A Ratiometric Fast-Response Fluorescent Probe Based on Dicyanoisophorone for Monitoring HClO in Paper Test Strips and Living Mice

A new dicyanoisophorone-based ratiometric fluorescent probe NOSA was synthesized and characterized. It showed a fast fluorescence response to HClO with the emission color change from dark green to bright red. NMR, IR, and HRMS suggested that the detection of NOSA to HClO may originate from the hydroxyl deprotection reaction by HClO on the molecule NOSA, which caused a red-shift of fluorescence. The probe NOSA displayed high selectivity and excellent anti-interference performance with a limit of detection at 3.835 × 10-7 M. The convenient paper test strips were successfully obtained and applied to the detection of HClO based on fluorescence color change with the varied NaClO concentration. Moreover, spiked recovery experiments in real water samples indicated that the probe NSOA could quantitatively detect HClO, and the fluorescence bio-imagings in vivo were carried out, and HClO detection in biosystems using NOSA was realized.

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.

Colorimetric and fluorometric bimodal amine chemosensor based on deprotonation-induced intramolecular charge transfer: Application to food spoilage detection

Amine derivatives are signature organic compounds generated from rotten protein food. Thus, sensitive detection of the presence of amines in protein foods can be a critical technique for monitoring their quality. In this study, we develop an organic chemosensor probe, 4-(2-(3-(dicyanomethylene)- 5,5-dimethylcyclohex-1-en-1-yl)vinyl)-N,N-diethylbenzenaminium chloride (DEAH), to effectively detect amines through discernible bimodal (colorimetric and fluorometric) changes. By exploiting the amine-triggered intramolecular charge transfer behavior, DEAH exhibits rapid color changes (<1 s) with an excellent detection limit (36.9 nM) and also fluorescence turn-on in response to amine gas. Moreover, it possesses detection capabilities in versatile conditions, including solutions, solids, and coated films, suggesting its practical applicability. In particular, DEAH shows dramatic color change from yellow to violet with exceptional color difference (△Eab) over 98, repeatable usability, and excellent selectivity to amines. Based on these compelling advantages, we successfully demonstrate real-time monitoring of amine gas generated from spoiled protein foods using DEAH-coated films.

A General Strategy Toward pH-Resistant Phenolic Fluorophores for High-Fidelity Sensing and Bioimaging Applications

Aryl alcohol-type or phenolic fluorophores offer diverse opportunities for developing bioimaging agents and fluorescence probes. Due to the inherently acidic hydroxyl functionality, phenolic fluorophores provide pH-dependent emission signals. Therefore, except for developing pH probes, the pH-dependent nature of phenolic fluorophores should be considered in bioimaging applications but has been neglected. Here we show that a simple structural remedy converts conventional phenolic fluorophores into pH-resistant derivatives, which also offer "medium-resistant" emission properties. The structural modification involves a single-step introduction of a hydrogen-bonding acceptor such as morpholine nearby the phenolic hydroxyl group, which also leads to emission bathochromic shift, increased Stokes shift, enhanced photo-stability and stronger emission for several dyes. The strategy greatly expands the current fluorophores' repertoire for reliable bioimaging applications, as demonstrated here with ratiometric imaging of cells and tissues.

Colorimetric and fluorescent dual-signals probes for naked-eye detection of hydrogen peroxide and applications in milk samples and in vivo

Excessive residual hydrogen peroxide (H₂O₂) disinfectant in food is harmful to human health. Therefore, it is necessary to develop efficient detection methods for H₂O₂ detection. In this work, we designed and synthesized five D-A molecules 3a-3e by introducing electron-donor substituents (-OCH₃ and -CH₃) to the electron-acceptor dicyanoisophorone skeleton in order to find out the suitable probes for H₂O₂ detection. Among them, two promising probes, 3a and 3c, are screened out according to structure-property relationships. Based on the principle of intramolecular charge transfer (ICT), 3a and 3c express colorimetric and fluorescent dual-signals towards H₂O₂ with low detection limits (0.20 μM and 0.14 μM) and rapid response (within 20 mins). The reaction mechanism between probes and H₂O₂ is determined by ¹H NMR and HRMS. Density functional theory (DFT) calculations are measured to study the regulation mechanism of structure adjustment on probs performance. Furthermore, a smartphone RGB analysis is utilized as a portable platform for the quantitative detection of H₂O₂ without complicated instruments, indicating a high efficiency and on-site detection method for H₂O₂. In addition, probes are applied to detect H₂O₂ in milk samples, HepG-2 cells and zebrafish, suggesting the promising applications in food samples and physiological systems.

A novel long excitation/emission wavelength fluorophore as platform utilized to construct NIR probes for bioimaging and biosensing

Near-infrared (NIR) fluorophores, especially dicyano-based fluorophores and xanthene-based hemicyanines, have beenput high expectation in bioimaging application due to their excellent optical properties. However, they suffer from inherentshortagessuch as short excitation/emission wavelength (less than 700 nm) or small Stokes shift (20-50 nm). Herein, we constructed a novel NIR dicyano-based fluorophore (DCO-HBTN). Toourknowledge, it is the first reported dicyano-based fluorophore of which the excitation/emission wavelength is more than 650 nm and Stokes shift is more than 100 nm. To demonstrate the feasibility of our efforts, we developed two NIR fluorescent probes (Probe-Cys and Probe-H₂S) based on the fluorophore, Probe-Cys displayed good selective and highly sensitive (LOD = 0.28 μM) recognition of Cys over Hcy and GSH, which was used to visualize endogenous Cys in tumor tissue. Probe-H₂S exhibited an. excellent specific and sensitive (LOD = 0.11 μM) response to H₂S, which was applied in monitoring H₂S releasing from the prodrug in vitro and in vivo.

A ratiometric fluorescent probe based on two-isophorone fluorophore for detecting cysteine

The key biological thiol, cysteine (Cys), which can participate in many physiological and pathological processes in the human body, has also been proofed to have considerable effects on redox homeostasis...

A novel NIR fluorescent probe with ratiometric imaging of cysteine in endoplasmic reticulum

We develop a large Stoke's shift ratiometric probe for imaging endoplasmic reticulum oxidative stress induced by Cytoxan.