Important Metal Ions Research Articles

Photoluminescent and Electrochemiluminescent Detection of Fe3+ Using Cyclometalated Iridium Complexes via Fe3+-Catalyzed Hydrolysis.

Ferric ion (Fe3+) is a biologically abundant and important metal ion. We developed several cyclometalated iridium complex-based molecular sensors (1, ppy-1, 1-phen, 1a, and 1-OMe) for the detection of Fe3+ using an acetal moiety as the reaction site. The acetal moiety in iridium complexes undergoes Fe3+-catalyzed hydrolysis and subsequent formation of a formyl group, resulting in turn-off photoluminescent and electrochemiluminescent responses. Sensor 1 showed excellent selectivity toward Fe3+ over other biologically important metal ions. Furthermore, we compared the performance of the sensors based on the structural differences of the iridium complexes, and revealed a relationship between the structure and chemical properties through electrochemical experiments and computational calculations.

Iron: Life’s primeval transition metal

Modern life requires many different metal ions, which enable diverse biochemical functions. It is commonly assumed that metal ions’ environmental availabilities controlled the evolution of early life. We argue that evolution can only explore the chemistry that life encounters, and fortuitous chemical interactions between metal ions and biological compounds can only be selected for if they first occur sufficiently frequently. We calculated maximal transition metal ion concentrations in the ancient ocean, determining that the amounts of biologically important transition metal ions were orders of magnitude lower than ferrous iron. Under such conditions, primitive bioligands would predominantly interact with Fe(II). While interactions with other metals in certain environments may have provided evolutionary opportunities, the biochemical capacities of Fe(II), Fe–S clusters, or the plentiful magnesium and calcium could have satisfied all functions needed by early life. Primitive organisms could have used Fe(II) exclusively for their transition metal ion requirements.

Redox-active sp2-c connected metal covalent organic frameworks for selective detection and reductive separation of uranium

It is economically desirable to develop a material that can simultaneously detect and recover uranium. Herein, a CC-bridged two-dimensional metal-covalent organic framework (Cu-BTAN-AO MCOF) was constructed by condensation of metal single crystals with a rigid structure (Cu3(PyCA)3) and cyano monomers (BTAN) via Knoevenagel reaction for simultaneous detection and adsorption of uranium. The amidoxime group within the pore and the presence of unsaturated Cu(I) in the framework facilitate the adsorption of uranyl ions onto the amidoxime group, leading to fluorescence quenching via the photoinduced electron transfer (PET) mechanism, achieving a detection limit of as low as 167 nM uranyl ions. Furthermore, Cu-BTAN-AO demonstrates exceptional efficiency in capturing uranium from wastewater characterized by rapid kinetics and superior selectivity. It is noteworthy that Cu-BTAN-AO is the first example of simultaneous detection, adsorption and chemical reduction of uranium using metal centers and functional groups in MCOF, indicating that Cu-BTAN-AO has great potential for the detection and recovery of uranium-containing wastewater. This design strategy may also be applicable to advancing sensing and energy materials for other important metal ions.

A hybrid fluorescent probe for the selective detection of divalent Hg2+ and trivalent Al3+ ions and their biological applications

Metals are extensively used for different applications in agriculture and industry. Accumulations of these metals in the environment lead to serious health concerns. Currently, fast and accurate detection of metal ions in the environment or biological system has become a critical issue. Hence, developing an appropriate tool for the detection of metals can help reduce environmental metal pollution and reduce health concerns. In the present study, a hybrid fluorescent probe or chemosensor for parallelly detecting two important metal ions (Mercury and Aluminium) has been designed and tested for its detection efficiency. The newly synthesized chemosensor 3′,6′-bis(ethylamino)-2′,7′-dimethyl-3H-spiro[isobenzofuran-1,9′-xanthen]-3-one (RS) was found to specifically detect Hg2+ and Al3+ ions with high sensitivity and selectivity. The chemical and physical properties of chemosensor RS were tested using single-crystal X-ray diffraction, UV and Fluorescence analysis. The quick response to Hg2+ and Al3+ is attributable to the creation of a coordinate bond present between the chemosensor RS and the metal ion. The selective sensing of chemosensor RS is due to the spirolactam ring opening followed by the development of proper coordinate geometry in the chemosensor. 1H NMR titration experiment and Job’s approach studies suggest a significant binding stoichiometry between the chemosensor RS and the metal ions at a 1:1 ratio. The limit of detection (LOD) of chemosensor RS was determined to be 1.88 µM for Al3+ and 1.75 µM for Hg2+ ions. The in vivo studies using two experimental animal models, Drosophila melanogaster (fruit fly) and Poecilia reticulate (guppy fish), clearly demonstrate its efficiency in detecting endogenously absorbed Hg2+ and Al3+. Thus, chemosensor RS can selectively and simultaneously detect Hg2+ and Al3+ in biological or environmental samples and can help us in monitoring metal leaching into the environment.

Application of antimicrobial properties of copper

The antimicrobial properties of copper ions can reduce the overgrowth of microorganisms to a certain extent. That reduces the amount of antibiotics used, to avoid superbugs and potential harm. The authors reviewed the antimicrobial mechanisms of copper and copper‐containing nanoparticles (NPs), focusing on the factors influencing their antimicrobial properties. They concluded that the antimicrobial properties were better in environments conducive to the precipitation of copper ions and exposure to microorganisms. Comparing copper with other metal ions leads to the question of why copper is such an important antimicrobial metal ion. In recent years, with the development of science and technology and the understanding of the microscopic world, scientists have skillfully applied the antimicrobial properties of copper in various settings, from direct contact with food to breeding and hygienic environments, and have confirmed the safety of the application. However, because of the toxic effect of NPs, the future goal is to synthesize a copper‐containing NP with good biocompatibility and antibacterial efficiency to benefit human society.

An ESIPT active coumarin-diphenyl azine-based AIEgen: Nanomolar Cu2+ ion sensing, Latent Fingerprinting, live-cell imaging, and real sample analysis

Designing economical and sensitive chemosensors for detecting important metal ions, like Cu2+ ions, is essential and remains a hot topic worldwide. In this investigation, we extended our investigation to design a specific diphenyl-azine-based skeletal system for the selective and sensitive detection of Cu2+ions. We reported a coumarin-diphenyl-azine-based AIEgen (C-1) using an improvised methodology with a large Stoke's shift (∼245 nm) for precisely sensing copper ions in solid, solution, and biological cells. The AIE-ESIPT properties of C-1 were validated using various sophisticated techniques. C-1 was found to be a promising selective and sensitive sensor of Cu2+ ions (nanomolar LOD value ∼10.38 nM) via colorimetric and TURNOFF fluorometric ways. The practical applicability of C-1 was analyzed via real-time estimation of copper ions in water samples (obtained from three varied locations) and in biological samples (urine and serum). The satisfactory recovery with a low RSD value indicates the potential of C-1 in detecting copper ions in actual samples. Estimating copper ions in urine and blood samples demonstrates the usefulness of C-1 in diagnosing disorders like Wilson's disease, which is caused by high concentrations of copper ions in the body. Additionally, we have detected Cu2+ions in live cells (HeLa cells) and carried out Latent Fingerprinting (Level 1 and Level 2) to validate its versatility in physiological and forensic applications. Overall, the proposed C-1 AIEgen is an ultrasensitive Cu2+ions sensor with innumerable applications in the physical world.

PH-dependent interactions of biologically important metal ions with hen egg white lysozyme based on its hydration properties: Thermodynamic and mechanistic insights

Importance of metal ion selectivity in biomolecules and their key role in proteins are widely explored. However, understanding the thermodynamics of how hydrated metal ions alter the protein hydration and their conformation is also important. In this study, the interaction of some biologically important Ca2+, Mn2+, Co2+, Cu2+, and Zn2+ ions with hen egg white lysozyme at pH 2.1, 3.0, 4.5 and 7.4 has been investigated. Intrinsic fluorescence studies have been employed for metal ion-induced protein conformational changes analysis. Thermostability based on protein hydration has been investigated using differential scanning calorimetry (DSC). Thermodynamic parameters emphasizing on metal ion-protein binding mechanistic insights have been well discussed using isothermal titration calorimetry (ITC). Overall, these experiments have reported that their interactions are pH-dependent and entropically driven. This research also reports the strongly hydrated metal ions as water structure breaker unlike osmolytes based on DSC studies. These experimental results have highlighted higher concentrations of different metal ions effect on the protein hydration and thermostability which might be helpful in understanding their interactions in aqueous solutions.

Glowing discoveries: Schiff base-cyanostilbene probes illuminating metal ions and biological entities.

Schiff bases featuring cyanostilbene units have emerged as versatile and highly effective probes for the selective detection of various metal ions as well as biologically important species. This review comprehensively highlights recent advances in the development and application of the probes, which exhibit remarkable Aggregation-Induced Emission (AIE), Twisted Intramolecular Charge Transfer (TICT), and Excited-State Intramolecular Proton Transfer (ESIPT) properties. These unique structural characteristics facilitate their potential applications in the detection of biologically important metal ions such as Zn2+, Fe3+, Cu2+, Hg2+ and Co2+ ions with high sensitivity and selectivity. Furthermore, these probes have demonstrated significant potential in the recognition of vital biological species, including arginine, hydrazine and hypochlorite (ClO-). The present review discusses the underlying detection mechanisms, emphasizing the role of the Schiff base and cyanostilbene moieties for the selective detection of particular biologically important entities. Moreover, this discussion highlights the practical applications, problems, and future directions in this fast-growing field, emphasizing the vital importance of these probes in both analytical chemistry and bioassays.

Unravelling the Metal Sensing Activity of a Biologically Relevant Fluorescent Crown Ether: A Unified Experimental and Theoretical Study.

1,4-dihydropyridines (DHPs) are biologically active. 1,4-DHP analogs with appropriate substituents also show characteristic fluorescence activity. Here, for the first time, we report a simple and easy synthesis of a novel fluorescent 1,4- DHP derivative of dibenzo[18]-crown-6 (2), which showed promising sensing ability towards physiologically important metal ions. The covalent linking of 1,4-DHP analog with dibenzo[18]-crown-6 instigates its fluorescence activity in (2) and makes it biologically relevant. (2) shows a noteworthy enhancement of fluorescence intensity toward Fe3+ and Ba2+ in methanol medium. DFT studies revealed that metal binding by the crown ether-O atoms leads to structural rigidity, enhancing the fluorescence intensity. Interestingly, (2) shows utility in the quantitative detection of Fe3+ ions in the biological (human blood serum) and food samples.

A Ratiometric Fluorescent Sensor Based on Chelation-Enhanced Fluorescence of Carbon Dots for Zinc Ion Detection

Zinc ion, one of the most important transition metal ions in living organisms, plays a crucial role in the homeostasis of the organism. The disorder of zinc is associated with many major diseases. It is highly desirable to develop selective and sensitive methods for the real-time detection of zinc ions. In this work, double-emitting fluorescent carbon dots (CDs) are prepared by a solvothermal method using glutathione, L-aspartic acid, and formamide as the raw materials. The carbon dots specifically recognize zine ions and produce a decrease in fluorescence intensity at 684 nm and an increase at 649 nm, leading to a ratiometric fluorescent sensor for zinc detection. Through surface modification and spectral analysis, the surface groups including carboxyl, carbonyl, hydroxyl, and amino groups, and C=N in heterocycles of CDs are revealed to synergistically coordinate Zn2+, inducing the structural changes in the emission site. The CDs can afford a low limit of detection of ~5 nM for Zn2+ detection with good linearity in the range of 0.02–5 μM, showing good selectivity as well. The results from real samples including fetal bovine serum, milk powder, and zinc gluconate oral solution indicated the good applicability of the CDs in the determination of Zn2+.

Cardiolipin deficiency leads to the destabilization of mitochondrial magnesium channel MRS2 in Barth syndrome.

Barth syndrome (BTHS) is a debilitating X-linked cardio-skeletal myopathy caused by loss-of-function mutations in TAFAZZIN, a cardiolipin (CL)-remodeling enzyme required for the maintenance of normal levels of CL species in mitochondrial membranes. At present, how perturbations in CL abundance and composition lead to many debilitating clinical presentations in BTHS patients have not been fully elucidated. Inspired by our recent findings that CL is essential for optimal mitochondrial calcium uptake, we measured the levels of other biologically important metal ions in BTHS mitochondria and found that in addition to calcium, magnesium levels are significantly reduced. Consistent with this observation, we report a decreased abundance of the mitochondrial magnesium influx channel MRS2 in multiple models of BTHS including yeast, murine myoblast, and BTHS patient cells and cardiac tissue. Mechanistically, we attribute reduced steady-state levels of MRS2 to its increased turnover in CL-deficient BTHS models. By expressing Mrs2 in well-characterized yeast mutants of the phospholipid biosynthetic pathways, we demonstrate a specific requirement of CL for Mrs2 abundance and assembly. Finally, we provide in vitro evidence for the direct binding of CL with human MRS2. Together, our study has identified a critical requirement of CL for MRS2 stability and suggests perturbation of mitochondrial magnesium homeostasis as a novel contributing factor to BTHS pathology.

Microfluidic Devices for Heavy Metal Ions Detection: A Review.

The contamination of air, water and soil by heavy metal ions is one of the most serious problems plaguing the environment. These metal ions are characterized by a low biodegradability and high chemical stability and can affect humans and animals, causing severe diseases. In addition to the typical analysis methods, i.e., liquid chromatography (LC) or spectrometric methods (i.e., atomic absorption spectroscopy, AAS), there is a need for the development of inexpensive, easy-to-use, sensitive and portable devices for the detection of heavy metal ions at the point of interest. To this direction, microfluidic and lab-on-chip (LOC) devices fabricated with novel materials and scalable microfabrication methods have been proposed as a promising approach to realize such systems. This review focuses on the recent advances of such devices used for the detection of the most important toxic metal ions, namely, lead (Pb), mercury (Hg), arsenic (As), cadmium (Cd) and chromium (Cr) ions. Particular emphasis is given to the materials, the fabrication methods and the detection methods proposed for the realization of such devices in order to provide a complete overview of the existing technology advances as well as the limitations and the challenges that should be addressed in order to improve the commercial uptake of microfluidic and LOC devices in environmental monitoring applications.

New Insight on the Formation of 2-Aminoacetophenone in White Wines

This study aimed to improve the understanding of 2-aminoacetophenone (2-AAP) formation in white wines, a compound responsible for atypical ageing (ATA) associated with a rapid loss of white wine fruity aroma and to the development of unpleasant odors. Two surveys performed in 139 white wines from Central Europe investigated the varietal effect on wine tendency to form 2-AAP during ageing. The role of some antioxidants and important transition metal ions present in wine (Fe, Cu and Mn) in the formation of 2-AAP was also investigated. The surveys highlighted that Muscat and Riesling wines showed significantly higher concentrations of 2-AAP than Chardonnay and some other regional varieties found in Central Europe such as Grüner Veltliner, Welschriesling and Zelen. The origin of such varietal effects could not be related to the level of any 2-AAP precursor. On the other hand, some of the important wine matrix effects were highlighted. A certain variability in capacity of different antioxidants to limit 2-AAP formation was observed. Supplementations of commercial tannins in wines tended to be more efficient than glutathione in preserving wines from the formation of 2-AAP. Transition metal ions significantly impacted 2-AAP synthesis through complex interactions. Generally, Fe and Mn tended to promote formation of 2-AAP, while the presence of Cu limited it. The higher concentration of transition metal ions significantly improved the efficiency of antioxidants to reduce 2-AAP formation. Further studies investigating the origin of varietal effects and the complex matrix effects involving metal ions and antioxidants in 2-AAP production are warranted.

Metanil Yellow Dye Encapsulated Layered Double Hydroxide of Nickel and Aluminium: A Fluorescent and Electrochemical Sensor for Pb2+ and Al3+ Ion

In this work, metanil yellow (MY) dye was successfully encapsulated with layered double hydroxide (LDH) of nickel and aluminium was latter synthesized by hydrothermal process. The prepared sensor (MY@NiAl-LDH) was investigated through various characterization techniques. The sensor served as a fluorescent turn-on sensor for Pb2+ ion and an electrochemical sensor for Al3+ ion. The fluorescent detection of Pb2+ is highly selective, reversible with relatively low limit of detection (LOD). It showed fluorescent enhancement mechanism through blocked PET process. Platinum disc electrode modified with MY@NiAl-LDH could selectively detect Al3+ ion by cyclic voltammetry in presence of other interfering metal ions. The present work aims to expand dye based layered double hydroxides sensors in the field of feasible detection of biological and environmentally important metal ions.

An overview of Schiff base-based fluorescent turn-on probes: a potential candidate for tracking live cell imaging of biologically active metal ions

This review focused on Schiff base-based fluorescent turn-on probes for detecting biologically important metal ions, paying primary attention to their biological applications.

Zinc in Human Health and Infectious Diseases.

During the last few decades, the micronutrient zinc has proven to be an important metal ion for a well-functioning immune system, and thus also for a suitable immune defense. Nowadays, it is known that the main cause of zinc deficiency is malnutrition. In particular, vulnerable populations, such as the elderly in Western countries and children in developing countries, are often affected. However, sufficient zinc intake and homeostasis is essential for a healthy life, as it is known that zinc deficiency is associated with a multitude of immune disorders such as metabolic and chronic diseases, as well as infectious diseases such as respiratory infections, malaria, HIV, or tuberculosis. Moreover, the modulation of the proinflammatory immune response and oxidative stress is well described. The anti-inflammatory and antioxidant properties of zinc have been known for a long time, but are not comprehensively researched and understood yet. Therefore, this review highlights the current molecular mechanisms underlying the development of a pro-/ and anti-inflammatory immune response as a result of zinc deficiency and zinc supplementation. Additionally, we emphasize the potential of zinc as a preventive and therapeutic agent, alone or in combination with other strategies, that could ameliorate infectious diseases.

A near-infrared Fluorescent Probe Based on Dicyanisophorone for the Detection of Zinc Ions (Zn2+) in Water and Living Cells.

As one of the important metal ions, zinc ions (Zn2+) are widely involved in various physiological and pathological processes, and play fundamental roles in neurotransmission, cell metabolism and apoptosis. However, the convenient monitor of Zn2+ in environmental and biological samples remains challenging. In this study, a small molecule dicyanoisophorone-based schiff base incorporating with o-phenylenediamine was synthesized. It can rapidly combine with Zn2+ to emit significant near-infrared fluorescence (maximum emission wavelength: 660nm), so it can be used as a probe to quantitatively detect Zn2+ in the range of 0-10μM, with a detection limit as low as 4.8nM, showing the probe has high sensitivity for Zn2+. And the probe has a fast response time to Zn2+ (less than 30s) and a large Stoke-shift (179nm). In addition, the high recovery rates in practical water samples, and the clear fluorescent images in living A549 cells were obtained, which are of great significance for the detection of Zn2+ in the environment and biosystem. Due to its simple operation, good selectivity and anti-interference ability, short detection time and high sensitivity, this probe has great application potential as a fast detection tool for Zn2+ in environmental water and biological samples.

Recent Achievements in Electrochemical and Optical Nucleic Acids Based Detection of Metal Ions.

Recently nucleic acids gained considerable attention as selective receptors of metal ions. This is because of the possibility of adjusting their sequences in new aptamers selection, as well as the convenience of elaborating new detection mechanisms. Such a flexibility allows for easy utilization of newly emerging nanomaterials for the development of detection devices. This, in turn, can significantly increase, e.g., analytical signal intensity, both optical and electrochemical, and the same can allow for obtaining exceptionally low detection limits and fast biosensor responses. All these properties, together with low power consumption, make nucleic acids biosensors perfect candidates as detection elements of fully automatic portable microfluidic devices. This review provides current progress in nucleic acids application in monitoring environmentally and clinically important metal ions in the electrochemical or optical manner. In addition, several examples of such biosensor applications in portable microfluidic devices are shown.

Overexpression of Nicotianamine Synthase (AtNAS1) Increases Iron Accumulation in the Tuber of Potato.

Iron (Fe) deficiency is a global health problem, especially in underdeveloped countries. Biofortification with genetic engineering methods has been used to improve Fe nutrition in a number of crops. Various steps, e.g., uptake, distribution, and storage, involved in Fe homeostasis have been manipulated to increase the Fe concentration in the edible portions of plants. Nicotianamine (NA) is an important metal ion chelator in plants. It promotes the mobility of Fe and decreases cellular Fe toxicity. Increasing the Fe content in crops by promoting NA synthesis could help decrease human diseases associated with Fe deficiency. In the present study, Arabidopsis thaliana nicotianamine synthase 1 (AtNAS1) was overexpressed in potato (Solanum tuberosum, St) under the control of the cauliflower mosaic virus 35S promoter. Transgenic plants had a significantly increased amount of Fe in tubers (52.7 µg/g dry weight, 2.4-fold the amount in wild-type tubers), while no differences in plant phenotype or yield were detected between transgenic and wild-type plants. The expression of genes involved in root mineral uptake and homeostasis, such as StYSL1, StIRT1, StFRO1, and StNAS, was also altered in the roots and leaves of the transgenic plants. Our results demonstrate that the manipulation of Fe chelation is a useful strategy for Fe nutrition improvement, and the increased Fe accumulation in tubers of transgenic potato plants is most likely caused by the increased movement of Fe from the leaf to the tuber.

Water-Dispersible Activatable Nanoprobe for Detecting Cadmium-Ion-Induced Oxidative Stress in Edible Crops via Near-Infrared Second-Window Fluorescence Imaging.

Edible crops are important in terms of food security and sustainable agriculture. Heavy-metal-ion contamination of water/soil has deleterious impacts on the growth of edible crops. Among the heavy metals, cadmium (Cd) is toxic to plants, people, and animals, as it is widely used in industry; it has become the most important metal ion in the soil/water pollution. Once the toxic Cd ion enters edible crops via the water/soil in which the crops grow, it will induce oxidative stress (overproduction of reactive oxygen species with H2O2 being the most abundant) in the crops, and strong oxidative stress leads to the crops' growth depression or inhibition. Hence, it is of great significance to accurately monitor the oxidative stress induced by Cd ions in edible crops, as the monitoring results could be employed for the early warning of Cd-ion pollution in water/soil. Herein, we design an activatable nanoprobe that can detect Cd-ion-induced oxidative stress in edible crops via near-infrared second-window (NIR-II) fluorescence imaging. The molecular probe IXD-B contains the diphenylamine-modified xanthene group acting as the electron-donating unit, bis(methylenemalononitrile)indan as the electron-accepting unit, and the methenephenylboronic acid group as the recognition moiety for H2O2 and the fluorescence quencher. The probe molecules being encapsulated by the amphiphilic DSPE-PEG2000 render the water-dispersible nanoprobe (IXD-B@DSPE-PEG2000). When the nanoprobe enters the edible crops, it can be activated by the overexpressed H2O2 therein and consequently emit strong NIR-II fluorescence signals for visualizing and tracking the oxidative stress in edible crops induced by Cd ions.