Near-Infrared Fluorescence Probe with a New Recognition Moiety for Specific Detection and Imaging of Aldehyde Dehydrogenase Expecting the Identification and Isolation of Cancer Stem Cells

A new near-infrared fluorescence probe for highly selective and sensitive detection and imaging of Butyrylcholinesterase in Alzheimer's disease mice

Butylcholinesterase (BChE) is a key enzyme in living system, closely related to liver and neurological diseases. It is very challenge to develop near-infrared (NIR) fluorescence probe methods for highly selective and sensitive detection of BChE in vivo. Based on the differences in active sites and spatial pockets between acetylcholinesterase (AChE) and BChE, a new NIR BChE-responsive fluorescence probe Probe-BChE (λex/λem = 600 nm/676 nm) was designed and synthesized by introducing dimethyl carbamate group as recognizing moiety to a NIR fluorophore hemicyanine skeleton. It was found that Probe-BChE specifically binds with BChE, rather than AChE, since BChE has a big cavity and strong intermolecular forces with Probe-BChE, which was supported by the molecular docking scores. The fluorescence method for the determination of BChE was developed with a detection limit of 0.14 U/mL BChE and high selectivity as well as short reaction time (∼3 s). The fluorescence imaging method using Probe-BChE efficiently image the levels of endogenous BChE in brains and main organs (heart, liver, spleen, lung and kidney) of Alzheimer's disease (AD) mice. The results reveal that the levels of endogenous BChE in old AD mice is higher than that in young AD mice, and endogenous BChE is enriched in the liver of AD mice. This work demonstrates that Probe-BChE is a promising fluorescence probe for imaging of endogenous BChE in AD mice. The design of NIR fluorescence probes for endogenous BChE in this work will promote to design NIR fluorescence probes for endogenous cholinesterase.

Illumination of Hydroxyl Radical Generated in Cells during Ferroptosis, Arabidopsis thaliana, and Mice Using a New Turn-On Near-Infrared Fluorescence Probe

Hydroxyl radical (·OH), taken as the most active and aggressive reactive oxygen species (ROS), plays an important role in cell redox regulation and ferroptosis processes. It is a great challenge to develop methods for highly selective and sensitive detection and imaging of ·OH. A new near-infrared (NIR) fluorescence probe Probe-HMP was designed and synthesized by introducing 3-methylpyrazolone as the specific recognition moiety to the hemicyanine backbone of the NIR fluorophore AXPI-NH2, which formed with the hydrazine group. Probe-HMP exhibited excellent detection performance in vitro, such as instantaneous response, low detection limit of 24 nM, and excellent selectivity without the interference from other ROS. Based on the actions of ·OH promoter phenylmercuric acetate (PMA) and ·OH scavenger 4-hydroxy-TEMPO (Tempol), Probe-HMP was successfully applied to obtain images of endogenous ·OH in HepG2 cells, Arabidopsis thaliana, and mice. The results show that Probe-HMP can stably and efficiently image endogenous ·OH, the fluorescence intensity of the experimental group incubated with PMA was higher than that of the control group incubated with Probe-HMP only, and a significant decrease could be observed in the inhibitor group incubated with Tempol. More importantly, Probe-HMP can achieve the detection of endogenous ·OH in HepG2 cells during ferroptosis by using erastin and deferoxamine mesylate (DFO) to induce or inhibit ferroptosis, revealing that the fluorescence intensity change of Probe-HMP was caused by ·OH generated and ferroptosis is accompanied by significant ·OH generation. The excellent performance of Probe-HMP makes it a promising candidate for exploring the physiological and pathological processes associated with ferroptosis.

Application of Intelligent Response Fluorescent Probe in Breast Cancer

As one of the leading cancers threatening women's lives and health, breast cancer is challenging to treat and often irreversible in advanced cases, highlighting the critical importance of early detection and intervention. In recent years, fluorescent probe technology, a revolutionary in vivo imaging tool, has gained attention in medical research for its ability to improve tumor visualization significantly. This review focuses on recent advances in intelligent, responsive fluorescent probes, particularly in the field of breast cancer, which are divided into five categories, near-infrared responsive, fluorescein-labeled, pH-responsive, redox-dependent, and enzyme-triggered fluorescent probes, each of which has a different value for application based on its unique biological response mechanism. In addition, this review also covers the strategy of combining fluorescent probes with various anti-tumor drugs, aiming to reveal the possibility of synergistic effects between the two in breast cancer treatment and provide a solid theoretical platform for the clinical translation of fluorescent probe technology, which is expected to promote the expansion of cancer treatment technology.

Near-Infrared Fluorescence Probe with a New Recognition Moiety for the Specific Detection of Cysteine to Study the Corresponding Physiological Processes in Cells, Zebrafish, and Arabidopsis thaliana

Cysteine (Cys), as one of the biological thiols, is related to many physiological and pathological processes in humans and plants. Therefore, it is necessary to develop a sensitive and selective method for the detection and imaging of Cys in biological organisms. In this work, a novel near-infrared (NIR) fluorescent probe, Probe-Cys, was designed by connecting furancarbonyl, as a new recognition moiety, with Fluorophore-OH via the decomposition of IR-806. The use of the furan moiety is anticipated to produce more effective fluorescence quenching because of the electron-donating ability of the O atom. Probe-Cys has outstanding properties, such as a new recognition group, an emission wavelength in the infrared region at 710 nm, a linear range (0-100 μM), a low detection limit of 0.035 μM, good water solubility, excellent sensitivity, and selectivity without the interference of Hcy, GSH, and HS-. More importantly, Probe-Cys could achieve the detection of endogenous Cys by reacting with the stimulant 1,4-dimercaptothreitol (DTT) and the inhibitor N-ethylmaleimide (NEM) in HepG2 cells and zebrafish. Ultimately, it was successfully applied to obtain images of Arabidopsis thaliana, revealing that the content of Cys in the meristematic zone was higher than that in the elongation zone, which was the first time that the NIR fluorescence probe was used to obtain images of Cys in A. thaliana. The superior properties of the probe exhibit its great potential for use in biosystems to explore the physiological and pathological processes associated with Cys.

Tunable fluorescent probes for detecting aldehydes in living systems

Aldehydes, pervasive in various environments, pose health risks at elevated levels due to their collective toxic effects via shared mechanisms. Monitoring total aldehyde content in living systems is crucial due to their cumulative impact. Current methods for detecting cellular aldehydes are limited to UV and visible ranges, restricting their analysis in living systems. This study introduces an innovative reaction-based trigger that leverages the exceptional selectivity of 2-aminothiophenol for aldehydes, leading to the production of dihydrobenzothiazole and activating a fluorescence response. Using this trigger, we developed a series of fluorescent probes for aldehydes by altering the fluorophore allowing for excitation and emission wavelengths across the visible to near-infrared spectral regions without compromising the reactivity of the bioorthogonal moiety. These probes exhibit remarkable aldehyde chemoselectivity, rapid kinetics, and high quantum yields, enabling the detection of diverse aldehyde types, both exogenous and endogenous, within complex biological contexts. Notably, we employed the most red-shifted near-infrared probe from this series to detect aldehydes in living systems, including biliary organoids and mouse organs. These probes provide valuable tools for exploring the multifaceted roles of aldehydes in biological functions and diseases within living systems, laying the groundwork for further investigations.

Detection of acetylcholinesterase and butyrylcholinesterase in vitro and in vivo using a new fluorescent probe

A new fluorescence probe OHPD that could specifically identify acetylcholinesterase/butyrylcholinesterase has been developed and successfully applied to imaging in vivo. Probe OHPD shows significant color change, high selectivity, high sensitivity, and low detection limit for the detection of cholinesterase. Moreover, the real-time imaging in situ indicated that endogenous cholinesterase was mainly present in the yolk sac of zebrafish.