Resorufin-based responsive probes for fluorescence and colorimetric analysis

Dual-functional probe-based multi-signal immunosensor platform for tropane alkaloids: Verification and evaluation

This study aims to realise rapid detecting of tropane alkaloids (TAs) in food. For this purpose, a broad-spectrum single-chain fragment variable was fused with horseradish peroxidase to create an antibody-enzyme complex (AEC) with antigen recognition and catalytic activity. A multi-signal immunosensor platform based on AEC in the direct competitive reaction mode was constructed using 3,3',5,5'-tetramethylbenzidine and 10-acetyl-3,7-dihydroxyphenoxazine as substrates. The sensitivity of TAs in the immunosensor platform ranged from 0.25 μg/kg to 7912.46 μg/kg. Honey was selected as a representative food sample, and the limit of detection of TAs in honey ranged from 0.02 μg/kg to 409.11 μg/kg, with a recovery rate of 65.7 %-117.1 % and a coefficient of variation less than 21.4 %. Results showed that the immunosensor platform possesses satisfactory accuracy and precision, which highlights its potential for practical applications and its suitability as an ideal tool for rapid screening of TAs in food.

Nitrogenation of Alkynes with Nitrones to Prepare Functionalized [1,4]Oxazinones through Csp-Csp2 Bond Cleavage

Herein, we report a novel strategy of hypervalent iodine(III) compound-mediated selective Csp-Csp2 bond cleavage of alkynes and C═N/N-O bond cleavage of nitrones and recombination of C-C/C-O/C-N multiple bonds to access various functionalized [1,4]oxazinones bearing a vicinal carbon stereocenter in good yields and high diastereoselectivity. Mechanistic studies revealed that the reaction undergoes a domino [4 + 3] cycloaddition, 1,3-rearrangement of N-O bond, intramolecular cyclization, dearomatization, and rearomatization over four steps in a single flask. The present method features good functional group tolerance, broad substrate scope, and C-C/C═N/N-O multiple bonds cleavage and recombination.

Nanoscopic visualization of microgel-immobilized cytochrome P450 enzymes and their local activity

Microgels provide a controlled microenvironment for enzymes, protecting them from degradation while enhancing stability and activity. Their customizable and biocompatible structure allows for targeted delivery and controlled release, making them ideal for transporting and preserving enzyme function in various applications. For such applications, detailed knowledge of the distribution of enzymes and their activity within the microgels is essential. We present a combination of different localization-based super-resolution fluorescence microscopy measurements to localise single Cytochrome P450 BM3 enzymes and compare their local catalytic activity.

Promising tools into oxidative stress: A review of non-rodent model organisms

Oxidative stress is a crucial concept in redox biology, and significant progress has been made in recent years. Excessive levels of reactive oxygen species (ROS) can lead to oxidative damage, heightening vulnerability to various diseases. By contrast, ROS maintained within a moderate range plays a role in regulating normal physiological metabolism. Choosing suitable animal models in a complex research context is critical for enhancing research efficacy. While rodents are frequently utilized in medical experiments, they pose challenges such as high costs and ethical considerations. Alternatively, non-rodent model organisms like zebrafish, Drosophila, and C. elegans offer promising avenues into oxidative stress research. These organisms boast advantages such as their small size, high reproduction rate, availability for live imaging, and ease of gene manipulation. This review highlights advancements in the detection of oxidative stress using non-rodent models. The oxidative homeostasis regulatory pathway, Kelch-like ECH-associated protein 1-Nuclear factor erythroid 2-related factor 2 (Keap1-Nrf2), is systematically reviewed alongside multiple regulation of Nrf2-centered pathways in different organisms. Ultimately, this review conducts a comprehensive comparative analysis of different model organisms and further explores the combination of novel techniques with non-rodents. This review aims to summarize state-of-the-art findings in oxidative stress research using non-rodents and to delineate future directions.

Phenotypic-Based Discovery and Exploration of a Resorufin Scaffold with Activity against Mycobacterium tuberculosis

Tuberculosis remains a leading cause of death by infectious disease. The long treatment regimen and the spread of drug-resistant strains of the causative agent Mycobacterium tuberculosis (Mtb) necessitates the development of new treatment options. In a phenotypic screen, nitrofuran-resorufin conjugate 1 was identified as a potent sub-micromolar inhibitor of whole cell Mtb. Complete loss of activity was observed for this compound in Mtb mutants affected in enzyme cofactor F420 biosynthesis (fbiC), suggesting that 1 undergoes prodrug activation in a manner similar to anti-tuberculosis prodrug pretomanid. Exploration of the structure-activity relationship led to the discovery of novel resorufin analogues that do not rely on the deazaflavin-dependent nitroreductase (Ddn) bioactivation pathway for their antimycobacterial activity. These analogues are of interest as they work through an alternative, currently unknown mechanism that may expand our chemical arsenal towards the treatment of this devastating disease.

Recent development in dual function fluorescence probes for HOCl and interaction with different bioactive molecules

Reactive oxygen species (ROS), reactive sulfur species (RSS), metal ions, and nitrogen species (RNS) play important roles in a variety of biological processes, such as a signal transduction, inflammation, and neurodegenerative damage. These species, while essential for certain functions, can also induce stress-related diseases. The interrelation between ROS, RSS, Metal ions and RNS underscores the importance of quantifying their concentrations in live cells, tissues, and organisms. The review emphasizes the use of small-molecule-based fluorescent/chemodosimeter probes to effectively measure and map the species' distribution with high temporal and spatial precision, paying particular attention to in vitro and in vivo environments. These probes are recognized as valuable tools contributing to breakthroughs in modern redox biology. The review specifically addresses the relationship of HOCl/ClO‾ (hypochlorous acid/Hypochlorite) with other reactive species. (Dual sensing probes).

Starting with screening strains to construct synthetic microbial communities (SynComs) for traditional food fermentation

With the elucidation of community structures and assembly mechanisms in various fermented foods, core communities that significantly influence or guide fermentation have been pinpointed and used for exogenous restructuring into synthetic microbial communities (SynComs). These SynComs simulate ecological systems or function as adjuncts or substitutes in starters, and their efficacy has been widely verified. However, screening and assembly are still the main limiting factors for implementing theoretic SynComs, as desired strains cannot be effectively obtained and integrated. To expand strain screening methods suitable for SynComs in food fermentation, this review summarizes the recent research trends in using SynComs to study community evolution or interaction and improve the quality of food fermentation, as well as the specific process of constructing synthetic communities. The potential for novel screening modalities based on genes, enzymes and metabolites in food microbial screening is discussed, along with the emphasis on strategies to optimize assembly for facilitating the development of synthetic communities.

A highly selective probe engineered to detect polarity and distinguish normal cells and tumor cells in tissue sections

Early diagnostics and therapies for diseases such as cancer are limited by the fact that the inducing factors for the development of cytopathies are not clear. The stable polarity of lipid droplets is a potential biomarker for tumor cells; however, the complex intracellular biological environment poses great difficulties for specific detection of the polarity. Therefore, to meet this pressing challenge, we designed a highly selective fluorescent probe, DCI-Cou-polar, which used the ICT mechanism to differentiate normal cells and tumor cells in tissue sections by detecting changes in the polarities of intracellular lipid droplets. The introduction of a cyclic amine at the 7-position of coumarin (benzoquinolizine coumarin) reduced its ability to donate electrons compared with the diethylamino group, which increased the probe selectivity while retaining the sensitivity to polarity. With NIR emission and large Stokes shifts, DCI-Cou-polar has high sensitivity to polarity, excellent photostability, and biocompatibility, and it tracks lipid droplets with high fidelity. Therefore, we believe that this polarity-sensitive probe provides information on the connection between the polarity of lipid droplets and tumors while improving the development of highly selective polarity probes.

γ-Glutamyltranspeptidase (GGT) Sensitive Fluorescence Probes for Cancer Diagnosis; Brief Review

Millions of deaths occur each year due to the late diagnosis of abnormal cellular growth within the body. However, the devastating impact of this can be significantly reduced if cancer metastasis is detected early through the use of enzymatic biomarkers. Among several biomarkers, γ-glutamyltranspeptidase (GGT) stands out as a member of the aminopeptidase family. It is primarily found on the surface of cancer cells such as glioma, ovarian, lung, and prostate cancer, without being overexpressed in normal cells or tissues. Recent years have witnessed significant progress in the field of cancer monitoring and imaging. Fluorescence sensing techniques have been employed, utilizing organic small molecular probes with enzyme-specific recognition sites. These probes emit a fluorescent signal upon interacting with GGT, enabling the imaging, identification, and differentiation of normal and cancerous cells, tissues, and organs. This review article presents a concise overview of recent progress in fluorescent probes developed for the selective detection of GGT, focusing on their applications in cancer imaging. It highlights the observed alterations in the fluorescence and absorption spectra of the probes before and after interaction with GGT. Additionally, the study investigates the changes in the probe molecule's structure following enzyme treatment, evaluates the sensor's detection limit, and consolidated imaging studies conducted using confocal fluorescence analysis. This comprehensive survey is expected to contribute to the advancement of sensing techniques for biomarker detection and cancer imaging, providing valuable insights for refining methodologies and inspiring future developments in this field.

Advances and Perspectives of Responsive Probes for Measuring γ-Glutamyl Transpeptidase

Gamma-glutamyltransferase (GGT) is a plasma-membrane-bound enzyme that is involved in the γ-glutamyl cycle, like metabolism of glutathione (GSH). This enzyme plays an important role in protecting cells from oxidative stress, thus being tested as a key biomarker for several medical conditions, such as liver injury, carcinogenesis, and tumor progression. For measuring GGT activity, a number of bioanalytical methods have emerged, such as chromatography, colorimetric, electrochemical, and luminescence analyses. Among these approaches, probes that can specifically respond to GGT are contributing significantly to measuring its activity in vitro and in vivo. This review thus aims to highlight the recent advances in the development of responsive probes for GGT measurement and their practical applications. Responsive probes for fluorescence analysis, including "off-on", near-infrared (NIR), two-photon, and ratiometric fluorescence response probes, are initially summarized, followed by discussing the advances in the development of other probes, such as bioluminescence, chemiluminescence, photoacoustic, Raman, magnetic resonance imaging (MRI), and positron emission tomography (PET). The practical applications of the responsive probes in cancer diagnosis and treatment monitoring and GGT inhibitor screening are then highlighted. Based on this information, the advantages, challenges, and prospects of responsive probe technology for GGT measurement are analyzed.

Molecular Accessibility and Diffusion of Resorufin in Zeolite Crystals

We have used confocal laser scanning microscopy on the small, fluorescent resorufin dye molecule to visualize molecular accessibility and diffusion in the hierarchical, anisotropic pore structure of large (~10 μm-sized) zeolite-β crystals. The resorufin dye is widely used in life and materials science, but only in its deprotonated form because the protonated molecule is barely fluorescent in aqueous solution. In this work, we show that protonated resorufin is in fact strongly fluorescent when confined within zeolite micropores, thus enabling fluorescence microimaging experiments. We find that J-aggregation guest-guest interactions lead to a decrease in the measured fluorescence intensity that can be prevented by using non-fluorescent spacer molecules. We characterized the pore space by introducing resorufin from the outside solution and following its diffusion into zeolite-β crystals. The eventual homogeneous distribution of resorufin molecules throughout the zeolite indicates a fully accessible pore network. This enables the quantification of the diffusion coefficient in the straight pores of zeolite-β without the need for complex analysis, and we found a value of 3×10-15  m2  s-1 . Furthermore, we saw that diffusion through the straight pores of zeolite-β is impeded when crossing the boundaries between zeolite subunits.

Electrochemical Synthesis of Phenothiazinone as Fluorophore and Its Application in Bioimaging

Phenothiazinone is a promising yet underutilized fluorophore, possibly due to the lack of a general accessibility. This study reports a robust and scalable TEMPO-mediated electrochemical method to access a variety of phenothiazinones from 2-aminothiophenols and quinones. The electrosynthesis proceeds in a simple cell architecture under mild condition, and notably carbon-halogen bond in quinones remains compared to conventional methods, enabling orthogonal downstream functionalization. Mechanistic studies corroborate that TEMPO exerts a protective effect in avoiding product decomposition at the cathode. In particular, benzophenothiazinones show intriguing luminescence in both solid and solution state, and thus their photophysical properties are scrutinized in detail. Further bio-imaging of the lipid droplets in living cells highlights the considerable promise of benzophenothiazinones as fluorescent dye in the biomedical fields.

Construction and Application of Multipurpose metal-organic frameworks -based Hydrogen Sulfide Probe

Hydrogen sulfide (H2S) is a toxic gas derived from the sulfur industry and trace H2S in the environment can cause serious ecological damage while inhalation can cause serious damage and lead to disease. Therefore, the real-time and accurate detection of trace sulfur ions is of great significance for environmental protection and early disease detection. Considering the shortcoming of current H2S probes in terms of stability and sensitivity, the development of novel probes is necessary. Herein, a novel metal-organic frameworks (MOF)-based material, UiO-66-NH2@BDC, was designed and prepared for the visual detection of H2S with rapid response (< 6 s) and low detection limit of S2- (0.13 µM) by hydrogen bonding. Based on its good optical performance, the UiO-66-NH2@BDC probe can detect S2- in various water environments. More importantly, UiO-66-NH2@BDC probe realize imaging S2- in cells and live zebrafish.

A colorimetric and fluorescent signaling probe for assaying Pd2+ in practical samples

We developed an optical signaling probe to detect Pd2+ ions in Pd-containing catalyst and drug candidate. The Pd2+ signaling probe (Res-DT) was readily prepared by reacting the versatile fluorochrome resorufin with phenyl chlorodithioformate. In a phosphate-buffered saline solution (pH 7.4) containing sodium dodecyl sulfate (SDS) as a signal-boosting surfactant, Res-DT exhibited a pronounced colorimetric response with a chromogenic yellow to magenta shift, leading to a substantial increase in the fluorescence intensity. The Pd2+ signaling performance of Res-DT was attributed to the Pd2+-promoted hydrolysis of the dithioate moiety. The probe displayed high selectivity toward Pd2+ ions and remained unaffected by commonly encountered coexisting components. Moreover, the detection limit of Res-DT for Pd2+ ions was 10 nM, and the signaling was achieved within 7 min. Furthermore, to demonstrate the real-world applicability of Res-DT, a Pd2+ assay was performed in Pd-containing catalyst and drug candidate using an office scanner as an easily accessible measurement device. Our results highlight the prospects of Res-DT as a tool to detect Pd2+ ions in various practical samples, with potential applications in catalysis, medicine, and environmental science.

A hydrogen sulfide and tyrosinase responsive dual-locked fluorophore for selective imaging of melanoma cells

A resorufin-based dual-locked fluorescent probe (RHT) was introduced to image melanoma cells selectively. RHT was shown to function as an AND molecular logic gate as it emitted a signal only in the presence of both hydrogen sulfide (H2S) and tyrosinase (Tyr), which are known to be overexpressed in melanoma cells. In vitro cell culture studies revealed that RHT can be activated with endogenous H2S and Tyr and allows selective imaging of B16-F10 cancer cells under confocal microscopy. RHT marks the first ever example of a fluorescent probe that is sequentially activated by H2S and Tyr.

A two-photon fluorescent probe for formaldehyde detection and regeneration in living cells

A two-photon excited fluorescent probe CMB-1 has been rationally developed for the detection and regeneration of formaldehyde based on a novel nucleophilic addition of a secondary amine to FA and subsequential alcoholysis reactivity mechanism. It enables a specific turn-on response towards formaldehyde and facilitates the monitoring of exogenous and endogenous formaldehyde in living cells via both one- and two-photon microscopy, with minimal influence on its native homeostasis and local concentration.

Fluorescence-based chemical tools for monitoring ultrasound-induced hydroxyl radical production in aqueous solution and in cells

We report the synthesis of hydroxyl-radical (˙OH) responsive fluorescent probes that utilise the 3,5-dihydroxybenzyl (DHB) functionality. 4-Methylumbeliferone-DHB (Umb-DHB) and resorufin-DHB (Res-DHB) in the presence of ˙OH radicals resulted in significant increases in their respective fluorescent emission intensities at 460 nm and 585 nm. The incubation of Res-DHB in HeLa cells followed by therapeutic ultrasound (1 MHz) resulted in a significant increase in fluorescence emission intensity thus permitting the ability to monitor ultrasound-induced ˙OH production in live cells.

Multiplex Chroma Response Wearable Hydrogel Patch: Visual Monitoring of Urea in Body Fluids for Health Prognosis

Visual wearable devices can rapid intuitively monitor biomarkers in body fluids to indicate the human health status and provide valuable reference for further medical diagnosis. However, unavoidable interference factors such as skin color, natural light, and background luminescence can interfere with the visualization accuracy of flexible wearable devices, limiting their practical sensing application. Here, we designed a wearable sensing patch via an embedded upconversion optical probe in a 3D porous polyacrylamide hydrogel, exhibiting a multiplex chroma response to urea based on the inner filter effect, which overcomes the susceptibility to external conditions due to its near-infrared excited luminescence and improves the resolution and accuracy of visual sensing. Furthermore, a highly compatible portable sensing platform combined with a smartphone was designed to achieve in situ rapid quantitative analysis of urea. The limit of detection values of the upconversion optical probe and hydrogel sensor are as low as 1.4 and 30 μM respectively, exhibiting the practicality in different scenarios. The designed sensing patch provides a convenient and accurate sensing strategy for the detection of biomarkers in body fluids and has the potential to be developed into a point-of-care device to provide disease early warning and clinical diagnosis.

Functional Imaging and Inhibitor Screening of Human Pancreatic Lipase by a Resorufin-Based Fluorescent Probe

Human pancreatic lipase (hPL) is a crucial digestive enzyme responsible for the digestion of dietary lipids in humans, and inhibition of hPL is effective in reducing triglyceride intake, thereby preventing and treating obesity. In this study, a series of fatty acids with different carbon chain lengths were constructed to the fluorophore resorufin based on the substrate preference of hPL. Among them, RLE was found to have the best combination of stability, specificity, sensitivity and reactivity towards hPL. Under physiological conditions, RLE can be rapidly hydrolyzed by hPL and released to resorufin, which triggered approximately 100-fold fluorescence enhancement at 590 nm. RLE was successfully applied for sensing and imaging of endogenous PL in living systems with low cytotoxicity and high imaging resolution. Moreover, a visual high-throughput screening platform was established using RLE, and the inhibitory effects of hundreds of drugs and natural products toward hPL were evaluated. Collectively, this study reports a novel and highly specific enzyme-activatable fluorogenic substrate for hPL that could serve as a powerful tool for monitoring hPL activity in complex biological systems and showcases the potential to explore physiological functions and rapid screening of inhibitors.

High-performance fluorescence probe for fast and specific visualization of norepinephrine in vivo and depression-like mice

Norepinephrine (NE), as an important neurotransmitter, is closely associated with the pathogenesis of anxiety and depressive disorders. Effective monitoring of NE fluctuation aids in the diagnosis of depression and the therapeutic assessment of the antidepressant intervention. The construction of novel fluorescent probes with high specificity towards NE for imaging in depression models is still in demand urgently. In this work, a novel resorufin-based red-emitting fluorescent probe for real-time tracking NE was developed. NE can significantly increase the fluorescence of probe LNE by triggering deprotection of carbonothioate ligand via nucleophilic substitution. The probe LNE demonstrated significant NE selectivity and sensitivity over other analytes in vitro. In addition, probe LNE showed a fast response time (<10 min), and the change in fluorescence signal was positively linked with NE concentration, which could be utilized to track the dysregulation of NE in vivo. More importantly, this powerful probe was successfully employed for real-time visual and imaging of NE in living cells and depression-like behavior animals.

Regulating the activity of boronate moiety to construct fluorescent probes for the detection of ONOO-in vitro and in vivo

Abnormal intracellular peroxynitrite (ONOO^-) concentration is related to oxidative damage, which is correlated with many pathological consequences, such as local inflammation and other diseases. In this work, a series of resorufin benzyl ether-based fluorescent probes were designed using boronate as a recognizing moiety installed on a phenyl moiety for ONOO^- detection via a self-immolation mechanism. The location of the boronate as well as the substitution patterns on the phenyl moiety were investigated and the responding behaviors of the designed probes to ONOO^-, other reactive oxygen species, and biothiols were examined. It was found that all the immolative probes were inevitably dominated by ONOO^-. Compared with other probes, p-Borate possessed favorable selectivity and high sensitivity to ONOO^-. Moreover, p-Borate was successfully used to detect ONOO^- in cells and inflamed mice.

Medicinal chemical optimization of fluorescent pyrrole-based COX-2 probes

Recent studies have demonstrated the ability of human prostaglandin-endoperoxide synthase 2 (COX-2) to guide the formation of fluorescent pyrroles through the Paal-Knorr reaction resulting in the discovery of a central motif. This initial discovery prompted further exploration of this motif for the design of COX-2 inhibitors through the modifications of the substituents on the pyrrole core. This effort led to the discovery of a set of pyrroles whose activity was comparable to Celecoxib, an orally prescribed nonsteroidal anti-inflammatory COX-2 inhibitor. Furthermore, structure-activity relationship (SAR) data, important for the discovery of COX-2 inhibitors, has been obtained.

Locked and Loaded: β-Galactosidase Activated Photodynamic Therapy Agent Enables Selective Imaging and Targeted Treatment of Glioblastoma Multiforme Cancer Cells

Selective detection and effective therapy of brain cancer, specifically, the very aggressive glioblastoma multiforme (GBM), remains one of the paramount challenges in clinical settings. While radiotherapy combined surgery is proposed as the main treatment course, it has several drawbacks such as complexity of the operation and common development of recurrent tumors in this course of patient care. Unique opportunities presented by photodynamic therapy (PDT) offer promising, effective, and precise therapy against GBM cells along with simultaneous imaging opportunities. However, activatable, theranostic molecular systems in PDT modality for GBM remained scarce. Specifically, even though elevated β-galactosidase (β-gal) activity in glioblastoma cells is well-documented, targeted, activatable therapeutic PDT agents have not been realized. Herein, we report a β-galactosidase (β-gal) activatable phototheranostic agent based on an iodinated resorufin core (RB-1) which was realized in only three steps with commercial reagents in 29% overall yield. RB-1 showed very high singlet oxygen (1O2) quantum yield (54%) accompanied by a remarkable turn-on response in fluorescence upon enzymatic activation. RB-1 was tested in different cell lines and revealed selective photocytotoxicity in U-87MG glioblastoma cells. Additionally, thanks to almost 7% fluorescence quantum yield (ΦF) despite extremely high 1O2 generation yield, RB-1 was also demonstrated as a successful agent for fluorescence imaging of U-87MG cells. Due to significantly lower (β-gal) activity in healthy cells (NIH/3T3), RB-1 stayed in a passive state and showed minimal photo and dark toxicity. RB-1 marks the first example of a β-gal activatable phototheranostic agent toward effective treatment of glioblastoma.

Construction of Spindle-Shaped Ti3+ Self-Doped TiO2 Photocatalysts Using Triethanolamine-Aqueous as the Medium and Its Photoelectrochemical Properties

To enhance the utilization efficiency of visible light and reduce the recombination of photogenerated electrons and holes, spindle-shaped TiO2 photocatalysts with different Ti3+ concentrations were fabricated by a simple solvothermal strategy using low-cost, environmentally friendly TiH2 and H2O2 as raw materials and triethanolamine-aqueous as the medium. The photocatalytic activities of the obtained photocatalysts were investigated in the presence of visible light. X-ray diffraction (XRD), Raman spectra, transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared (FT-IR) spectra were applied to characterize the structure, morphologies, and chemical compositions of as-fabricated Ti3+ self-doped TiO2. The concentration of triethanolamine in the mixed solvent plays a significant role on the crystallinity, morphologies, and photocatalytic activities. The electron–hole separation efficiency was found to increase with the increase in the aspect ratio of as-fabricated Ti3+ self-doped TiO2, which was proved by transient photocurrent response and electrochemical impedance spectroscopy.

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.

Fluorescent-based nanosensors for selective detection of a wide range of biological macromolecules: A comprehensive review

Thanks to their unique attributes, such as good sensitivity, selectivity, high surface-to-volume ratio, and versatile optical and electronic properties, fluorescent-based bioprobes have been used to create highly sensitive nanobiosensors to detect various biological and chemical agents. These sensors are superior to other analytical instrumentation techniques like gas chromatography, high-performance liquid chromatography, and capillary electrophoresis for being biodegradable, eco-friendly, and more economical, operational, and cost-effective. Moreover, several reports have also highlighted their application in the early detection of biomarkers associated with drug-induced organ damage such as liver, kidney, or lungs. In the present work, we comprehensively overviewed the electrochemical sensors that employ nanomaterials (nanoparticles/colloids or quantum dots, carbon dots, or nanoscaled metal-organic frameworks, etc.) to detect a variety of biological macromolecules based on fluorescent emission spectra. In addition, the most important mechanisms and methods to sense amino acids, protein, peptides, enzymes, carbohydrates, neurotransmitters, nucleic acids, vitamins, ions, metals, and electrolytes, blood gases, drugs (i.e., anti-inflammatory agents and antibiotics), toxins, alkaloids, antioxidants, cancer biomarkers, urinary metabolites (i.e., urea, uric acid, and creatinine), and pathogenic microorganisms were outlined and compared in terms of their selectivity and sensitivity. Altogether, the small dimensions and capability of these nanosensors for sensitive, label-free, real-time sensing of chemical, biological, and pharmaceutical agents could be used in array-based screening and in-vitro or in-vivo diagnostics. Although fluorescent nanoprobes are widely applied in determining biological macromolecules, unfortunately, they present many challenges and limitations. Efforts must be made to minimize such limitations in utilizing such nanobiosensors with an emphasis on their commercial developments. We believe that the current review can foster the wider incorporation of nanomedicine and will be of particular interest to researchers working on fluorescence technology, material chemistry, coordination polymers, and related research areas.

A specifically triggered turn-on fluorescent probe platform and its visual imaging of HClO in cells, arthritis and tumors

Understanding disease-related processes at the molecular level is of great importance for the prevention and treatment of diseases. However, due to the lack of effective analytical tools, it is challenging to gain insight into the relationships between a specific bioactive molecule and the associated disease. Herein, a rapid turn-on resorufin-based fluorescent probe platform utilizing the HClO-specific oxidative cleavage of the amide was constructed, allowing the visualization of HClO in vitro and in vivo. These probes could quickly respond to HClO (< 50 s) with high selectivity and sensitivity (12-153 nM). The probe REClO-6 had the fastest response (30 s) and the highest sensitivity (12 nM), and was successfully used for the imaging of endogenous and exogenous HClO in cells and zebrafish. Notably, it was also successfully applied to the imaging of HClO in mouse arthritis and solid tumors. This study provided a rapid imaging analysis tool, which would be used to investigate the relationship between HClO and the disease-related physiological processes.

Resorufin-based fluorescent probe with elevated water solubility for visualizing fluctuant peroxynitrite in progression of inflammation

Inflammation is a significant protective response in biological systems and associated with various diseases. Peroxynitrite (ONOO^-) as a highly active oxidant participates in the inflammatory process of organisms. Thus, it is necessary to construct novel fluorescent probes for exploring inflammation-related diseases through detecting endogenous ONOO^-. Resorufin-based fluorescent probes for testing ONOO^- were rare and suffered from poor water solubility. In this work, we elaborately designed three resorufin-based incorporating isatin derivatives probes RF-ITs and successfully obtained two highly selective probes RF-IT-OC and RF-IT-EG for ONOO^-. Comparing the other two probes, RF-IT-EG containing triethylene glycol monomethyl ether on isatin moiety displayed better water solubility (3.2 mg/L), faster response rate (60 s), larger signal-to-noise ratio (103-fold) and lower detection limit (87 nM) for monitoring ONOO^-. The cells imaging results manifested that probe RF-IT-EG could be applied to trace endogenous ONOO^- with inappreciable cytotoxicity. Moreover, the RF-IT-EG was capable of tracking the fluctuation of endogenous ONOO^- in LPS-stimulated inflamed mouse leg models. This work will provide a faithful and promising probe for illustrating the roles of ONOO^- in various inflammation-related diseases.

Trihexyltetradecylphosphonium chloride based ratiometric fluorescent nanosensors for multiplex anion discrimination

A multiplex anion-responsive platform was developed with [THTP][Cl] and ETH5350, providing colorimetric and spectroscopic transformations. By choosing suitable ionophores, a pool of nanosensors for extended anions could be achieved.

Design and engineering of a dual-mode absorption/emission molecular switch for all-optical encryption

Photochemical reactions that produce a detectable change in the spectroscopic properties of organic chromophores can be exploited to harness the principles of Boolean algebra and design molecule-based logic circuits. Moreover, the logic processing capabilities of these photoactive molecules can be directed to protect, encode, and conceal information at the molecular level. We have designed a photochemical strategy to read, write and encrypt data in the form of optical signals. We have synthesized a supramolecular system based on the known dye resazurin, and investigated a series of photochemical transformations that can be used to regulate its absorption and emission properties upon illumination with ultraviolet or visible light. We have then examined the logic behaviour of the photochemistry involved, and illustrated its potential application in data encryption.

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.

Effective Diagnosis of Foot-And-Mouth Disease Virus (FMDV) Serotypes O and A Based on Optical and Electrochemical Dual-Modal Detection

Foot-and-mouth disease virus (FMDV) is a highly contagious disease that affects cloven-hoofed animals. The traditional diagnostic methods for FMDV have several drawbacks such as cross-reactivity, low sensitivity, and low selectivity. To overcome these drawbacks, we present an optical and electrochemical dual-modal approach for the specific detection of FMDV serotypes O and A by utilizing a magnetic nanoparticle labeling technique with resorufin β-d-glucopyranoside (res-β-glc) and β-glucosidase (β-glc), without the use of typical lateral flow assay or polymerase chain reaction. FMDV serotypes O and A were reacted with pan-FMDV antibodies that recognize all seven FMDV serotypes (O, A, C, Asia 1, SAT 1, SAT 2, and SAT 3). The antigen–antibody complex was then immobilized on magnetic nanoparticles and reacted with β-glc-conjugated FMDV type O or type A antibodies. Subsequently, the addition of res-β-glc resulted in the release of fluorescent resorufin and glucose owing to catalytic hydrolysis by β-glc. The detection limit of fluorescent signals using a fluorescence spectrophotometer was estimated to be log(6.7) and log(5.9) copies/mL for FMDV type O and A, respectively, while that of electrochemical signals using a glucometer was estimated to be log(6.9) and log(6.1) copies/mL for FMDV type O and A, respectively. Compared with a commercially available lateral flow assay diagnostic kit for immunochromatographic detection of FMDV type O and A, this dual-modal detection platform offers approximately four-fold greater sensitivity. This highly sensitive and accurate dual-modal detection method can be used for effective disease diagnosis and treatment, and will find application in the early-stage diagnosis of viral diseases and next-generation diagnostic platforms.

Recent advances in colorimetry/fluorimetry-based dual-modal sensing technologies

Tailored to the increasing demands for sensing technologies, the fabrication of dual-modal sensing technologies through combining two signal transduction channels into one method has been proposed and drawn considerable attention. The integration of two sensing signals not only promotes the analytical efficiency with reduced assumption, but also improves the analytical performances with enlarged detection linear range, enhanced accuracy, and boosted application flexibility. The two top-rated output signals for developing dual-modal sensors are colorimetric and fluorescent signals because of their outstanding merits for point of care applications and real-time sensitive sensing. Given the rapid development of material chemistry and nanotechnology, the recent decade has witnessed great advance in colorimetric/fluorimetric signal based dual-modal sensing technologies. The new sensing strategy leads to a broad avenue for various applications in disease diagnosis, environmental monitoring and food safety because of the complementary and synergistic effects of the two output signals. In this state-of-the-art review, we comprehensively summarize different types of colorimetric/fluorimetric dual-modal sensing methods by highlighting representative research in the last 5 years, digging into their sensing methodologies, particularly the working principles of the signal transduction systems. Then, the challenges and future prospects for boosting further development of this research field are discussed.

Optical detection of sulfur mustard contaminated surfaces based on a sprayable fluorescent probe

A water-based sprayable functional polymer was immobilized with the fluorescent probe DPXT and was used as a chemo-sensor for rapid localization of surface contamination by sulfur mustard.

Discovery of a highly efficient nitroaryl group for detection of nitroreductase and imaging of hypoxic tumor cells

Hypoxia is a pathological hallmark of solid tumors. Detection of hypoxia is therefore of great interest for tumor diagnosis and treatment. As a well-established biomarker of hypoxia, nitroreductase (NTR) has been widely exploited in the development of hypoxia-responsive fluorescent probes on the basis of its enzymatic activity to reduce nitroaryl groups. However, studies on the relationship between the nitroaryl structure and the probe performance for optimal probe design are still rare. Here we report a comparative investigation of nitroaryl groups and identification of the optimal nitroaryl structure for developing new fluorescent probes with extremely high efficiency in the detection of NTR and the imaging of hypoxic tumor cells. Specifically, we synthesized a series of resorufin-based fluorescent probes containing different nitroaryl groups, compared their fluorescence responses to NTR, and identified 2-nitro-N-methyl-imidazolyl as the optimal nitroaryl group that is much more efficient than the most widely used 4-nitrophenyl for NTR detection. The structure-performance relationship was then studied by theoretical molecular docking, revealing the unique features of 2-nitro-N-methyl-imidazolyl in binding and reaction with NTR. We further incorporated the 2-nitro-N-methyl-imidazolyl group into a near-infrared (NIR) hemicyanine fluorophore and developed a NIR fluorescent probe NFP-7 for the detection of NTR and hypoxic tumor cells. NFP-7 exhibits a strong fluorescence increase toward NTR in vitro with an ultrafast (within 40 seconds to fluorescence maximum) and ultrasensitive (0.2 ng mL-1 detection limit) response. NFP-7 has also been demonstrated for imaging the degree of hypoxia in live tumor cells and, more importantly, in a murine tumor model. Our study provides important insights into hypoxia probe development and new tools for hypoxia imaging.