A novel ratiometric sensor for the fast detection of palladium species with large red-shift and high resolution both in aqueous solution and solid state

A highly selective fluorescent probe (OHBT) was designed and synthesized by linking the ESIPT fluorophore N-(3-(benzo[d]thiazol-2-yl)-4-(hydroxyphenyl) benzamide) (HBTBC) to the palladium specificity response group, allyl group, for the detection of palladium species in aqueous solution. The allyl group can be hydrolyzed by Pd⁰ species through the Pd⁰-catalyzed Tsuji–Trost reaction and thus release the fluorophore HBTBC, which shows two emission bands. The maximum emission spectra originated from the enol and keto forms at 415 and 555 nm respectively and with no overlap, which implies the high resolution of the palladium detection. The palladium species can also be detected by paper strip because of the solid-state fluorescence of probe HOBT catalyzed by palladium. This method was successfully applied in the palladium related Suzuki–Miyaura coupling reaction and the detection limit is lower than 1 μM.     

Ratiometric electrochemical detection of Pd•••π interactions: application towards electrochemical molecular logic gates

Abstract

The widespread and large scale use of platinum group metals, especially palladium, in a wide variety of industrial applications has seen their levels in wastewater streams, roadside dust and even pharmaceuticals significantly rise over recent years. Due to the possible environmental damage and potential health risk this may cause, there is now substantial demand for inexpensive, efficient and robust methods for the detection of palladium. Based upon self-immolative linker technologies, we have designed and synthesised a number of allyl ether-functionalised electrochemical probes to determine the optimum probe structure required to deliver a ratiometric electrochemical detection method capable of achieving a limit of detection of <1 mg/mL within 20 min through the use of disposable screen-printed carbon electrodes. Combined with an enzymatic assay, this method was then used to achieve a proof-of-principle ratiometric electrochemical molecular logic gate.     

Colorimetric and ratiometric fluorescent detection of bisulfite by a new HBT-hemicyanine hybrid

A novel HBT-hemicyanine hybrid was prepared. This hybrid not only displays a large red-shifted (Δλ = 125 nm) emission compared to the well known ESIPT dye HBT, but also can be used as a new probe for rapid, colorimetric and ratiometric fluorescent detection of bisulfite with high selectivity and sensitivity in aqueous solution. The detection limit of this probe for HSO₃⁻ was calculated to be about 56 nM with a linear range of 0–25 μM. The potential application of this probe was exampled by detection of bisulfite in real food samples and living cells. Overall, this work not only provided a new ratiometric sensing platform, but also provided a new promising colorimetric and ratiometric fluorescent probe for bisulfite.     

A Turn‐On Fluorescent Probe for Highly Selective and Sensitive Detection of Palladium

A novel turn‐on fluorescent probe for the detection of palladium has been designed. The probe can selectively and sensitively detect palladium in solution, and the limit of detection was calculated to be 11.4 nmol·L^?1. Furthermore, the probe was successfully used for fluorescence imaging of palladium in living cells.     

A Water‐Soluble ESIPT Fluorescent Probe with High Quantum Yield and Red Emission for Ratiometric Detection of Inorganic and Organic Palladium

A novel fluorescent probe with a high quantum yield (0.41), large Stokes shifts (255 nm), and red emission (635 nm) was designed to detect all typical oxidation states of palladium species (0, +2, +4) by palladium‐mediated terminal propargyl ethers cleavage reaction in water solution without any organic media. The probe showed a high selectivity and excellent sensitivity for palladium species, with a detection as low as 57 nM (6.2 μg L^?1).     

A colorimetric and ratiometric fluorescent probe for palladium

A colorimetric and ratiometric fluorescent probe for the palladium species has been developed based on the Pd(0)-catalyzed cleavage of an allyoxycarbonyl group of amines under mild conditions. The probe displays a highly sensitive and selective response with significant changes in both color (from colorless to jade-green) and fluorescence (from blue to green), through the ICT process.     

基于缩硫醛脱保护机制的比例计量型Hg~(2+)荧光探针及其斑马鱼活体造影应用

利用汞离子特异性诱导缩硫醛脱保护,引发分子内电荷转移发生改变的机制,设计合成了一种新型的激发型比例计量汞离子荧光探针.该探针在与汞离子结合后其最大激发波长由410 nm红移至485 nm,两个波长下的荧光强比值(F485/F410)由0.06增长至5.02.同时该探针对汞离子表现出了良好的比例计量响应选择性和较快的响应速度,并且检测限低于美国环境保护组织的饮用水标准.共聚焦造影研究发现,该探针可以应用于活细胞及5天龄斑马鱼幼体中的汞离子的检测.利用该性质对Hg2+在斑马鱼体内分布及毒性进行了初步的研究.     

A ratiometric fluorescent probe for thiols based on a tetrakis(4-hydroxyphenyl)porphyrin-coumarin scaffold

In this work, we have designed and synthesized the compound Ratio-HPSSC, based on a tetrakis(4-hydroxyphenyl)porphyrin-coumarin scaffold, as a new ratiometric fluorescent probe for thiols. The ratiometric probe Ratio-HPSSC is highly selective and sensitive to thiols. Importantly, the novel ratiometric probe exhibited a remarkable change in emission color from red to blue. This key feature allows Ratio-HPSSC to be employed for thiol detection by simple visual inspection. Furthermore, we have demonstrated that Ratio-HPSSC is suitable for ratiometric fluorescence imaging of thiols in living cells. We believe that the new ratiometric probe will find interesting applications in chemistry, biology, and medicine.     

A rational approach to emission ratio enhancement of chemodosimeters via regulation of intramolecular charge transfer

The sensitivity as well as dynamic range of a ratiometric probe is determined by the ratio of emission intensities at two wavelengths. Thus, it is highly desirable to acquire a large ratiometric fluorescence response at two wavelengths. However, ratiometric fluorescent signals are intrinsic characteristics of the particular probe-analyte interactions. The design for fluorescent probes with a large ratiometric signal remains a challenging task. There is still a lack of a proper approach to enhance the ratiometric fluorescence response for fluorescent chemodosimeters. Herein, we introduced a novel strategy to increase the emission ratios of a chemodosimeter via modulation of intramolecular charge transfer.     

A nanoparticle-supported fluorescence resonance energy transfer system formed via layer-by-layer approach as a ratiometric sensor for mercury ions in water

This article describes the design and preparation of a novel fluorescence resonance energy transfer (FRET)-based ratiometric sensor with the polymer nanoparticle as scaffold for detecting Hg²⁺ in aqueous media. In this study, a fluorescent dye fluorescein isothiocyanate (FITC, served as the donor) and a spirolactam rhodamine derivative (SRHB, served as mercury ion probe) were covalently attached onto polyethylenimine (PEI) and polyacrylic acid (PAA) respectively; and a ratiometric sensing system was then formed through the deposition of the donor- and probe-containing polyelectrolytes onto the negatively charged polymer particles via the layer-by-layer approach. The ratiometric fluorescent signal change of the system is based on the intra-particle fluorescence resonance energy transfer (FRET) process modulated by mercury ions. Under optimized structural and experimental conditions, the particle-based detection system exhibits stable response for Hg²⁺ in aqueous media. More importantly, in this newly developed particle-based detection system formed by LBL approach, varied numbers of the PAA/PEI layers which served as the spacer could be placed between the donor-containing layer and the probe-containing layer, hence the donor–acceptor distance and energy transfer efficiency could be effectively tuned (from ca. 25% to 76%), this approach has well solved the problem for many particle-based FRET systems that the donor–acceptor distance cannot be precisely controlled. Also, it is found that the ratiometric sensor is applicable in a pH range of 4.6–7.3 in water with the detection limit of 200 nM. This approach may provide a new strategy for ratiometric detection of analytes in some environmental and biological applications.     

Ratiometric fluorescence imaging of cellular glutathione

A fluorescent probe (1) with a hydrogen bond was designed for the detection of GSH. The probe exhibited a rapid and ratiometric fluorescence response to GSH through a Michael reaction and allowed us to obtain clear cellular images for GSH.     

Ratiometric and turn-on monitoring for heavy and transition metal ions in aqueous solution with a fluorescent peptide sensor

A novel fluorescent peptide sensor containing tryptophan (donor) and dansyl fluorophore (acceptor) was synthesized for monitoring heavy and transition metal (HTM) ions on the basis of metal ion binding motif (Cys-X-X-X-Cys). The peptide probe successfully exhibited a turn on and ratiometric response for several heavy metal ions such as Hg²⁺, Cd²⁺, Pb²⁺, Zn²⁺, and Ag⁺ in aqueous solution. The enhancements of emission intensity were achieved in the presence of the HTM ions by fluorescent resonance energy transfer (FRET) and chelation enhanced fluorescence (CHEF) effects. The detection limits of the sensor for Cd²⁺, Pb²⁺, Zn²⁺, and Ag⁺ were lower than the EPA's drinking water maximum contaminant levels (MCL). We described the fluorescent enhancement, binding affinity, and detection limit of the peptide probe for HTM ions.     

Ratiometric fluorescence chemodosimeter for mercuric ions through the Hg(II)-mediated propargyl amide to oxazole transformation

A coumarin-based alkyne was developed as a fluorescent chemodosimeter for the selective detection of mercuric ion. The probe showed a highly selective and ratiometric response toward Hg(II) ion over other metal ions with a micromolar level of limit of detection.     

A colorimetric and ratiometric fluorescent probe for quantification of bovine serum albumin

A 4-aminonaphthalimide-based ratiometric fluorescent probe 1 employing the internal charge transfer (ICT) mechanism was designed and synthesized to detect bovine serum albumin (BSA). The interaction of 1 and BSA was investigated by fluorescence and UV-vis absorption spectroscopy. Upon treatment with BSA, the probe successfully exhibited a ratiometric fluorescent response at 540 nm and 480 nm. The fluorescent intensity ratio at 540 nm and 480 nm (F(540)/F(480)) increases linearly with BSA concentration in the range of 0-75.0 μg mL(-1) and the detection limit was about 2.4 ng mL(-1). Our strategy is expected to provide a methodology to quantify BSA either by a normal or by a ratiometric and colorimetric way with high sensitivity.     

A Single‐Wavelength‐Emitting Ratiometric Probe Based on Phototriggered Fluorescence Switching of Graphene Quantum Dots

Ratiometric fluorescent probes are of great importance in research, because a built‐in correction for environmental effects can be provided to reduce background interference. However, the traditional ratiometric fluorescent probes require two luminescent materials with different emission bands. Herein a novel ratiometric probe based on a single‐wavelength‐emitting material is reported. The probe works by regulating the luminescent property of graphene quantum dots with UV illumination as activator. The ratiometric sensor shows high sensitivity and specificity for iron ions. Moreover, the ratiometric sensor was successfully employed to monitor ferritin levels in Sprague Dawley rats with chemical‐induced acute liver damage. The proposed single‐wavelength ratiometric fluorescent probe may greatly broaden the applicability of ratiometric sensors in diagnostic devices, medical applications, and analytical chemistry.     

Recent Progress of Small-Molecule Ratiometric Fluorescent Probes for Peroxynitrite in Biological Systems

Peroxynitrite (ONOO⁻) as a major reactive oxygen species plays important roles in cellular signal transduction and homeostatic regulation. Precise detection of ONOO⁻ in biological systems is vital for exploring its physiological and pathological function. Among numerous detection methods, fluorescence imaging technology using fluorescent probes offers some advantages, including simple operation, high sensitivity and selectivity, as well as real-time and nondestructive detection. In particular, ratiometric fluorescent probes, in which the built-in calibration of the two emission bands prevents interference from the biological environment, have been extensively employed to monitor the fluctuation of bioactive species. In this review, we will discuss small-molecule ratiometric fluorescent probes for ONOO⁻ in live cells or in vivo, which involves chemical structures, response mechanisms, and biological applications. Moreover, the challenges and future prospects of ONOO⁻-responsive ratiometric fluorescent probe are also proposed.     

Monitoring the pH fluctuation of lysosome under cell stress using a near-infrared ratiometric fluorescent probe

Cell stress responses are associated with numerous diseases including diabetes, neurodegenerative diseases, and cancer. Several events occur under cell stress, in which, are protein expression and organelle-specific pH fluctuation. To understand the lysosomal pH variation under cell stress, a novel NIR ratiometric pH-responsive fluorescent probe (BLT) with lysosomes localization capability was developed. The quinoline ring of BLT combined with hydrogen ion which triggered the rearrangement of π electrons conjugated at low pH medium, meanwhile, the absorption and fluorescent spectra of BLT showed a red-shifts, which gived a ratiometric signal. Moreover, the probe BLT with a suitable pK_a value has the potential to discern changes in lysosomal pH, either induced by heat stress or oxidative stress or acetaminophen-induced (APAP) injury stress. Importantly, this ratiometric fluorescent probe innovatively tracks pH changes in lysosome in APAP-induced liver injury in live cells, mice, and zebrafish. The probe BLT as a novel fluorescent probe possesses important value for exploring lysosomal-associated physiological varieties of drug-induced hepatotoxicity.     

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.     

Rational design of a highly reactive ratiometric fluorescent probe for cyanide

A novel highly reactive ratiometric fluorescent cyanide probe was judiciously designed based on 2-formylacrylonitrile moiety as a new cyanide reaction site. A DFT study was conducted to rationalize the extremely high reactivity nature of the ratiometric fluorescent cyanide probe.     

A ratiometric fluorescent probe for iron(III) and its application for detection of iron(III) in human blood serum

A simple and versatile ratiometric fluorescent Fe³⁺ detecting system, probe 1, was rationally developed based on the Fe³⁺-mediated deprotection of acetal reaction. Notably, this reaction was firstly employed to design fluorescent Fe³⁺ probe. Upon treatment with Fe³⁺, probe 1 showed ratiometric response, with the fluorescence spectra displaying significant red shift (up to 132 nm) and the emission ratio value (I₅₂₂/I₃₉₀) exhibiting approximately 2362-fold enhancement. In addition, the probe is highly sensitive (with the detection limit of 0.12 μM) and highly selective to Fe³⁺ over other biologically relevant metal ions. The sensing reaction product of the probe with Fe³⁺ was confirmed by NMR spectra and mass spectrometry. TD-DFT calculation has demonstrated that the ratiometric response of probe 1 to Fe³⁺ is due to the regulation of intramolecular charge transfer (ICT) efficiency. Moreover, the practical utility in fluorescence detection of Fe³⁺ in human blood serum was also conducted, and probe 1 represents the first ratiometric fluorescent probe that can be used to monitor Fe³⁺ level in human blood serum. Finally, probe 1 was further employed in living cell imaging with pancreatic cancer cells, in which it displayed low cytotoxicity, satisfactory cell permeability, and selective ratiometric response to Fe³⁺.