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The reactive nitrogen species (RNS) in lysosomes play a major role during the regulation of lysosomal microenvironment. Nitroxyl (HNO) belongs to active nitrogen species (RNS) and is becoming a potential diagnostic and therapeutic biomarker. However, the complex synthesis routes of HNO in biosystem always hinder the exact determination of HNO in living cells. Here, a rhodamine-based fluorescent probe used to determine nitroxyl (HNO) in lysosomes was constructed and synthesized. 2-(Diphenylphosphino)benzoate was utilized as the sensing unit for HNO and morpholine was chose as the targeting group for lysosome. Before the addition of HNO, the probe displayed a spirolactone structure and almost no fluorescence was found. After the addition of HNO, the probe existed as a conjugated xanthene form and an intense green fluorescence was observed. The fluorescent probe possessed fast response (3 min) and high selectivity for HNO. Furthermore, fluorescence intensity of the probe linearly related with the HNO concentration in the range of 6.0 × 10 -8 to 6.0 × 10 -5  mol L -1 . The detection limit was found to be 1.87 × 10 -8  mol L -1 for HNO. Moreover, the probe could selectively targeted lysosome with excellent biocompatibility and had been effectually utilized to recognize exogenous HNO in A549 cells., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Inc. All rights reserved.)

The incorporation of gem-difluoromethylene units into organic molecules remains a formidable challenge. Conventional methodologies for constructing aryldifluoromethyl derivatives relied on the use of high-functional fluorinating regents under harsh conditions. Herein, we report general and efficient photoredox catalytic systems for defluoroalkylation of readily available trifluoromethylarenes through selective C-F cleavage to deliver gem-difluoromethyl radicals which proceed through reductive addition to both electron-donating and withdrawing alkenes under transition-metal free conditions. Mechanistic studies reveal that thiol serves as both photocatalyst and HAT reagent under visible light irradiation. This synergistic photocatalysis and HAT catalysis protocol exhibits ample and salient features such as high chemo- and regioselectivity, broad substrate scope, amenable gram-scale synthesis and late-stage modification of bioactive molecules.

Nitroxyl (HNO) is an important reactive nitrogen that is associated with various states in physiology and pathology and plays a unique function in living systems. So, it is important to exploit fluorescent probes with high sensitivity and selectivity for sensing HNO. In this paper, a novel ratiometric fluorescent probe for HNO was developed utilizing intramolecular charge transfer (ICT) and fluorescence resonance energy transfer (FRET) mechanisms. The probe selected coumarin as energy donor, naphthalimide as energy receptor and 2-(diphenylphosphino)benzoate as the sensing site for detecting HNO. When HNO was not present, the 2-(diphenylphosphino)benzoate unit of the probe restricted electron transfer and the ICT process could not occur, leading to the inhibition of FRET process as well. Thus, in the absence of HNO the probe displayed the intrinsic blue fluorescence of coumarin. When HNO was added, the HNO reacted with the 2-(diphenylphosphino)benzoate unit of the probe to yield a hydroxyl group which resulting in the opening of ICT process and the occurring of FRET process. Thus, after providing HNO the probe displayed yellow fluorescence. In addition, the probe showed good linearity in the ratio of fluorescence intensity at 545 nm and 472 nm (I 545 nm /I 472 nm ) with a concentration of HNO (0.1-20 μM). The probe processed a detection limit of 0.014 μM and a response time of 4 min. The probe also specifically identified HNO over a wide pH scope (pH = 4.00-10.00), including physiological conditions. Cellular experiments had shown that this fluorescent probe was virtually non-cytotoxic and could be applied for ratiometric sensing of HNO in A549 cells., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Hydrogen polysulfide (H 2 S n , n≥2), as a kind of active sulfur species (RSS), has become a hot topic in RSS. It can regulate the biological activity of many proteins through S-sulfhydrylation of cysteine residues (protein Cys-SSH), and has a protective effect on cells. Although there have been some studies on hydrogen polysulfide, its production, degradation pathway and regulation mechanism still need further be researched. In presented study, an original lysosome-localized fluorescent probe for determining H 2 S n was developed utilizing rhodamine as the fluorogen. The probe used morpholine as the locating unit of lysosomes and chose 2-fluoro-5-nitrobenzoate as the recognizing group. Before adding H 2 S n , the proposed probe displayed a spironolactone structure and emitted very weak fluorescence. After adding H 2 S n , a conjugated xanthene was formed and the probe demonstrated green fluorescence. When the H 2 S n concentration was varied from 6.0×10 -7 mol·L -1 to 10.0×10 -5 mol·L -1 , the fluorescence intensity of the probe was linearly dependent on the H 2 S n concentration. And the detection limit was 1.5×10 -7 mol·L -1 . The presented probe owned a fast response speed, good selectivity, excellent sensitivity and broad pH work scope. In addition, the probe had been well utilized to sense endogenic and exogenic H 2 S n in lysosomes., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

A tyrosinase-activatable fluorescent probe with endoplasmic reticulum targetability was developed for the first time. It can ratiometrically fluoresce and hence be used to monitor refluxed tyrosinase into the endoplasmic reticulum.

Accurate detection of labile analytes through activity based fluorogenic sensing is meaningful but remains a challenge because of nonrapid reaction kinetic. Herein, we present a signaling reporter engineering strategy to accelerate azoreduction reaction by positively charged fluorophore promoted unstable anion recognition for rapidly sensing sodium dithionite (Na 2 S 2 O 4 ), a kind of widespread used but harmful inorganic reducing agent. Its quick decomposition often impedes application reliability of traditional fluorogenic probes in real samples because of their slow responses. In this work, four azo-based probes with different charged fluorophores (positive, zwitterionic, neutral, and negative) were synthesized and compared. Among of them, with sequestration effect of positively charged anthocyanin fluorophore for dithionite anion via electrostatic attraction, the cationic probe Azo-Pos displayed ultrafast fluorogenic response (∼2 s) with the fastest response kinetic ( k pos ' = 0.373 s -1 ) that is better than other charged ones ( k zwi ' = 0.031 s -1 , k neu ' = 0.013 s -1 , k neg ' = 0.003 s -1 ). Azo-Pos was demonstrated to be capable to directly detect labile Na 2 S 2 O 4 in food samples and visualize the presence of Na 2 S 2 O 4 in living systems in a timely fashion. This new probe has potential as a robust tool to fluorescently monitor excessive food additives and biological invasion of harmful Na 2 S 2 O 4 . Moreover, our proposed accelerating strategy would be versatile to develop more activity-based sensing probes for quickly detecting other unstable analytes of interest.

Photo-Fenton-like technology based on H 2 O 2 is considered as an ideal strategy to generate reactive oxygen species (ROS) for antibiotic degradation, but O 2 overflow in the process severely limits the utilization efficiency of H 2 O 2 . Herein, we fabricate Bi 2 MoO 6 (BMO) photocatalyst modified with Frustrated Lewis pairs (FLPs) as a Fenton catalyst model for enhancing reuse of spilled O 2 . The FLPs created by the introduction of cerium and oxygen vacancy were found to contribute to regulate the electronic structure of BMO and further improve the acidic and basic properties of photocatalyst surface. More importantly, the frustrated acid and base sites can enhance the H 2 O 2 and O 2 interfacial adsorption process and provide an Ce 4+ -O v -O 2- active site on the surface of Ce-BMO nanosheets, which can promote O 2 /•O 2 - / 1 O 2 /H 2 O 2 redox cycles to achieve high H 2 O 2 utilization efficiency. Specifically, in the experiment using tetracycline as a photocatalytic degradation object, the degradation activity of Ce-BMO was 2.15 times higher than that of BMO pure phase. Quenching experiments and EPR assays also confirmed that 1 O 2 and •O 2 - were the dominant oxidative species. This study systematically reveals the design of Fenton photocatalytic active sites at the atomic scale and provides new insights into constructing FLPs photocatalysts with high H 2 O 2 utilization efficiency., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Myrosinase (Myr), as a unique β-thioglucosidase enzyme capable of converting natural and gut bacterial metabolite glucosinolates into bioactive agents, has recently attracted a great deal of attention because of its essential functions in exerting homeostasis dynamics and promoting human health. Such nutraceutical and biomedical significance demands unique and reliable strategies for specific identification of Myr enzymes of gut bacterial origin in living systems, whereas the dearth of methods for bacterial Myr detection and visualization remains a challenging concern. Herein, we present a series of unique molecular probes for specific identification and imaging of Myr-expressing gut bacterial strains. Typically, an artificial glucosinolate with an azide group in aglycone was synthesized and sequentially linked with the probe moieties of versatile channels through simple click conjugation. Upon gut bacterial enzymatic cleavage, the as-prepared probe molecules could be converted into reactive isothiocyanate forms, which can further act as reactive electrophiles for the covalent labeling of gut bacteria, thus realizing their localized fluorescent imaging within a wide range of wavelength channels in live bacterial strains and animal models. Overall, our proposed method presents a novel technology for selective gut bacterial Myr enzyme labeling in vitro and in vivo . We envision that such a rational probe design would serve as a promising solution for chemoprevention assessment, microflora metabolic mechanistic study, and gut bacterium-mediated physiopathological exploration.

As a high reactive oxygen species (ROS) and a reactive nitrogen species (RNS), peroxynitrite anion (ONOO - ) is widely present in organisms and plays influential roles in physiological and pathological processes. It is of great significance to develop effective fluorescent probes for imaging peroxynitrite variation in living systems. Herein we present a novel fluorescent probe TQC0 for monitoring ONOO - based on the iminocoumarin platform, and this probe was synthesized by the knoevenagel condensation between a dihydropyridine-salicylaldehyde derivative and 2-benzothiazole-acetonitrile, and subsequently masked with the boronate moiety. The obtained probe TQC0 exhibited a high signal-to-noise ratio (206-fold) and a quick 'turn-on' response (about 10 min) with great selectivity and sensitivity. Furthermore, the probe TQC0 was successfully applied for imaging ONOO - in living cells with low cytotoxicity., (© 2024 John Wiley & Sons Ltd.)

Au@MnO 2 nanoparticles (NPs), as core-shell nanostructures, have been widely used in ions, molecules and enzyme activities detection due to their stable properties and easy preparation, but their application in bacterial pathogens detection is rarely reported. In this work, Au@MnO 2 NPs is employed for Escherichia coli (E. coli) detection through monitoring and measuring β-galactosidase (β-gal) activity based enzyme-induced color-code single particle enumeration (SPE) method. In the existence of E. coli, p-aminophenylβ-D-galactopyranoside (PAPG) can be hydrolyzed to generate p-aminophenol (AP) by the endogenous β-gal of E. coli. MnO 2 shell reacts with AP and produces Mn 2+ , causing the blue shift of the localized surface plasmon resonance (LSPR) peak and color change of the probe from bright yellow to green. With the SPE method, the amount of E. coli can be quantified readily. The detection limit reaches 15 CFU/mL with dynamic range from 100 to 2900 CFU/mL. Besides, this assay is effectively employed to monitor E. coli in river water sample. The designed sensing strategy provides an ultrasensitive and low cost way for E. coli detection and has the possibility to detect other bacteria in environmental monitoring and food quality analysis., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)

Hydrogen sulfide (H 2 S) plays a cytoprotective role during mitophagy by detoxifying superfluous reactive oxygen species (ROS), and its concentration fluctuates in this process. However, no work has been reported to reveal the variation in H 2 S levels during autophagic fusion of lysosomes and mitochondria. Herein, we present a lysosome-targeted fluorogenic probe, named NA-HS, for real-time monitoring of H 2 S fluctuation for the first time. The newly synthesized probe exhibits good selectivity and high sensitivity (detection limit of 23.6 nM). Fluorescence imaging results demonstrated that NA-HS could image exogenous and endogenous H 2 S in living cells. Interestingly, the colocalization results revealed that the level of H 2 S was upregulated after autophagy began because of the cytoprotective effect, and was finally gradually reduced during subsequent autophagic fusion. This work not only affords a powerful fluorescence tool to monitor the variations in H 2 S levels during mitophagy, but also offers new insights into targeting small molecules for elaborating the complex cellular signal pathways., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests., (Copyright © 2023. Published by Elsevier B.V.)

As an important member of reactive oxygen species, hydrogen peroxide (H 2 O 2 ) plays a key role in oxidative stress and cell signaling. Abnormal levels of H 2 O 2 in lysosomes can induce damage or even loss of lysosomal function, leading to certain diseases. Therefore, real-time monitoring of H 2 O 2 in lysosomes is very important. In this work, we designed and synthesized a novel lysosome-targeted fluorescent probe for H 2 O 2 -specific detection based on a benzothiazole derivative. A morpholine group was used as a lysosome-targeted unit and a boric acid ester was chosen as the reaction site. In the absence of H 2 O 2 , the probe exhibited very weak fluorescence. In the presence of H 2 O 2 , the probe showed an increased fluorescence emission. The fluorescence intensity of the probe for H 2 O 2 displayed a good linear relationship in the concentration range of H 2 O 2 from 8.0 × 10 -7 to 2.0 × 10 -4 mol·L -1 . The detection limit was estimated to be 4.6 × 10 -7 mol·L -1 for H 2 O 2 . The probe possessed high selectivity, good sensitivity and short response time for the detection of H 2 O 2 . Moreover, the probe had almost no cytotoxicity and had been successfully applied to confocal imaging of H 2 O 2 in lysosomes of A549 cells. These results illustrated that the developed fluorescent probe in this study could provide a good tool for the determination of H 2 O 2 in lysosomes., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Inc. All rights reserved.)

Herein, we develop a Rh(III)-catalyzed intermolecular regioselective dearomative spirocyclization of 2-aryl-3-nitrosoindoles with alkynes, featuring the redox-neutral and atom-economic construction of spiroindoline-3-one oximes bearing a C2 spirocyclic quaternary carbon center under mild conditions. Both aryl alkyl alkynes and 1,3-diynes generally proceeded smoothly in the reaction with moderate to good regioselectivities. DFT calculations provided in-depth insights into the reaction mechanism and disclosed the origins of the regioselectivities.

A three-component strategy was developed for 3-phenyl-9 H -imidazo[1,5- a ]indol-9-one preparation from indole-2-carboxaldehydes, aromatic aldehydes, and ammonium acetate under copper catalysis conditions. In this process, a new five-membered ring was formed and the C3 position in the indole substrate was selectively oxidized into a ketone skeleton using oxygen as the sole oxidant and ammonium acetate as the nitrogen source. Furthermore, same products also could be achieved from indole-2-carboxaldehydes and benzyl amines under similar reaction conditions.

A visible-light induced direct C(sp 3 )-H functionalization of alkylarenes with trifluoromethyl ketones has been reported to access valuable benzyl-substituted trifluoromethyl alcohols in a stoichiometric manner. Readily available petroleum-derived alkylarenes are employed as latent benzylation reagents. With a bromine radical as the hydrogen atom transfer reagent, primary, secondary, and tertiary benzyl C-H bonds are suitable coupling partners. Additionally, the late-stage modification of bioactive molecules highlights the potential application of this approach.

A microdots array-based fluoremetric method with superwettability profile has been developed for the simultaneous and separate detection of Fe 3+ and Cu 2+ ions in red wine samples. A wettable micropores array was initially designed with high density by using polyacrylic acid (PAA) and hexadecyltrimethoxysilane (HDS), followed by the NaOH etching route. Zinc metal organic frameworks (Zn-MOFs) were fabricated as the fluorescent probes to be immobilized into the micropores array to obtain the fluoremetric microdots array platform. It was found that the fluorescence of Zn-MOFs probes could decrease significantly in the presence of Fe 3+ and/or Cu 2+ ions towards their simultaneous analysis. Yet, the specific responses to Fe 3+ ions could be expected if using histidine to chelate Cu 2+ ions. Moreover, the developed Zn-MOFs-based microdots array with superwettability profile can enable the accumulation of targeting ions from the complicated samples without any tedious pre-processing. Also, the cross-contamination of different samples droplets can be largely avoided so as to facilitate the analysis of multiple samples. Subsequently, the feasibility of simultaneous and separate detection of Fe 3+ and Cu 2+ ions in red wine samples was demonstrated. Such a design of microdots array-based detection platform may promise the wide applications in analyzing Fe 3+ and/or Cu 2+ ions in the fields of food safety, environmental monitoring, and medical diseases diagnostics., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)

A highly site-selective trifluoromethylaminoxylation of activated and unactivated olefins was reported under metal-free conditions. The method provides direct access to diverse β-trifluoromethyl trisubstituted hydroxylamines, tertiary alcohols, isoxazolines, isoxazolidines, and amino alcohols. The SET process between hydroxylamine and the hypervalent iodine-CF 3 reagent is proposed to produce two free radicals for the regio- and diastereoselective addition to alkenes. The synthetic potential of the protocol was established via the late-stage functionalization of the products and a series of postreaction modifications.

A facile method for the rapid synthesis of benzoacridines has been described. This protocol promoted by p-toluenesulfonic acid starts from aromatic aldehydes and N-phenyl naphthylamines, affording a variety of benzoacridines in 30-90 % yields under metal-free conditions. The present approach involves a cascade of condensation, Friedel-Crafts alkylation, annulation and dehydroaromatization in one pot., (© 2023 Wiley-VHCA AG, Zurich, Switzerland.)

A metal-free method for the construction of 2-substituted quinolines and benzo[ f ]quinolines from aromatic amines, aldehydes, and tertiary amines has been demonstrated. Cheap and readily available tertiary amines acted as the vinyl source. A new pyridine ring was selectively formed via [4 + 2] condensation that was promoted by ammonium salt under neutral conditions and an oxygen atmosphere. This strategy provided a new route for the preparation of various quinoline derivatives with different substituents at the pyridine ring, which provides the possibility of further modification.

An iodine-containing reagent promoted three-component method for the selective synthesis of phenothiazines and bis-phenothiazines has been developed. The present protocol starts from simple and easily available cyclohexanones, elemental sulfur, and inorganic ammonium salts, selectively producing phenothiazines and bis-phenothiazines in satisfactory yields under aerobic conditions. This method has the advantages of simple and readily available starting materials and metal-free conditions, affording a facile and practical approach for the preparation of phenothiazines and bis-phenothiazines.

A CuBr 2 -catalyzed annulation of 2-bromo- N -arylbenzimidamide with selenium/sulfur powder for the synthesis of benzo[ d ]isoselenazole and benzo[ d ]isothiazole in generally good yields was investigated. This synthetic strategy features good substrate scope and functional group tolerance. Furthermore, the corresponding products could be converted into N -aryl indoles via rhodium III -catalyzed ortho C-H activation of the N -phenyl ring, providing an efficient approach for axial aromatic molecules.

Ferritin plays an important role in regulating the homeostasis of iron in cells by storing/releasing iron. Current methods usually explored the determination of iron content, but in-situ imaging of the iron storage/release from ferritin in cells cannot be achieved. Hence, an engineered self-assembled biomimetic-compartmented nanoprobe (APO@CDs) has been constructed. The protein shell of APO (apoferritin) acted as ion channel module to control iron ions entering/exiting ferritin cavity; the inner core of CDs (carbon dots) acted as signal module for iron ions response. Compared with CDs, the response sensitivity and specificity to iron ions (Fe3 + ) have been improved by using APO@CDs, and the cytotoxicity was significantly reduced. Additionally, compared with cells containing APO@CDs alone, the normalized fluorescence gray value of Fe 3+ -treated cells was significantly decreased (0.275), indicating that Fe 3+ has effectively entered the ferritin. Furtherly, that of Fe 3+ -treated cells incubated with deferoxamine (DFO) was significantly enhanced (0.712), showing that Fe 3+ was released from ferritin under the mediation of DFO. The results demonstrate that APO@CDs can be successfully applied to in-situ imaging of iron storage/release from ferritin in cells, providing a potential platform for the in-situ dynamic study of the iron storage/release in biomedical field., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier B.V. All rights reserved.)

A four-component synthesis of tetrasubstituted pyrroles was developed under metal-free conditions. The pyrrole ring was formed in one pot through [2 + 1 + 1 + 1] condensation using ammonium salt as the nitrogen source. In this strategy, 1,4-naphthoquinones and maleimides were used as the versatile C2 fragments to provide substituted benzo[ f ]isoindole-4,9-diones and pyrrolo[3,4- c ]pyrrole-1,3-diones, respectively. This work is highlighted by using ammonium salt as the nitrogen source, readily available starting materials and multibond formation (two C-C and two C-N bonds) in a single operation.

Photocatalytic CO 2 reduction and H 2 production are a competitive reaction, and existing active sites cannot take into account the simultaneous gas-solid and liquid-solid reaction processes. Hence, a metallic aerogel (CuAg 2.5 ) with dual active sites was constructed via straightforward in-situ reduction process. CuAg 2.5 aerosol has larger porosity and CO 2 adsorption capacity, which enables H 2 O and CO 2 to fully contact it. The CuAg 2.5 can also construct the cooperative dual active sites, which can conduct CO 2 reduction reaction on Ag surface and proton reduction reaction on Cu surface, respectively, thereby efficiently guiding the rapid migration of photogenerated carriers. The yields of CO (18533 µmol g -1 ) and H 2 (20340 µmol g -1 ) for CuAg 2.5 are much higher than those of single metals. The ratio of CO and H 2 can also regulated via changing the ratio of Ag and Cu. This work gives new insights into the fabrication of unique high-efficiency plasmonic photocatalysts., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier Inc. All rights reserved.)

The effective photoredox-mediated oxidative thiolation and cyclization of N -arylacrylamides with thiols leads to biologically interesting 3-thionated oxindoles through C-S and C-C bond formation. This process represents a straightforward reaction that starts from non-prefunctionalized thiolating reagents. Mechanistic studies demonstrated that the TBHP serves as a key radical initiator with visible-light catalysis.

Covalent organic frameworks (COFs) were fabricated with a hierarchical flower-like hollow structure, possessing a large specific surface area, high porosity, and excellent environmental stability. In situ growth of noble silver nanoparticles (AgNPs) onto COFs was conducted yielding COF-Ag nanozymes. The structural advantages of COFs can ensure the uniform dispersion and effective size control of AgNPs. More interestingly, the oxidase-like catalytic activity of the obtained COF-Ag nanozymes could be enhanced in the presence of Hg 2+ ions, which could specifically interact with AgNPs to form Ag-Hg alloys. A COF-Ag catalysis-based colorimetric platform was thereby constructed for highly selective and sensitive analysis of Hg 2+ ions, showing a linear concentration range from 0.050 to 10.0 μM, with a limit of detection of about 3.7 nM. Besides, the developed colorimetric strategy was successfully applied for detecting Hg 2+ ions in human blood with favorable detection recoveries, indicating its potential for applications in the biomedical analysis, environmental monitoring, and food safety fields.

A visible and sensitive assay for the quantitative detection of β-glucosidase (β-glu) activity based on Au@CeO 2 core-shell nanoparticles (Au@CeO 2 NPs) is described. As a hydrolytic enzyme, β-glu can promote the hydrolysis of β-arbutin to hydroquinone (HQ), which can trigger the decomposition of the CeO 2 shell. With the single-particle enumeration (SPE) strategy coupled with dark field optical microscopy (DFM), an obvious color alteration of single Au@CeO 2 NPs during the etching process can be observed in real-time. By statistically calculating the number of the etched nanoparticles, the β-glu activity level can be quantified accurately. This assay displays a broad linear range from 0.5 to 50 mU⋅mL -1 and low detection limit of 0.12 mU⋅mL -1 . In addition, this method was successfully used to determine β-glu in real samples and acquires satisfactory recoveries in the range of 97.1-102.0%. This study provides a visualization analysis method for β-glu, which may be helpful for monitoring other targets in the future., (© 2022. The Author(s), under exclusive licence to Springer-Verlag GmbH Austria, part of Springer Nature.)

A Pd-catalyzed C-O cross-coupling of O -acyl hydroxylamines and tertiary or secondary alkyl electrophiles was reported without the cleavage of the rather fragile N-O bond. The described strategy provides direct access to congested N , N , O -trisubstituted hydroxylamines bearing an α-quaternary carbon center under mild conditions in high yields and features exclusively chemoselective C-O bond formation, a broad substrate scope, and excellent functional group tolerance. The synthetic potential of the cross-coupling was established via pharmaceuticals derivatizations and a series of postcatalytic modifications.

We have reported a metal-free protocol for the synthesis of indenoquinolinones and 2-substituted quinolines via [4 + 2] cycloaddition reaction using readily available 2-aminobenzaldehydes and ketones as starting materials. Different quinoline derivatives can be selectively synthesized by changing the type of ketones. O 2 and dimethyl sulfoxide (DMSO) as co-oxidants play an important role in the synthesis of indenoquinolinones. This condensation/oxidation strategy involves the formation of C-N, C-C, and C-O bonds, with the advantages of high yields and a broad substrate range.

A nanozyme with 2D/1D heterostructure has been fabricated by the in-situ growth of molybdenum disulfide nanosheets (MoS 2 NSs) onto single-walled carbon nanotubes (SWCNTs). It was discovered that the so-obtained SWCNTs@MoS 2 nanozyme could exhibit greatly improved peroxidase-like catalysis, due to that the formed 2D/1D interfacial coupling in the heterostructure might provide more active sites and exhibit enhanced charge transferring during the catalytic reactions, as confirmed by the X-ray photoelectron spectroscopy, photoluminescence, electrochemical impedance spectra and radical capturing experiments. Furthermore, the catalysis of the developed nanozyme could be selectively inhibited by glutathione (GSH) through the competitive consumption of hydroxyl radicals with enzyme substrate in the catalytic reaction system. A SWCNTs@MoS 2 catalysis-based colorimetric strategy was further proposed for the quantitative analysis of GSH with the concentrations linearly ranging from 0.01 to 1000.0 μM. Besides, the feasibility of the developed colorimetric method was evaluated by monitoring GSH separately in the extractions from hela cells and human serum, promising the extensive applications for monitoring various biological species like GSH in the clinical laboratory. Importantly, such a fabrication route for nanozyme with 2D/1D heterostructure may pave the way towards the wide applications for designing various nanzymes with improved catalysis., (Copyright © 2022 Elsevier B.V. All rights reserved.)

A simple and high-throughput colorimetric analysis array has been constructed for quantifying H 2 O 2 in milk using Fe 3 O 4 quantum dots (QDs), which were coated with sodium alginate (SA) and chromogenic substrate onto the arrayed capillary tubes. It was discovered that the Fe 3 O 4 QDs could present larger peroxidase-like catalysis than Fe 3 O 4 nanoparticles (NPs). Particularly, dramatically enhanced catalysis activity could be achieved for Fe 3 O 4 QDs if coated with SA films. Moreover, the use of SA could protect Fe 3 O 4 QDs to expect the improved environmental stability. A capillary arrays-based high-throughput colorimetric platform was thereby developed for the detection of H 2 O 2 in milk, with levels linearly ranging from 10 to 400 μM. Importantly, the developed colorimetric platform with the capillarity power for automatic fetching of multiple samples may promise the practical applications for extensive monitoring of multiple H 2 O 2 samples for food safety., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

A three-starting-material four-component reaction strategy is described to construct thienopyrrolediones (TPDs) from the simplest raw materials, elemental sulfur, aldehydes, and β-ketoamides, under transition metal free conditions. Compared with traditional multistep reaction sequences, this process is simple, efficient, environmentally friendly, and atom-economic and has laid the foundation for further development of an easily synthesized TPD unit.

Nowadays, test strips are widely applied, but their use is mostly limited to the qualitative or half-quantitative analysis of targets. The main reason for their limited use is the "Coffee Ring Effect" (CRE) of probe materials, which leads to a heterogeneous probe distribution and poor testing reproducibility and sensitivity. In the present work, a fluorescent test strip was fabricated with a suppressed CRE of silver nanocluster (AgNC) probes coated by gelatin (Gel) under vacuum-aided fast lyophilization. Uniform and stable deposition of AgNC probes was achieved onto the test strips with a high loading capacity. The AgNCs displayed specific responses to Hg 2+ ions, allowing sensitive and quantitative analysis in the linear concentration ranges from 0.20 to 50000 nM with a limit of detection of 0.10 nM. Given the advantages of rapid and facile preparation, CRE suppression, high biocompatibility, and cost-effectiveness, such a fabrication protocol may pave the way for the design of various test strips-based devices for point-of-care analytical applications in the fields of environmental monitoring, food quality analysis, and clinical diagnostics.

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., (Copyright © 2022 Elsevier B.V. All rights reserved.)

Water-soluble non-conjugated polymer dots (PDs) have been synthesized using hyperbranched polyethyleneimine (PEI) and dihydroxybenzaldehyde (DHB) for the first time via the Schiff base reaction at room temperature. The yielded non-conjugated PDs of PEI-DHB could display the well-defined spheric structure and good water solubility. In contrast to the common PDs otherwise showing blue emission, the PEI-DHB PDs could give out strong green fluorescence in aqueous media. Especially, the fluorescence of the PEI-DHB PDs could be specifically quenched by MnO 2 nanosheets through the inner filter effects and further restored by the thiocholine that could reduce MnO 2 nanosheets into Mn 2+ . Herein, thiocholine could be produced in hydrolysis reaction of acetylthiocholine catalyzed by the acetylcholinesterase (AChE), of which the catalytic activity could be irreversibly inhibitted by the introduction of organophosphates. A highly selective fluorimetric method was thereby been developed for the detection of organophosphorus pesticides using dimethyl-dichloro-vinyl phosphate as a model. The linear concentrations ranges from 0.050 to 2.5 μM. Importantly, the non-conjugated PDs probes with strong green fluorescence and high water solubility may promise the extensive applications in the environmental, food, and clinical analysis fields., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that can have appeared to influence this work., (Copyright © 2022 Elsevier B.V. All rights reserved.)

A novel strategy for the preparation of functional carbazoles through NaI-catalyzed formal [4 + 2] annulation of 2-(indol-3-yl)cyclohexanones and alkynes/alkenes has been developed. The present approach started from easily available raw materials and provided a variety of tetrahydrobenzo[ c ]carbazolones in satisfactory yields under metal- and solvent-free conditions. Furthermore, the products could be further transformed into structurally valuable carbazole-based conjugated derivatives.

The C-S bond formation from aryl halides and thiols has been well established under various catalytic systems. In this work, user-friendly sulfinates have been exploited as an efficient sulfenylating reagent in the C-S couplings through visible-light-induced photo/nickel dual catalysis under base- and external reductant-free conditions. A large number of aryl sulfide products were accessed with high selectivity and high tolerance of various functionalities.

A magnet-renewable electroanalytical strategy has been initially developed for monitoring hydrogen sulfide (H 2 S) in aquaculture freshwater systems using magnetic Fe 3 O 4 -loaded silver metal-organic framework (Fe 3 O 4 @Ag-MOF). The magnetic composites were synthesized by a hydrothermal route and further attached onto the magnetic electrodes. It was discovered that the Fe 3 O 4 @Ag-MOF-based electrochemical sensors could exhibit the extremely sharp and steady signals of solid-state Ag/AgCl electrochemistry at a lower potential. Furthermore, the highly specific and irreversible S-Cl replacement reactions could occur in the presence of H 2 S, so as to induce the conversion of AgCl into non-electroactive Ag 2 S with the rational decline of Ag/AgCl signals. Importantly, the Fe 3 O 4 @Ag-MOF-modified electrodes could be renewed simply by the removal of the magnet after each of the detection cycles for the next immobilization of Fe 3 O 4 @Ag-MOF probes. The developed electroanalytical method could facilitate the detection of H 2 S in the linear range from 4.0 to 1400 nM, with a limit of detection down to 2.0 nM. Besides, it was employed to detect H 2 S in aquaculture freshwater samples of fish, crab, and shrimp, showing the satisfactory results., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier B.V. All rights reserved.)

Hypochlorous acid (HOCl) was crucial for maintaining the homeostasis in cells and plays vital roles in many physiological and pathological processes. In this work, a highly selective fluorescent probe for hypochlorous acid in living cells was constructed and prepared based on a naphthalene derivative. A naphthalene derivative was utilized as the fluorescent group, and N , N -dimethylthiocarbamate was applied as the selective recognition site for HOCl. Before adding HOCl, the fluorescent probe exhibited weak fluorescence. Upon adding HOCl, the fluorescent probe displayed remarkable fluorescence enhancement. The fluorescence intensity at 502 nm showed a linear response to the concentration of HOCl from 3.0 × 10 -7 to 1.0 × 10 -5  mol·L -1 . The detection limit was estimated to be 1.5 × 10 -7  mol·L -1 for HOCl. The fluorescent probe showed fast response and outstanding selectivity toward HOCl. It owned good biocompatibility and had also been successfully applied in the confocal imaging of exogenous and endogenous HOCl in living cells., Competing Interests: The authors declare that they have no conflicts of interest., (Copyright © 2022 Jingguo Sun et al.)

Rapid emergence of new strains of drug-resistant H1N1 influenza viruses calls for effective drugs for the controls prior to their outbreaks. In the present work, electrochemical H1N1 RNA beacons have been newly designed for exploring the potentiality of an anticancer agent of Bleomycin (BLM) with Fe (ΙΙ) ions (BLM-Fe(ΙΙ)) alternatively the treatment of drug-resistant H1N1 strains with H274Y gene mutation. Herein, biotinylated (-) ssRNA of H1N1 virus and its complementary (+) ssRNA were labeled with electrochemical signal probes of ferrocene and anthraquinone, respectively. The resultants were hybridized and conjugated with avidin-modified magnetic beads to create electrochemical RNA beacons. The electrochemical signal variation of the H1N1 RNA beacon treated with the RNA degradation agent of BLM-Fe(ΙΙ) were monitored. Results indicate that the BLM-Fe(ΙΙ) agent could effectively cleave both H1N1 dsRNAs and ssRNAs at selective cutting sites, as evidenced by the mass spectrometry analysis. This indicates that the BLM-Fe(II) agent could be utilized to block the viral-host infection process by curbing the host-cell viral RNA-mRNA transcription or inactivate the viruses through the cleavage of viral genomes. The efficiency of the BLM-Fe(ΙΙ) agent was verified with clinical seasonal H1N1 samples using real-time polymerase chain reaction. The therapeutic gene drug of BLM-Fe(ΙΙ) holds great potential for controlling new strains of H1N1 virus resistant to clinical antiviral drugs. More importantly, the so designed RNA beacons may provide a rapid, sensitive and cost-effective platform of drug screening by monitoring the drug-DNA/RNA interactions., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2021 Elsevier B.V. All rights reserved.)

A high-throughput and selective fluorimetric platform has been constructed for the analysis of ammonia in blood by using a polymer-stabilized metal-organic framework (MOF) of porous NH2-MIL-125, which was coated onto a wettable microwells array constructed on an indium tin oxide (ITO) substrate. It was found that the nitrogen plasma treatment for the ITO substrate could create a super-hydrophilic interface that combined with the hydrophobic pattern yielded a wettable microwells array, enabling the condensation-based enrichment of targets from the sample droplets. Moreover, the NH2-MIL-125 MOF encapsulated using polymers could be firmly coated onto the microwells to act as fluorescent probes for sensing NH3 with enhanced responses. In addition, the use of the polymer polyvinyl pyrrolidone could protect and stabilize the crystals of NH2-MIL-125 probe in aqueous media, revealing the improved hydrophilicity and significantly depressed signal background. The as-developed fluorimetric platform, containing a MOF-coated microwells array, can enable the detection of ammonia in blood, with concentrations ranging linearly from 0.10 to 300 μM. More importantly, this plasma treatment-based fabrication route may hold promise for designing different wettable microwells arrays for the high-throughput detection of multiple targets in the fields of biomedical analysis and environmental monitoring.

The multifunctional hemin@carbon dot hybrid nanozymes (hemin@CD) with simultaneous peroxidase-like activity and fluorescence signalling property was prepared for the first time. Based on these properties, hemin@CD was applied to develop a dual-channel fluorescent probe for H 2 O 2 and H 2 O 2 -based biocatalytic systems. By virtue of the peroxidase-like activity, hemin@CD can catalyze the oxidative coupling of 4-aminoantipyrine with phenol in the presence of H 2 O 2 to form a pink-red quinoneimine dye with a maximum absorbance at 505 nm. Under the excitation wavelength of 480 nm, the green fluorescence of hemin@CD peaks at 540 nm and is quenched by the generated quinoneimine dye due to an inner filter effect, and also by H 2 O 2 because of dynamic quenching. Thus, a colorimetric and fluorimetric dual-channel optical probe for H 2 O 2 is obtained. Due to the glucose/xanthine transformations under formation of H 2 O 2 by the relevant oxidase catalysis, the probe can be applied for detection of glucose and xanthine. The colorimetric detection limits for H 2 O 2 , glucose and xanthine are 0.11, 0.15, 0.11 μM, and the and fluorimetric detection limits are 0.15, 0.15, 0.12 μM, respectively. Graphical abstractSchematic representation of the colorimetric and fluorimetric dual probe for H 2 O 2 , glucose and xanthine based on the multifunctional emin@carbon dot) hybrid nanozymes with simultaneous peroxidase-like activity and fluorescence signalling property.

The unrepaired apurinic/apyrimidinic site (AP site) in mitochondrial DNA (mtDNA) promotes misincorporation of nucleotides and further causes serious damage for the living organism. Thus, accurate quantitative detection of AP sites in mtDNA in a rapid, highly sensitive, and highly selective fashion is important for the real-time evaluation of mtDNA oxidative damage. In this study, a targeting mtDNA ultrasensitive AP site-specific fluorescent rotor ( BTBM-CN 2 ) was designed by the strategy of molecular conformation torsion adjustment ratio fluorescent signal. The specific recognition reaction is activated when it encountered AP sites in mtDNA within 20 s, and BTBM-CN 2 presented a "turn-on" red fluorescence signal at 598 nm. Then, about 100 s later, BTBM-CN 2 emitted a new green fluorescence signal at 480 nm, which is mainly due to the activation of the rate-limiting reaction. With increasing numbers of AP sites (1-40 in 1 × 10 5 bp of mtDNA), the fluorescence emission at 598 nm decreased gradually, and the new emission at 480 nm increased. Intracellular experiments indicated that BTBM-CN 2 could detect AP sites in mtDNA in a rapid and quantitative fashion with high selectivity and ultrasensitivity. On the basis of the emergence of the fluorescence signal at 480 nm and its signal strength, the cell whose mtDNA was damaged could be screened by flow cytometry and its degree of damage could be evaluated in real time by comet assay. Hence, the rotor may have potential applications varying from accurate and ultrasensitive detection of AP sites to the real-time evaluation of the oxidative damage in living cells.

Nanozymes' activities could be regulated by a simple and effective pH change in an in situ manner. In this work, for the first time, the peroxidase-like activity of Ni/Co layered double hydroxides (LDHs) was regulated via the alkaline-promoted reaction of fluorogenic substrate homovanillic acid and H 2 O 2 , and a promising tool for pH sensing was developed over the pH range of 8.3-9.6. As peroxidase nanozyme model, Ni/Co LDHs showed ease of preparation, low-cost, and water-solubility, which played an important role in this luminescence system. Based on the pH-dependent regulation of the Ni/Co LDHs activity, we constructed the bioassay platform for the determination urea, urease, penicillin G, and penicillinase with a wide linear range of 17-1000 µM, 3.3-270 mU mL -1 , 3.3-1300 µM and 3.3-100 mU mL -1 , respectively. This study not only demonstrated the alkaline-promoted modulation the nanozymes' activities, but also established a facile approach to develop novel bioassays., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Nanomaterial-based peroxidase-mimetics are an emerging research field that promises to produce alternatives to horseradish peroxidase for a variety of applications. Generally, some peroxidase-mimetics substrates are used in acidic condition (pH ≤ 7). Then, it is necessary to screen some peroxidase-mimetics substrates suitable for basic condition because that some peroxidase-mimetics leached ions in acidic solution. In this paper, using Ni/Co layered double hydroxides (LDHs) as a nano-peroxidase mimic model, we evaluated three fluorogenic substrates suitable for basic condition though experimental conditions, reaction kinetic and glucose detection assay. And the detection of glucose method based on homovanillic acid (HVA) as fluorescent substrate gave wide linear range (0.02-20 μM) and low detection limit (0.01 μM). We also developed a novel platform that could study the inhibitory effects of ascorbic acid and glutathione based on the system of Ni/Co LDHs-HVA-H 2 O 2 ., (Copyright © 2017 Elsevier B.V. All rights reserved.)

The synthesized NiCo 2 O 4 mesoporous spheres (MS) displayed intrinsic peroxidase and oxidase-like activity were firstly reported. The catalytic mechanism of the oxidase-like activity of NiCo 2 O 4 MS was analyzed in detail using the electron spin resonance (ESR) method. It is found that NiCo 2 O 4 MS could directly oxidize 3,3',5,5'-tetramethylbenzidine (TMB) but did not produce 1 O 2 and ·OH. And the mechanism of the peroxidase-like activity of NiCo 2 O 4 MS was also verified that the oxidation of TMB stemmed from not only ·OH but also 1 O 2 . Based on the NiCo 2 O 4 MS showed excellent peroxidase-like activity over a broad temperature range, especially at normal body temperature, a detection tool was designed for glucose determination in diabetics' serum samples. And this detection method based on NiCo 2 O 4 MS gave a lower limit of detection than the method using Co 3 O 4 NPs and NiO NPs, as the single-component oxides of NiCo 2 O 4 . Our study may open up the possibility to make a great influence on the next generation of enzyme mimetics system., (Copyright © 2016 Elsevier B.V. All rights reserved.)

In the present study, a simple strategy was developed for Ni/Co layered double hydroxides (LDHs) as a substitute for natural peroxidase. The obtained Ni/Co LDHs exhibited ease of preparation, low-cost, and water-solubility; importantly, this material showed high catalytic activity in neutral pH solutions (phosphate buffer, Tris-HCl buffer, and even water). Benefitting from Ni/Co LDHs having a similar pH and temperature with specificity oxidase, such as glucose oxidase, choline oxidase, acetylcholinesterase, etc., a novel one-step method for a biosensor was developed in water. Glucose detection was selected as an application model system to evaluate the performance of this method, which showed a linear detection range from 0.5 μM to 100 μM with a detection limit (DL) of 0.1 μM. We also extended the one-step method to detect acetylcholine (ACh) by taking advantage of the specific catalytic reaction of acetylcholinesterase (AChE) and choline oxidase (ChOx). The linear detection range was from 10 μM to 150 μM with the DL of 1.62 μM. The proposed method had ease of operation, simple steps, and was rapid for glucose and ACh detection in real samples. On the basis of these advantages and virtues, Ni/Co LDHs could become attractive nanozymes in biotechnology and bioassays, and create a great influence on the next generation of enzyme mimetic systems.

In contrast to one-photon microscopy, two-photon probe-based fluorescent imaging can provide improved three-dimensional spatial localization and increased imaging depth. Consequently, it has become one of the most attractive techniques for studying biological events in living cells and tissues. However, the quantitation of these probes is primarily based on single-emission intensity change, which tends to be affected by a variety of environmental factors. Ratiometric probes, on the other hand, can eliminate these interferences by the built-in correction of the dual emission bands, resulting in a more favorable system for imaging living cells and tissues. Herein, for the first time, we adopted a through-bond energy transfer (TBET) strategy to design and synthesize a small molecular ratiometric two-photon fluorescent probe for imaging living cells and tissues in real time. Specifically, a two-photon fluorophore (D-π-A-structured naphthalene derivative) and a rhodamine B fluorophore are directly connected by electronically conjugated bond to form a TBET probe, or Np-Rh, which shows a target-modulated ratiometric two-photon fluorescence response with highly efficient energy transfer (93.7%) and two well-resolved emission peaks separated by 100 nm. This novel probe was then applied for two-photon imaging of living cells and tissues and showed high ratiometric imaging resolution and deep-tissue imaging depth of 180 μm, thus demonstrating its practical application in biological systems.