MRI-based Sensors for In Vivo Imaging of Metal Ions in Biology

Although much is known about the diverse roles of metal ions in biology, most of the acquired knowledge was obtained with fluorescent dyes or electrophysiological approaches. However, the ability to non-invasively monitor variation in metal ions and to assess their physiological distribution in health and disease is very limited. Recent advances in the field of molecular magnetic resonance imaging (MRI) have offered new capabilities through the design and development of MRI-responsive sensors for a wide range of applications, including the ability to sense and spatially map metal ions. Here, we briefly summarize the recent progress in the development and performance of MRI sensors designed to monitor metal ions in biology while emphasizing their in vivo uses, their limitations, and remaining challenges. Among the proposed MRI-sensors, Zn²⁺ and Ca²⁺ responsive agents are those that have already been used in live intact subjects, and therefore, these will be emphasized here.     

Binding of several heavy metal ions by polyaspartyl polymers and their application to some Chinese herbal medicines

Water‐insoluble polyaspartyl polymers were synthesized by using water as medium instead of organic medium. Taking Ca²⁺ as a reference, the binding of several heavy‐metal ions, including Pb²⁺, Cd²⁺, Hg²⁺, Cr³⁺, Cu²⁺, and Mn²⁺, by polyaspartyl polymers was studied. The experimental results revealed that polyaspartate is an excellent binding agent for the investigated heavy‐metal ions. These cation ions were bound to polyaspartate polymer by the same mechanism as Pb²⁺, which can be explained by ion exchange model. Since polyaspartate has a protein‐resembling structure that is sensitive to trace heavy metal, it was used to remove some trace heavy‐metal elements in Chinese herbal medicines. It was found that polyaspartate material was an effective agent for the removal of Pb²⁺, Cd²⁺, and Hg²⁺ ions from glycyrrhizin, angelica, and gynostemma pentaphyllum. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Selectivity of heavy metal ions at acidic supramolecular surfaces

Langmuir monolayers containing surface carboxylic acid head groups were examined in order to characterize their selectivity to metal ion adsorption. Experimental data of ion adsorption obtained by surface isotherms and FTIR spectroscopy were analyzed using a thermodynamic-and-electrochemical model. Among bivalent ions examined (Cr²⁺, Pb²⁺, Cu²⁺, Cd²⁺, Zn²⁺, Ca²⁺, Ni²⁺, and Ba²⁺), Langmuir monolayers showed the highest selectivity to chromium ions. In addition, it was found that adsorption constants of the surface ions are quite different from binding constants of the bulk ions. The results show important implications to sensing and separating metal ions by the use of acidic supramolecular materials.     

Process Design of Groundnut Husk Waste for Pb2+ and Cd2+ Ions Mitigation in Drinking Water Purification

This present work has explored a novel application of modified Arachis hypogaea (groundnut) husk on mitigation of toxic Pb²⁺ and Cd²⁺ ions in aqueous phase. Ecotoxicological assessment of exhausted adsorbent was investigated as per standard OECD guidelines. Standard deviation, correlation coefficient, and the reduced chi square test were evaluated and compared statistically on experimental data. The results showed good sorption capacities—31.62 and 29.78 mg g^?l for Pb²⁺ and Cd²⁺ ions, respectively. Pseudo first-order rate kinetics was well correlated for Pb²⁺ and Cd²⁺ ions sorption over all kinetic models. The sorption data was in good agreement with the Freundlich isotherm for Pb²⁺ and the Sips model for Cd²⁺ ions sorption. The sorption capacity was endothermic in nature. Pb²⁺ ions desorption was three times faster than Cd²⁺ ions. The sorption mechanism was plausibly explained by spectroscopic techniques. Herein, the tailored abundant agro-waste material is a competitive sorbent and may be exploited in decontamination of metal ions in a wide range of concentrations. Supplemental materials are available for this article. Go to the publisher's online edition of Separation Science and Technology to view the free supplemental file.     

The preparation and properties of chelates of transition metal ions with the homopolymer and copolymers of p-vinylbenzoylacetone

p-Vinylbenzoylacetone (VBA) was prepared by the condensation of p-vinylacetophenone and ethyl acetate. This monomer was homopolymerized and copolymerized with acrylamide or maleic anhydride to produce polymers which would chelate substantial amounts of transition metal ions such as Cu²⁺, Ni²⁺, Co²⁺, Eu³⁺, and VO²⁺. In the case of the Cu²⁺ and Ni²⁺ chelates, about 80–90% of the metal ion could be eluted by dilute mineral acids. The resulting eluted products apparently have a somewhat porous structure because they are capable of rechelating these ions from water solution, even though the solid homopolymer which had not been chelated and eluted is too hydrophobic to chelate very much metal ion from water solution. The eluted Cu²⁺ chelate readily reaccepted Cu²⁺ ions from water solution and discriminated against Ni²⁺ almost completely. However, the eluted Ni²⁺ chelate would reaccept both Cu²⁺ and Ni²⁺ ions, but exhibited a strong preference for Cu²⁺ ions in competitive batch experiments. The VO²⁺ chelate was an effective heterogeneous phase catalyst for the epoxidation of allyl alcohols such as geraniol with tert-butylhyroperoxide. The chelate was stable under these oxidative conditions and could be recovered unchanged and reused.     

Effect of magnesium carbonate on the uptake of aqueous zinc and lead ions by natural kaolinite and clinoptilolite

Adsorption behavior of Zn²⁺ and Pb²⁺ ions on kaolinite and clinoptilolite, originating from natural resources, was studied as a function of contact time and concentration. Zn²⁺ and Pb²⁺ ions are quickly adsorbed on both minerals and the uptake of the latter is more favored. The uptake of both ions was then examined on kaolinite–MgCO₃ and clinoptilolite–MgCO₃ mixtures over a metal ions range from 1 to 10 000 mg/L. The sorption behavior of Zn²⁺ and Pb²⁺ on pure MgCO₃ was also studied. MgCO₃ is much more effective in the retention of Zn²⁺ and Pb²⁺ ions, in particular at higher concentrations. The large increase in the retarded amounts of both ions was associated with formation of the hydroxy-carbonate phases; namely hydrozincite for Zn²⁺, and cerussite and hydrocerussite in the case of Pb²⁺.     

Fluorescence enhancement of coumarin–quinoline by transition metal ions: Detection of paramagnetic Ni2+ and Co2+

A readily available coumarin–quinoline was employed as a novel fluorescent probe for paramagnetic Co²⁺ and Ni²⁺ ions, which are well-known fluorescence quenchers. NMR and IR indicated that the enhanced fluorescence response was attributable to coordination of the paramagnetic Ni²⁺ or Co²⁺ ions with the coumarin–quinoline compound. Given the difficulty of designing enhanced fluorescent probes for paramagnetic Co²⁺ and Ni²⁺ ions, the coumarin–quinoline compound may inspire the further development of more sophisticated sensing constructs for the fluorescence detection of these transition metal ions.     

Preparation of thiourea functionalized polyvinyl alcohol‐coated magnetic nanoparticles and their application in Pb2+ ions adsorption

We have prepared a novel kind of magnetic nanoparticle with high adsorption capacity and good selectivity for Pb²⁺ ions by modifying the magnetic nanoparticles with polyvinyl alcohol (PVA) and thiourea. The resultant magnetic nanoparticles were used to adsorb Pb²⁺ ions from aqueous solution. The influence of the solution pH, the adsorption time, the adsorption temperature, coexisting ions, and the initial concentration of Pb²⁺ ions on the adsorption of Pb²⁺ ions were investigated. The results indicated that Pb²⁺ ions adsorption was an endothermic reaction, and adsorption equilibrium was achieved within 30 min. The optimal pH for the adsorption of Pb²⁺ ions was pH 5.5, and the maximum adsorption capacity of Pb²⁺ ions was found to be 220 mg/g. Moreover, the coexisting cations such as Ca²⁺, Co²⁺, and Ni²⁺ had little effect on adsorption of Pb²⁺ ions. The regeneration studies showed that thiourea functionalized PVA‐coated magnetic nanoparticles could be reused for the adsorption of Pb²⁺ ions from aqueous solutions over five cycles without remarkable change in the adsorption capacity. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40777.     

Influence of the Metal Ions Cr3+, Fe3+, Ni2+ and Cu2+ on the Stability and Oxygen Consumption of Acrylic and Methacrylic Acid

For the safe and trouble‐free operation of a manufacturing plant and the safe storage of acrylic, as well as methacrylic monomers, it is important to know the polymerization stability as a function of the process parameters (temperature, oxygen concentration, and impurities, e.g., metal ions). Contamination with metal ions can be caused by the corrosion of steel units. Therefore, the influence of the metal ions Cr³⁺, Fe³⁺, Ni²⁺ and Cu²⁺ in the concentration range of 0–10 ppm (g g^–1) on the polymerization behavior and the oxygen consumption of acrylic and methacrylic acid were examined in this work. It was shown that Cr³⁺, Ni²⁺, and Cu²⁺ ions extend the inhibition period of acrylic acid (AA) and methacrylic acid (MAA) and reduce the O₂ consumption. Fe³⁺ ions, however, cause a decrease of the inhibition period and in the case of AA an increase of the O₂ consumption, which leads, in the end, to a faster unintentional polymerization. Therefore, alloys which contain iron should be avoided as far as possible in the construction of AA plants. Fe³⁺‐ions show the opposite influence towards MAA, here the presence of Fe³⁺ shows a stabilizing effect.     

Selective Transport of Alkali and Alkaline Earth Metallic Ions through a Supported Liquid Membrane Containing Tripentyl Phosphate as a Carrier

Abstract

A selective transport system for alkali and alkaline earth metallic ions with a perchlorate ion as a pairing ion species through a supported liquid membrane (SLM) containing tripentyl phosphate (TPP) as a carrier is described. The SLM used is a porous polypropylene membrane impregnated with TPP solution in o-nitrophenyloctylether. The effects of the pairing ion species, the initial perchlorate concentration, and the TPP concentration on metallic ion transportability are examined under various experimental conditions. The permeation velocities of the metallic ions in the transport system followed the sequence Li⁺?Na⁺>K⁺>Mg²⁺; that is, a highly selective transport for Li⁺ ion was observed. Compared with the transport rates of alkali metallic ions, those of transition metallic ions such as Cu²⁺ and Fe³⁺ ions are very low. The permeation velocities of alkali and alkaline earth metallic ions through an SLM are dependent on the concentrations of perchlorate and TPP. Equations for the permeation velocities of Li⁺, Na⁺, K⁺, and Mg²⁺ ions through an SLM, based on two concentrations of perchlorate and TPP, are proposed.     

Application of a Novel Hybrid Cation Exchange Material in Metal Ion Separations

A novel hybrid cation exchange material of the class of tetravalent metal acid (TMA) salt, titanium diethylene triamine pentamethylene phosphonate (TiDETPMP) has been synthesized by the sol gel method. The material has been analyzed by spectroscopy and thermal methods. Physico-chemical and ion exchange characteristics have also been studied. The distribution coefficient (K _d ) has been determined in aqueous as well as various electrolyte media/concentrations for Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺ (transition metal ions) and Cd²⁺, Hg²⁺, Pb²⁺, Bi³⁺ (heavy metal ions) using TiDETPMP. Based on the differential affinity/selectivity, the breakthrough capacity (BTC) and elution behavior of various metal ions towards TiDETPMP, a few binary and ternary metal ions separations have been carried out.     

Adsorption characteristics of metal ions by CO2-fixing Chlorella sp. HA-1

Single and binary metal systems were employed to investigate the removal characteristics of Pb²⁺, Cu²⁺, Cd²⁺, and Zn²⁺ by Chlorella sp. HA-1 that were isolated from a CO₂ fixation process. Adsorption test of single metal systems showed that the maximum metal uptakes were 0.767 mmol Pb²⁺, 0.450 mmol Cd²⁺, 0.334 mmol Cu²⁺ and 0.389 mmol Zn²⁺ per gram of dry cell. In the binary metal systems, the metal ions on Chlorella sp. HA-1 were adsorbed selectively according to their adsorption characteristics. Pb²⁺ ions significantly inhibited the adsorption of Cu²⁺, Zn²⁺, and Cd²⁺ ions, while Cu²⁺ ions decreased remarkably the metal uptake of Cd²⁺ and Zn²⁺ ions. The relative adsorption between Cd²⁺ and Zn²⁺ ions was reduced similarly by the presence of the other metal ions.     

REMOVAL OF TOXIC Pb2+ IONS BY SYNTHETIC HYDROXYAPATITES

The removal behavior of toxic Pb²⁺ ions from aqueous and nonaqueous solutions by two synthetic hydroxyapatites (S-1 and S-2) has been investigated by using both batch and column methods.

It was found that Pb²⁺ ions in the both solutions were easily removed to the apatite samples mainly by cation-exchange reactions between the Pb²⁺ ions in the solutions and Ca²⁺ ions of the samples at room temperature. Further, in the system of aqueous PbF₂ solutions, anion-exchange reactions between F^? ions in the solutions and OH ^? ions of the samples occurred simultaneously and the liberated OH ^? and Ca²⁺ ions influenced removal behavior of Pb²⁺ and F^? ions. The maximum removal amount of Pb²⁺ ions from the aqueous solutions was 400?mg per g of S-1. Pb^? ions in the waste water from lead plating factories were completely removed to the apatite samples. In this manner, it was found that the apatites, especially S-1 can be employed as a new removal agent for the treatment of poisonous Pb²⁺ ions in waste water.     

Novel surface ionic imprinting materials prepared via couple grafting of polymer and ionic imprinting on surfaces of silica gel particles

In this paper, a new surface molecular imprinting technique is put forward, and a kind of novel ion-imprinted polymers (IIPs) were prepared through a new approach: firstly functional macromolecule polyethyleneimine (PEI) was grafted onto the surfaces of silica gel particles via the coupling grafting method (“grafting to” method) and the composite material PEI/SiO₂ with chemical linking was formed; secondly the ionic imprinting was carried out towards the macromolecule PEI grafted on the surface of silica particles using Cu²⁺ or Cd²⁺ ion as a template, epichlorohydrin (ECH) as a crosslinking agent and by coordination linkage actions, and Cu²⁺ ion (or Cd²⁺ ion)-imprinted material IIP-PEI/SiO₂ was prepared. The binding characteristics of IIP-PEI/SiO₂ for Cu²⁺ ion (or Cd²⁺ ion) were studied in detail by adopting both static and dynamic methods. The experimental results show that the ion-imprinting material IIP-PEI/SiO₂ has specific recognition ability for the template ions, and this character displays mainly in two aspects: (1) it has high affinity for the template ions, its binding amounts for the template ions are much greater than that of the non-imprinted composite material PEI/SiO₂, and the adsorption capacity enhances nearly two times compared to PEI/SiO₂; (2) it has excellent selectivity for the template ions, for the IIP-PEI/SiO₂ by using Cu²⁺ as template ion, its selectivity coefficients relative to Zn²⁺ and Ni²⁺ are 80.21 and 86.08, respectively, and for the IIP-PEI/SiO₂ by using Cd²⁺ as template ion, its selectivity coefficients relative to Cr³⁺ and Pb²⁺ are 77.05 and 88.22, respectively. Besides, the imprinting material IIP-PEI/SiO₂ has a fine elution property using HCl solution as eluent. The obtained imprinting material by using the new surface molecular imprinting techniques possesses superexcellent binding property for template molecules or ions because of the distribution of imprinted cavities in a thin polymer layer and smaller diffusion barrier.     

New modified poly (ethylene terephthalate) (MPET)-based adsorbent for heavy metal ions

Modified poly(ethylene terephthalate) (MPET) samples of both powder and fiber types, which contain sodium 5-sulfodimethyl isophthalate as the third comonomer component, were explored as an adsorbent for the elimination of heavy metal ions, e.g., Cr³⁺, Pb²⁺, and Cd²⁺, in wastewater. The ions were preferentially adsorbed on finer particles at a lower temperature and pH 4 and were exothermically chemisorbed onto the MPETs via an ionic interaction. It was also found that among the ions Cr³⁺ is the most preferentially adsorbed, followed by Pb²⁺ and Cd²⁺ ions and the adsorption capability of MPETs increased considerably with the presence of phenol. The separation factor indicated that the MPET fiber wastes may possibly be reutilized as an economical adsorbent for heavy metal ions in wastewater.     

Effects of added metal ions on the interaction of chitin and partially deacetylated chitin with an azo dye carrying hydroxyl groups

The binding of chrome violet, which is a monoazo dye and involves two hydroxyl groups in the o and o′ positions to an azo group, to chintin and partially decetylated chitin, was examined in the presence of metal ions. Zn²⁺ and Cu²⁺ ions do not perceptively influence the binding affinity of chrome voilet to chitin. In contrast, Co²⁺ ion enhances the binding and Ni²⁺ ion suppresses it. In the lower free dye concentrations the dye uptake by partially deceteylated chitin was tremendously enhanced by adding. Co²⁺ ion in the buffer solution of pH 5. The dye uptake by the polymer was considerably increased by the addition of Cu²⁺ ion at pH 5 and became much larger at pH 6. The amount corresponded to that in the presence of Co²⁺ ion. To investigate further the action of added metal ions, a cobalt- or a chrome–complex dye was prepared, and the binding properties for the polymers were compared with those of chrome violet in the presence of Co²⁺ and Cu²⁺ ions. Some possible mechanisms for the enhancement of chrome violet binding by the addition of Co²⁺ and Cu²⁺ ions are described. © 1995 John Wiley & Sons, Inc.     

Synthesis and study of the chelating properties of 3-carboxy-4-hydroxyacetophenone-formaldehyde resins

3-Carboxy-4-hydroxyacetophenone (CHAP) was polycondensed with various proportions of formaldehyde using alcoholic alkali as catalyst. The resin samples, designated as CHAP-F, have been characterized by elemental analyses and IR spectroscopy, by estimation of their number average molecular weights (M?_n), by measurement of intrinsic viscosity, and by TGA. Polymeric metal chelates of one CHAP-F sample with Cu²⁺, Fe³⁺, Co²⁺, Ni²⁺, and UO₂²⁺ ions have been prepared and characterized. Ion-exchanging properties of one CHAP-F resin sample for Fe³⁺, Cu²⁺, and Ni²⁺ metal ions are studied by the application of the batch-equilibration method.     

Adsorption from aqueous solution by δ-manganese dioxide I. Adsorption of the alkaline-earth cations

The adsorption isotherms of M²⁺ ions (M = Mg, Ca, Sr or Ba) were determined at pH 7.0 and at different temperatures. The adsorbent, δ-MnO₂, was converted to the K⁺ form prior to adsorption and about 1.5 mol K⁺ ions were released per mol of M²⁺ ions adsorbed. The adsorption capacity at a given temperature increased in the series: Mg²⁺ < Ca²⁺ ≦ Sr²⁺ < Ba²⁺. This was explained by an ion exchange mechanism between hydrated ions: K⁺ ions in the outer Helmholtz layer and M²⁺ ions in the bulk of the solution. The radii of the hydrated ions decreased in the series: Mg²⁺ > Ca²⁺ > Sr²⁺ > Ba²⁺. The adsorption of M²⁺ ions at pH values below the point of zero charge (pH 3.3) was significant for Mg²⁺ ions only. Although adsorption was not strictly reversible, the results fitted the Langmuir isotherm and ‘apparent heats of adsorption’, Q, were calculated. The endothermic heats (Q = 20,18, 11 and 5 kJ mol^?1 for Mg²⁺, Ca²⁺, Sr²⁺ and Ba²⁺ adsorption respectively) indicated positive entropy contributions which are expected for the adsorption mechanism suggested. The decrease in Q down the alkaline-earth group was correlated to the entropy effects and to the hydration numbers of the cations.     

Concentration and separation of aqueous solutions of Cu2+, Ni2+, Fe3+ by dextran

The effects of water-soluble polymers on the concentration and separation of the aqueous solutions of the metal ions have been studied. The separation of metal ions can be possible by ultrafiltration-complexation process. The effect of Dextran, which is a water-soluble polymer, on the concentration and separation of metal ions (Cu²⁺, Ni²⁺, Fe³⁺) have been investigated by using EC-PEG 4000 alloy membranes. The permeability of these membranes for metal ions has been rrecorded at constant pressure but different pH values. It has been notices that the highest water-permeable membrane is also permeable towards Cu²⁺ and Ni²⁺, but has shown a considerable retention for Fe³⁺ as a result of the hydrolysis of Fe³⁺. The retentions of metallic ions and metallic-ion-Dextran couples have been determined at constant pressure but different pH and polymer concentration values. It has been shown that Fe³⁺/Ni²⁺ and Fe³⁺/Cu²⁺ couples can be separated by using Dextran. © 1995 John Wiley & Sons, Inc.     

Preparation and adsorption properties of poly(N‐vinylformamide/acrylonitrile) chelating fiber for heavy metal ions

In this article we report a new chelating fiber that was prepared from a hydrolyzate of poly(N‐vinylformamide/acrylonitrile) by a wet‐spinning method. This fiber contains chelating groups, such as amidine groups, amino groups, cyano groups, and amide groups, with high densities. We examined the chelating abilities for several metal ions with this fiber, and present the morphological merit of the fibrous product compared with the globular resin. Based on the research results, it is shown that the fiber has higher binding capacities and better adsorption properties for heavy metal ions than the resin. The pH value of the metal ion solution shows strong influences on the adsorption of the metal ions. The maximum adsorption capacities of the fiber for Cu²⁺, Cr³⁺, Co²⁺, Ni²⁺, and Mn²⁺ are 112.23, 88.11, 141.04, 108.06, and 73.51 mg/g, respectively. In mixed metal ions solution, the fiber adsorbs Cr³⁺, Cu²⁺ and Co²⁺ efficiently. The adsorbed metal ions can be quantitatively eluted by hydrochloric acid. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 1378–1386, 2002