of inorganic materials have been used in fluorescent imaging, this may cause safety concerns about cumulative toxicity. Considering the unknown long-term toxicity, these inorganic nanomaterials are difficult to translate to the clinic.…”

“…In addition, activatable organic NIR-II fluorescent probes generate fluorescent signals in the living system only after responding to the target analyte, thereby displaying a higher SBR. Thus, they have attracted increased attention for biomedical and clinical research ( Zhang et al, 2022b ). Activatable organic NIR-II fluorescence probes have been used in the detection of reactive oxygen species (ROS), reactive nitrogen species (RNS), reactive sulfur species (RSS), pH, viscosity and enzyme.…”

Water-Dispersible Activatable Nanoprobe for Detecting Cadmium-Ion-Induced Oxidative Stress in Edible Crops via Near-Infrared Second-Window Fluorescence Imaging

“…Fluorescence imaging is a noninvasive method, − which is conducive to detecting and monitoring the variation of in situ biomarkers in a real-time manner in plants. − As for in vivo fluorescence imaging in plants, the imaging quality in the shorter wavelength range (e.g., visible light (400–700 nm) or NIR-I range (700–900 nm)) is usually compromised or eroded because such pigments as chlorophylls, anthocyanins, and carotenoids in plants usually have absorptions in the visible-light wavelength range and exhibit fluorescence in the visible-light or NIR-I wavelength range. − However, near-infrared second window (NIR-II, emission: 900–1700 nm) fluorescence imaging can achieve much superior imaging performance, − owing to no interference from plant-related pigments in the NIR-II wavelength range.…”