A ratiometric fluorescent probe for alkaline phosphatase with high sensitivity

Alkaline phosphatase(ALP)is one of essential biomarkers in mammalian tissue.Here we report a ratiometric probe for ALP,which is rationally designed and synthesized by employing ESIPT fluorophore N-(3-(benzo[d]thiazol-2-yl)-4-hydroxyphenyl)benzamide(BTHPB).The enzymatic dephosphorylation converts the probe to BTHPB,which exhibits a large spectral red-shift(120 nm),allowing extremely high sensitivity of ALP sensing at 0.004 mU/mL.The probe also shows excellent biocompatibility and has been applied for monitoring the endogenic ALP in living cells.     

A ratiometric near-infrared naphthalimide-based fluorescent probe with high sensitivity for detecting Fe2+ in vivo

Iron is one of the essential trace elements in the human body. It plays an important role in human biology and pathology. Deregulation of iron levels in cells is associated with disease development. In this work, we synthesized a novel near-infrared intramolecular charge transfer (ICT) based ratiometric fluorescent probe to detect Fe²⁺, by using naphthalimide and indole moieties as building blocks. Our work showed that the radiometric probe has excellent selectivity, sensitivity and rapid response. Moreover, we could successfully perform real-time monitoring of Fe²⁺ in HeLa cells and C. elegans.     

A ratiometric fluorescent probe for zinc ions based on the quinoline fluorophore

A ratiometric fluorescent zinc probe 1 of carboxamidoquinoline with a carboxylic acid group was designed and synthesised. Probe 1 exhibits high selectivity for sensing Zn²⁺; about a 13-fold increase in fluorescence emission intensity and an 82?nm red-shift of fluorescence emission are observed upon binding Zn²⁺ in EtOH/H₂O (1?:?1, V/V) solution. The ratiometric fluorescence response is attributed to the 1?:?1 complex formation between probe 1 and Zn²⁺ which has been utilised as the basis for the selective detection of Zn²⁺. The analytical performance characteristics of the proposed Zn²⁺-sensitive probe were investigated. The linear response range covers a concentration range of Zn²⁺ from 2.0?×?10^?6 to 5.0?×?10^?5?mol?L^?1 and the detection limit is 2.7?×?10^?7?mol?L^?1. The determination of Zn²⁺ in both tap and river water samples shows satisfactory results.     

An effective colorimetric and ratiometric fluorescent probe for bisulfite in aqueous solution

We have developed the first two-photon colorimetric and ratiometric fluorescent probe, BICO, for the detection of bisulfite (HSO₃⁻) in aqueous solution. The probe contains coumarin and benzimidazole moieties and can detect HSO₃⁻ based on the Michael addition reaction with a limit of detection 5.3 × 10⁻⁸ M in phosphate-buffered saline solution. The probe was used to detect bisulfite in tap water, sugar and dry white wine. Moreover, test strips were made and used easily. We successfully applied the probe to image living cells, using one-photon fluorescence imaging. BICO overcomes the limitations in sensitivity of previously reported probes and the solvation effect of bisulfite, which demonstrates its excellent value in practical application.     

A ratiometric fluorescent sensor for Ag(I) with high selectivity and sensitivity

A bicyclic cycloadduct 1 bearing a pyrenyl moiety has been synthesized and investigated as a ratiometric fluorescent sensor for AgI. In an aqueous ethanol solution of 1, the presence of silver ion induces the formation of a 1:2 metal-ligand complex, which exhibits a strong intensity enhancement of the pyrene excimer emission at the expense of the emission of monomeric pyrene.     

A colorimetric,ratiometric and water-soluble fluorescent probe for simultaneously sensing glutathione and cysteine/homocysteine

A chlorinated coumarin-aldehyde was developed as a colorimetric and ratiometric fluorescent probe for distinguishing glutathione (GSH), cystenine (Cys) and homocysteine (Hcy). The GSH-induced substitution-cyclization and Cys/Hcy-induced substitution-rearrangement cascades lead to the corresponding thiol-coumarin-iminium cation and amino-coumarin-aldehyde with distinct photophysical properties. The probe can be used to simultaneously detect GSH and Cys/Hcy by visual determination based on distinct different colors – red and pale-yellow in PBS buffer solution by two reaction sites. From the linear relationship of fluorescence intensity and biothiols concentrations, it was determined that the limits of detection for GSH, Hcy and Cys are 0.08, 0.09 and 0.18 μM, respectively. Furthermore, the probe was successfully used in living cell imaging with low cell toxicity.     

A ratiometric fluorescent chemodosimeter for Cu(II) in water with high selectivity and sensitivity

Coumarin derivative 1 was synthesized as an efficient ratiometric chemodosimeter for the detection of Cu(II) in 99% water/DMSO (v/v) at pH 7.0. Mechanism studies suggested that 1 formed a complex with Cu(II) at 2:1 ratio accompanied by quenching of green fluorescence at 524 nm; when the solution was heated to 50 °C for 30 min, Cu(II)-promoted hydrolysis of coumarin lactone moiety of 1 occurred with bright blue fluorescence at 451 nm emerged. With fluorescence intensity ratio detection at 451 nm and 524 nm, 1 features an excellent sensitivity with the detection limit of 15 nmol L⁻¹ toward Cu(II) and a good selectivity over other metal ions.     

A highly sensitive naphthalimide-based fluorescent probe for detection of Cu2+ via selective hydrolysis reaction and its application in practical samples

A novel fluorescent probe CN3, containing 1,8-naphthalimide and picolinate units, was synthesized, and its structure was characterized by ¹H nuclear magnetic resonance spectroscopy (H NMR), ¹³C nuclear magnetic resonance spectroscopy (C NMR), and mass spectroscopy techniques. The detection property of CN3 toward copper ions (Cu²⁺) has been investigated in ethanol–HEPES buffer (v/v = 1/1, pH = 7.40) solution by UV–Vis absorption and fluorescence emission spectra. The results showed that CN3 had a highly selective and sensitive fluorescence quenching response to Cu²⁺, which was attributed to the generation of weak fluorescent N-ethyl-4-hydroxyphenyl-1,8- naphthalimide (compound 2) in polar ethanol–HEPES buffer (v/v = 1/1, pH = 7.40) via selective hydrolysis reaction. The detection of CN3 for Cu²⁺ was not influenced in the presence of other competing metal ions, and the limit of detection was as low as 50.0 nM. Therefore, the color of CN3 changed from colorless to yellowish when the Cu²⁺ was added. Furthermore, the fluorescent probe CN3 was utilized to detect Cu²⁺ in real water samples with fine performance.     

A ratiometric fluorescent probe for palladium detection based on an allyl carbonate group functionalized hemicyanine dye

A novel ratiometric fluorescent probe for palladium species was synthesized based on an allyl carbonate group, a novel reaction site, and a hemicyanine dye. The probe displays relatively rapid response, high selectivity, and anti-disturbance toward palladium in HEPES buffers without additional reagents. The detection mechanism, palladium triggers the cleavage of allyl carbonate in the probe and then decarboxylation of the product to induce the ratiometric fluorescence response, was verified using UV–vis and mass spectrometry analysis. The probe was successfully applied for ratiometric fluorescent detection of palladium in tap water, river water, and in fetal bovine serum.     

A ratiometric near-infrared naphthalimide-based fluorescent probe with high sensitivity for detecting Fe2+ in vivo

Iron is one of the essential trace elements in the human body. It plays an important role in human biology and pathology. Deregulation of iron levels in cells is associated with disease development. In this work, we synthesized a novel near-infrared intramolecular charge transfer (ICT) based ratiometric fluorescent probe to detect Fe²⁺, by using naphthalimide and indole moieties as building blocks. Our work showed that the radiometric probe has excellent selectivity, sensitivity and rapid response. Moreover, we could successfully perform real-time monitoring of Fe²⁺ in HeLa cells and C. elegans.     

A borondipyrrolemethene-based turn-on fluorescent probe for silver ion with high sensitivity and selectivity and its application in water samples and living cells

A borondipyrrolemethene-based compound (1) is synthesized and used as a “turn-on” fluorescent probe for silver ions (Ag⁺). The probe displays highly sensitive fluorescence response toward Ag⁺ with a 40-fold fluorescence enhancement when 60 μM of Ag⁺ is added. The fluorescence intensity of the probe is linearly dependent on Ag⁺ concentration ranging from 0.05 to 60 μM. And the detection limit (LOD) can reach 0.02 μM, which complies with the standard of World Health Organization (WHO) for drinking water (0.9 μM). Moreover, the probe shows remarkable selectivity for Ag⁺ over other metal ions. Furthermore, the response behavior of 1 toward Ag⁺ is pH independent in the neutral range from 6.0 to 8.0. The response of 1 toward Ag⁺ is fast (response time is less than 2 min) and reversible chemically. What’s more, the sensing mechanism of probe 1 toward Ag⁺ is verified by mass spectra (MS) and density functional theory (DFT) calculations. In particular, the probe is applied for detection of Ag⁺ in water samples and living cells successfully.     

A chloroacetate based ratiometric fluorescent probe for cysteine detection in biosystems

The specific detection of cysteine (Cys) over homocysteine (Hcy), glutathione (GSH) and other amino acids is of great significance for studying its biological functions as well as for the diagnosis of related diseases. Chloroacetyl group was often used as a reaction site for cysteine fluorescent probes for its sensitivity and selectivity. However, high background fluorescence and low stability are common problems encountered by such probes. Here, four chloroacetyl group based fluorescent probes (C1, C2, C3, and H4) was synthesized for a comparative study. We found that the inefficient quenching ability of chloroacetyl group turned into an advantage when connected with a ratiometric fluorophore. With the modification of chloroacetyl group, probe H4 displayed excellent ratiometric property and great selectivity for Cys, the stability was also improved. Additionally, the probe was successfully applied for quantitative detection of Cys in fetal bovine serum and real-time imaging in living HeLa cells with low toxicity.     

A Rapid,Highly Sensitive and Selective Phosgene Sensor Based on 5,6-Pinenepyridine

The toxicity of phosgene (COCl₂) combined with its extensive use as a reactant and building block in the chemical industry make its fast and accurate detection a prerequisite. We have developed a carboxylic derivative of 5,6-pinenepyridine which is able to act as colorimetric and fluorimetric sensor for phosgene in air and solution. For the first time, the formation of a pyrido-[2,1-a]isoindolone was used for this purpose. In solution, the sensing reaction is extremely fast (under 5 s), selective and highly sensitive, with a limit of detection (LOD) of 9.7 nM/0.8 ppb. When fixed on a solid support, the sensor is able to detect the presence of gaseous phosgene down to concentrations of 0.1 ppm, one of the lowest values reported to date.     

A boronate-based ratiometric fluorescent probe for fast selective detection of peroxynitrite

Given that peroxynitrite (ONOO^?) is profoundly associated with health and diseases, a new fluorescent probe ABT was designed and synthesized for detection of ONOO^?. ABT manifested not only ratiometric fluorescence signals simultaneously in response to concentrations of ONOO^? (within 10?s), but high selectivity and sensitivity towards ONOO^? over other physiological relevant species (detection limit?=?26.3?nM). Moreover, ABT worked in a broad pH range with biological relevance. Thus, ABT could be used to quantitative detection of ONOO^? concentration and has the potential to efficiently monitor ONOO^? in living organisms.     

Developing a novel ratiometric fluorescent probe based on ESIPT for the detection of pH changes in living cells

As an important parameter of intracellular metabolism, pH plays important roles in maintaining normal physiological processes. The abnormal pH could cause disorder of cell function which may cause neurological diseases. Herein, we present two novel ratiometric fluorescent probes to detect pH changes. The probes employed 2-(2′-hydroxyphenyl)benzothiazole as fluorescent platform, and displayed desirable fluorescence response to pH on the basis of excited state intramolecular proton transfer (ESIPT) process. The probe BtyC-1 showed green fluorescence at 546 nm under acidic conditions, while it displayed strong blue fluorescence at 473 nm and weak green fluorescence at 546 nm under alkaline conditions. Biological experiments demonstrated that the probe BtyC-1 could be successfully applied for the ratiometric imaging of cellular pH and the NH₄Cl-induced pH changes in living cells.     

利用聚(N-异丙基丙烯酰胺-co-丙烯酸)银纳米团簇构建宽pH响应范围的激发比率型荧光探针EI北大核心CSCD

以N-异丙基丙烯酰胺(NIPAM)和丙烯酸(AA)为pH敏感单体,合成聚(N-异丙基丙烯酰胺-co-丙烯酸),并以此作为模板制备了pH敏感的聚(N-异丙基丙烯酰胺-co-丙烯酸)银纳米团簇。结合了时间分辨荧光、透射电镜(TEM)、红外光谱(FT-IR)方法,对团簇的光学性能进行了研究。团簇的荧光对不同的pH具有灵敏的响应。团簇的荧光强度与pH在4.95~11.02的范围内呈线性关系,高pH(11.02)与低pH(4.95)相比,荧光强度降低约62.4%。同时,305 nm与453 nm处荧光激发强度的比值(I;/I;)与pH在5.94~11.02的宽范围内成线性关系,利用该荧光比率可以对pH进行定量检测。     

A mitochondria-targeted fluorescent probe for ratiometric detection of hypochlorite in living cells

A new fl uorescent probe 1 was designed for mitochondrial localization and ratiometric detection of hypochlorite in living cells. It is noteworthy that a high Pearson’s co-localization coeffi cient (Rr) we have obtained was calculated to be 0.97.     

A new prodrug-derived ratiometric fluorescent probe for hypoxia: high selectivity of nitroreductase and imaging in tumor cell

Based on the hypoxia prodrug moiety of p-nitrobenzyl, a selective ratiometric fluorescent sensor (RHP) for the detection of microenvironment hypoxia was designed and synthesized. RHP can be selectively activated by bioreductive enzymes (NTR) and results in an evident blue to green fluorescent emission wavelength change in both solution phases and in cell lines, which might be the first fluorescent ratiometric probe for hypoxia in solid tumors.     

A ratiometric merocyanine-based fluorescent probe for detecting hydrazine in living cells and zebra fish

We developed a merocyanine-based fluorescent probe,NEPB,for tracing hydrazine(N_2 H_4) in a ratiometric manner with large Stokes shifts and long emission wavelength.The fluorescence color of probe NEPB changed from green to yellow upon addition of hydrazine.Probe NEPB displayed high selectivity and sensitivity to hydrazine in solution,and could ratiometrically monitor N_2 H_4 in living cells and zebrafish with low cytotoxicity.