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Here, a dual lock-and-key fluorescence probe was developed for visualizing the inflammatory process in myocardial H9C2 cells. The probe possessed two-photon properties, viscosity sensitivity, and hydrogen peroxide (H 2 O 2) responsiveness. A thiocarbamate spacer between fluorophore and H 2 O 2 responsive unit enabled the release of carbonyl sulfide (COS). This rapidly converts to the anti-inflammatory hydrogen sulfide (H 2 S) by the ubiquitous enzyme carbon anhydrase. The probe displayed a dual response towards hydrogen peroxide and viscosity in vitro. No obvious fluorescence changes were observed towards either hydrogen peroxide or viscosity alone. In cellular experiments, the probe demonstrated good biocompatibility, low toxicity, and was shown responses towards exogenous and endogenous hydrogen peroxide under viscosity conditions. LPS induced cell inflammation showed it was able to effectively alleviate the inflammation-caused damage by releasing H 2 S and eliminating H 2 O 2. The new protocol demonstrates its promising to achieve diagnosis and treatment of cellular inflammatory process. [Display omitted] • A dual response fluorescence probe possessing viscosity sensitivity, and hydrogen peroxide responsiveness was developed. • Hydrogen sulfide was generated from self-immolation of carbonyl sulfide, catalysed under carbon anhydrase. • The probe showed turn on fluorescence responses towards hydrogen peroxide and viscosity in vitro. • The probe was able to effectively alleviate the inflammation-caused damage through releasing H 2 S and eliminating H 2 O 2. [ABSTRACT FROM AUTHOR]

The abnormally elevated expression level of glutathione (GSH) has been observed in various human cancer cells and tissue. Thus, effective methods for glutathione detection are of great importance in early diagnosis of cancer. However, many fluorescent probes for GSH detection suffer from the interference of the abundantly existent nucleophilic biomolecules in biological environment. In this work, we propose a sequential activation strategy to overcome this problem by designing and synthesizing a series of 1,3,5-triazinyl resorufin turn-on fluorescent probe (Probes 1–3). As two electrophilic sites are presented in probes, GSH sequentially reacts with the resorufin and the triazine moiety, resulting in significant fluorescence augmentation (up to 165.0-fold). Designed probes possess low limit of detection as low as 1.8 μM). Cellular fluorescent imaging has been successfully applied to selectively detect GSH in several living cells. [Display omitted] • Novel sequential activation strategy allows the Probe 1–3 to detect GSH with high selectivity. • Designed fluorescent probes exhibited strong fluorescence intensity as response. • Designed probes realized GSH visualization in multiple cells with high fidelity. [ABSTRACT FROM AUTHOR]

Hydrogen sulfide (H 2 S) is a multifunctional gaseous signaling molecule that plays a vital role in several biological processes. In the present study, a BODIPY-based fluorescent probe called 8-[4-((1,4,7,10-tetraazacyclododecane)methyl)phenyl]-4,4-difluoro-1,3,5,7-tetramethyl-4-bora-3a, 4a-diaza- s -indacene (BA–Cyclen)–Cu was designed and synthesized; this probe is a Cu(Ⅱ) complex that uses Cu(Ⅱ) decomplexation to achieve the sensitive and rapid detection of aqueous H 2 S via the "turn-on" mode. We observed that BA–Cyclen–Cu exhibited good membrane permeability, low toxicity, and lysosome-targeting ability, facilitating H 2 S detection in living cells. Furthermore, we demonstrated the potential biological applications of the probe by measuring exogenous H 2 S originating from Na 2 S and GYY4137, a slow-release donor, and endogenous H 2 S generated via the catalysis of cystathionine- β -synthase in both normal (H9c2) and cancerous (U87) cells. Moreover, BA–Cyclen–Cu was successfully used to detect exogenous H 2 S by the external standard method in fetal bovine serum, the serum of a healthy person, and the serum of a patient with liver cancer. [Display omitted] • BA-Cyclen-Cu displayed high selectivity, sensitivity and fast response toward H 2 S with "turn-on" mode. • BA-Cyclen-Cu have a good performance on exogenous/endogenous H 2 S sensing in cancer cells and normal cells. • BA-Cyclen-Cu was successfully used to detect H 2 S in serum samples. [ABSTRACT FROM AUTHOR]

Determining the activity of lysosomal β-hexosaminidase in cells is of great importance for understanding the roles that these enzymes play in pathophysiological events. Herein, we designed the new fluorescent probe, βGalNAc-Rhod-CM(NEt 2), which consisted of a βGalNAc-linked rhodol unit serving as a β-hexosaminidase reactive fluorogenic moiety and a N,N′ -diethylaminocoumarin (CM(NEt 2)) group acting as a fluorescence marker for determining the degree of cell permeabilization. Treatment of βGalNAc-Rhod-CM(NEt 2) with β-hexosaminidase promoted generation of Rhod-CM(NEt 2), thereby leading to an increase in the intensity of fluorescence of Rhod. However, this probe did not respond to the functionally related glycosidase, O-GlcNAcase. The detection limit of βGalNAc-Rhod-CM(NEt 2) for β-hexosaminidase was determined to be 0.52 nM, indicating that it has high sensitivity for this enzyme. Furthermore, the probe functioned as an excellent fluorogenic substrate for β-hexosaminidase with k cat and K m values of 17 sec−1 and 22 μM, respectively. The results of cell studies using βGalNAc-Rhod-CM(NEt 2) showed that levels of β-hexosaminidase activity in cells can be determined by measuring the intensity of fluorescence arising from Rhod and that the intensity of fluorescence of CM(NEt 2) can be employed to determine the degree of cell permeabilization of the probe. Utilizing the new probe, we assessed β-hexosaminidase activities in several types of cells and evaluated the effect of glucose concentrations in culture media on the activity of this enzyme. [Display omitted] • Development of the sensitive and selective fluorescent probe for β-hexosaminidase. • Determination of levels of β-hexosaminidase activities in several types of cells. • Evaluation of effect of glucose concentrations in media on β-hexosaminidase activity. [ABSTRACT FROM AUTHOR]

Dopamine (DA) is a biomolecule that plays a critical part in the functioning of our brains by promoting motivation, maintaining focus, and altering mood. Excessive or low-level concentrations of DA in the human brain led to a dangerous neurological disorder. It is significantly important to trace the precise amount of DA to prevent such risky brain disease. Recently, heteroatoms-doped carbon dots (H-CDs) have attracted great attention for their capacity to detect biomolecules, metal ions, organic solvents, chemical dyes, etc. In this review, we have provided a comprehensive summary of the emerging trends in the heteroatom functional dopamine-doped carbon dots (DA-CDs), which are based on DA used as starting substances or functionalizing agents. Our analysis encompasses a detailed exploration of the synthetic methods, physical and chemical properties of carbon dots derived from dopamine, as well as their diverse range of applications. Additionally, we have also discussed the application of H-CDs in the dopmine detection by using various fluorescent, colorimetric, and electrochemical techniques. [Display omitted] • A comprehensive summary of heteroatoms-doped carbon dots based on dopamine as hybrid agents or detected substances. • The introduction of physicochemical properties and application for dopamine-synthesized or functionalized CDs.To discuss the application of heteroatoms-doped carbon dots (H-CDs) in dopamine detection. • To discuss the application of heteroatoms-doped carbon dots (H-CDs) in dopamine detection. [ABSTRACT FROM AUTHOR]

Nitroreductase (NTR) is a frequently used biomarker for the assessment of hypoxia level in tumors. As one of the main sources of enzymes, the dysfunction of lysosomes typically leads to various diseases. In this study, an NTR-triggered lysosome-targeting probe, M-TPE-P, was designed based on a tetraphenylethylene core. DFT calculation indicated that the probe possessed a narrow singlet–triplet energy gap (ΔE ST), rendering it an efficient photosensitizer. The docking affinity of M-TPE-P to NTR revealed a strong structural match between them. Photophysical properties demonstrated that the probe exhibited high selectivity and sensitivity in a broad pH rang for detecting NTR with k cat / K m as 2.18 × 104 M−1 s−1. The detection limit was determined to be 53.6 ng/mL in 80 % PBS/DMSO solution. Cell imaging studies showed the probe could trace intracellular NTR behavior with green fluorescence. The colocalization analysis indicated its excellent lysosome-targeting specificity. In addition, the probe exhibited effective ROS generation ability and significant PDT effect after NIR irradiation, positioning it as a promising photosensitizer for cancer treatment. Schematic Representation of the NTR-responsive fluorescence turn-on photosensitizer for lysosomes imaging and photodynamic therapy. [Display omitted] • An NTR-responsive fluorescence turn-on probe M-TPE-P for lysosomes imaging was developed. • M-TPE-P showed high selectivity and sensitivity with a low detection limit toward NTR. • M-TPE-P displayed time-dependent behaviors, excellent lysosomes targeting and ROS generation ability in 4T1 cells. • The structure relationship between the probe M-TPE-P and NTR was demonstrated by DFT and docking calculations. [ABSTRACT FROM AUTHOR]

Glutathione (GSH) as one most abundant thiol, acts as important roles in regulating cellular redox activities, and various diseases are closely related with its abnormal levels. Thus, monitoring intracellular GSH levels is essential for understanding cellular metabolism of many related diseases. In this work, we firstly reported a new fluorescence turn-on sensor, which was capable of selectively, sensitively and rapid sensing GSH over other thiols, especially cysteine and homocysteine in solutions and living cells. A meso -aryltellurium boron dipyrromethene (BODIPY) was firstly designed and synthesized, which showed silenced emission due to an efficient photoinduced electron transfer (PET) process from electron-rich Te to BODIPY, and then upon exposure to GSH, the meso -Te-C bond could be rapidly cleaved by the thiol group of GSH, thus resulting in an obvious fluorescence "turn-on" phenomenon through inhibition of the PET effect. This probe exhibited excellent selectivity and sensitivity towards GSH with a short response time of 2 min, showing a remarkable fluorescence enhancement observed at 541 nm with a large fluorescence quantum yield increase from nearly 0 to 0.73 upon excitation at 500 nm in PBS/CH 3 CN (9/1, v/v). The detection limit towards GSH was further calculated to be 1.7 nM by the linear fluorescence change at 541 nm in the GSH-concentration ranging from 0 to 4 μM. Furthermore, its sensing mechanism was validated by using mass spectrometry, confirming the rapid cleavage of the Te–C bond by GSH. Finally, cell imaging experiments demonstrated that this probe could successfully detect GSH in living cells, highlighting its potential for rapid and sensitive detection of intracellular GSH level changes. Therefore, a new meso -aryltellurium-BODIPY fluorescence turn-on sensor was firstly developed, which could selectively, sensitively and fast detect cellular GSH over other thiols based on the rapid cleavage of the meso Te–C bond. Herein, we report for the first time a novel meso -aryltellurium-BODIPY-based fluorescent probe for selective, sensitive and fast detection of GSH over other thiols with an absolutely fluorescent "turn-on" phenomenon through the substitution reaction in solutions and living cells. [Display omitted] • A meso -aryltellurium boron dipyrromethene (BODIPY) was rationally designed and synthesized. • This probe could selectively, sensitively and fast detect GSH over other thiols with an absolute fluorescence turn-on effect. • It sensing mechanism was based on the rapid cleavage of the meso Te–C bond by GSH. • Cell imaging experiments confirmed its potential for sensitive and rapid detection of intracellular GSH level changes. [ABSTRACT FROM AUTHOR]

Oxidative stress plays significant roles in the development of various diseases. H 2 O 2 acts as a signaling molecule physiologically or harmful substance pathologically and the mitochondria are one of the most active places for the generation of H 2 O 2. Thus, a new mitochondria-targeted probe 1 for H 2 O 2 detection was synthesized herein, based on D-π-A structure with a large Stokes shift (150 nm) due to its ICT process. To improve its water solubility and sensitivity, probe 2 with PEG chain and probe 3 with two responsive boronated groups were then designed based on the structure of probe 1. As a result, the fluorescence intensity of probe 2 was far higher than that of probe 1 and probe 3 not only in vitro experiment but in cell imaging study with a larger linear range and signal-to-noise ratio, rendering it the best probe for further exogenous and endogenous H 2 O 2 detection in Hela cells. [Display omitted] • Based on the principle of donor-π-acceptor and p -pinacolborylbenzyl group as recognition part, three novel probes for H 2 O 2 were designed. • These near-infrared probes with a large Stokes shift (150 nm) had good selectivity and sensitivity toward H 2 O 2. • The fluorescence intensity of the PEGylated probe was far higher than those of other probes not only in vitro experiment but in cell imaging study. • The probes had good mitochondria-targeting capacities. [ABSTRACT FROM AUTHOR]

Cyanide detection methods are urgently needed due to the highly lethal to human beings. Herein, we report two fluorescence probes (Probe 1 and Probe 2) based on cyanoethylene group for cyanide anion (CN−) detection. The selective recognition for CN− was confirmed by the completely opposite green fluorescence of Probe 1 and red fluorescence of Probe 2 observed by fluorescence spectra and naked eyes. The probes take advantages of the large Stokes shift (~160 nm), rapid response (30 s), anti-interference performance and low detection limit (Probe 1 : 12.4 nM, Probe 2 : 101 nM). The sensing mechanism is certificated to the nucleophilic attack of CN− to electron-deficient cyanoethylene group of probes, which was demonstrated by 1H NMR titration, HR-MS, Job's plot and IR spectroscopy. Density functional theory (DFT) calculations were carried out to analyze the mechanism in theory. Further, practical applications were studied. Easy-to-use test strips treated with Probe 1 or Probe 2 are capable of CN− detection in pure drinking water. The good biocompatibility and membrane penetrability have achieved the bioimaging capability of Probe 1 and Probe 2 in living HepG-2 cells, making the probes promising for use in real lives. [Display omitted] • Probes show high selectivity towards cyanide (CN−) and good anti-interference ability against other competing anions. • Probes show high reactivity in aqueous media, making them can be used in actual environment and biological system. • Probes are capable of CN− detection by easy-to-use test in pure drinking water. • Probes have large Stokes shifts and low cytotoxicity so that they can be utilized as CN− sensors in living cells. [ABSTRACT FROM AUTHOR]

Hydrazine (N 2 H 4) plays an important role in industrial production, but it is highly toxic, leaking or exposing it will pollute the environment and cause serious harm to human beings. Therefore, it is necessary to use a simple and effective method to detect N 2 H 4 in environmental systems and organisms. Herein, a novel water-soluble fluorescent probe based on coumarin fluorophore, 2-(7-(diethylamino)-2-oxo-2H-chromen-3-yl)isoindoline-1,3-dione (C-Z1), is reported. The fluorescence intensity of the probe at 530 nm was enhanced gradually with the addition of N 2 H 4 , and the maximum enhancement was about 28 times. The probe has good selectivity and sensitivity, the detection limit of hydrazine hydrate is 1.48 × 10−7 M, and the response mechanism of the probe is proved by theoretical calculation and experiment. C-Z1 has been shown to detect N 2 H 4 in a variety of environmental samples, including water, soil, air, cells, zebrafish and plants. In addition, C-Z1 can be made into test strips for easy portability and used for rapid quantitative detection of N 2 H 4 in the field by its distinct change in fluorescence color. Thus, C-Z1 has great potential for the analysis and detection of environmental contaminants. In this paper, the deprotection of phthalimide is used as a strategy for the detection of hydrazine. We designed and synthesized a water-soluble probe C-Z1 for the detection of N 2 H 4. its absorption and emission spectra vary regularly with the concentration of the N 2 H 4 solution. C-Z1 can detect N 2 H 4 in environmental water samples, soil, and air. Portable paper test strips based on C-Z1 can be easily prepared and are well used for in situ detection of N 2 H 4. Most importantly, the successful application of the probe in cell imaging, zebrafish imaging, and Arabidopsis imaging demonstrates the potential application of the probe in biological and environmental aspects. [Display omitted] • C-Z1 is a novel probe for the detection of N 2 H 4 , which has not been reported in other literature. • The probe is a water-soluble fluorescent probe and has a maximum fluorescence intensity of 28-fold. • The probe possesses low toxicity and can be used for fluorescence imaging of cells, zebrafish and arabidopsis. • Accurate determination of hydrazine is realized in real environmental samples. • The probes are simple to prepare and can be made into test strips for physical environmental testing. [ABSTRACT FROM AUTHOR]

Telomerase (TE) is a promising diagnostic and prognostic biomarker for many cancers. Quantification of TE activity in living cells is of great significance in biomedical and clinical research. Conventional fluorescence-based sensors for quantification of intracellular TE may suffer from problems of fast photobleaching and auto-fluorescence of some endogenous molecules, and hence are liable to produce false negative or positive results. To address this issue, a fluorescence-SERS dual-signal nano-system for real-time imaging of intracellular TE was designed by functionalizing a bimetallic Au@Ag nanostructure with 4- p -mercaptobenzoic acid (internal standard SERS tag) and a DNA hybrid complex consisted of a telomerase primer strand and its partially complimentary strand modified with Rhodamine 6G. The bimetallic Au@Ag nanostructure serves as an excellent SERS-enhancing and fluorescence-quenching substrate. Intracellular TE will trigger the extension of the primer strand and cause the shedding of Rhodamine 6G-modified complimentary strand from the nano-system through intramolecular DNA strand displacement, resulting in the recovery of the fluorescence of Rhodamine 6G and decrease in its SERS signal. Both the fluorescence of R6G and the ratio between the SERS signals of 4- p -mercaptobenzoic acid and Rhodamine 6G can be used for in situ imaging of intracellular TE. Experimental results showed that the proposed nano-system was featured with low background, excellent cell internalization efficiency, good biocompatibility, high sensitivity, good selectivity, and robustness to false positive results. It can be used to distinguish cancer cells from normal ones, identify different types of cancer cells, as well as perform absolute quantification of intracellular TE, which endows it with great potential in clinical diagnosis, target therapy and prognosis of cancer patients. [Display omitted] • A dual-signal nanosensor was developed for imaging of telomerase in living cells. • Au@Ag nanoparticles served as fluorescence quenching and SERS enhancing substrate. • The results of the fluorescence and SERS channels can provide mutual confirmation. • The SERS channel of the nanosensor can help identify false positive results. [ABSTRACT FROM AUTHOR]

The in situ precise quantification and simultaneous imaging of low abundance microRNAs (miRNAs) within living cells is critical for cancer diagnosis, yet it remains a significant challenge. Leveraging the excellent sensitivity and spatiotemporal resolution of dark-field microscopy (DFM) and fluorescence imaging, we have successfully devised a novel detection approach using dual-signal reporter probes (DSRPs). These probes allow for highly sensitive detection of miRNA-21 in living cells via toehold-mediated strand displacement cascades. The DSRPs were constructed by Au nanoparticles and Ag nanoclusters core-satellite nanostructures. After the recognition of miRNA-21, the strand displacement cascades were triggered, inducing the disassembly of the Au/Ag core-satellite nanostructure with apparent scattering intensity decrease and peak wavelength shifts. Additionally, the fluorescence of Ag clusters could be recovered and further enhanced when in close proximity to specific guanine-rich strands. The dual-signal response capability enables the accurate detection of miRNA-21 from 1 fM to 1 nM, with a limit of detection reached 0.75 fM. DFM and fluorescent imaging of living cells efficiently confirms the applicable detection of miRNA-21 in complex detection media. The biosensor based on DSRPs represents a promising nanoplatform for visual monitoring and imaging of biomolecules in living cells, even at the single particle level. [Display omitted] • Dual-signal reporter probes was proposed based on core-satellite nanostructures. • Target microRNA triggered the strand displacement cascades on the probe surface. • The dual signals of LSPR shifts and fluorescence enhancement were induced. • Accurate detection and simultaneous imaging of intracellular microRNA were realized. [ABSTRACT FROM AUTHOR]

Recently, using nanomaterials to enhance the endocytosis capability and sensitivity of probes for RNA imaging in living cells has gotten the attention of many researchers. Nanomaterials, as a reliable alternative to transfection reagents, could prevent nucleic acid probes from being degraded by DNase, and bring them into sub-cellular locations for efficient internalization. Therefore, nanomaterial-based fluorescent probes (NFPs) provide a promising sensing platform to realize in situ RNA detection and imaging, which can reveal the expression of RNA at single cell level and provide large amount of information about RNA spatial localization. Meanwhile, many RNAs are in low abundance in living cells, resulting in difficulty in sensitive detection. Thus, the incorporation of NFPs and signal amplification strategy offers a broader prospect for the detection of RNAs, that have been proven as predominant therapeutic targets or diagnostic biomarkers. Herein, the purpose of our review is to first introduce the general procedure of NFPs used for in situ RNA imaging and how nanomaterials deliver these probes into living cells. Further, we focused on different kinds of nanomaterials that are mainly used for sensitive detection of RNAs and those in low abundance, through different signal read-out modes. Nanomaterial-based fluorescent probe (NFP) provides a promising sensing platform to realize effectively cellular endocytosis and intracellular RNA Imaging in situ. In our review, we try to basically introduce the whole progress of NFPs used for in situ RNA imaging, particularly focusing on the endocytic pathways that nanomaterials deliver these probes into living cells, as well as different kinds of nanomaterials that are mainly used for sensitive signal detection of RNAs, especially for those in low abundance. [Display omitted] • Monitoring the level of RNA expression, can assist our understanding of the progression, diagnosis and further treatment of tumor. • NFPs has high internalization efficiency and excellent biocompatibility to achieve cellular uptake and RNA imaging in situ. • Different kinds of nanomaterials for detection of RNAs, especially for those in low abundance, are summarized. [ABSTRACT FROM AUTHOR]