A TPA-caged precursor of (imino)coumarin for “turn-on” fluorogenic detection of Cu

We strategize to utilize the precursors of (imino)coumarin fluorophores to deliver novel reactive Cu⁺ probes, where tris[(2-pyridyl)-methyl] amine (TPA) works as a reactive receptor towards Cu⁺. To verify this strategy, CP1, a representative probe and relevant sensing behaviors towards Cu⁺ are presented here. CP1 features good solubility and fast response for monitoring labile copper in aqueous solution and live cells. The sensing mechanism of CP1 is determined by HPLC titration and mass spectrometric analysis. The probe CP1 exhibits a 60-fold fluorescence enhancement and a detection limitation of 10.8 nM upon the detection of Cu⁺. CP1 is further applied for imaging labile copper in live cells. This work provides a starting point for future development of Cu⁺ probes, based on in situ formation of (imino)coumarin scaffolds, as well as their further investigations of copper signaling and biological events.     

Label-free sensing of pH and silver nanoparticles using an “OR” logic gate

Many natural phenomena are associated with the presence of two or more separate variables. We report here an “OR” DNA logic gate based on a luminescent platinum(II) switch-on probe for silver nanoparticles and pH, both of which may be considered putative indicators of pollution. The modulation of metal complex/double-stranded DNA complex phosphorescence by Ag⁺ and H⁺ was used to construct a simple, rapid and label-free method for the label-free detection of pH and nanomolar Ag⁺ ions and nanoparticles in aqueous solutions with high selectivity.     

A fluorescent probe based on N-butylbenzene-1,2-diamine for Cu(II) and its imaging in living cells

A fluorescent probe LZ-N with naphthalimide as fluorophore and N-butylbenzene-1,2-diamine as a new recognition moiety for copper ion was designed and synthesized. The probe LZ-N exhibits high selectivity for Cu²⁺ ion in aqueous media (CH₃CN:H₂O = 1:1) over all the other metal ions in our study, more than 20-fold fluorescence enhancement by coordinating with Cu²⁺, and the maximum emission intensity independence in the range of pH 2.06–9.25. The results of ¹H-NMR titration, time-resolved fluorescence decay measurement, and computational optimization illuminate the mechanisms of Cu²⁺ and probe LZ-N. Confocal fluorescence images and cell viability values test show the high fluorescence enhancement of probe LZ-N for exogenous Cu²⁺ in living cells.     

基于香豆素的增强型铜离子荧光探针及其在细胞成像中的应用

以香豆素为荧光团,设计合成了一种反应型铜离子荧光探针Cou-P。Cou-P对Cu~(2+)表现出高选择性、荧光增强性识别。分别用紫外可见光谱、荧光光谱、质谱等方法研究了Cou-P识别Cu~(2+)机理,结果表明Cou-P先形成Cou-P/Cu~(2+)(1∶1)配合物,Cou-P/Cu~(2+)配合物进一步被过量的Cu~(2+)催化水解为3-(carboxylic acid)-7-(diethylamino)-coumarin (Cou-COOH)。另外,Cou-P表现出低细胞毒性、良好的过膜性能,成功地用于MCF-7细胞中Cu~(2+)检测。     

Development of an Efficient Biosensor for the In Vivo Monitoring of Cu+ and pH in the Brain: Rational Design and Synthesis of Recognition Molecules

An efficient biosensor was created for the ratiometric monitoring of Cu⁺ and pH in the brain using both current and potential outputs. A series of N ,N ‐bis(2‐[2‐(ethylthio)ethyl])‐based (NS4s) derivatives was designed for the specific recognition of Cu⁺. After systematically evaluating the electrochemical parameters of Cu⁺ oxidation by tuning alkyl chain length, polyaromatic structure, and substitute group site of NS4, N ,N ‐bis(2‐[2‐(ethylthio)ethyl])‐2‐naphthamide (NS4‐C1) was finally optimized for Cu⁺ detection as it showed the most negative potential and the largest current density. At the same time, 9,10‐anthraquinone was used as a selective pH sensor with 2,2′‐azino‐bis(3‐ethylbenzthiazoline‐6‐sulfonic acid) as an internal reference. This single biosensor with both current and potential signal outputs can simultaneously determine Cu⁺ concentrations from 0.5 to 9.5 μm and pH values ranging from 6.0 to 8.0. The efficient biosensor was applied to the simultaneous detection of Cu⁺ and pH in the live brain. The average levels of Cu⁺ were reported for the first time in the cortex, hippocampus, and striatum in a mouse model of Alzheimer's disease.     

Cuprous complexes and dioxygen. IX. Formation of a unique trimeric species Cu3L and Ligand Oxidation (L  cis,cis-1, 3, 5-cyclohexanetriamine)

The complexation of Cu⁺ by the potentially tripod like ligand cis, cis-1, 3, 5 cyclohexanetriamine (chta) has been studied potentiometrically in aqueous acetonitrile (an). The expected tetracoordinated species Cu (chta) ? (an)⁺ was formed only at rather high pH with log K (Cu (an)⁺ + chta ? Cu (chta) · (an)⁺) = 6.94. Quite unexpectedly the most stable complex in neutral solution was the trimetric species Cu³ (chta) with log K (3 Cu⁺ + 2 chta ? Cu³ (chta)) = 31.75. In addition, the ternary complexes Cu (LH²) · (an)³⁺ and Cu (LH) · (an)²⁺ (L = chta) are formed at low pH. From model considerations, Cu³ (chta) must contain two ligand molecules with all amino groups in equatorial position, linked by three linearly coordinated Cu⁺-ions. Cu₃ (chta)³⁺₂ shows no measurable reactivity towards dioxygen. At pH values above 9, very rapid O₂-uptake due to Cu (chta) · (an)⁺ is observed. In this reaction, Cu⁺-autoxidation is stoichiometrically coupled to ligand oxidation, followed by a much slower Cu-catalyzed secondary reaction of the primary oxidation product of chta. Hydrogen peroxide and likely also superoxide, are involved in the coupled Cu⁺/ligand oxidation.     

Extraction of metal picrates by lipophilic hexamide and hexamine derivatives of azacrown [18]-N6

To determine the metal ion complexing ability of high molecular weight macrocyclic polyamines and polyamides, lipophilic derivatives of azacrown [18]-N₆ (hexacyclen) were prepared. Transition and heavy metal picrates, but not alkali and alkaline earth picrates, were extracted from water into chloroform and transported from water through chloroform into a second water phase by the hexa-4-dodecyloxybenzoyl and hexa-3,4-bis-dodecyloxybenzoyl amide derivatives1 and2 and by the hexa-4-dodecyloxybenzyl amine derivative3 of [18]-N₆ (hexacyclen). The relative amounts of picrates extracted by hexamine3 from a pH 5 aqueous solution were Cu²⁺Ag⁺Pb²⁺> Hg²⁺>Zn²⁺>Co²⁺>Ni²⁺Cd²⁺. Using a pH 7 receiving phase, none of the metal ions were transported rapidly through chloroform, and only Co²⁺, Cu²⁺, and Pb²⁺, were transported rapidly into a pH 11 aqueous phase. The hexamide2, but not hexamide1, extracted significant amounts of the picrates of Cu²⁺, Ag⁺, and Hg²⁺, and transported Cu²⁺ and Ag⁺ but not Hg²⁺.     

Interfacially Super-Assembled Benzimidazole Derivative-Based Mesoporous Silica Nanoprobe for Sensitive Copper (II) Detection and Biosensing in Living Cells

Mesoporous silica nanoparticles (MSNs) functionalized with benzimidazole-derived fluorescent molecules (DHBM) are fabricated via a feasible interfacial superassembly strategy for the highly sensitive and selective detection of Cu²⁺. DHBM-MSN exhibits an obvious quenching effect on Cu²⁺ in aqueous solutions, and the detection limit can be as low as 7.69×10⁻⁸ M. The DHBM-MSN solid-state sensor has good recyclability, and the silica framework can simultaneously improve the photostability of DHBM. Two mesoporous silica nanoparticles with different morphologies were specially designed to verify that nanocarriers with different morphologies do not affect the specific detectionability. The detection mechanism of the fluorescent probe was systematically elucidated by combining experimental results and density function theory calculations. Moreover, the detection system was successfully applied to detect Cu²⁺ in bovine serum, juice, and live cells. These results indicate that the DHBM-MSN fluorescent sensor holds great potential in practical and biomedical applications.     

Concentration and Separation of Ni2+, Cu2+ and Co2+ by Back Extraction Chromatography Using Lix 64N and Cationic Resins

Abstract

This paper describes the method for the concentration of Cu²⁺ by liquid-liquid extraction using Lix 64N solutions in kerosene, followed by back extraction chromatography.

It consists of a pass of the organic phase through columns filled with cationic resins (H⁺) which contains only the water surrounding the grains.

The effect of the pH of the aqueous film surrounding the resin grains on the capacity of Vionit CS-3 (-SO₃H) and Vionit CM-14 (-SH) has been established.

The loading curves of these resins have been drawn, as the optimum pH of the aqueous film and the resin capacities shown to increase in the order -SH < -SO₃H.

The effect of the flow-rate on the loading and the optimum elution conditions have been also determined.

A mechanism for the ion-exchange process is proposed.     

A Novel Naked-Eye and Dual-Channel Responsive Fluorescent Probe for Cu2+ Based on 3,4-Disubstituted-1,8-naphthalimide

A new 3,4-disubstituted-1,8-naphthalimide derivative H1 was designed and synthesized as a selective fluorescent probe for Cu²⁺ over miscellaneous metal ions in aqueous media. Upon mixing with Cu²⁺ in CH₃OH:H₂O (1:1, volume ratio), the increase of fluorescence intensity and a bathochromic shift of absorbance of H1 could be observed with a notable color response (changing from yellow to pink). Furthermore, Cu²⁺ coordinates to the probe H1 and a 1:1 metal-ligand complex was formed.     

Adsorption of heavy metals by layered double hydroxides grown in situ on Al foam

We investigated the adsorption of heavy metal ions on a nanostructured coating of zinc-aluminum layered double hydroxides (Zn-Al LDHs) grown on aluminum foam by one-step hydrothermal process. This approach aimed to increase the interactive surface and provide a more practical medium for removal of toxic heavy metals from aqueous media. The foam coated with LDH was characterized by using scanning electron microscopy and X-ray diffraction. After immersion in a copper-rich water solution, X-ray photoelectron spectroscopy demonstrated the occurrence of adsorbed copper on the LDH-coated foam with two oxidation states: particles of metallic copper Cu⁰ with oxidized surface Cu⁺¹. X-ray diffraction showed the presence of Cu⁺² in the LDH structure.     

A Dinuclear Ruthenium(II) Complex as a One‐ and Two‐Photon Luminescent Probe for Biological Cu2+ Detection

A new dinuclear Ru^II polypyridyl complex, [(bpy)₂Ru(H₂bpip)Ru(bpy)₂]⁴⁺ ( RuH₂bpip , bpy=2,2‐bipyridine, H₂bpip=2,6‐pyridyl(imidazo[4,5‐f][1,10]phenanthroline), was developed to act as a one‐ and two‐photon luminescent probe for biological Cu²⁺ detection. This Ru^II complex shows a significant two‐photon absorption cross section (400 GM) and displays a remarkable one‐ and two‐photon luminescence switch in the presence of Cu²⁺ ions. Importantly, RuH₂bpip can selectively recognise Cu²⁺ in aqueous media in the presence of other abundant cellular cations (such as Na⁺, K⁺, Mg²⁺, and Ca²⁺), trace metal ions in organisms (such as Zn²⁺, Ag⁺, Fe³⁺, Fe²⁺, Ni²⁺, Mn²⁺, and Co²⁺), prevalent toxic metal ions in the environment (such as Cd²⁺, Hg²⁺, and Cr³⁺), and amino acids, with high sensitivity (detection limit≤3.33×10^?8 M ) and a rapid response time (≤15 s). The biological applications of RuH₂bpip were also evaluated and it was found to exhibit low cytotoxicity, good water solubility, and membrane permeability; RuH₂bpip was, therefore, employed as a sensing probe for the detection of Cu²⁺ in living cells and zebrafish.     

Phenoxazine‐based Near‐infrared Fluorescent Probes for the Specific Detection of Copper (II) Ions in Living Cells

Abstract : It is well known that copper ions play a critical role in various physiological processes. However, a variety of human diseases are tightly correlated with copper overload. Although there are numerous fluorescent probes capable of detecting copper ions, most of them are “turn‐off” probes owing to copper (II) ions fluorescence quenching effect, resulting in poor sensitivity. Herein, a novel “turn‐on” near‐infrared (NIR) fluorescent probe PZ‐N based on phenoxazine was designed and synthesized for the selective detection of copper (II) ions (Cu²⁺). Upon the addition of Cu²⁺, the probe could quickly react with Cu²⁺ and emit strong fluorescence, along with colour change from colourless to obvious blue. Moreover, the probe PZ‐N showed good water solubility, high selectivity, and excellent sensitivity with low limit of detection (1.93 nM) towards copper (II) ions. More importantly, PZ‐N was capable of effectively detecting Cu²⁺ in living cells.     

Near-Infrared Fluorimetric Determination of Copper(Ⅱ) Ions Using CdHgTe Nanorods as Probe

Stable water‐soluble CdHgTe nanorods with an emission wavelength at 722 nm, obtained by doping Hg²⁺ into CdTe nanorods, has been used as a near‐infrared region (NIR) probe to investigate their interaction with copper(II) ions. A new fluorimetric method for the determination of copper(II) ions has been developed based on the quenching effect of copper(II) ions on the emission of CdHgTe nanorods. The mechanism studies show that an effective electron transfer from nanorods to the copper(II) ions occurred based on the coordination reaction between copper(II) ions and the carboxyl groups on the nanorods surface, which could be responsible for the emission quenching of CdHgTe nanorods. Under optimum conditions, the linear range of the calibration curve for the determination of Cu²⁺ is from 8.0×10^?9 to 1.0×10^?6 mol/L and the detection limit is 2.0×10^?9 mol/L. Owing to low background interference of NIR measurement, the proposed method displays relative high sensitivity and selectivity. Especially, some physiologically important cations almost do not interfere with the determination of Cu²⁺. The proposed method was also applied to the determination of trace Cu²⁺ in real aqueous samples with satisfactory results.     

Chemical characteristics of the products of the complexation reaction between copper(II) and a tetra-aza macrocycle in the presence of chloride ions

The reaction of copper(II) perchlorate with the hydrochloride salt of 3,6,9,15-tetra-azabicyclo[9.3.1]penta-deca-1,11,13-triene (L1) in acetonitrile forms two macrocyclic complexes that can be characterized: [L1Cu^IICl][ClO₄] (1) and [L1Cu^IICl]₂[CuCl₄] (2). The structural, electronic, and redox properties of these complexes were studied using spectroscopy (EPR and UV–visible) and electrochemistry. In addition, the solid-state structure of 1 was obtained using X-ray diffraction. The copper(II) is five-coordinate ligated by four N-atoms of the macrocycle and a chloride atom. EPR studies of 1 both in DMF and aqueous solution indicate the presence of a single copper(II) species. In contrast, EPR studies of 2 performed in frozen DMF and in the solid-state reveal the presence of two spectroscopically distinct copper(II) complexes assigned as [L1Cu^IICl]⁺ and [Cu^IICl₄]^2?. Lastly, electrochemical studies demonstrate that both [L1Cu^IICl]⁺ and [Cu^IICl₄]^2? are redox active. Specifically, the [L1Cu^IICl]⁺ undergoes a quasi-reversible Cu(II)/(I) redox reaction in the absence of excess chloride. In the presence of chloride, however, the chemical irreversibility of this couple becomes evident at concentrations of chloride that exceed 50 mM. As a result, the presence of chloride from the chemical equilibrium of this latter species impedes the reversibility of the reduction of [L1Cu^IICl]⁺ to [L1Cu^ICl]⁰.     

A Chromo-Fluorogenic Naphthoquinolinedione-Based Probe for Dual Detection of Cu2+ and Its Use for Various Water Samples

The presence of an abnormal amount of Cu²⁺ in the human body causes various health issues. In the current study, we synthesized a new naphthoquinolinedione-based probe (probe 1) to monitor Cu²⁺ in different water systems, such as tap water, lakes, and drain water. Two triazole units were introduced into the probe via a click reaction to increase the binding affinity to a metal ion. In day-light, probe 1 dissolved in a mixed solvent system (HEPES: EtOH = 1:4) showed a vivid color change from light greenish-yellow to pink in the presence of only Cu²⁺ among various metal ions. In addition, the green luminescence and fluorescence emission of the probe were effectively bleached out immediately after Cu²⁺ addition. The limit of detection (LOD) of the probe was 0.5 µM when a ratio-metric method was used for metal ion detection. The fluorescence titration data of the probe with Cu²⁺ showed a calculated LOD of 41.5 pM. Hence, probe 1 possesses the following dual response toward Cu²⁺ detection: color change and fluorescence quenching. Probe 1 was also useful for detecting Cu²⁺ spiked in tap/lake water as well as the cytoplasm of live HeLa cells. The current system was investigated using ultraviolet-visible and fluorescence spectroscopy as well as density functional theory calculations (DFT).     

Fluorometric sensing of Cu ion with smart fluorescence light-up probe, triazolylpyrene (Py)

We report the detection of Cu²⁺ ion with fluorescence light-up probe, triazolylpyrene (^TNDMBPy). Thus, the probe showed a remarkable fluorescence enhancement of both of the monomer and excimer emissions and a 2:1 probe-Cu²⁺ complexation with high selectivity, high stability constant and low detection limit. Formation of the excimer was also rationalized on the basis of DFT calculation. Our probe is also capable of sensing SDS micelle-encapsulated-Cu²⁺ ion in aqueous media with high association constant, thus, showing its practical utility. Thus, our probe could be used as an efficient Cu²⁺ ion selective fluorescence light-up probe, and may find applications in chemical and biological systems.     

A novel BF<Subscript>2</Subscript>–curcumin-based fluorescent chemosensor for detection of Cu<Superscript>2+</Superscript> in aqueous solution and living cells

A novel BF₂–curcumin-based chemosensor 1, namely monopicolinate of BF₂–curcumin complex, was designed, synthesized and applied for the detection of Cu²⁺ in aqueous buffer solution and living cells. Sensor 1 exhibited sensitive naked-eye color change toward Cu²⁺ from blue to pink in TBS solution and the detection limit was estimated to be 0.12 µM. The selectivity of sensor 1 for Cu²⁺ was high over competing metal ions (Ag⁺, Cu⁺, Hg²⁺, Mg²⁺, Ca²⁺, Co²⁺, Zn²⁺, Mn²⁺, Ni²⁺, Fe²⁺ and Fe³⁺). Based on the experimental results, the sensing mechanism was proposed for the Cu²⁺ triggered hydrolysis of 1 to BF₂–curcumin which has unique chromogenic and fluorogenic properties. Compared with other chemosensors with a similar mechanism, chemosensor 1 had a comparatively large Stokes shift and the emission wavelength was close to NIR. Moreover, cell imaging investigations indicated that sensor 1 has the potential to be applied for practical Cu²⁺ detection in biological systems.     

Copper oxide on Cu/Al2O3-TiO2 catalystsTG,FTIR-CO absorption and catalytic activity in the NO reduction by CO

TG, FTIR-(CO absorption), and catalytic activity in the NO reduction by CO were used to characterize Cu/Al₂O₃-TiO₂ catalysts prepared by co-gelling aluminum tri-sec-butoxide and titanium iso-propoxide at pH 9 and at pH 3 gelling conditions. Under nitrogen flow, copper oxide decomposition, oxygen storage capacity (OSC) and sample dehydroxylation (total mass loss) was followed by TG. The CuO decomposition forming Cu⁰, Cu⁺¹ was observed by means of FTIR (CO absorption) spectra. In pH 9 sample the large amount of Cu⁰ was observed. At low total mass loss and high Cu⁰/Cu⁺¹+Cu⁺² ratio (pH 9 sample) a lowest light-off in the NO reduction by CO was observed. This revised version was published online in July 2006 with corrections to the Cover Date.     

Cu2+-selective turn-on fluorescence signaling based on metal-induced hydrolysis of pyrenecarbohydrazide

We developed a simple Cu²⁺-selective turn-on fluorescence signaling probe based on the hydrolysis of 1-pyrenecarbohydrazide (1) to 1-pyrenecarboxylic acid. Probe 1 exhibited prominent fluorescence signaling of Cu²⁺ ions in a 10% aqueous Tris-buffered (pH 7.0) DMSO solution with a detection limit of 5.93 × 10^?8 M. Signaling with control compounds derived from pyreneacetic acid and pyrenebutyric acid showed that the fluorescence signal became less pronounced as the distance between the hydrazide functionality and the pyrene fluorophore increased. As a practical application, this probe was employed for the determination of Cu²⁺ in a simulated semiconductor wastewater.