Novel pyrrolidine-alkylamino-substituted dicyanoisophorone derivatives as near-infrared fluorescence probe for imaging ß-amyloid in vitro and in vivo.

BACKGROUND: The formation of amyloid-ß (Aß) plaques is one of the key neuropathological hallmarks of Alzheimer's disease (AD). Near-infrared (NIR) probes show great potential for imaging of Aß plaques in vivo and in vitro. Dicyanoisophorone (DCIP) based Aß probes have attracted considerable attention due to their exceptional properties. However, DCIP probes still has some drawbacks, such as short emission wavelength (<650 nm) and low fluorescence intensity after binding to Aß. It is clear that further modification is needed to improve their luminescence efficiency and sensitivity. RESULTS: We designed and synthesize four novel pyrrolidine-alkylamino-substituted DCIP derivatives (6a-d) as imaging agents for ß-amyloid (Aß) aggregates. Compound 6c responds better to Aß aggregates than the other three compounds (6a, 6b and 6d) and its precursor DCIP. The calculated detection limit is to be as low as 0.23 µM. Compound 6c shows no cytotoxicity in the tested concentration for SH-SY5Y and HL-7702 cells. Additionally, compound 6c is successfully applied to monitor Aß aggregates in live SH-SY5Y cells and APP/PS1 transgenic mice. The retention time in the transgenic mice brain is much longer than that of age-matched wild-type mice. SIGNIFICANCE: The results indicates that compound 6c had an excellent ability to penetrate the blood-brain barrier and it could effectively distinguish APP/PS1 transgenic mice and wide-type mice. This represents its promising applications for Aß detection in basic and biomedical research.

Recent Advances in Organic Small-Molecule Fluorescent Probes Based on Dicyanoisophorone Derivatives.

Fluorescent probe technology holds great promise in the fields of environmental monitoring and clinical diagnosis due to its inherent advantages, including easy operation, reliable detection signals, fast analysis speed, and in situ imaging capabilities. In recent years, a wide range of fluorescent probes based on diverse fluorophores have been developed for the analysis and detection of various analytes, yielding significant achievement. Among these fluorophores, the dicyanoisophorone-based fluorophores have garnered significant attention. Dicyanoisoporone exhibits minimal fluorescence, yet possesses a robust electron-withdrawing capability, rendering it suitable for constructing of D-π-A structured fluorophores. Leveraging the intramolecular charge transfer (ICT) effect, such fluorophores exhibit near-infrared (NIR) fluorescence emission with a large Stokes shift, thereby offering remarkable advantages in the design and development of NIR fluorescence probes. This review article primarily focus on small-molecule dicyanoisoporone-based probes from the past two years, elucidating their design strategies, detection performances, and applications. Additionally, we summarize current challenges while predicting future directions to provide valuable references for developing novel and advanced fluorescence probes based on dicyanoisoporone derivatives.

A near-infrared fluorescent probe for detecting hydrazine metabolized from isoniazid in living cells.

Isoniazid is a drug for treating tuberculosis, but hydrazine (N2 H4 ), the major metabolite of isoniazid, can cause hepatotoxicity. Therefore, monitoring the content of N2 H4 in time is of great significance for studying the hepatotoxicity induced by isoniazid. In this study, a near-infrared fluorescent probe (BC-N) was designed and synthesized based on the specific reaction of acetyl ester with N2 H4 . BC-N exhibits excellent selectivity, sensitivity, and biocompatibility. In addition, BC-N is applied in the visualization of N2 H4 produced from isoniazid in living cells and is a potential tool for monitoring hepatotoxicity induced by isoniazid.

A dicyanoisophorone-based ICT fluorescent probe for the detection of Hg2+ in water/food sample analysis and live cell imaging.

Mercury ions are notoriously difficult to biodegradable, and its abnormal bioaccumulation in the human body through the food chain can cause various diseases. Therefore, the quantitative and real-time detection of Hg2+ is very extremely important. Herein, we have brilliant designed and synthesized (E)-O-(4-(2-(3-(dicyanomethylene)-5,5-dimethylcyclohex-1-en-1-yl)vinyl)phenyl) O-phenyl carbonothioate (ICM-Hg) as a selective fluorescent probe for Hg2+ detection in real samples and intracellular staining. ICM-Hg displayed high specificity toward Hg2+ by activating the intramolecular charge transfer (ICT) process, resulting in distinguished color change from colorless to bright yellow along with noticeable switch on yellow fluorescence emission. The fluorescent intensity of ICM-Hg at 585 nm shows a well linear relationship in the range of Hg2+ concentration (0-45 µM), and the detection of limit for Hg2+ is calculated to be 231 nM. Promisingly, ICM-Hg can efficiently detect Hg2+ in real samples including tap water, tea, shrimp, and crab with quantitative recovery as well as the intracellular fluorescence imaging.

Discrimination of Pd-species by an ultra-fast, long wavelength and biocompatible fluorescent sensor: Its on-site kit assay, drug, and cancer/epithelial cell studies.

Extensive use of palladium in many catalysts and catalytic converters causes a high degree of pollution of water and soil resources. Therefore, there is an urgent need to develop rapid and sensitive palladium probes. Herein, a novel "turn-on" near-infrared (NIR) fluorescence and colorimetric probe for Pd has been designed on the basis of the deallylation of the probe, followed by the release of NIR emissive fluorophore through the Tsuji-Trost reaction. The probe can selectively discriminate between the oxidation states of Pd0 and Pd2+. Sensing results demonstrates that the probe has excellent selectivity, sensitivity, fast response time, NIR fluorescence, high biocompatibility, and low detection limit for the Pd detection over a series metal ion. The probe has been successfully applied in visualization of residual Pd content from water, soil, drug and living cell samples by fluorescence observation with the naked eye.

Two near-infrared fluorescent probes based on dicyanoisfluorone for rapid monitoring of Zn2+and Pb2.

Zinc (Zn2+) and lead (Pb2+) ions in the environment have important effects on human health and environmental safety. Therefore, it is necessary to effectively detect them by a convenient and reliable analysis method. In this study, two near-infrared fluorescent probes for the fast determination of Zn2+and Pb2+were synthesized by a simple Schiff base reaction between the dicyanoisophorone skeleton and carbohydrazide derivatives. Among them, the probe with the thiophene-2-carbohydrazide group showed a selective fluorescence response to Zn2+and Pb2+with a maximum emission wavelength of 670 nm. And the detection limits of the probe for Zn2+and Pb2+were 1.59 nM and 1.65 nM, respectively. In contrast the probe modified by the furan-2-carbohydrazide group achieved quantitative detection of Zn2+, with a detection limit of 2.7 nM. These results were attributed to the fact that the probes bind to Zn2+and Pb2+in stoichiometric ratios of 1:1, blocking the intramolecular PET effect. Furthermore, these two probes can be recycled through the action of EDTA and have been successfully used to detect Zn2+and Pb2+in real water samples.

Modulating donor of dicyanoisophorone-based fluorophores to detect human serum albumin with NIR fluorescence.

It is urgently needed to develop NIR-fluorescent probe for detection of human serum albumin (HSA) since the interference of short-wavelength-fluorescence from endogenous species in real serum and urine. However, most previous reports were located in the short-wavelength region (<600 nm). In this work, a series of dicyanoisophorone (DCO)-based fluorophores 1-4 with different donor groups have been designed and investigated. A systematic study of their photophysical properties has been carried out. Among these probes, 4 exhibited NIR emission with the highest fluorescence brightness and the most sensitive signal response to HSA. Further studies demonstrated that 4 could strongly bind into the DS1 pocket of HSA with a 1:1 ratio. Importantly, the method based on 4 has been proven to be capable of sensing HSA in real serum and urine samples.

Selective detection of peroxynitrite in living cells by a near-infrared diphenyl phosphinate-based dicyanoisophorone probe.

A new NIR fluorescent probe for detection of ONOO- has been developed, which possesses a large Stokes shift, good selectivity and low cytotoxicity. This NR-ONOO probe exhibits a strong turn-on near-infrared fluorescence response toward ONOO- ion under excitation at 560 nm and has been successfully applied in detecting ONOO- in living HeLa cells.

Design and application of near-infrared fluorophore based on a novel thiazolidinedione-functionalized dicyanoisophorone.

A novel dicyanoisophorone (DCI)-based NIR fluorophore employing 2, 4-thiazolidinediones as the modification site was designed for fluorescence imaging. The fluorophore was assessed as a switchable reporter for H2O2 and the probe exhibited lysosomes-targeted, a large turn-on fluorescence signal at 720 nm with a large stokes shift (150 nm) and can be used in biological systems. The ability of the novel fluorophore to emit NIR fluorescence through a "turn-on" activation mechanism makes it a promising fluorophore for in vivo imaging applications. The strategy of introducing the thiazolidinediones with the easy modification site into the fluorophore has a good application prospect to expand the application of the NIR fluorophore.

A dicyanoisophorone-based highly sensitive and selective near-infrared fluorescent probe for sensing thiophenol in water samples and living cells.

Thiophenol (PhSH) is an important sulfhydryl compound in organic synthesis, but it is also a volatile environmental pollutant with high toxicity to organisms. Herein, we reported a novel near-infrared (NIR) probe (1) for turn-on fluorescence detection of PhSH. The probe was prepared by coupling 2,4-dinitrophenyl (DNP) to a dicyanoisophorone-based fluorophore (2). PhSH can specifically perform a nucleophilic aromatic substitution on probe 1 and result in the release of fluorophore 2, thus achieving a turn-on fluorescence response (λem = 693 nm). A dramatic color change from red (λabs = 525 nm) to blue (λabs = 668 nm) was also observed. This fluorescent assay displayed a large Stokes shift (∼133 nm) and a high sensitivity for PhSH, as well as a low detection limit (34 nM). Moreover, probe 1 was successfully applied to monitor PhSH in real water samples and image PhSH in living cells.

A near-infrared fluorescent probe based on boric acid hydrolysis for hydrogen peroxide detection and imaging in HeLa cells.

Using the characteristics of hydrogen peroxide that are able to cleave phenyl-boric acid selectively and efficiently, we here report a dicyanoisophorone-boric acid (DCP-BA)-based near-infrared (NIR) fluorescent probe for detection of hydrogen peroxide. This probe shows a rapid, highly selective, and sensitive detection process for hydrogen peroxide with a significant NIR fluorescent turn-on response that has been successfully applied to detect exogenous hydrogen peroxide in HeLa cells.

A Near-infrared Fluorescent Probe of Dicyanoisophorone Derivatives for Selective Detection and Fluorescence Cellular Imaging of Palladium.

Palladium (Pd) has been acknowledged to be a rare inner transition metal, which plays a pivotal role in many fields. This article focuses on developing a safe and effective near-infrared fluorescent probe, MW-PD, which would make a great contribution to the detection of palladium residue in drugs, especially trace residues. The fluorescent probe was rationally designed by combining the dicyanoisophorone fluorophore with an allyloxycarbonyl group. Based on the Tsuji-Trost reaction, the probe exhibited high selectivity and sensitivity toward Pd (0) over other common metal ions with a low detection limit (8.0 nM). Moreover, MW-PD showed biocompatibility and was successfully applied to imaging Pd (0) in Hela cells.

Real-time monitoring of γ-Glutamyltranspeptidase in living cells and in vivo by near-infrared fluorescent probe with large Stokes shift.

γ-Glutamyltranspeptidase (GGT) is a cell surface-bound enzyme that is closely implicated in various physiological disorders such as tumor. Thus, an efficient method for monitoring GGT is extremely important for biological studies and disease diagnosis. Herein, a near-infrared fluorescent probe (TMN-Glu) has been developed for turn-on trapping of GGT activity in vitro and in vivo based on conjugating a dicyanoisophorone derivative fluorophore with a GGT activatable γ-glutamyl amide moiety. Advantages of the probe include near-infrared emission (658 nm), with large Stokes shift (213 nm), high specificity, high sensitivity (LOD = 0.024 U/L), low cytotoxicity and high imaging resolution, allowing for the real-time imaging endogenous GGT in living cells. Probe TMN-Glu was highly feasible to report on the GGT levels in different types of cells. Notably, we also demonstrated its applicability in real-time visualizing endogenous GGT in tumor-bearing nude mice with low background interference. These results indicated that the probe held great promise for real-time sensing and tracking GGT in complex biological systems, which would be useful for basic researches and clinical diagnosis of GGT-related diseases.

Cancer-Specific Biomarker hNQO1-Activatable Fluorescent Probe for Imaging Cancer Cells In Vitro and In Vivo.

Human NAD(P)H quinone oxidoreductase-1 (hNQO1) is an important cancer-related biomarker, which shows significant overexpression in malignant cells. Developing an effective method for detecting NQO1 activity with high sensitivity and selectivity in tumors holds a great potential for cancer diagnosis, treatment, and management. In the present study, we report a new dicyanoisophorone (DCP) based fluorescent probe (NQ-DCP) capable of monitoring hNQO1 activity in vitro and in vivo in both ratiometric and turn-on model. NQ-DCP was prepared by conjugating dicyanoisophorone fluoroprobe with hNQO1 activatable quinone propionic acid (QPA), which remain non-fluorescent until activation by tumor-specific hNQO1. NQ-DCP featured a large Stokes shift (145 nm), excellent biocompatibility, cell permeability, and selectivity towards hNQO1 allowed to differentiate cancer cells from healthy cells. We have successfully employed NQ-DCP to monitor non-invasive endogenous hNQO1 activity in brain tumor cells in vitro and in xenografted tumors developed in nude mice.

A Novel Dicyanoisophorone-Based Ratiometric Fluorescent Probe for Selective Detection of Cysteine and Its Bioimaging Application in Living Cells.

A selective and ratiometric turn-on fluorescent probe was designed and synthesized by using a novel dicyanoisophorone-based derivative and acrylate moiety. The probe displayed high stability and good selectivity to cysteine (Cys) over homocysteine (Hcy) and glutathione (GSH). It also exhibited rapid response to Cys within 180 s. Most importantly, the fluorescence intensity ratio at 590 and 525 nm (I590/I525) was linearly dependent on the Cys concentration in the range from 0 to 40 µM and the detection limit calculated to be 0.48 µM. This probe was also applied for bioimaging of intracellular Cys in living HeLa cells with low cytotoxicity.