Development of a fluorescence-based sensor for rapid diagnosis of cyanide exposure

Can the cyanide metabolite, 2-aminothiazoline-4-carboxylic acid, be used for forensic verification of cyanide poisoning?

PURPOSE

Forensic verification of cyanide (CN) poisoning by direct CN analysis in postmortem blood is challenging due to instability of CN in biological samples. CN metabolites, thiocyanate (SCN-) and 2-aminothiazoline-4-carboxylic acid (ATCA), have been proposed as more stable biomarkers, yet it is unclear if either is appropriate for this purpose. In this study, we evaluated the behavior of CN biomarkers in postmortem swine and postmortem blood to determine which serves as the best biomarker of CN exposure.

METHODS

CN, SCN-, and ATCA were measured in postmortem swine (N = 8) stored at 4 °C and postmortem blood stored at 25 °C (room temperature, RT) and 37 °C (typical human body temperature, HBT).

RESULTS

Following CN poisoning, the concentration of each CN biomarker increased well above the baseline. In postmortem swine, CN concentrations declined rapidly (t1/2 = 34.3 h) versus SCN- (t1/2 = 359 h, 15 days) and ATCA (t1/2 = 544 h, 23 days). CN instability in postmortem blood increased at RT (t1/2 = 10.7 h) and HBT (t1/2 = 6.6 h). SCN- and ATCA were more stable than CN at all storage conditions. In postmortem swine, the t1/2s of SCN- and ATCA were 15 and 23 days, respectively. While both the t1/2s of SCN- and ATCA were relatively lengthy, endogenous levels of SCN- were much more variable than ATCA.

CONCLUSION

While there are still questions to be answered, ATCA was the most adept forensic marker of CN poisoning (i.e., ATCA produced the longest half-life, the largest increase above baseline levels, and most stable background concentrations).

Brilliant quantum dots' photoluminescence from a dual-resonance plasmonic grating

Semiconductor quantum dots (QDs) have recently caused a stir as a promising and powerful lighting material applied in real-time fluorescence detection, display, and imaging. Photonic nanostructures are well suited for enhancing photoluminescence (PL) due to their ability to tailor the electromagnetic field, which raises both radiative and nonradiative decay rate of QDs nearby. However, several proposed structures with a complicated manufacturing process or low PL enhancement hinder their application and commercialization. Here, we present two kinds of dual-resonance gratings to effectively improve PL enhancement and propose a facile fabrication method based on holographic lithography. A maximum of 220-fold PL enhancement from CdSe/CdS/ZnS QDs are realized on 1D Al-coated photoresist (PR) gratings, where dual resonance bands are excited to simultaneously overlap the absorption and emission bands of QDs, much larger than those of some reported structures. Giant PL enhancement realized by cost-effective method further suggests the potential of better developing the nanostructure to QD-based optical and optoelectronic devices.

Selective and Effective Sensing of Cyanide Ion with no Interference in Water by Phenothiazine-indolium Fused Optical Sensor

The sensor with electron donor phenothiazine-2-carbaldehyde and electron acceptor indolium carboxylic acid, is developed with an intramolecular charge transfer transition between them. The synthesized molecule senses cyanide ion in water. The cyanide ion reacts with the molecule via nucleophilic addition in the indolium ring with a noticeable purple to colorless change in the solution observed. Also with the cyanide ion interaction, the sensor exhibits change in UV-visible absorption and fluorescence spectra. While the other ion does not show spectral and visual changes when interacts with the sensor molecule. Also the interference study reveals that the molecule is highly selective towards cyanide ion. Different source of water samples confirms the CN- ion sensing efficiency of the molecule. 1:1 interaction between the molecule PTI and cyanide ion is confirmed from the results of Jobs plot, 1H NMR and HRMS. Paper strips were prepared and this can act as a simple tool to sense cyanide ion in various water samples.

Fluorescence-based ratiometric sensors as emerging tools for CN- detection: Chemical structures, sensing mechanisms and applications

Hazardous cyanide anions (CN-) are increasingly threatening the environment and human health due to their widespread use in industry and many other fields. Over the past three decades, a large number of probes have been reported to sensitively and selectively detect this toxic anion, while a rather limited number of ratiometric fluorescent probes have been developed. The ratiometric probes have significant potential in bio-imaging and biomedical applications because of the ability to detect CN- in a quick, convenient and affordable way. In this review, we introduce 42 ratiometric fluorescent probes reported in the past 6 years (2018-2023) for CN- detection. Our description includes the chemical structures, photo-physical properties, CN- sensing mechanisms, solution color changes, limits of detection (LODs) and/or various applications of these chemical probes. This review provides guidelines for design and development of a new ratiometric probe for effective CN- detection.

Spectral and theoretical analysis of derivatives of 1,2,3,3-tetramethyl-3H-indolium iodide (TMI), a highly selective derivatization reagent of cyanide, and their utility for the analysis of cyanide concentrations in beverages

We develop a specific derivatization gas chromatography-mass spectrometry (GC-MS) method for cyanide using 1,2,3,3-tetramethyl-3H-indium iodide as the derivatization reagent. The derivative compounds were synthesized and characterized using 1H nuclear magnetic resonance (NMR), 13C NMR, and Fourier transform infrared (FT-IR) spectroscopy. The high selectivity of this derivatization for cyanide is supported by calculations and activation energy comparisons. We applied this method to pure water, green tea, orange juice, coffee cafe au lait, and milk. Derivatization was performed by diluting 20 μL of sample solution with 0.1 M NaOH and adding 100 μL of saturated borax solution and 100 μL of 8 mM TMI solution, each drink was completed in 5 min at room temperature, and selected ion (m/z = 200) monitoring analysis was linear (R2 > 0.998) at 0.15 to 15 μM, with detection limits of 4-11 μM were shown. This method is expected to be widely used in forensic toxicology analysis and can be applied to beverages, which are forensically important field samples.

Bioimaging and detecting endogenous and exogenous cyanide in foods, living cells and mice based on a turn-on mitochondria-targeted fluorescent probe

A novel fluorescent probe, with advanced features including "turn-on" fluorescence response, high sensitivity, good compatibility, and mitochondria-targeting function, has been synthesized based on structural design for detecting and visualizing cyanide in foods and biological systems. An electron-donating triphenylamine group (TPA) was employed as the fluorescent and an electron-accepting 4-methyl-N-methyl-pyridinium iodide (Py) moiety was used as a mitochondria-targeted localization unit, which formed intramolecular charge transfer (ICT) system. The "turn-on" fluorescence response of the probe (TPA-BTD-Py, TBP) toward cyanide is attributed two reasons, one is the insertion of an electron-deficient benzothiadiazole (BTD) group into the conjugated system between TPA and Py, and the other is the inhibition of ICT induced by the nucleophilic addition of CN^-. Two active sites for reacting with CN^- were involved in TBP molecule and high response sensitivity were observed in tetrahydrofuran solvent containing 3 % H₂O. The response time could be reduced to 150 s, the linear range was 0.25-50 μM, and the limit of detection was 0.046 μM for CN^- analysis. The TBP probe was successfully applied to the detection of cyanide in food samples prepared in aqueous solution, including the sprouting potato, bitter almond, cassava, and apple seeds. Furthermore, TBP exhibited low cytotoxicity, clear mitochondria-localizing capability in HeLa cells and excellent fluorescence imaging of exogenous and endogenous CN^- in living PC12 cells. Moreover, exogenous CN^- with intraperitoneal injection in nude mice could be well monitored visually by the "turn-on" fluorescence. Therefore, the strategy based on structural design provided good prospects for optimizing fluorescent probes.

Development of AIEE active fluorescent and colorimetric probe for the solid, solution, and vapor phase detection of cyanide: smartphone and food applications

Apart from environmental implications, the extreme toxicity of cyanide can lead to sudden human death upon prolonged exposure to it. Hence, rapid and low-level on-site detection of cyanide has earned paramount significance in the present era. Therefore, an AIEE active and piezofluorochromic Schiff base (probe 2) was synthesized which exhibited highly selective fluorescence enhancement based nanoscale (LOD; 6.17 nM) detection of CN^-. The interaction mode was attributed to the deprotonation of the probe by the cyanide that was confirmed through ¹H NMR titration, pH, theoretical studies, and switchable fluorescence response upon the addition of HCl. Advantageously, probe 2 displayed solid and vapor phase recognition of cyanide which is the first of its kind as far as we know. The excellent sensing potential of the probe was satisfactorily applied for the detection of cyanide in food, natural soil, and industrial wastewater. Additionally, probe 2 showed an immediate colorimetric response towards cyanide which was favorably integrated through a smartphone. Finally, the switchable fluorescence response of the probe was used to design an INHIBIT logic gate. Therefore, the multifunctional probe 2 displayed excellent practical potential for cyanide detection which was the ultimate goal of our work.

Benzoindoxazine derivatives containing carbazole for detection of CN- and its application in plant seed extracts and cell imaging

Cyanide (CN^-) is a highly toxic compound that exists in many substances and is harmful to the environment and human health. Therefore, it is of great significance to develop excellent CN^- ion probes, especially solvent-induced on-off fluorescent probes. Based on the condensation reaction of indolo[2,1-b][1,3]oxazine molecules with aldehydes, probes (E)-13a-(2-(9-ethyl-9H-carbazol-3-yl)vinyl)-14,14-dimethyl-10-nitro-13a,14-dihydro-8H-benzo[e]benzo[5,6][1,3]oxazino[3,2-a]indole (NCO) and (E)-13a-(2-(9-benzyl-9H-carbazol-3-yl)vinyl)-14,14-dimethyl-10-nitro-13a,14-dihydro-8H-benzo[e]benzo[5,6][1,3]oxazino[3,2-a]indole (NBO) were synthesized to detect CN^-. Compared with other cyanogen ion probes, NCO and NBO have special carbazole ring structures and large conjugate systems. When CN^- is added to the probe-detection solution, color changes that are visible to the naked eye can occur. The UV-vis spectrum test using differential spectroscopy shows that the probe (i) has excellent solvent-induced switching characteristics and stability (CH₃OH-H₂O) and (ii) high selectivity, anti-interference ability, and sensitivity for the detection of CN^-. The fluorescence limit of detections (LODs) are 1.05 µM for NCO and 1.34 µM for NBO. The UV LODs are 0.83 µM for NCO and 0.87 µM for NBO. Fluorescence spectroscopy shows that the probe has remarkable fluorescence properties. Fluorescence titration experiments, liver cancer cell (Hep G2) imaging, and cytotoxicity experiments all show that the probes have high biocompatibility, low toxicity, high cell permeability, and high sensitivity for the detection of CN^- in cells. In addition, NCO and NBO have been successfully used for the detection of cyanogenic glycosides in the seeds of ginkgo, crabapple, apple, and cherry. Test strips were fabricated to detect CN^-. After adding CN^-, the color of the test strip changed significantly-from brown to light yellow; thus, the test strips have a high application value in the fields of drug quality control, drug safety testing, and pharmacological research.

Cyanine-based Fluorescent Probe for Cyanide Ion Detection

Cyanine-based probe-possessing indolium iodide and indole unit were synthesized in two-step with easy available raw material: a potential probe for the cyanide ion detection. The detecting ability of the probe was investigated and confirmed by a visual and instrumental approach. A noticeable color change from orange to colorless obtained only for cyanide ions and other added ions does not impart any changes visually and through UV and Fluorescence technique. To confirm the mechanism of sensing 1H-NMR recorded. From the result, the peak belonging to N-methyl displayed an upfield shift from 4.01 δ ppm to 2.74 δ ppm due to the disappearance of indolium iodide ion and the olefin protons peaks were shifted from 7.19 to 6.17 and 8.70 to 7.20 δ ppm confirms the nucleophilic addition of cyanide ion to the probe. Test kit from filter paper prepared for the real-time monitoring cyanide ion. The prepared strip is effective in detecting cyanide ion with a visual color change.

A new chemosensor for cyanide in blood based on the Pd complex of 2-(5-bromo-2-pyridylazo)-5-[N-n-propyl-N-(3-sulfopropyl)amino]phenol

A new indirect chemosensor for the detection of cyanide in blood is developed. 2-(5-Bromo-2-pyridylazo)-5-[N-n-propyl-N-(3-sulfopropyl)amino]phenol, a yellow dye, forms a blue-coloured complex with palladium ions. The yellow colour of this complex is regained upon reaction with cyanide ions. The complex shows high selectivity for the detection of cyanide over 16 other anions. The system was applied to two different methods for the detection of cyanide in human whole blood. As a quantitative absorbance method, blood samples were mixed with acid, and the resulting vaporised hydrogen cyanide was absorbed in an alkaline solution containing the complex in a Conway cell. The resulting absorbance response of the solution at 450 nm is linear over the range 4-40 μM (R2 = 1.000), and the limit of detection is 0.6 μM. Furthermore, the complex-soaked paper is applicable as a test strip for cyanide detection. When a test strip is used with 0.5 mL of blood, the limit of detection is 15 μM. The detection limits of these two methods are below the toxic blood cyanide concentration (19 μM). Therefore, both methods allow the quantification and screening of cyanide in blood samples. Furthermore, the test strip is low cost and enables on-site analysis.

Excited State Intramolecular Proton Transfer (ESIPT)-Based Sensor for Ion Detection

C-2 and C-5 substituted imidazole skeleton was synthesized through a one-pot two-step strategy. Synthesized molecule emits the light on ESIPT (excited-state intramolecular proton transfer). This molecule was utilized for its proton donor ability, and we have observed that fluoride and cyanide ions can be detected selectively. Different cations and anions were selected to observe the response of the synthesized molecule. However, there were not any fluorometric and colorimetric response except for fluoride and cyanide ions. Detection limits of fluoride and cyanide ions were found to be 9.22 μM and 11.48 μM, respectively. ¹H-NMR spectra for the solution of the sensor and TBAF (tetrabuthylammoniumfluoride) were used for the identification of [L]^-[HF₂]^- species. 3 equiv. TBAF saturated the solution of the sensor in d₆-DMSO, and some of the proton resonances shifted to upfield due to the through-bond effect. The disappearance of NH proton with 0.5 equiv. TBAF or TBACN (tetrabuthylammoniumcyanide) showed that there was a proton abstraction by fluoride and cyanide ions, instead of the hydrogen bond. Solid-state application was utilized, and paper test strips were applied. Emission differences emerged when the sensor loaded strips were reacted with TBAF. Time resolved experiments revealed that solution of the sensor and TBAF in DMSO have multiexponential decay, and one of the lifetime was measured as 13.4 ns.

Rational Design of an ICT-Based Chemodosimeter with Aggregation-Induced Emission for Colorimetric and Ratiometric Fluorescent Detection of Cyanide in a Wide pH Range

An alkoxy-substituted 1,3-indanedione-based chemodosimeter 1 with an aggregation-induced emission (AIE) characteristic was rationally designed and synthesized for the ultrasensitive and selective sensing of cyanide in a wide pH range of 3.0-12.0. The nucleophilic addition of cyanide to the β-conjugated carbon of the 1,3-indanedione group obstructs intramolecular charge transfer (ICT) and causes a significant change in the absorption and fluorescence spectra, enabling colorimetric and ratiometric fluorescent detection of cyanide in a 90% aqueous solution. The cyanide-sensing mechanism is supported by single-crystal X-ray diffraction analysis, time-dependent density functional theory (TD-DFT) calculations, and 1H NMR titration experiments. Sensor 1 exhibits strong yellow fluorescence in the solid state due to the AIE effect, and the paper probes containing 1 can be conveniently used to sense cyanide by the naked eye. Furthermore, chemodosimeter 1 was successfully used for sensing cyanide in real environmental water samples.

Fluorous and Fluorogenic Derivatization for Selective Liquid Chromatographic Analysis of Cyanide in Human Plasma

A liquid chromatographic (LC) method with fluorous derivatization for the determination of cyanide in human plasma is described. In this method, the cyanide was transformed to a fluorous and fluorogenic compound by derivatizing with 2,3-naphthalenedialdehyde and perfluoroalkylamine reagent under mild reaction conditions (a reaction time of 5 min at room temperature). The obtained derivative was successfully retained on the perfluoroalkyl-modified LC column with the use of a high concentration of organic solvent in the mobile phase, whereas non-fluorous derivative was hardly retained, followed by fluorometric detection at excitation and emission wavelengths of 420 and 490 nm, respectively. Under the optimized conditions, the limit of detection and the limit of quantification for cyanide in a 5-μL injection volume were 1.3 μg/L (S/N = 3) and 4.4 μg/L (S/N = 10), respectively. The recovery from spiked human plasma was achieved in the range of 54 - 90% within a relative standard deviation of 3.5%. The feasibility of this method was further evaluated by applying it to the analysis of human plasma samples.

One-Step Assembly of Fluorescence-Based Cyanide Sensors from Inexpensive, Off-The-Shelf Materials

We report a simple and versatile approach to assemble sensitive and selective fluorescence “turn-on” sensors for cyanide by combining three off-the-shelf materials; namely fluorescent dye, 1-vinyl imidazole polymer, and cupric chloride. The cyanide-sensing species is a non-fluorescent fluorophore-polymer-Cu²⁺ complex; which forms as a result of the imidazole polymer’s ability to bind both fluorophore and fluorescence quencher (Cu²⁺). Cyanide removes Cu²⁺ from these complexes; thereby “turning-on” sensor fluorescence. These sensors are water-soluble and have a detection limit of ~2.5 μM (CN⁻) in water. Our ternary complex-based sensing approach also enables facile emission tuning; we demonstrate the convenient, synthesis-free preparation of blue and green-emitting sensors using distyrylbiphenyl and fluorescein fluorophores, respectively. Furthermore; these ternary complexes are easily immobilized using agarose to create cyanide-sensing hydrogels; which are then used in a simple; novel microdiffusion apparatus to achieve interference-free cyanide analysis of aqueous media. The present study provides an inexpensive approach for portable; interference-free cyanide detection.

Ratiometric and sensitive cyanide sensing using dual-emissive gold nanoclusters

The detection of cyanide anion (CN^-), a highly toxic pollutant, has attracted growing attention in the past years. In this work, a nanosensor composed of hyperbranched polyethyleneimine (hPEI)-assisted dual-emissive gold nanoclusters (DE-Au NCs) is proposed for ratiometric detection of CN^- based on surface valence state-driving etch. The ratiometric color change of fluorescence is based on a fact that the red-emissive Au NCs with a high content of surface Au(I) can be easily etched by CN^-, while the blue-emissive Au NCs with nearly neutral character can resist CN^-. Because of the specific gold-CN^- chemistry and electrostatic attraction between the positively charged hPEI protecting layer and the negatively charged CN^-, the DE-Au NC-based nanosensor provides high selectivity toward CN^- over other anions with a limit of detection of 10 nM. Practical application of the proposed DE-Au NC nanosensor is verified by satisfying recoveries of CN^- determination in river water and urine samples. Graphical abstract.

Assembling PVP-Au NPs as portable chip for sensitive detection of cyanide with surface-enhanced Raman spectroscopy

Cyanide (C≡N) can lead to blood, cardiovascular system, and nervous system disorders owing to the acute and chronic toxicity; thus, aiming at the group or individual poisoning incidents, it is necessary to develop the sensitive and credible method for rapid on-site detection of poisons cyanide. Surface-enhanced Raman spectroscopy (SERS) with the advantages of providing fingerprint information of target molecules and single-molecules sensitivity has been widely used in on-site analysis; however, the SERS measurements always suffer from the problem of the stability of substrates. Here, the polyvinylpyrrolidone (PVP)-stabilized Au NPs (PVP-Au NPs) have been assembled through the simple, convenient evaporation-induced strategy with the large-scale hotspots substrates. The presence of PVP can not only facilitate the assembly of Au NPs but also prevent the corrosion of CN^- towards the Au NPs with the formation of [Au (CN)₂]^-1, providing high stable and reproducible SERS signals. Moreover, the PVP-Au NPs have been assembled on the Si wafer to fabricate the portable SERS chip for rapid on-site detection of CN^- with an RSD of 5.8% and limitation of 100 ppb. Furthermore, by coupling a portable Raman spectrometer, the SERS spectra of CN^- spiked into different specimens to simulate the poison samples have been collected and analyzed on SERS chips with the recovery of 89-103% and RSD not higher than 11.3%. Consequently, the fabricated SERS chip with assembled PVP-Au NPs can provide sensitive and credible detection for CN^- in different specimens, and then would satisfy the rapid on-site evaluation of CN^- in poisoning incidents with the portable Raman spectrometer. Graphical Abstract.

Diagnosis of cyanide poisoning using an automated, field-portable sensor for rapid analysis of blood cyanide concentrations

Cyanide (both HCN and CN^- are represented by CN) has multiple industrial applications, is commonly found in some foods, and is a component of fire smoke. Upon exposure, CN blocks production of adenosine triphosphate, causing cellular hypoxia and cytotoxic anoxia, which can eventually result in death. Considering CN's quick onset of action and the long analysis times associated with current techniques, the objective of this study was to develop and validate a rapid and field-portable sensor to detect blood CN concentrations focusing on both concentration and diagnostic accuracy. The sensor takes advantage of the chemical properties of CN by converting it exclusively to HCN via acidification of whole blood. High-speed headspace transfer is used to deliver HCN to a capture solution where it is reacted with naphthalene dialdehyde and taurine to produce a fluorescent β-isoindole product. Simple spectrofluorometric analysis of the product provides quantitative analysis of CN from whole blood in 60 s and requires only 25 μL of blood (obtainable via fingerstick). A limit of detection of 5 μM, a linear range of 10-200 μM (with ≥15 μM considered CN exposed), and excellent accuracy (100 ± 15%) and precision (≤15.2% relative standard deviation) were obtained. To evaluate the diagnostic accuracy of the sensor, rabbit blood samples (N = 190, including 24 blinded samples) were analyzed by both the sensor and a lab-based spectrophotometric method. An excellent positive correlation was obtained between the sensor and the lab-based method (R² ˃ 0.995) confirming the concentration accuracy of the CN sensor. Moreover, the sensor produced no false positives or negatives when diagnosing CN poisoning.

Tri-(2-picolyl)amine-modificated triarylborane: Synthesis, photophysical properties and distinguish for cyanide and fluoride anions in aqueous solution

We designed and synthesized a tri-(2-picolyl) amine (TPA) functionalized triarylborane, 1-(6-(4-(dimesitylboryl)phenyl)pyridin-2-yl)-N,N-bis(pyridin-2-ylmethyl)methanamine (PB2). The photophysical properties of PB2 were thoroughly explored. Moreover, PB2 can capture CN^- and F^- in aqueous solution through strong chelation induced by the synergy of a boron atom and metal ion gripped by TPA to display entirely different fluorogenic responses such as fluorescence enhancement for CN^- and fluorescence quenching for F^-. The results of TOF-MS-EI analysis and theoretical calculations indicate that the complexing of PB2 with CN^- formed a 2-to-2 adduct with a stabilized configuration, resulting in strong emission. The complexing of PB2 with F^- formed a 1-to-1 adduct with a loose configuration, resulting in weak emission. In pure water, the detection limit of PB2 for CN^- is 0.79 μM, and in H₂O/THF (1:9 v/v) system, the detection limits of PB2 for CN^- and F^- can reach 0.39 and 2.12 μM, respectively, indicating its potential application for effective detection and discrimination of CN^- and F^-.

Determination of Cyanide in Water and Food Samples Using an Efficient Naphthalene-Based Ratiometric Fluorescent Probe

Monitoring cyanide levels in water and food samples is crucial. Herein, we rationally developed a simple and efficient fluorescent probe for cyanide determination. The probe displayed selective ratiometric fluorescent response to cyanide. In addition, after treatment with cyanide, the fluorescence ratios (I ₅₀₉/I ₄₆₆) exhibited a good linearity with cyanide concentration in the range of 0-60 μM, and the detection limit was determined to be 0.23 μM (S/N = 3). Significantly, the practical application demonstrated that the probe was able to quantitatively detect cyanide concentration in natural water samples. Monitoring of endogenous cyanide in cherry nut by the probe was also successfully conducted. Notably, upon fabrication of test strips, the probe could be conveniently utilized for field measurement of cyanide in bitter almond without relying on sophistical instruments. Furthermore, the cyanide in potato tissues was determined for the first time by means of fluorescence imaging.

A novel near-infrared ratiometric fluorescent probe for cyanide and its bioimaging applications

A new near-infrared ratiometric type fluorescent probe was prepared. 3-formyl BODIPY derivatives without substituent group in the 2, 6-position was obtained through DDQ oxidation reaction. Furthermore, it reacted with indole salt to produce probe. This probe bears indolium group as the recognition site and the 3-formyl-BODIPY as fluorophore. The specific detection of cyanide was conducted the nucleophilic attack of cyanide toward the indolium group of the probe, breaking the intramolecular charge transfer (ICT) effect and generating a ratio change in the fluorescence signal. The probe has high selectivity and sensitivity for cyanide. Moreover, cell experiments indicated this probe was benign to HepG-2 cells, and has the potential application in imaging CN^- in living HepG-2 cells.

Fluorescent imidazole-based chemosensors for the reversible detection of cyanide and mercury ions

Imidazole-based conjugate acts as a reversible sensor towards CN⁻ and Hg²⁺ in CH₃CN–H₂O.

A cyanide-triggered hydrogen-bond-breaking deprotonation mechanism: fluorescent detection of cyanide using a thioacetohydrazone-functionalized bispillar[5]arene

Bispillar[5]arene-based fluorescent sensor was used for fluorescent detection of cyanide anions through deprotonation accompanied by intermolecular hydrogen bond breakage.

Dicarbohydrazide based chemosensors for copper and cyanide ions via a displacement approach

Ligands attached to pyridine dicarbohydrazide were synthesized and characterized using NMR, FT-IR, elemental analysis, UV-visible spectroscopy, mass spectrophotometry, emission spectra and single crystal X-ray diffraction, and were assessed for their ability to sense copper and cyanide ions.

Alternate injections coupled with flow-gated capillary electrophoresis for rapid and accurate quantitative analysis of urine samples

Capillary electrophoresis (CE) is a powerful separation technique with advantages over HPLC in terms of separation efficiency, speed, and cost. However, CE suffers in poor reproducibility in quantitative chemical analysis, which is one of major drawbacks preventing its widespread use in routine analytical laboratories. Here we report a novel strategy to enhance the quantitative capability of flow-gated CE. The platform integrated dual flow branches to respectively supply a sample and its standard additions that were then alternately injected into a single capillary for rapid separations (typically 20-90 s). A micro-fabricated switch was used to enable the alternate injections. It was assumed that the analytical system maintained constant conditions during neighboring injections that served as external self-standards for quantitation. This strategy was expected to reduce uncertainties caused by the fluctuation in capillary conditions and the drift of detection systems. Experimental results demonstrated that the dual-branch flow-gated CE coupled with alternate injections significantly improved the reproducibility with respect to peak height ratios under deliberate variations in injection volumes, separation voltages, optical focusing, and laser power; and thus the interday precision was ensured. To demonstrate its applicability, cyanide and amino acids in human urine were quantified rapidly with the one-point standard addition method after fluorogenic derivatization with naphthalene-2,3-dicarboxaldehyde (NDA), and the measurement accuracy was validated by determining the recovery of standard cyanide added to a urinary matrix. This strategy would be valuable to enable the quantitative capability of flow-gated CE in the measurements of a broad range of analytes, especially those lacking suited internal standards.

A benzopyrylium–phenothiazine conjugate of a flavylium derivative as a fluorescent chemosensor for cyanide in aqueous media and its bioimaging

A new benzopyrylium–phenothizine conjugate (BP) has been synthesized for CN⁻sensing.

Multifunctional Polymer Ligand Interface CdZnSeS/ZnS Quantum Dot/Cy3-Labeled Protein Pairs as Sensitive FRET Sensors

High-quality CdZnSeS/ZnS alloyed core/thick-shell quantum dots (QDs) as energy donors were first exploited in Förster resonance energy transfer (FRET) applications. A highly efficient ligand-exchange method was used to prepare low toxicity, high quantum yield, stabile, and biocompatible CdZnSeS/ZnS QDs densely capped with multifunctional polymer ligands containing dihydrolipoic acid (DHLA). The resulting QDs can be applied to construct QDs-based Förster resonance energy transfer (FRET) systems by their high affinity interaction with dye cyanine 3 (Cy3)-labeled human serum albumin (HSA). This QD-based FRET protein complex can serve as a sensitive sensor for probing the interaction of clofazimine with proteins using fluorescence spectroscopic techniques. The ability of FRET imaging both in vitro and in vivo not only reveals that the current FRET system can remain intact for 2 h but also confirms the potential of the FRET system to act as a nanocarrier for intracellular protein delivery or to serve as an imaging probe for cancer diagnosis.

Several hemicyanine dyes as fluorescence chemosensors for cyanide anions

Four hemicyanine dyes as chemosensors for cyanide anions were synthesized easily. Their photophysical properties and recognition properties for cyanide anions were investigated. The results indicate that all the dyes can recognize cyanide anions with obvious color, absorption and fluorescence change. The recognition mechanism analysis basing on in situ (1)H NMR and Job plot data indicates that to the compounds with hydroxyl group, the recognition mechanism is intramolecular hydrogen bonding interaction. However, to the compounds without hydroxyl group, cyanide anion is bonded to carbon-carbon double bond in conjugated bridge and induces N(+)CH3 to neutral NCH3. Fluorescence of the compounds is almost quenched upon the addition of cyanide anions.

Detection of cyanide by a novel probe with a V-shaped structure based on aggregation of the probe adduct

A novel V-shaped probe is reported with extremely rapid response, high selectivity and very low detection limit to cyanide anions in aqueous solution based on the intensely emissive aggregates of the probe adduct.

A colorimetric and ratiometric fluorescent probe for the selective detection of cyanide anions in aqueous media and living cells

Based on the internal charge transfer (ICT) mechanism, a novel colorimetric and ratiometric fluorescent probe was developed for highly selective and sensitive detection of cyanide ion in aqueous media.

Lighting up the gold nanoparticles quenched fluorescence by silver nanoparticles: a separation distance study

Fluorescence intensity of a pre-quenched fluorophore was enhanced by over 100-fold through plasmon coupling interactions, even brighter than unquenched ones.

A direct and rapid method to determine cyanide in urine by capillary electrophoresis

Cyanides are poisonous chemicals that widely exist in nature and industrial processes as well as accidental fires. Rapid and accurate determination of cyanide exposure would facilitate forensic investigation, medical diagnosis, and chronic cyanide monitoring. Here, a rapid and direct method was developed for the determination of cyanide ions in urinary samples. This technique was based on an integrated capillary electrophoresis system coupled with laser-induced fluorescence (LIF) detection. Cyanide ions were derivatized with naphthalene-2,3-dicarboxaldehyde (NDA) and a primary amine (glycine) for LIF detection. Three separate reagents, NDA, glycine, and cyanide sample, were mixed online, which secured uniform conditions between samples for cyanide derivatization and reduced the risk of precipitation formation of mixtures. Conditions were optimized; the derivatization was completed in 2-4min, and the separation was observed in 25s. The limit of detection (LOD) was 4.0nM at 3-fold signal-to-noise ratio for standard cyanide in buffer. The cyanide levels in urine samples from smokers and non-smokers were determined by using the method of standard addition, which demonstrated significant difference of cyanide levels in urinary samples from the two groups of people. The developed method was rapid and accurate, and is anticipated to be applicable to cyanide detection in waste water with appropriate modification.