Hydrazine Group Research Articles

A novel fluorescent probe for formaldehyde based on hydrazone formation for real food samples detection and bioimaging

Formaldehyde (FA) is an active carbonyl structure that is widely used in people's daily life, such as preservatives and fixatives. Furthermore, formaldehyde is highly toxic and has been listed as one of the three major indoor pollutants. Therefore, the development of highly sensitive and selective fluorescent probes is of great biological importance. In this article, probe X is designed to identify formaldehyde by a light-induced electron transfer (PET) process between the naphthalimide derivative and the hydrazine group based on hydrazone formation. Moreover, the probe has good optical response and excellent linearity over a wide range of formaldehyde concentrations, ensuring that formaldehyde concentration values in real complex food samples can be quantitatively recorded. In addition, the probe can monitor the changes of formaldehyde levels in living cells with good biocompatibility and image resolution.

Eliminating Voids and Residual PbI2 beneath a Perovskite Film via Buried Interface Modification for Efficient Solar Cells.

The commercialization process of perovskite solar cells (PSCs) is markedly restricted by the power conversion efficiency (PCE) and long-term stability. During fabrication and operation, the bottom interface of the organic-inorganic hybrid perovskite layer frequently exhibits voids and residual PbI2, while these defects inevitably act as recombination centers and degradation sites, affecting the efficiency and stability of the devices. Therefore, the degradation and nonradiative recombination originating from the buried interface should be thoroughly resolved. Here, we report a multifunctional passivator by introducing malonic dihydrazide as an interfacial chemical bridge between the electron transport layer and the perovskite (PVK) layer. MADH with hydrazine groups improves the surface affinity of SnO2 and provides nucleation sites for the growth of PVK, leading to the reduced residual PbI2 and the voids resulting from the inhomogeneous solvent volatilization at the bottom interface. Meanwhile, the hydrazine group and carbonyl group synergistically coordinate with Pb2+ to improve the crystal growth environment, reducing the number of Pb-related defects. Eventually, the PCE of the PSCs is significantly enhanced benefiting from the reduced interfacial defects and the increased carrier transport. Moreover, the reductive nature of hydrazide further inhibits I2 generation during long-term operation, and the device retains 90% of the initial PCE under a 1 sun continuous illumination exposure of 700 h.

Engineering the pore environment of antiparallel stacked covalent organic frameworks for capture of iodine pollutants

Radioiodine capture from nuclear fuel waste and contaminated water sources is of enormous environmental importance, but remains technically challenging. Herein, we demonstrate robust covalent organic frameworks (COFs) with antiparallel stacked structures, excellent radiation resistance, and high binding affinities toward I2, CH3I, and I3− under various conditions. A neutral framework (ACOF-1) achieves a high affinity through the cooperative functions of pyridine-N and hydrazine groups from antiparallel stacking layers, resulting in a high capacity of ~2.16 g/g for I2 and ~0.74 g/g for CH3I at 25 °C under dynamic adsorption conditions. Subsequently, post-synthetic methylation of ACOF-1 converted pyridine-N sites to cationic pyridinium moieties, yielding a cationic framework (namely ACOF-1R) with enhanced capacity for triiodide ion capture from contaminated water. ACOF-1R can rapidly decontaminate iodine polluted groundwater to drinking levels with a high uptake capacity of ~4.46 g/g established through column breakthrough tests. The cooperative functions of specific binding moieties make ACOF-1 and ACOF-1R promising adsorbents for radioiodine pollutants treatment under practical conditions.

Proton Affinity and Conformational Integrity of a 24-Atom Triazine Macrocycle across Physiologically Relevant pH.

For 24-atom triazine macrocycles, protonation of the heterocycle leads to a rigid, folded structure presenting a network of hydrogen bonds. These molecules derive from dynamic covalent chemistry wherein triazine monomers bearing a protected hydrazine group and acetal tethered by the amino acid dimerize quantitatively in an acidic solution. Here, lysine is used, and the product is a tetracation. The primary amines of the lysine side chains do not interfere with quantitative yields of the desired bis(hydrazone) at concentrations of 5-125 mg/mL. Mathematical modeling of data derived from titration experiments of the macrocycle reveals that the pKa values of the protonated triazines are 5.6 and 6.7. Changes in chemical shifts of resonances in the 1H NMR spectra corroborate these values and further support assignment of the protonation sites. The pKa values of the lysine side chains are consistent with expectation. Upon deprotonation, the macrocycle enjoys greater conformational freedom as evident from the broadening of resonances in the 1H and 13C NMR spectra indicative of dynamic motion on the NMR time scale and the appearance of additional conformations at room temperature. While well-tempered metadynamics suggests only a modest difference in accessible conformational footprints of the protonated and deprotonated macrocycles, the shift in conformation(s) supports the stabilizing role that the protons adopt in the hydrogen-bonded network.

A lanthanide metal–organic framework containing a hydrazine group for highly sensitive luminescent sensing of formaldehyde gas

A hydrazine-functionalized LnMOF was developed for highly sensitive formaldehyde gas detection with a low detection limit of 41.7 ppb.

Enteromorpha Prolifera Polysaccharide-Derived Injectable Hydrogel for Fast Intraoperative Hemostasis and Accelerated Postsurgical Wound Healing Following Tumor Resection.

Intraoperative bleeding and delayed postsurgical wound healing caused by persistent inflammation can increase the risk of tumor recurrence after surgical resection. To address these issues, Enteromorpha prolifera polysaccharide (PEP) with intrinsic potentials for hemostasis and wound healing, is chemically modified into aldehyde-PEP and hydrazine-PEP. Thereby, an injectable double-network hydrogel (OPAB) is developed via forming dual dynamic bonding of acylhydrazone bonds between the decorated aldehyde and hydrazine groups and hydrogen bonds between hydroxyl groups between boric acid and PEP skeletons. The OPAB exhibits controllable shape-adaptive gelation (35.0 s), suitable mechanical properties, nonstimulating self-healing (60 s), good wet tissue adhesion (30.9kPa), and pH-responsive biodegradability. For in vivo models, owing to these properties, OPAB can achieve rapid hemostasis within 30 s for the liver hemorrhage, and readily loading of curcumin nanoparticles to remarkably accelerate surgical wound closure by alleviating inflammation, re-epithelialization, granulation tissue formation, and collagen deposition. Overall, this multifunctional injectable hydrogel is a promising material that facilitates simultaneous intraoperative hemorrhage and postsurgical wound repair, holding significant potential in the clinical managements of bleeding and surgical wounds for tumor resection.

Quantitative Colorimetric Sensing of Carbidopa in Anti-Parkinson Drugs Based on Selective Reaction with Indole-3-Carbaldehyde.

The quality of life of patients affected by Parkinson's disease is improved by medications containing levodopa and carbidopa, restoring the dopamine concentration in the brain. Accordingly, the affordable quality control of such pharmaceuticals is very important. Here is reported the simple and inexpensive colorimetric quantification of carbidopa in anti-Parkinson drugs by the selective condensation reaction between the hydrazine group from carbidopa and the formyl functional group of selected aldehydes in acidified hydroalcoholic solution. An optical assay was developed by using indole-3-carbaldehyde (I3A) giving a yellow aldazine in EtOH:H2O 1:1 (λmax~415 nm) at 70 °C for 4 h, as confirmed by LC-MS analysis. A filter-based plate reader was used for colorimetric data acquisition, providing superior results in terms of analytical performances for I3A, with a sensitivity ~50 L g-1 and LOD ~0.1 mg L-1 in comparison to a previous study based on vanillin, giving, for the same figures of merit values, about 13 L g-1 and 0.2-0.3 mg L-1, respectively. The calibration curves for the standard solution and drugs were almost superimposable, therefore excluding interference from the excipients and additives, with very good reproducibility (avRSD% 2-4%) within the linear dynamic range (10 mg L-1-50 mg L-1).

Computational chemistry‐assisted design of hydrazine‐based fluorescent molecular rotor for viscosity sensors

AbstractDeep understanding of the fluorescence quenching mechanisms of probes plays a crucial role in developing their practical applications. The fluorescence quenching mechanism of hydrazine‐based fluorescence probes needs to be clarified up to the present. Herein, we designed and synthesized a new hydrazine‐based fluorescence probe (HA‐Na) based on the naphthalimide skeleton. We clarified the molecular origin of the non‐fluorescence of this probe with the aid of computational chemistry and spectroscopic analysis. We showed that the significant rotation of the hydrazine group in the excited state potential energy surface, which caused the complete charge separation, was responsible for the fluorescence quenching of the probe in an organic solvent. Once the rotation was prevented in an aggregative state or high‐viscosity solution, the fluorescence of the probe recovered. In other words, the fluorescence quenching mechanism of hydrazine‐based fluorescence probes was attributed to the formation of a twisted intramolecular charge transfer (TICT) state. More importantly, we demonstrated that this fluorescence molecular rotor could be used to monitor the autophagy process in living cells by detecting lysosomal viscosity changes during starvation. Altogether, this work provides an essential theoretical basis for the developing potential hydrazine‐based fluorescence molecular rotors.

Chromium decorated leaf-like N-doped carbon anchoring with active Cr-Nx sites as oxidase mimics for isoniazid sensing

Research about constructing transition metal-based N-doped carbon nanozymes with high-performance for sensing applications has attracted great attention. Here, a novel Cr decorated N-doped carbon (Cr-NC) derived from zeolite imidazolate framework-leaf with unique Cr-Nx active sites was developed via pyrolysis strategy. The nanosheet structure endowed Cr-NC with highly exposed active sites for promoting O2 adsorption and cleavage into reactive OH, O2− and 1O2, for oxidizing 3,3′,5,5′-tetramethylbenzidine (TMB), showing oxidase-like activity. Compared with that of N-doped carbon (NC), the catalytic activity of Cr-NC oxidase mimic was increased by 19.55 times. Cr species doping in carbon matrix could promote electron transfer ability of Cr-NC and Cr-Nx anchoring in Cr-NC was the major active sites in improving the oxidase-like performance of NC. The Cr-NC displayed a good affinity to TMB and a fast reaction velocity, showing the Km value of 0.54 mM and the Vmax of 3.03 × 10−7 M/s. Since isoniazid (INH) contains hydrazine groups, which inhibits the oxidation of TMB, a sensitive and highly selective assay for INH was established based on the oxidase-like activity of Cr-NC. The linear response of the detection platform to INH ranges from 0.25 to 50 μM with the detection limit (3σ/k) of 0.22 μM and the relative standard deviation (RSD, n = 3) less than 3.5%. The platform has been successfully applied to the determination of INH in real pharmaceutical preparations.

O-methyltransferase-like enzyme catalyzed diazo installation in polyketide biosynthesis

Diazo compounds are rare natural products possessing various biological activities. Kinamycin and lomaiviticin, two diazo natural products featured by the diazobenzofluorene core, exhibit exceptional potency as chemotherapeutic agents. Despite the extensive studies on their biosynthetic gene clusters and the assembly of their polyketide scaffolds, the formation of the characteristic diazo group remains elusive. l-Glutamylhydrazine was recently shown to be the hydrazine donor in kinamycin biosynthesis, however, the mechanism for the installation of the hydrazine group onto the kinamycin scaffold is still unclear. Here we describe an O-methyltransferase-like protein, AlpH, which is responsible for the hydrazine incorporation in kinamycin biosynthesis. AlpH catalyses a unique SAM-independent coupling of l-glutamylhydrazine and polyketide intermediate via a rare Mannich reaction in polyketide biosynthesis. Our discovery expands the catalytic diversity of O-methyltransferase-like enzymes and lays a strong foundation for the discovery and development of novel diazo natural products through genome mining and synthetic biology.

Structural variety of Co2+, Ni2+, Pd2+, and Pt4+ complexes of a hydrazone based on Girard's T: Synthesis, spectroscopic, molecular docking simulation on CTX‐M‐14 β‐lactamase, and theoretical (DFT) studies

The reaction of ethyl isothiocyanate with Girard's T affords a new hydrazone named 2‐(2‐N,N,N‐trimethyl‐2‐oxoethane‐1‐auminium chloride [EtGT]). Its structure was confirmed by single crystal X‐ray diffraction. Also, the isolations and characterizations of new metal complexes with EtGT were confirmed by elemental analyses, IR, UV‐visible, magnetic measurements, 13C‐NMR, 1H‐NMR, and thermal analyses. IR spectra suggest that the ligand acts as a bidentate coordinating either via the carbonyl oxygen and the nitrogen atom of the hydrazine group or through the sulfur (C=S and/or C‐S) and the NH groups. The computational estimation of EtGT and its complexes were approved with the Gaussian 09 W program in DFT/B3LYP. DPPH and ABTS are two free radical scavenger tests that were utilized in order to evaluate the antioxidant potential of complexes in vitro. Furthermore, the biological effectiveness of the ligand and its complexes against bacteria varieties Gram (+ve) and Gram (−ve) bacteria was in vitro investigated. Also, antifungal action was investigated utilizing inhibition zone diameter. Moreover, the ligand and its complexes also exhibited a broad spectrum of DNA degradation effects, as measured by agarose gel electrophoresis. Cyclic voltammetry of Co2+ with different concentrations was measured experimentally. Molecular docking is exercised to examine the inhibitor characteristics of complexes through binding propensity with CTX‐M‐14 β‐lactamase (Class A).

Molecular mechanism for the activation of the potent hepatotoxin acetylhydrazine: Identification of the initial N-centered radical and the secondary C-centered radical intermediates.

Acetylhydrazine (AcHZ), a major human metabolite of the widely-used anti-tuberculosis drug isoniazid (INH), was considered to be responsible for its serious hepatotoxicity and potentially fatal liver injury. It has been proposed that reactive radical species produced from further metabolic activation of AcHZ might be responsible for its hepatotoxicity. However, the exact nature of such radical species remains not clear. Through complementary applications of ESR spin-trapping and HPLC/MS methods, here we show that the initial N-centered radical intermediate can be detected and identified from AcHZ activated by transition metal ions (Mn(III)Acetate and Mn(III) pyrophosphate) and myeloperoxidase. The exact location of the radical was found to be at the distal-nitrogen of the hydrazine group by 15N-isotope-labeling techniques via using 15N-labeled AcHZ we synthesized. Additionally, the secondary C-centered radical was identified unequivocally as the reactive acetyl radical by complementary applications of ESR spin-trapping and persistent radical TEMPO trapping coupled with HPLC/MS analysis. This study represents the first detection and unequivocal identification of the initial N-centered radical and its exact location, as well as the reactive secondary acetyl radical. These findings should provide new perspectives on the molecular mechanism of AcHZ activation, which may have potential biomedical and toxicological significance for future research on the mechanism of INH-induced hepatotoxicity.

Thiourea bacterial cellulose imprinted aerogel construction by oriented assembly for selective adsorption of Er(III) from rare earth leachate

The selective recovery of Er(III) from the leachate is of environmental and economic importance based on the non-renewability and strategic position of high-value heavy rare earth elements. In this study, functionalize bacterial cellulose (BC) with unique three-dimensional network structure was used as the oriented imprinting framework for construction of thiourea BC imprinted aerogel (DBCT-IIPS). The oriented assembly process allows all the imprinted sites to be located on the surface of the BC, which greatly improves the mass transfer efficiency compared to the conventional imprinting process. Experimental analysis shows that functional modification of BC and the crosslinking of hydrazine group greatly improve the stability and adsorption properties of aerogel materials. Adsorption experiments showed that DBCT-IIPS can fast and selectively adsorb Er(III) from rare earth leachate. The maximum adsorption capacity reaches 65.43 mg g−1. After 5 times of adsorption and desorption, adsorption capacity of DBCT-IIPS can still maintain 81.6% of the initial capacity. So, DBCT-IIPS can efficiently and selectively recover of Er(III) from rare earth leachate.

A Model for the Rapid Assessment of Solution Structures for 24-Atom Macrocycles: The Impact of β-Branched Amino Acids on Conformation.

Experiment and computation are used to develop a model to rapidly predict solution structures of macrocycles sharing the same Murcko framework. These 24-atom triazine macrocycles result from the quantitative dimerization of identical monomers presenting a hydrazine group and an acetal tethered to an amino acid linker. Monomers comprising glycine and the β-branched amino acids threonine, valine, and isoleucine yield macrocycles G-G, T-T, V-V, and I-I, respectively. Elements common to all members of the framework include the efficiency of macrocyclization (quantitative), the solution- and solid-state structures (folded), the site of protonation (opposite the auxiliary dimethylamine group), the geometry of the hydrazone (E), the C2 symmetry of the subunits (conserved), and the rotamer state adopted. In aggregate, the data reveal metrics predictive of the three-dimensional solution structure that derive from the fingerprint region of the 1D 1H spectrum and a network of rOes from a single resonance. The metrics also afford delineation of more nuanced structural features that allow subpopulations to be identified among the members of the framework. Well-tempered metadynamics provides free energy surfaces and population distributions of these macrocycles. The areas of the free energy surface decrease with increasing steric bulk (G-G > V-V ∼ T-T > I-I). In addition, the surfaces are increasingly isoenergetic with decreasing steric bulk (G-G > V-V ∼ T-T > I-I).

Computational and Experimental Evidence for Templated Macrocyclization: The Role of a Hydrogen Bond Network in the Quantitative Dimerization of 24-Atom Macrocycles.

In the absence of preorganization, macrocyclization reactions are often plagued by oligomeric and polymeric side products. Here, a network of hydrogen bonds was identified as the basis for quantitative yields of macrocycles derived from the dimerization of monomers. Oligomers and polymers were not observed. Macrocyclization, the result of the formation of two hydrazones, was hypothesized to proceed in two steps. After condensation to yield the monohydrazone, a network of hydrogen bonds formed to preorganize the terminal acetal and hydrazine groups for cyclization. Experimental evidence for preorganization derived from macrocycles and acyclic models. Solution NMR spectroscopy and single-crystal X-ray diffraction revealed that the macrocycles isolated from the cyclization reaction were protonated twice. These protons contributed to an intramolecular network of hydrogen bonds that engaged distant carbonyl groups to realize a long-range order. DFT calculations showed that this network of hydrogen bonds contributed 8.7 kcal/mol to stability. Acyclic models recapitulated this network in solution. Condensation of an acetal and a triazinyl hydrazine, which adopted a number of conformational isomers, yielded a hydrazone that adopted a favored rotamer conformation in solution. The critical hydrogen-bonded proton was also evident. DFT calculations of acyclic models showed that the rotamers were isoenergetic when deprotonated. Upon protonation, however, energies diverged with one low-energy rotamer adopting the conformation observed in the macrocycle. This conformation anchored the network of hydrogen bonds of the intermediate. Computation revealed that the hydrogen-bonded network in the acyclic intermediate contributed up to 14 kcal/mol of stability and preorganized the acetal and hydrazine for cyclization.

A new quinoline based probe with large Stokes shift and high sensitivity for formaldehyde and its bioimaging applications

As a common reactive metabolite in living organisms, abnormal levels of formaldehyde may cause diseases such as cancer and Alzheimer's disease. Therefore, it is important to develop a sensitive and efficient method to understand the role of formaldehyde in physiology and pathology. Herein, a new fluorescent probe 4-phenyl-2-(trifluoromethyl) quinolin-7-hydrazino (QH-FA) was prepared for the detection of formaldehyde in near-total aqueous media with hydrazine as the reaction site and quinoline derivatives as the fluorophore. After reacting with formaldehyde, the hydrazine group formed methylenehydrazine and the fluorescence was significantly enhanced (223-fold) with large Stokes shift of 140 nm. Furthermore, the response of QH-FA to formaldehyde could be finished with in only 10 min with good selectivity, and can distinguish formaldehyde from other aldehydes. More remarkably, the estimated limit of detection of QH-FA is 8.1 nM, which is superior to those of previously reported formaldehyde fluorescent probes. At the end, we detected formaldehyde in cells and zebrafish using QH-FA in a near-total aqueous system and obtained fluorescence images by confocal microscopy.

Fluorescent probe for detection of formaldehyde based on UiO-66-NH2

Formaldehyde (FA) is a harmful substance commonly found in the environment, so effective testing is essential. Consequently, we designed and synthesized a novel fluorescent probe, which is based on covalent post-synthetic modification (PSM) of UiO-66-NH2 by naphthylamide (NI). The combination of the metal-organic frameworks (MOFs) and the covalent PSM makes the probe with large amount of hydrazine group exposed on the surface, which results excellent FA sensing performance like an ultrafast response time (20 ​s) and a low detection limit of 0.167 ​μM. The presence of covalent bonds can lock the fluorophore and prevent strong π-π interactions to exhibit aggregation-induced emission (AIE). Further we confirmed that such probe can be applied to real water samples and portable test strip experiment. In addition, experimental evidence such as fluorescence lifetime decay curves suggest that the main mechanism of fluorescence quenching is Förster resonance energy transfer (FRET).

Janus-Faced Fluorescence Imaging Agent for Malondialdehyde and Formaldehyde in Brains

Carbonyl stress caused by reactive carbonyl species (RCS) is closely related to various brain diseases. As the highly reactive, highly toxic, and lipophilic RCS, malondialdehyde (MDA) and formaldehyde (FA) could easily cross the blood-brain barrier (BBB) and induce protein dysfunction or cross-linking in the brain. Do MDA and FA coordinately regulate the physio-pathological processes of the brain? To answer the question, first of all, powerful identification and sensing tools are needed. However, competent probes for simultaneously analyzing MDA and FA in living brains are lacking, which originates from the following three challenges: (1) MDA and FA are difficult to distinguish due to their great similarity in structure and reactivity; (2) to achieve simultaneous and discriminable imaging, same excitation and different emissions are preferable; and (3) the detection of MDA and FA in living brains require the materials to pass through the BBB. Thus, we created a two-photon fluorescent agent, TFCH, for MDA/FA. The hydrazine group in TFCH could successfully differentiate MDA/FA at 440/510 nm under same excitation. Moreover, the lipophilic trifluoromethyl group (-CF3) in TFCH prompts it to traverse the BBB, thereby realizing the coinstantaneous visualization of MDA and FA in the living brain. Using TFCH, we observed the excessive production of MDA and FA in living PC12 cells under carbonyl stress and oxidative stress. Notably, for the first time, two-photon fluorescence imaging indicated the synchronous increase of MDA and FA in living brains of mice with depression. Altogether, this work provides a promising tool for revealing the carbonyl stress-related molecular mechanism involved in brain diseases.

Synthesis, Characterizations, Crystal Structure, DFT, and Hirshfeld Surface Analysis of 4-Cyclohexyl-1-(thiophene-2-carbonyl)thiosemicarbazide

The crystal structure of the thiosemicarbazide derivative 4-cyclohexyl-1-(thiophene-2-carbonyl)thiosemicarbazide (ChtcTSC), C12H17N3OS2, is reported here. The title compound ChtcTSC has been characterized by various physicochemical techniques viz UV–Vis., Infrared, and NMR. It crystallizes in the monoclinic system having space group P21/c. The dihedral angle between the thiophene and cyclohexyl rings is 60.7(4)°. The crystal packing is established by intermolecular N–H⋯O packing interactions involving a three-center donor hydrogen bond between the keto oxygen atom of the thiophene group and H atoms belonging to the hydrazine group which links the molecules into chains along the (011) plane of the unit cell. Hydrogen bonds between the hydrazine hydrogen atom and one of the thiophene groups and C–H⋯Cg π -ring interactions provide added stability to the crystal packing. The fingerprint plots associated with Hirshfeld surface analysis indicate that there are different types of weak interactions viz. O⋯H–C, O⋯H–N, and S⋯H–C. The geometry optimization has been performed using the DFT method, and geometrical parameters thus obtained for ChtcTSC correlate with the single-crystal X-ray data. The TD-DFT study showed a small HOMO and LUMO energy gap of 2.869 eV. The electronic transition from the ground state to the excited state due to a transfer of electrons from HOMO to LUMO levels is mainly associated with the n → π* transition.Graphical AbstractThe crystal structure of 4-cyclohexyl-1-(thiophene-2-carbonyl)thiosemicarbazide (ChtcTSC) is reported here where the title compound ChtcTSC has been characterized by various physiochemical techniques including UV–Vis., Infrared, NMR, DFT and Hirshfeld surface analysis.

Design of a New Hydrazine Moiety-Based Near-Infrared Fluorescence Probe for Detection and Imaging of Endogenous Formaldehyde In Vivo.

Formaldehyde (FA), the smallest molecular aldehyde with strong reducing properties, could regulate body homeostasis endogenously during physiological and pathological processes. The effective near-infrared (NIR) fluorescent probe is needed as a visualizer of FA in biologic organisms. In this work, a novel NIR fluorescent Probe-NHNH2 was designed on the basis of Probe-NH2 via introducing a strong nucleophilic hydrazine group, which can be used as a quenching and recognizing moiety for the detection of FA. With the treatment of FA, the hydrazine group of Probe-NHNH2 undergoes condensation and achieves a turn-on NIR fluorescence signal at a wavelength of 706 nm. The spectroscopic performance of Probe-NHNH2 for FA was evaluated, and it exhibited high sensitivity and selectivity for the detection of FA in solution. Moreover, compared to the amine moiety-based Probe-NH2, which our group reported, we found that hydrazine moiety-based Probe-NHNH2, exhibited a better reaction time of within 10 min and a lower detection limit of 0.68 μM, reflecting that the reaction of FA with hydrazine moiety is faster and more sensitive than that of FA with the amino group. More importantly, Probe-NHNH2 was successfully applied to real-time imaging of endogenous FA by reacting with effective stimulant tetrahydrofolate and scavenger sodium bisulfite in zebrafish and mice. It is expected that we can provide a new rapid, sensitive NIR fluorescence theoretical basis for FA detection and in vivo imaging applications.