All-Nontoxic Fluorescent Probe for Biothiols and Its Clinical Applications for Real-Time Glioblastoma Visualization

A Simple Fluorescent Probe for Biothiols Detection and Imaging of Living Cells In Vivo Based on a Hemicyanine Derivative

Biothiols play essential roles in various biological processes and are closely associated with diseases such as cancer, neurodegenerative disorders, and cardiovascular diseases. To monitor biothiols in organisms and living cells, we developed a novel intramolecular charge transfer (ICT)-based probe, hemicyanine-2,4-dinitrobenzenesulfonamide(HCD), by coupling a hemicyanine dye with 2,4-dinitrobenzenesulfonyl chloride.The HCD probe exhibits remarkable sensitivity, with low detection limits of 0.32 µM for Cys, 0.72 µM for Hcy, and 0.27 µM for GSH, and demonstrates high selectivity for biothiols in the presence of various interfering species. The detection mechanism was thoroughly validated using high-resolution mass spectrometry (HRMS), UV-Vis spectroscopy, fluorescence spectroscopy and Density Functional Theory (DFT) calculation. Furthermore, the applicability of HCD was successfully demonstrated in human urine samples and in vivo settings using RAW264.7 cells, confirming its potential as a powerful tool for monitoring endogenous biothiols in biological systems.

Recent Advances of Nitrobenzoselenadiazole for Imaging and Therapy

The development and practical applications of multifunctional organic fluorophores have garnered significant attention in translational research in recent years. Among the fluorophores, nitrobenzodioxazole (NBD) has been widely used in various fields due to its small size and neutral character, both of which are advantageous for biorelated applications. However, NBD presents some limitations, including (1) suboptimal photophysical properties for in vivo applications and (2) its monofunctional nature, which restricts its use in fluorescence-based bioimaging and sensing. To overcome these challenges, recent research has focused on the development of nitrobenzoselenadiazole (NBSD) derivatives, a selenium analog of NBD. In this review article, we systematically summarize recent advancements in the development of NBSD and highlight examples of its application in translational research as a multifunctional organic fluorophore. We also explore the potential applications of NBSD and present representative case studies, providing valuable context for the ongoing development of new NBSD derivatives in the field of fluorophore-related material science.

COX-2-targeted fluorescent probe for ClO- monitoring in precise cancer detection

Hypochlorite anion (ClO-) is closely associated with cancer development and progression, necessitating precise monitoring of ClO- in tumor sites, and Cyclooxygenase-2 (COX-2 is highly expressed in tumor cells. So we rationally designed two ClO--specific responsive fluorescent probes COX2-ClO1 and COX2-ClO2, using indomethacin (IMC) as the COX-2 targeting moiety and methylene blue as fluorophore unit. Both probes exhibited high selectivity and sensitivity towards ClO- in the in vitro solution assays and possess excellent biocompatibility in cellular experiments. Compared to COX2-ClO1, COX2-ClO2 exhibited superior targeting specificity for COX-2, enabling precise differentiation between tumor cells and normal cells and allowing imaging of both exogenous and endogenous ClO- in the in vivo experiments. Moreover, COX2-ClO2 could accurately target the tumor site in xenograft mice and is likely metabolized by the kidneys.

Dual-Channel fluorescent detection of Biothiols: A novel probe for Distinguishing Cysteine, Homocysteine, Glutathione, and N-Acetylcysteine in cellular environments

Biothiols, including cysteine (Cys), homocysteine (Hcy), glutathione (GSH), and N-acetylcysteine (NAC), possess similar chemical structures and properties but play crucial, distinct roles in biological cells and blood serum. Imbalances in the concentrations of these biothiols are associated with various diseases, highlighting the importance of precise discrimination, especially between Cys and other biothiols. Owing to the similarity of the chemical properties of Cys, Hcy, GSH, and NAC, developing an effective methodology to differentiate these thiol compounds is challenging. In this study, we designed and synthesized a novel dual-channel fluorescent probe, hereafter referred to as CNTC, by integrating coumarin and acrylonitrile. This probe enabled the simultaneous discrimination of Cys from Hcy, GSH, and NAC, producing distinct fluorescent signals: blue for Cys and green for Hcy, GSH, and NAC. CNTC exhibited rapid response kinetics (within 30 min) and impressive detection limits of 0.31, 0.11, 0.029, and 0.032 μM for Cys, Hcy, GSH, and NAC, respectively. Furthermore, CNTC was successfully applied in the fluorescence imaging of both exogenous and endogenous Cys, Hcy, GSH, and NAC in living cells. The remarkable analytical and bioimaging capabilities of CNTCin vivo establish it as a promising tool for elucidating the pathophysiological roles of biothiols, particularly Cys, Hcy, GSH, and NAC.

Regulating Sensing Patterns in Fluorescent Probes for Discriminative Detection of Biothiols

Discerning and quantifying the critical biothiols cysteine (Cys), homocysteine (Hcy), and glutathione (GSH) are vital for understanding their synergistic roles in biological systems. In this study, we synthesized a series of phenylethynylcoumarin fluorescent probes with varied structures to investigate the mechanisms underlying biothiol detection. We found that different substituents (-OCH3, -H, -CN) at the para-position of the phenylacetylene, combined with an aldehyde group at the 3-position of the coumarin, significantly affected the probes' reactivity and produced distinct response patterns toward biothiols. These insights enable the strategic development of fluorescent probes tailored to provide the personalized and discriminative detection of these biothiols. Additionally, probes CPOMe and CPCN were specifically evaluated for their efficacy in physiological environments, demonstrating their ability to accurately distinguish between Cys, Hcy, and GSH in living cells through unique fluorescent signals.

BT-DNBS: a novel cyanine-based turn-on fluorescent probe with large Stokes shift for sensitive and selective detection of biothiols in live-cell imaging

Detecting biothiols like glutathione (GSH), homocysteine (Hcy), and cysteine (Cys) is key to understanding their roles in health and disease. We developed BT-DNBS, a cyanine-based turn-on fluorescent probe with a dinitrobenzenesulfonyl (DNBS) quencher group. Upon biothiol interaction, the quencher is cleaved, restoring fluorescence. The resulting probe BT-NH shows a maximum emission wavelength at 630 nm and a large Stokes shift (≈200 nm), enhancing detection accuracy. Low cytotoxicity and high time resolution make BT-DNBS suitable for live-cell imaging. Imaging of A431 cells confirmed intracellular biothiol detection, with NEM pre-treatment reducing fluorescence, verifying specificity. BT-DNBS holds promise for biomedical research, particularly in disease diagnostics.

A facile near-infrared xanthene fluorescence probe for visualizing of hypochlorous acid in vitro and in vivo

BACKGROUND

Hypochlorous acid (HClO) is an important biomarker for inflammation, cardiovascular disease, and even cancer. It is of great significance to accurately monitor and quantitatively analyze the fluctuations of HClO to better understand their physiological functions. Traditional HClO detection methods such as high-performance liquid chromatography (HPLC), and mass spectrometry are preferred, but are costly and unsuitable in vivo. Near-infrared (NIR) fluorescence imaging has the advantages of high sensitivity, high temporal and spatial resolutions, minimal autofluorescence, and deep tissue penetration, which facilitates its application in biological systems. Therefore, the development of sensitivity and simple NIR fluorescence monitoring HClO methods in vivo and in vitro is essential and desirable.

RESULTS

Herein, we present a NIR probe NOF3 by integrating the rhodamine scaffold and HClO-triggered moiety for the real-time detection of HClO in vitro and in vivo. NOF3 reacts with the HClO and releases the NOF-OH fluorophore of emitted signals at 730 nm, which is in the NIR region. The designed probe detected concentrations of HClO ranging from 0 to 17 μM with a low detection limit of 0.146 μM, presenting excellent sensitivity and selectivity toward HClO over other species. NOF3 manifests significantly turn-on NIR fluorescent signals in response to HClO concentration, which makes it favorable for monitoring dynamic HClO distribution in vivo. We exemplify NOF3 for the tracking of endogenously overexpressed HClO distribution in RAW 264.7 cells, and further realize real-time in vivo bioimaging of HClO activity in inflammation mice.

SIGNIFICANCE

The facile NIR NOF3 probe was successfully applied to visualize endogenous and exogenous HClO in living cells and mice. This study provides not only an effective tool for spatial and temporal resolution HClO bioimaging in vivo but also possesses great potential for use in future research on HClO-related biology and pathology.

In Situ Activatable Nitrobenzene-Cysteine-Copper(II) Nano-complexes for Programmed Photodynamic Cancer Therapy

Photodynamic therapy (PDT) has been used to reduce cancerous and precancerous cells via reactive oxygen species (ROS) generation from photosensitizers. Numerous photosensitizers are available today to treat a variety of diseases, but their therapeutic efficacy is hindered within the tumor microenvironment, and there are safety concerns associated with their non-specific activation. In this work, we disclosed a nano-therapeutic based on in situ activatable nitrobenzene-cysteine-copper(II) nano-complexes (NCCNs) that work within cancer cells. Among the NCCNs, CyP shows outstanding potential as a promising candidate for programmed photodynamic cancer therapy with its unique properties such as (i) bright near-infrared imaging, (ii) chemodynamic therapeutic effect, (iii) photodynamic therapeutic effect (types I and II), and (iv) anti-cancer effect by anti-angiogenesis in early cancer stage under light. Overall, this work opens up exciting possibilities for the development of innovative and effective treatments for cancer, paving the way for future advancements in the clinical medicine field.

Water-Soluble Dual-Channel Fluorescent Probe for Sensitive Detection of Biothiols In Vitro and In Vivo

Benefiting from high spatiotemporal resolution, deep tissue penetration, and excellent sensitivity, fluorescence imaging technology has been widely applied in cancer diagnosis and treatment. In recent years, a large number of fluorescent probes for monitoring the levels of endogenous biothiols have been reported, which have significant implications for cancer diagnosis and treatment. However, most probes still suffer from poor biological compatibility and easy attachment by the environment. This work presents the development of a water-soluble dual-channel fluorescent probe, named MAL-NBD, for sensitively detecting biothiols. Nonfluorescent MAL-NBD is transformed into fluorescent groups MAL and NBD-SR/NR through nucleophilic substitution by biologically active thiols, producing dual-channel fluorescence signals for precise detection of biologically active thiols. Taking advantage of the excellent biocompatibility and low biotoxicity, MAL-NBD is successfully used for imaging HeLa cancer cells and zebrafish larvae, promoting its potential application for the precise detection of biological thiols involved in physiological and pathological processes.

Spindle Monitor: A Tool for Real-Time Assessment and Concurrent Treatment of Postoperative Tumor Prognosis

Cancer surgery remains a mainstay in clinical treatment. However, the efficacy of subsequent therapies largely depends on the precise evaluation of postoperative prognoses, underscoring the critical need for a comprehensive and accurate assessment of surgical outcomes. Nanoprobes targeting tumors offer a promising solution for visual prognostic assessment. In this study, we developed a "Spindle Monitor" system, designated as APPADs (Au NBPs@PDA-pep-AS1411-Dox), composed of core-shell nanoparticles. The core was made up of gold nanobipyramids (Au NBPs), coated with polydopamine (PDA), and subsequently loaded with peptide chains, AS1411, and doxorubicin (Dox). Upon deployment in the acidic tumor microenvironment (TME), APPADs released substantial amounts of Dox, initiating the apoptotic process. This triggered the activity of caspase-3, which is a crucial executor in the apoptotic pathway. Consequently, DEVD, a specific recognition site for caspase-3, was cleaved, enabling the disconnection of FITC-conjugated peptide chains and the recovery of fluorescence. Through assessing this fluorescence imaging effect, local laser irradiation could be precisely guided to the postoperative site, facilitating a synergistic combination of photothermal therapy and chemotherapy. Specifically, our "Spindle Monitor" APPADs had been validated to achieve accurate fluorescence imaging in vitro and in vivo, which demonstrated its potential value as a versatile tool for evaluating postoperative prognosis in surgical treatments, such as thyroid cancer, and assessing chemotherapy efficacy in difficult cases, like late-stage osteosarcoma. This promising tool lays a good foundation for development in visual prognosis evaluation after tumor surgery.

Recent Progress in the Rational Design of Biothiol-Responsive Fluorescent Probes

Biothiols such as cysteine, homocysteine, and glutathione play significant roles in important biological activities, and their abnormal concentrations have been found to be closely associated with certain diseases, making their detection a critical task. To this end, fluorescent probes have become increasingly popular due to their numerous advantages, including easy handling, desirable spatiotemporal resolution, high sensitivity, fast response, and favorable biocompatibility. As a result, intensive research has been conducted to create fluorescent probes for the detection and imaging of biothiols. This brief review summarizes recent advances in the field of biothiol-responsive fluorescent probes, with an emphasis on rational probe design, including the reaction mechanism, discriminating detection, reversible detection, and specific detection. Furthermore, the challenges and prospects of fluorescence probes for biothiols are also outlined.