Development of ratiometric fluorescent probe for zinc ion based on indole fluorophore

A water-soluble ratiometric fluorescent probe ZID-1 has been developed on the basis of an internal charge transfer (ICT) mechanism. Upon complexation with Zn²⁺ under physiological conditions, ZID-1 exhibits a significant blue shift of 77 nm in the emission spectrum. The fluorescent behavior of ZID-1 suggests that the pyridyl group incorporated into the fluorophore coordinates the metal ion as the fourth ligand and affords an appropriate binding affinity (K_d = 17.1 nM) for the intracellular imaging of Zn²⁺.     

A sensitive and selective ratiometric near IR fluorescent probe for zinc ions based on the distyryl-bodipy fluorophore

A novel distyryl-substituted boradiazaindacene (bodipy) dye with an emission peak moving hypsochromically from 730 to 680 nm on Zn(II) ion binding seems to be promising as one of the very few water-soluble fluorescent chemosensors emitting in the near IR region.     

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 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.     

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.     

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 ratiometric fluorescent probe with high sensitivity and selectivity for phosgene sensing in solution and gas

Phosgene has attracted wide attention because of its important applications and value in modern industry, agriculture, and other fields, though it easily leaks and is difficult to detect. In this work, we designed and synthesized a naphthalimide-based fluorescent probe, which is easy to prepare, stable, and able to discriminate between phosgene, acetyl chloride, oxalyl chloride, thionyl chloride, phosphorus oxychloride, and tosyl chloride. Our results indicate that the probe can react with phosgene selectively and sensitively, showing remarkable ratiometric fluorescence changes. Furthermore, the probe can be made into test strips, which can determine phosgene in air effectively. The present work provides a novel class of naphthalimide-based derivatives with potential application in phosgene sensing in real time simply and safely with further optimization.     

A ratiometric and exclusively selective Cu fluorescent probe based on internal charge transfer (ICT)

A new ratiometric and exclusively selective fluorescent probe N-butyl-4,5-di[N-(phenyl)-2-(amino)-acetamino]-1,8-naphthalimide (1) was designed and synthesized on the basis of the mechanism of internal charge transfer (ICT). The probe 1 showed exclusively selectivity for Cu^II in the presence of a variety of other metal ions in aqueous ethanol solutions and the binding mode of probe 1 with Cu^II was 1:1 metal-ligand complex. Fluorescent emission spectra of probe 1 in the presence of Cu^II showed a 50 nm blue shift, which is from 521 nm to 471 nm. Furthermore, probe 1 shows the same fluorescent change with the Cu^II in living cells.     

Quantum dot-based "turn-on" fluorescent probe for detection of zinc and cadmium ions in aqueous media

Health or environmental issue caused by abnormal level of metal ions like Zn²⁺ or Cd²⁺ is a worldwide concern. Developing an inexpensive and facile detection method for Zn²⁺ and Cd²⁺ is in urgent demand. Due to their super optical properties, fluorescent quantum dots (QDs) have been developed as a promising alternative for organic dyes in fluorescence analysis. In this study, a CdTe QDs-based sensitive and selective probe for Zn²⁺ and Cd²⁺ in aqueous media was reported. The proposed probe worked in fluorescence “turn-on” mode. The initial bright fluorescence of CdTe QDs was effectively quenched by sulfur anions (S²⁻). The presence of Zn²⁺ (or Cd²⁺) can “turn-on” the weak fluorescence of QDs quenched by S²⁻ due to the formation of ZnS (or CdS) passivation shell. Under optimal conditions, a good linear relationship between the fluorescence response and concentration of Zn²⁺ (or Cd²⁺) could be obtained in the range from 1.6 to 35 μM (1.3–25 μM for Cd²⁺). The limit of detection (LOD) for Zn²⁺ and Cd²⁺ were found to be 1.2 and 0.5 μM, respectively. Furthermore, the present probe exhibited a high selectivity for Zn²⁺ and Cd²⁺ over other metal ions and was successfully used in the detection of Zn²⁺ or Cd²⁺ in real water samples.     

A new quinoline-based chemosensor in ratiometric sensing of Hg2+ ions

A new quinoline-based chemosensor 1 has been designed and synthesised. Its metal ion-binding properties have been documented in organic and aqueous organic solvents. While chemosensor 1 recognises Hg²⁺ ions (K _a = 2.15 × 10⁴ M^? 1) by exhibiting ratiometric change in emission in CHCl₃/CH₃OH (1:1, v/v), under similar condition both Zn²⁺ and Cd²⁺ ions are sensed by significant non-ratiometric increase in emission with measurable red shift. In DMSO/H₂O (5:95, v/v), the sensor 1 exhibits a greater selectivity towards Hg²⁺ ions (K _a = 9.20 × 10³ M^? 1) over the other metal ions examined.     

Design of OFF/ON fluorescent thiol probes based on coumarin fluorophore

This paper presents a series of first-and second-generation click-modified coumarin-based fluorescent probes for thiols.These molecules demonstrate high turn-on fluorescent response and good selectivity towards aromatic thiols over other relevant reactive sulfur species,reactive oxygen species and common nucleophiles.Moreover,probe 1a can detect thiols in the reduced rabbit plasma sample.Therefore,this approach provides a particularly impressive tool for detecting thiol in biological systems.     

A highly selective fluorescent probe for Hg based on a rhodamine-coumarin conjugate

A fluorescent probe 1 for Hg²⁺ based on a rhodamine-coumarin conjugate was designed and synthesized. Probe 1 exhibits high sensitivity and selectivity for sensing Hg²⁺, and about a 24-fold increase in fluorescence emission intensity is observed upon binding excess Hg²⁺ in 50% water/ethanol buffered at pH 7.24. The fluorescence response to Hg²⁺ is attributed to the 1:1 complex formation between probe 1 and Hg²⁺, which has been utilized as the basis for the selective detection of Hg²⁺. Besides, probe 1 was also found to show a reversible dual chromo- and fluorogenic response toward Hg²⁺ likely due to the chelation-induced ring opening of rhodamine spirolactam. The analytical performance characteristics of the proposed Hg²⁺-sensitive probe were investigated. The linear response range covers a concentration range of Hg²⁺ from 8.0 × 10⁻⁸ to 1.0 × 10⁻⁵ mol L⁻¹ and the detection limit is 4.0 × 10⁻⁸ mol L⁻¹. The determination of Hg²⁺ in both tap and river water samples displays satisfactory results.     

A ratiometric fluorescent probe for cyanide based on FRET

On the basis of FRET from 4-(N,N-dimethylamino)benzamide to fluorescein, a new ratiometric fluorescence probe bearing a hydrazone binding unit was developed for highly selective and sensitive detection of CN(-) in aqueous solution.     

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 novel design method of ratiometric fluorescent probes based on fluorescence resonance energy transfer switching by spectral overlap integral

A ratiometric measurement, namely, simultaneous recording of the fluorescence intensities at two wavelengths and calculation of their ratio, allows greater precision than measurements at a single wavelength, and is suitable for cellular imaging studies. Here we describe a novel method of designing probes for ratiometric measurement of hydrolytic enzyme activity based on switching of fluorescence resonance energy transfer (FRET). This method employs fluorescent probes with a 3'-O,6'-O-protected fluorescein acceptor linked to a coumarin donor through a linker moiety. As there is no spectral overlap integral between the coumarin emission and fluorescein absorption, the fluorescein moiety cannot accept the excitation energy of the donor moiety and the donor fluorescence can be observed. After cleavage of the protective groups by hydrolytic enzymes, the fluorescein moiety shows a strong absorption in the coumarin emission region, and then acceptor fluorescence due to FRET is observed. Based on this mechanism, we have developed novel ratiometric fluorescent probes (1-3) for protein tyrosine phosphatase (PTP) activity. They exhibit a large shift in their emission wavelength after reaction with PTPs. The fluorescence quenching problem that usually occurs with FRET probes is overcome by using the coumarin-cyclohexane-fluorescein FRET cassette moiety, in which close contact of the two dyes is hindered. After study of their chemical and kinetic properties, we have concluded that compounds 1 and 2 bearing a rigid cyclohexane linker are practically useful for the ratiometric measurement of PTPs activity. The design concept described in this paper, using FRET switching by spectral overlap integral and a rigid link that prevents close contact of the two dyes, should also be applicable to other hydrolytic enzymes by introducing other appropriate enzyme-cleavable groups into the fluorescein acceptor.     

A fluorescent probe for zinc ions based on N-methyltetraphenylporphine with high selectivity

N-methyl-alpha,beta,gamma,delta-tetraphenylporphine (NMTPPH) has been used to detect trace amount of zinc ions in ethanol-water solution by fluorescence spectroscopy. The fluorescent probe undergoes a fluorescent emission intensity enhancement upon binding to zinc ions in EtOH/H(2)O (1:1, v/v) solution. The fluorescence enhancement of NMTPPH is attributed to the 1:1 complex formation between NMTPPH and Zn(II) which has been utilized as the basis for the selective detection of Zn(II). The linear response range covers a concentration range of Zn(II) from 5.0x10(-7) to 1.0x10(-5)mol/L and the detection limit is 1.5x10(-7)mol/L. The fluorescent probe exhibits high selectivity over other common metal ions except for Cu(II).