Novel fluorescence biosensor custom-made for protein tyrosine phosphatase 1B detection based on titanium dioxide-decorated single-walled carbon nanohorn nanocomposite

This paper presents a new fluorescent approach for the detection of protein tyrosine phosphatase 1B (PTP1B) based on titanium dioxide-decorated single-wall carbon nanohorns (TiO₂-SWCNHs). The novel TiO₂-SWCNHs nanocomposite was synthesized and characterized for the first time and the phosphorylated peptide as the substrate of PTP1B was designed. Properties of SWCNHs and TiO₂ were combined by growing nano-sized TiO₂ particles on SWCNHs, resulting in TiO₂-SWCNHs. TiO₂ provides SWCNHs a large adsorption surface area and can specifically bind to phosphopeptide substrate. TiO₂-SWCNHs effectively quenched the fluorescence of the phosphorylated peptide substrate labeled by the fluorophore, and the system had a low fluorescence background. In the presence of PTP1B, dephosphorylation of the peptide occurred owing to the reaction between PTP1B and the peptide, causing the separation of the dye-labeled peptide from TiO₂-SWCNHs, which resulted in fluorescence enhancement of the reaction system. Thus, a simple and rapid strategy for the detection of PTP1B activity was developed, with a detection limit of 0.01 ng/mL and linear range of 0-10 ng/mL. The system can be used to detect PTP1B in serum using the standard addition method. This system provides a new approach for screening PTP1B inhibitors.

Expansion of the Strigolactone Profluorescent Probes Repertory: The Right Probe for the Right Application

Strigolactones (SLs) are intriguing phytohormones that not only regulate plant development and architecture but also interact with other organisms in the rhizosphere as root parasitic plants (Striga, Orobanche, and Phelipanche) and arbuscular mycorrhizal fungi. Starting with a pioneering work in 2003 for the isolation and identification of the SL receptor in parasitic weeds, fluorescence labeling of analogs has proven a major strategy to gain knowledge in SL perception and signaling. Here, we present novel chemical tools for understanding the SL perception based on the enzymatic properties of SL receptors. We designed different profluorescent SL Guillaume Clavé (GC) probes and performed structure-activity relationship studies on pea, Arabidopsis thaliana, and Physcomitrium (formerly Physcomitrella) patens. The binding of the GC probes to PsD14/RMS3, AtD14, and OsD14 proteins was tested. We demonstrated that coumarin-based profluorescent probes were highly bioactive and well-adapted to dissect the enzymatic properties of SL receptors in pea and a resorufin profluorescent probe in moss, contrary to the commercially available fluorescein profluorescent probe, Yoshimulactone Green (YLG). These probes offer novel opportunities for the studies of SL in various plants.

A Critical Review on Organic Small Fluorescent Probes for Monitoring Carbon Monoxide in Biology

Endogenous carbon monoxide (CO) is an important intracellular gas messenger that is intimately involved in many physiological and pathological processes. The abnormal concentration of CO in living organisms can cause many diseases. Therefore, it is of great significance to monitor CO in biological samples. Fluorescent probe technology provides an effective and convenient method for CO monitoring, with the advantages of high selectivity and sensitivity, fast response time and in situ fluorescence imaging in biological tissues, which is favored by the majority of researchers. In this paper, the research progress of CO fluorescent probes since 2018 is reviewed, and the design, detection mechanism and biological application of the related fluorescent probes are summarized. And the relationship between the structure and performance of the probes is discussed. Furthermore, the development trend and application prospect of CO fluorescent probes are prospected.

Regioselective Difluoromethane sulfonylation and Triflylation of Resorufin Derivatives

Reported herein is a regioselective difluoromethane sulfonylation or triflylation of resorufin derivatives, which allows easy access to 2-difluoromethane sulfonylated or triflylated resorufin derivatives in good yields. The installation of a difluoromethane sulfonyl group significantly increases the solubility of the chromophore and expands its Stokes shift. A difluoromethane sulfonylated resorufin-based fluorogenic probe proved to be able to image enzyme activity in live cells with a stronger fluorescence signal compared with its resorufin counterpart.

Resorufin-based responsive probes for fluorescence and colorimetric analysis

The fluorescence imaging technique has attracted increasing attention in the detection of various biological molecules in situ and in real-time owing to its inherent advantages including high selectivity and sensitivity, outstanding spatiotemporal resolution and fast feedback. In the past few decades, a number of fluorescent probes have been developed for bioassays and imaging by exploiting different fluorophores. Among various fluorophores, resorufin exhibits a high fluorescence quantum yield, long excitation/emission wavelength and pronounced ability in both fluorescence and colorimetric analysis. This fluorophore has been widely utilized in the design of responsive probes specific for various bioactive species. In this review, we summarize the advances in the development of resorufin-based fluorescent probes for detecting various analytes, such as cations, anions, reactive (redox-active) sulfur species, small molecules and biological macromolecules. The chemical structures of probes, response mechanisms, detection limits and practical applications are investigated, which is followed by the discussion of recent challenges and future research perspectives. This review article is expected to promote the further development of resorufin-based responsive fluorescent probes and their biological applications.

A fluorescent probe for monitoring PTP-PEST enzymatic activity

Phosphatase non-receptor type 12 (PTPN12 or PTP-PEST) is a critical regulator of cell migration, acting as a tumor suppressor in cancer. Decreases in PTP-PEST expression correlate with aggressive phenotypes in hepatocellular carcinoma (HCC). Despite the importance of PTP-PEST in cellular signaling, methods to directly monitor its enzymatic activity are lacking. Herein, we report the design, synthesis, and optimization of a probe to directly monitor PTP-PEST enzymatic activity via a fluorescent readout. This activity sensor, termed pPEST1tide, is capable of detecting as little as 0.2 nM recombinant PTP-PEST. In addition, we demonstrate that this probe can selectively report on PTP-PEST activity using a panel of potential off-target enzymes. In the long-term, this activity probe could be utilized to identify small molecule modulators of PTP-PEST activity as well as provide a prognostic readout for HCC.

Fluorogenic probes for imaging cellular phosphatase activity

The ability to visualize enzyme activity in a cell, tissue, or living organism can greatly enhance our understanding of the biological roles of that enzyme. While many aspects of cellular signaling are controlled by reversible protein phosphorylation, our understanding of the biological roles of the protein phosphatases involved is limited. Here, we provide an overview of progress toward the development of fluorescent probes that can be used to visualize the activity of protein phosphatases. Significant advances include the development of probes with visible and near-infrared (near-IR) excitation and emission profiles, which provides greater tissue and whole-animal imaging capabilities. In addition, the development of peptide-based probes has provided some selectivity for a phosphatase of interest. Key challenges involve the difficulty of achieving sufficient selectivity for an individual member of a phosphatase enzyme family and the necessity of fully validating the best probes before they can be adopted widely.

Fluorogenic probes for disease-relevant enzymes

Traditional biochemical methods for enzyme detection are mainly based on antibody-based immunoassays, which lack the ability to monitor the spatiotemporal distribution and, in particular, the in situ activity of enzymes in live cells and in vivo. In this review, we comprehensively summarize recent progress that has been made in the development of small-molecule as well as material-based fluorogenic probes for sensitive detection of the activities of enzymes that are related to a number of human diseases. The principles utilized to design these probes as well as their applications are reviewed. Specific attention is given to fluorogenic probes that have been developed for analysis of the activities of enzymes including oxidases and reductases, those that act on biomacromolecules including DNAs, proteins/peptides/amino acids, carbohydrates and lipids, and those that are responsible for translational modifications. We envision that this review will serve as an ideal reference for practitioners as well as beginners in relevant research fields.

A long-wavelength ultrasensitive colorimetric fluorescent probe for carbon monoxide detection in living cells

A long-wavelength ultrasensitive colorimetric fluorescent probe was developed to track carbon monoxide in living cells.

Enzyme-Activated Fluorogenic Probes for Live-Cell and in Vivo Imaging

Fluorogenic probes, small-molecule sensors that unmask brilliant fluorescence upon exposure to specific stimuli, are powerful tools for chemical biology. Those probes that respond to enzymatic catalysis illuminate the complex dynamics of biological processes at a level of spatiotemporal detail and sensitivity unmatched by other techniques. Here, we review recent advances in enzyme-activated fluorogenic probes for biological imaging. We organize our survey by enzyme classification, with emphasis on fluorophore masking strategies, modes of enzymatic activation, and the breadth of current and future applications. Key challenges such as probe selectivity and spectroscopic requirements are described alongside therapeutic, diagnostic, and theranostic opportunities.

Interrogating Protein Phosphatases with Chemical Activity Probes

Protein phosphatases, while long overlooked, have recently become appreciated as drivers of both normal- and disease-associated signaling events. As a result, the spotlight is now turning torwards this enzyme family and efforts geared towards the development of modern chemical tools for studying these enzymes are well underway. This Minireview focuses on the evolution of chemical activity probes, both optical and covalent, for the study of protein phosphatases. Small-molecule probes, global monitoring of phosphatase activity through the use of covalent modifiers, and targeted fluorescence-based activity probes are discussed. We conclude with an overview of open questions in the field and highlight the potential impact of chemical tools for studying protein phosphatases.

Intracellular endogenous glutathione detection and imaging by a simple and sensitive spectroscopic off–on probe

A new colorimetric and fluorescent off–on probe is constructed, synthesized and applied to indicate fluctuations in intracellular GSH levels selectively and sensitively under the stimulation of chemicals and drugs.

Recent progresses in small-molecule enzymatic fluorescent probes for cancer imaging

An overview of recent advances in small-molecule enzymatic fluorescent probes for cancer imaging, including design strategies and cancer imaging applications.

Real time detection of ESKAPE pathogens by a nitroreductase-triggered fluorescence turn-on probe

The identification of bacterial pathogens is the critical first step in conquering infection diseases. A novel turn-on fluorescent probe for the selective sensing of nitroreductase (NTR) activity and its initial applications in rapid, real-time detection and identification of ESKAPE pathogens have been reported.