Pertraction of cadmium and zinc ions using a supported liquid membrane impregnated with different carriers

An experimental study on the removal of Cd²⁺ and Zn²⁺ through a supported liquid membrane using a mixture of mono-(2-etylhexyl) ester of phosphoric acid (M2EHPA) and bis-(2-etylhexyl) ester of phosphoric acid (D2EHPA) as carriers is presented. Parameters affecting the Cd²⁺ and Zn²⁺ pertraction such as feed concentration, carrier concentration, pH of the stripping phase, and TBP (tributyl phosphate) concentration were analyzed using the Taguchi method. Optimal experimental conditions for Cd²⁺ and Zn²⁺ pertraction were obtained using the analysis of variance (ANOVA) after a 6 h separation with the initial feed concentration of 8.9 × 10^?4 mol L^?1, carrier concentration of 20 vol. %, TBP concentration of 4 vol. %, and pH of 0.5. Then, under optimum conditions, a comparison of M2EHPA, D2EHPA, and bis-(2,4,4-trimethylpentyl)monothiophosphinic acid (Cyanex 302) was performed. Effective pertraction of Cd²⁺ and Zn²⁺ using these carriers was observed in the following order: mixture of M2EHPA and D2EHPA, D2EHPA, Cyanex 302. It was also found that the presence of one metal ion in the feed solution reduces the pertraction rate of the other one.     

speciation of Cadmium(II) Using Donnan Dialysis and Differential-Pulse Anodic Stripping Voltammetry in a Flow-Injection System

Abstract

A flow-injection/Donnan dialysis/differential pulse anodic stripping voltammetry system was developed for the determination of free cadmium concentrations, [Cd²⁺], in solutions containing organically complexed Cd(II). A small dialysis cell with a strong cation-exchange membrane separating the sample and the receiver channels, was equilibrated in a flow-injection system. The ionic strength of sample and receiver solutions was 0.1 M, with NaNO₃ as the bulk electrolyte. By determining a constant fraction of the Cd²⁺ associated with the membrane phase, [Cd²⁺] of the samples could be measured.

Experimentally determined [Cd²⁺] corresponded well with those calculated, using tabulated stability constants, when citric acid, nitrilotriacetic acid, and oxalic acid were added as ligands. Thus, negatively charged and uncharged complexes were excluded from the membrane. Using the experimental design presented, [Cd²⁺]>5 × 10^×8 M could be determined, but there is a great potential for increasing the sensitivity of the method.

In solutions containing 1.0 μM Cd(II) and 200 mg fulvic acid/l, the inorganic fraction (Cd²⁺ CdNO₃ ⁺ decreased from 57% to 10% when the pH increased from 4.04 to 5.51. In a soil solution from an orthic podzol, having a high concentration of dissolved organic carbon (22.4 mM), the inorganic fraction constituted 53% of the total Cd(II) concentration.     

Accurately measuring respiratory activity of single living cells by scanning electrochemical microscopy

Scanning electrochemical microscopy (SECM) is a powerful tool to examine the respiratory activity of living cells. However, in SECM measurements of cell respiratory activity, the signal recorded usually also includes the signal corresponding to the cell topography. Therefore, measurements of cell respiratory activity using conventional SECM techniques are not accurate. In the present work, we develop a method for accurate measurement of the respiratory activity of single living cells using SECM. First, cells are immobilized on a glass substrate modified with collagen. Then, a Pt ultramicroelectrode tip of SECM held at −0.50 V is scanned along the central line across a living cell and a SECM scan curve, i.e., the relationship of the tip current versus the displacement (the first scan curve) is recorded with a negative peak. The peak current i_p on this first scan curve is composed of i_p1, which corresponds to the cell respiratory activity and i_p2, which corresponds to the cell topography. In order to isolate the i_p2 component, the cell is killed by exposing it to 1.0 × 10⁻³ mol/L KCN for 10 min. The tip is then scanned again with the same trace over the dead cell, and a second SECM scan curve is recorded. Noting that the topography of the dead cell is the same as that of the living cell, this second scan curve with a negative peak corresponds now only to the cell topography. Thus, i_p2 is obtained from the second SECM scan curve. Finally, i_p1 corresponding to the respiratory activity of the living cell can be accurately calculated using i_p1 = i_p − i_p2. This method can be used to monitor real-time change in the respiratory activity of single cells after exposing them to KBr, NaN₃ and KCN.     

Metal Ions as Activators of Hypoxia Inducible Factor

Activation of antihypoxic program under the action of a number of transition and heavy metals has been studied using cell-based HIF1 ODD-luc and HRE-luc reporters. It has been demonstrated that Au³⁺, Pb²⁺, Sn²⁺, Hg²⁺ are weak HIF1 ODD-luc activators, likely reflecting their weak competition for the ironbinding site in the active center of HIF prolyl hydroxylase. Metals capable of replacing iron–Mn²⁺, Zn²⁺, Cu²⁺ и Ni²⁺–activate at high submillimolar concentrations, which indicates low permeability of the cell membrane for transition metals. The highest activation is observed for Co²⁺ and Cd²⁺, however, Cd²⁺ is highly toxic even at 10 μM, in contrast to Co²⁺, which activates both reporters without toxicity signs up to 25 μM for 24 h. A significant activation by Co²⁺ is observed already in low micromolar range of concentrations, which can be recommended for use in hypoxia mimicking.     

A Naphthalimide‐Based Cd2+ Fluorescent Probe with Carbamoylmethyl Groups Working as Chelators and PET‐Promoters under Neutral Conditions

We have developed a novel naphthalimide‐based Cd²⁺ fluorescent probe ( 1 ), featuring almost no background response, high sensitivity and selectivity toward Cd²⁺ through its high association constant [K=(2.10±0.423)×10⁶], and a practical working pH range. Membrane‐permeability was conferred on 1 by replacing the imide and amide substituents with n‐butyl groups, and hence the derivative ( 4 ) has found practical utility on fluorescent imaging of Cd²⁺ in HeLa cells. Comparison of fluorescent properties between various compounds derived from 1 has demonstrated that the carbamoylmethyl groups in 1 function not only as Cd²⁺ chelators but also as promoters for photoinduced electron transfer (PET) by lowering the basicity of the two tertiary amino groups. As a result, 1 and 4 exhibited highly practical performance as Cd²⁺ probes under neutral conditions.     

Filming a live cell by scanning electrochemical microscopy: label-free imaging of the dynamic morphology in real time

ABSTRACT: The morphology of a live cell reflects the organization of the cytoskeleton and the healthy status of the cell. We established a label-free platform for monitoring the changing morphology of live cells in real time based on scanning electrochemical microscopy (SECM). The dynamic morphology of a live human bladder cancer cell (T24) was revealed by time-lapse SECM with dissolved oxygen in the medium solution as the redox mediator. Detailed local movements of cell membrane were presented by time-lapse cross section lines extracted from time-lapse SECM. Vivid dynamic morphology is presented by a movie made of time-lapse SECM images. The morphological change of the T24 cell by non-physiological temperature is in consistence with the morphological feature of early apoptosis. To obtain dynamic cellular morphology with other methods is difficult. The non-invasive nature of SECM combined with high resolution realized filming the movements of live cells.     

Proangiogenic cells enhanced persistent and physiologic neovascularization compared with macrophages

Proangiogenic cells (PACs) display surface markers and secrete angiogenic factors similar to those used by myelomonocytic cells, but, unlike myelomonocytic cells, PACs enhance neovascularization activity in experimental ischemic diseases. This study was performed to reveal the differential neovascularization activities of PACs compared with those of myelomonocytic cells. We cultured PACs and CD14⁺-derived macrophages (Macs) for 7 days. Most of the surface markers and cytokines in the two cell types were alike; the exceptions were KDR, β8 integrin, interleukin-8 and monocyte chemotactic protein-1. Unlike Macs, PACs significantly enhanced mesenchymal stem cell (MSC) transmigration. PACs and Macs increased neovascularization activity in an in vitro co-culture of human umbilical vein endothelial cells and MSCs and in an in vivo cotransplantation in Matrigel. However, the use of Macs resulted in inappropriately dilated and leaky vessels, whereas the use of PACs did not. We induced critical hindlimb ischemia in nude mice, and then transplanted PACs, Macs or vehicle into the mice. We obtained laser Doppler perfusion images weekly. At 2 weeks, mice treated with PACs showed significantly enhanced perfusion recovery in contrast to those treated with Macs. After day 7, when cells were depleted using a suicidal gene, viral thymidine kinase, to induce apoptosis of the cells in vivo by ganciclovir administration, we found that the improved perfusion was significantly abrogated in the PAC-treated group, whereas perfusion was not changed in the Mac-treated group. PACs caused an increase in healthy new vessels in in vitro and in vivo models of angiogenesis and enhanced long-term functional neovascularization activity in the hindlimb ischemia model, whereas Macs did not. Nevertheless, the angiogenic potential and long-term functional results for a specific cell type should be validated to confirm effectiveness and safety of the cell type for use in therapeutic angiogenesis procedures.     

Interfering influence of silver on the voltammetric behaviour of Cd2+ and Zn2+ ions on hmde in supporting electrolytes containing nitrates

A new kind of secondarily formed peaks was found in cyclic and stripping voltammetry in neutral sulphate, perchlorate and nitrate supporting electrolytes containing some divalent cations and a substance (for example O₂), the reduction of which gives as a by-product OH^? ions. The hydroxides deposited in the vicinity of the mercury electrode, in the course of a cathodic scan, react during the anodic scan according to the reaction Hg+Me(OH)₂=Hg(OH)₂+Me²⁺+2e forming a new, separate anodic peak.It was found that silver exerts a catalytic effect on the reduction of NO₃^? ions on the mercury electrode. In neutral nitrate supporting electrolyte containing Ag⁺ ions the hydroxides of some cations (Cd²⁺, Zn²⁺, Mn²⁺, Co²⁺ and Ni²⁺) were deposited during the cathodic scan or during the preelectrolysis. Afterwards, in the course of the anodic scan, a new peak, of the kind described above, was observed. The same effect was formerly interpreted, for Zn²⁺ and Cd²⁺, as evidence for the formation of intermetallic compounds, AgZn and AgCd.     

Gamma irradiation-induced Cd2+ and Pb2+ removal from different kinds of water

Gamma irradiation-induced removal of cadmium ion (Cd²⁺) and lead ion (Pb²⁺) in different kinds of water was investigated. It is observed that solution pH, dissolved oxygen (DO) concentration, sodium carbonate and EDTA played an important effect on Cd²⁺ and Pb²⁺ removal. Low solution pH, low DO concentration and sodium carbonate were favorable for removal of Cd²⁺ and Pb²⁺ by reducing species, while the presence of EDTA in solution restrained Cd²⁺ and Pb²⁺ reduction. Pb²⁺ removal percentage was higher compared to that of Cd²⁺ at the same experimental conditions. Cd²⁺ and Pb²⁺ removal under different conditions was well described by the pseudo-first-order kinetics model. Cd²⁺ and Pb²⁺ removal in different water followed an increasing order: water inflow<surface water<effluent<ground water. In addition, gamma irradiation resulted in a slight decrease in pH and TOC values of water inflow of municipal sewage treatment plant.     

A Highly Selective Two‐Photon Fluorescent Probe for Detection of Cadmium(II) Based on Intramolecular Electron Transfer and its Imaging in Living Cells

A new quinoline‐based probe was designed that shows one‐photon ratiometric and two‐photon off–on changes upon detecting Cd²⁺. It exhibits fluorescence emission at 407 nm originating from quinoline groups in Tris‐HCl (25 mM , pH 7.40), H₂O/EtOH (8:2, v/v). Coordination with Cd²⁺ causes quenching of the emission at 407 nm and simultaneously yields a remarkable redshift of the emission maximum to 500 nm with an isoemissive point at 439 nm owing to an intramolecular charge‐transfer mechanism. Thus, dual‐emission ratiometric measurement with a large redshift (Δλ=93 nm) and significant changes in the ratio (F₅₀₀/F₄₃₉) of the emission intensity (R/R₀ up to 27) is established. Moreover, the sensor H₂L displays excellent selectivity response, high sensitive fluorescence enhancement, and strong binding ability to Cd²⁺. Coordination properties of H₂L towards Cd²⁺ were fully investigated by absorption/fluorescence spectroscopy, which indicated the formation of a 2:1 H₂L/Cd²⁺ complex. All complexes were characterized by X‐ray crystallography, and TD‐DFT calculations were performed to understand the origin of optical selectivity shown by H₂L. Two‐photon fluorescence microscopy experiments have demonstrated that H₂L could be used in live cells for the detection of Cd²⁺.     

Simultaneous Titration of Ternary Mixtures of Pb(II), Cd(II) and Cu(II) with Potentiometric Electronic Tongue Detection

An automatic titration method is reported to resolve ternary mixtures of transition metals (Pb²⁺, Cd²⁺ and Cu²⁺) employing electronic tongue detection and a reduced number of pre‐defined additions of EDTA titrant. Sensors used were PVC membrane selective electrodes with generic response to heavy‐metals, plus an artificial neural network response model. Detection limits obtained were ca. 1 mg L^?1 for the three target ions and reproducibilities 3.0 % for Pb²⁺, 4.1 % for Cd²⁺ and 5.2 % for Cu²⁺. The system was applied to contaminated soil samples and high accuracy was obtained for the determination of Pb²⁺. In the determination Cd²⁺ and Cu²⁺, sample matrix showed a significant effect.     

A Selective,Nontoxic, OFF–ON Fluorescent Molecular Sensor Based on 8‐Hydroxyquinoline for Probing Cd2+ in Living Cells

In spite of the fact that cadmium(II) has been recognized as a highly toxic element and that excessive exposure to this metal ion has been reported to have many adverse effects on human health, very few selective and specific fluorescent probes are available for imaging Cd²⁺ in living cells. Herein, we report the spectroscopic and photochemical characterization of 5‐(5‐chloro‐8‐hydroxyquinolinylmethyl)‐2,8‐dithia‐5‐aza‐2,6‐pyridinophane ( L ) as a fluorescent sensor for the selective imaging of Cd²⁺ in living cells. In particular, the response of L to Cd²⁺ was first assessed in aqueous solutions, sodium dodecyl sulfate micelles, and liposomes, and subsequently in living cells by fluorescence microscopy techniques. Cytofluorimetric analyses of leukemic HL‐60 cells loaded with L also allowed evaluation of the toxicity of the probe and the selective analysis of its intracellular fluorescence in the presence of Cd²⁺. Furthermore, the 1:1 complex species [Cd( L )H₂O]²⁺ responsible for the OFF–ON chelation enhancement of fluorescence (CHEF) effect on L was structurally characterized; time‐dependent DFT calculations allowed the prediction of theoretical excitations, which were comparable with the experimental ones.     

The effect of tourmaline on cell membrane of nitrosomonas europaea and biodegradation of micropollutant

As a kind of ammonia‐oxidizing bacteria, Nitrosomonas europaea (N. europaea) was chosen as a research model to study the alteration of cell membrane in the presence of tourmaline and biodegradation of acetochlor. atomic force microscopy images reveal that the presence of tourmaline substantially changes the structure of the outer membrane of the cell responsible for the cell permeability. SEM images show that the introduction of tourmaline makes the cell lose its ability to resist lysozyme owing to the damages. The fluorescence polarization has shown a significant decrease in membrane fluidity and the increase of permeability of cell membrane. Ca²⁺ and Mg²⁺ was measured using inductively coupled plasma mass spectrometry and was found in the supernatant from the cells treated by tourmaline. Tourmaline can improve the efficiency of biodegradation of acetochlor for N. europaea. It is proposed that the cell permeability is slightly increased, and the absorbability of nutrition from the medium becomes easier. As a result, N. europaea grows faster in the presence of tourmaline than the native cells. Copyright © 2014 John Wiley & Sons, Ltd.     

基于苯并噻唑Zn2+荧光探针及其细胞造影应用

设计合成基于苯并噻唑Zn²⁺荧光增强型探针BHP,在HEPES缓冲液中测其对Zn²⁺识别性能。实验结果表明,BHP对Zn²⁺有较高的选择性,对其他金属离子如Cd²⁺,Fe²⁺,Ni²⁺,Pb²⁺,Hg²⁺,Al³⁺,Mn²⁺,Ag⁺,Cu²⁺,Co²⁺,Na⁺,K⁺,Mg²⁺和Ca²⁺无明显荧光增强响应。BHP与Zn²⁺按1：1计量比配位,在生理条件下荧光强度不受pH值影响。在HeLa细胞中对Zn²⁺的造影表明BHP可用于生物体Zn²⁺检测。     

Proanthocyanin-Capped Biogenic TiO2 Nanoparticles with Enhanced Penetration,Antibacterial and ROS Mediated Inhibition of Bacteria Proliferation and Biofilm Formation: A Comparative Approach

Biofunctionalized TiO₂ nanoparticles with a size range of 18.42±1.3 nm were synthesized in a single-step approach employing Grape seed extract (GSE) proanthocyanin (PAC) polyphenols. The effect of PACs rich GSE corona was examined with respect to 1) the stability and dispersity of as-synthesized GSE-TiO₂-NPs, 2) their antiproliferative and antibiofilm efficacy, and 3) their propensity for internalization and reactive oxygen species (ROS) generation in urinary tract infections (UTIs) causing Gram-negative Pseudomonas aeruginosa and Gram-positive Staphylococcus saprophyticus strains. State-of-the-art techniques were used to validate GSE-TiO₂-NPs formation. Comparative Fourier transformed infrared (FTIR) spectral analysis demonstrated that PACs linked functional -OH groups likely play a central role in Ti⁴⁺ reduction and nucleation to GSE-TiO₂-NPs, while forming a thin, soft corona around nascent NPs to attribute significantly enhanced stability and dispersity. Transmission electron microscopic (TEM) and inductively coupled plasma mass-spectroscopy (ICP-MS) analyses confirmed there was significantly (p<0.05) enhanced intracellular uptake of GSE-TiO₂-NPs in both Gram-negative and -positive test uropathogens as compared to bare TiO₂-NPs. Correspondingly, compared to bare NPs, GSE-TiO₂-NPs induced intracellular ROS formation that corresponded well with dose-dependent inhibitory patterns of cell proliferation and biofilm formation in both the tested strains. Overall, this study demonstrates that -OH rich PACs of GSE corona on biogenic TiO₂-NPs maximized the functional stability, dispersity and propensity of penetration into planktonic cells and biofilm matrices. Such unique merits warrant the use of GSE-TiO₂-NPs as a novel, functionally stable and efficient antibacterial nano-formulation to combat the menace of UTIs in clinical settings.     

Voltammetric determination of facilitated ion transfer across the water/1,2-dichloroethane interface

The facilitated transfer characteristics of Cd²⁺ ion by 4-morpholinoacetophenone-4-ethyl-3-thiosemicarbazone (MAPET) across water/1,2-dicholoroethane (1,2-DCE) interface and its electrochemical properties were investigated by voltammetric measurements. Cyclic voltammetry (CV) was employed to examine the transfer in the conditions of the ligand (organic phase) in excess and the obtained transfer peaks have reversible nature at different metal concentrations and scan rates. The dependence of the obtained half-wave transfer potential on MAPET concentration showed that the equilibrium is effectively displaced towards a 1: 3 (Cd²⁺: ligand) stoichiometry with an association constant of logβ ₃ ⁰ = 12.96 ± 0.09 for the Cd²⁺ ion, corresponding to the TIC/TID mechanism.     

Quinoline-based highly selective and sensitive fluorescent probe specific for Cd2+ detection in mixed aqueous media

Quinoline-based fluorescent probe as a recognition unit was designed and synthesized in this study. The probe R1 displayed excellent selectivity and sensitivity for cadmium ions (Cd²⁺) over a wide range of metal ions in acetonitrile-water (MeCN-H₂O) mixed solution. In order to better understand the recognition mechanism between probe and Cd²⁺, the density functional theory calculations were performed. Finally, the colorimetric experiment result was observed and conveniently monitored by the naked eye, and a visual detection limit of 4 × 10^?6 mol L^?1 was achieved. These experimental results indicated the promising potential of the probe to detect Cd²⁺ in biological system. Furthermore, the probe R1 was successfully used for the highly sensitive detection of Cd²⁺ in living cells.     

Two‐Photon Probes for Zn2+ Ions with Various Dissociation Constants. Detection of Zn2+ Ions in Live Cells and Tissues by Two‐Photon Microscopy

A series of Zn²⁺‐selective two‐photon fluorescent probes (AZnM1−AZnN) that had a wide range of dissociation constants (K_d^TP=8 nm‐ 12 μM ) were synthesized. These probes showed appreciable water solubility (>3 μM ), cell permeability, high photostability, pH insensitivity at pH>7, significant two‐photon action cross‐sections (86–110 GM) upon complexation with Zn²⁺, and can detect the Zn²⁺ ions in HeLa cells and in living tissue slices of rat hippocampal at a depth of >80 μm without mistargeting and photobleaching problems. These probes can potentially find application in the detection of various amounts of Zn²⁺ ions in live cells and intact tissues.     

Light-regulated permeability of rhodopsin-phospholipid membrane vesicles.

Abstract—Light absorption by rhodopsin in receptor cell membranes initiates the excitation of the receptor cell. Rhodopsin-phospholipid membrane vesicles were studied to localize initial transduction events. Rhodopsin-phospholipid recombinant membranes are thermally stable and light sensitive and may be chemically regenerated after bleaching in the same manner as receptor cell membranes. Rhodopsin-containing vesicles prepared from unsaturated phosphatidylcholine (PCho) or PCho and phosphatidylethanolaminc display kinetics for the metarhodopsin I to II transition which are comparable to those of receptor cell membranes. NMR spectroscopy was used to examine the permeability of the membrane vesicles to added shift (Eu³⁺) or relaxation reagents (Mn²⁺, Co²⁺). Unexposed rhodopsin-phospholipid vesicles are sealed to ion movement and become permeable after light exposure. Selected ions (Ca²⁺, Mn²⁺, Co²⁺) may be photoreleased from the interior of loaded membrane vesicles. The quantity released is proportional to the initial ionic concentration. The number of ions released/rhodopsin bleached is dependent on the light intensity, and high yields (40–160) of Ca²⁺/rhodopsin bleached are observed at low levels of light bleaching. The present results indicate that rhodopsin spans the phospholipid bilayer membrane, and are consistent with an increase in the permeability of the membrane initiated by light excitation of rhodopsin.     

New acridine derivatives bearing immobilized azacrown or azathiacrown ligand as fluorescent chemosensors for Hg and Cd

Two new acridine derivatives bearing azacrown or azathiacrown ligand were synthesized as fluorescent chemosensors for Hg²⁺ and Cd²⁺ in aqueous solution. Compounds 1 and 2 displayed selective CHEF (chelation enhanced fluorescence) effects with Hg²⁺ or Cd²⁺ among the metal ions examined. The practical use of these probes was demonstrated by their applications to the detection of Hg²⁺ and Cd²⁺ ions in mammalian cells.