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A novel polyhedral oligomeric silsesquioxane nanohybrid fluorescent sensor designed based on an osmotic mechanism for specific detection and intelligent scavenging of magnesium ions
Given the importance of Magnesium (Mg) assay for efficacy evaluation of medicinal and edible homologous (MEH), an electrochemical sensor is designed by exploiting the cooperative properties of metal–organic frameworks (MOFs) and gold nanoparticles (AuNPs). To be specific, the constructed bimetallic MOFs ((FeZr)MOF) are designed by using Zr(IV) and Fe(III) clusters as metal sources, which provide a large platform for AuNPs attachment to design signal probes. Benefitting from the catalytic properties of (FeZr)MOF toward hydroxylamine, electrochemical signal is attained for Mg ²⁺ analysis with the detection limit to be 3 μM (corresponding to 0.072 μg g ⁻¹ ). Relying on DNAzymes as recognition elements, good anti‐jamming is achieved for Mg ²⁺ analysis against the coexisting ions in Puerarin, Chinese wolfberry, hawthorn and dangshen. With the superiority of rapid response, acceptable sensitivity and specificity, the electrochemical sensor provides a useful pattern for assessing the pharmacological effects of MEH substances, pointing to reasonable selection and combination of multiple health function dietary therapy formulas.
Detection of trace magnesium ion (Mg²⁺) is important in environmental and health monitoring. In this work, high‐performance Mg²⁺ sensor was developed from label‐free carbon dots. The novel carbon dots were prepared for the first time from natural rubber through the two‐step pyrolysis and hydrothermal method. They showed selectivity towards Mg²⁺ against a range of metal ions in solution and yielded a detection limit of 4.3 μM. The Mg²⁺ detection in real water samples showed an excellent recovery of 97.21 to 99.21 %. A paper‐based sensor was also fabricated as a portable device, showing a detection limit of 8.0 μM. UV‐vis and X‐ray absorption studies provided some evidences of the unique dynamic interactions between carbon dots and Mg²⁺ ions. In summary, the novelty of this work lies upon (i) developing a methodology of converting abundant, low‐cost natural rubber into carbon dots and (ii) fabricating sensitive and selective sensors from the label‐free carbon dots for the detection of Mg²⁺ both in solution and as paper‐based devices. The findings in this work will therefore have potential for environmental and health monitoring applications.
A Schiff base fluorescent probe compound H2L (N′‐(4‐bromo‐2‐hydroxy‐benzylidene)‐3‐hydroxy‐2naphthohydrazide) was synthesized using 3‐hydroxy‐2‐naphthoic acid hydrazide as raw material. The structure of H2L was characterized by NMR, IR, MS, and XRD methods. The fluorescence performance of H2L was studied by UV and FS. The results show that in 1 : 4 water system /DMSO solution (water system: 20 % triethanolamine:0.1 mol/L L‐cysteamine acid=1 : 1), H2L can be used to quickly identify Mg²⁺ with an obvious fluorescence enhancement and redshift. A color change “light green→bright yellow” can be clearly observed with the naked eye. The Mg²⁺ concentration shows a good linear relationship in the range of 0–1.0×10⁻⁵ mol/L, with a detection limit of 1.77×10⁻⁷ mol/L with good stability and reversibility. The response mechanism was explored through Job's curve, NMR titration and MS, which showed that Mg²⁺ can form a 1 : 1 complex with H2L. A gel (SAL) was prepared by doping H2L into sodium alginate (SA). SAL was found to show good adsorption properties for Mg²⁺ and can be easily distinguished by the naked eye under ultraviolet light. The microscopic morphology and composition of SAL before and after Mg²⁺ adsorption were analyzed by SEM‐EDS. H2L can be used for the qualitative detection of Mg²⁺ in actual water samples without being affected by other common metal ions, and has potential application value in the field of environmental detection.
In this study, a naphthalene Schiff-base P which serves as a dual-analyte probe for the quantitative detection of Al³⁺ and Mg²⁺ has been designed. The proposed probe showed an ‘‘off–on’’ fluorescent response toward Al³⁺ in ethanol–water solution (1 : 9, v/v, pH 6.3, 20 mM HEPES) over other metal ions and anions, while the detection by the probe could be switched to Mg²⁺ by regulating the pH from 6.3 to 9.4. The sensing mechanisms of P to Al³⁺/Mg²⁺ are attributed to inhibition of the photo-induced electron transfer (PET) process by the formation of 1 : 1 ligand–metal complexes. More importantly, the probe was applied successfully in living cells for the fluorescent cell-imaging of Al³⁺ and Mg²⁺.
Magnesium (Mg) is the second most abundant cation in mammalian cells, and it is essential for numerous cellular processes including enzymatic reactions, ion channel functions, metabolic cycles, cellular signaling, and DNA/RNA stabilities. Because of the versatile and universal nature of Mg2+, the homeostasis of intracellular Mg2+ is physiologically linked to growth, proliferation, differentiation, energy metabolism, and death of cells. On the cellular and tissue levels, maintaining Mg2+ within optimal levels according to the biological context, such as cell types, developmental stages, extracellular environments, and pathophysiological conditions, is crucial for development, normal functions, and diseases. Hence, Mg2+ is pathologically involved in cancers, diabetes, and neurodegenerative diseases, such as Parkinson’s disease, Alzheimer’s disease, and demyelination. In the research field regarding the roles and mechanisms of Mg2+ regulation, numerous controversies caused by its versatility and complexity still exist. As Mg2+, at least, plays critical roles in neuronal development, healthy normal functions, and diseases, appropriate Mg2+ supplementation exhibits neurotrophic effects in a majority of cases. Hence, the control of Mg2+ homeostasis can be a candidate for therapeutic targets in neuronal diseases. In this review, recent results regarding the roles of intracellular Mg2+ and its regulatory system in determining the cell phenotype, fate, and diseases in the nervous system are summarized, and an overview of the comprehensive roles of Mg2+ is provided.
Active reabsorption of magnesium (Mg2+ ) in the distal convoluted tubule (DCT) of the kidney is crucial for maintaining Mg2+ homeostasis. Impaired activity of the Na+ -Cl- -cotransporter (NCC) has been associated with hypermagnesiuria and hypomagnesemia, while increased activity of NCC, as observed in patients with Gordon syndrome, is not associated with alterations in Mg2+ balance. To further elucidate the possible interrelationship between NCC activity and renal Mg2+ handling, plasma Mg2+ levels and urinary excretion of sodium (Na+ ) and Mg2+ were measured in a mouse model of Gordon syndrome. In this model, DCT1-specific expression of a constitutively active mutant form of the NCC-phosphorylating kinase, SPAK (CA-SPAK), increases NCC activity and hydrochlorothiazide (HCTZ)-sensitive Na+ reabsorption. These mice were normomagnesemic and HCTZ administration comparably reduced plasma Mg2+ levels in CA-SPAK mice and control littermates. As inferred by the initial response to HCTZ, CA-SPAK mice exhibited greater NCC-dependent Na+ reabsorption together with decreased Mg2+ reabsorption, compared to controls. Following prolonged HCTZ administration (4 days), CA-SPAK mice exhibited higher urinary Mg2+ excretion, while urinary Na+ excretion decreased to levels observed in control animals. Surprisingly, CA-SPAK mice had unaltered renal expression of Trpm6, encoding the Mg2+ -permeable channel TRPM6, or other magnesiotropic genes. In conclusion, CA-SPAK mice exhibit normomagnesemia, despite increased NCC activity and Na+ reabsorption. Thus, Mg2+ reabsorption is not coupled to increased thiazide-sensitive Na+ reabsorption, suggesting a similar process explains normomagnesemia in Gordon syndrome. Further research is required to unravel the molecular underpinnings of this phenomenon and the more pronounced Mg2+ excretion after prolonged HCTZ administration.
Magnesium is an essential ion for numerous physiological processes. MgtE is a Mg 2+ selective channel involved in the maintenance of intracellular Mg 2+ homeostasis, whose gating is regulated by intracellular Mg 2+ levels. Here, we report that ATP binds to MgtE, regulating its Mg 2+-dependent gating. Crystal structures of MgtE–ATP complex show that ATP binds to the intracellular CBS domain of MgtE. Functional studies support that ATP binding to MgtE enhances the intracellular domain affinity for Mg 2+ within physiological concentrations of this divalent cation, enabling MgtE to function as an in vivo Mg 2+ sensor. ATP dissociation from MgtE upregulates Mg 2+ influx at both high and low intracellular Mg 2+ concentrations. Using site-directed mutagenesis and structure based-electrophysiological and biochemical analyses, we identify key residues and main structural changes involved in the process. This work provides the molecular basis of ATP-dependent modulation of MgtE in Mg 2+ homeostasis.
Background:
Magnesium (Mg2+), the second most abundant cation in the cell, is woven into a multitude of cellular functions. Dysmagnesemia is associated with multiple diseases and, when severe, can be life-threatening.
Summary:
This review discusses Mg2+ homeostasis and function with specific focus on renal Mg2+ handling. Intrarenal channels and transporters related to Mg2+ absorption are discussed. Unraveling the rare genetic diseases with manifestations of dysmagnesemia has greatly increased our understanding of the complex and intricate regulatory network in the kidney, specifically, functions of tight junction proteins including claudin-14, -16, -19, and -10; apical ion channels including: TRPM6, Kv1.1, and ROMK; small regulatory proteins including AC3 and ANK3; and basolateral proteins including EGF receptor, γ-subunit (FXYD2) of Na-K-ATPase, Kir4.1, CaSR, CNNM2, and SLC41A. Although our understanding of Mg2+ handling of the kidney has expanded considerably in the last two decades, many questions remain. Future studies are needed to elucidate a multitude of unknown aspects of Mg2+ handling in the kidney.
Key message:
Understanding rare and genetic diseases of Mg2+ dysregulation has expanded our knowledge and furthers the development of strategies for preventing and managing dysmagnesemia.
A novel highly selective chemosensor for Mg²⁺ ions based on the naphthalene group as the fluorophore has been designed and synthesized, which shows a fluorescence turn-on response from colorless to green for Mg²⁺ ions in DMSO–H2O solutions. L could perform as an “OFF–ON” molecular switch, which was cyclically controlled by Mg²⁺ and EDTA. Moreover, further study demonstrated that the detection limit for the fluorescence response of L to Mg²⁺ was down to 9.2 × 10⁻¹⁰ M, which was lower than with other sensors for Mg²⁺. Test strips based on L were also fabricated, which could act as a convenient and efficient Mg²⁺ test kit. The sensor L could detect Mg²⁺ in two different sources of water, distilled and tap water.
Although the magnesium ion (Mg(2+)) is one of the most abundant divalent cations in cells and known to play critical roles in many physiological processes, its mobilization and underlying mechanisms are still unknown. Here, we describe a novel fluorescent Mg(2+) probe, "KMG-104-AsH", composed of a highly selective fluorescent Mg(2+) probe, "KMG-104", and a fluorescence-recoverable probe, "FlAsH", bound specifically to a tetra-cysteine peptide tag (TCtag), which can be genetically incorporated into any protein. This probe was developed for molecular imaging of local changes in intracellular Mg(2+) concentration. KMG-104-AsH was synthesized and its optical properties were investigated in vitro. The fluorescence intensity of KMG-104-AsH (at λem/max = 540 nm) increases by more than 10-fold by binding to both the TCtag peptide and Mg(2+), and the probe is highly selective for Mg(2+) (Kd/Mg = 1.7 mM, Kd/Ca >100 mM). Application of the probe for imaging of Mg(2+) in HeLa cells showed that this FlAsH-type Mg(2+) sensing probe is membrane-permeable and binds specifically to tagged proteins, such as TCtag-actin and mKeima-TCtag targeted to the cytoplasm and the mitochondrial intermembrane space. KMG-104-AsH bound to TCtag responded to an increase in intracellular Mg(2+) concentration caused by the release of Mg(2+) from mitochondria induced by FCCP, a protonophore that eliminates the inner-membrane potential of mitochondria. This probe is expected to be a strong tool for elucidating the dynamics and mechanisms of intracellular localization of Mg(2+).
Glioblastoma (GBM) is the most common lethal brain tumor with dismal treatment outcomes and poor response to chemotherapy. As the regulatory center of cytogenetics and metabolism, most tumor chemotherapeutic molecules exert therapeutic effects in the nucleus. Nanodrugs showing the nuclear aggregation effect are expected to eliminate and fundamentally suppress tumor cells. In this study, a nanodrug delivery system based on polyhedral oligomeric silsesquioxane (POSS) is introduced to deliver drugs into the nuclei of GBM cells, effectively enhancing the therapeutic efficacy of chemotherapy. The nanoparticles are modified with folic acid and iRGD peptides molecules to improve their tumor cell targeting and uptake via receptor‐mediated endocytosis. Nuclear aggregation allows for the direct delivery of chemotherapeutic drug temozolomide (TMZ) to the tumor cell nuclei, resulting in more significant DNA damage and inhibition of tumor cell proliferation. Herein, TMZ‐loaded POSS nanoparticles can significantly improve the survival of GBM‐bearing mice. Therefore, the modified POSS nanoparticles may serve as a promising drug‐loaded delivery platform to improve chemotherapy outcomes in GBM patients.
In view of the fluorescent switching properties and anti-fatigue properties of diarylethene, a diarylethene fluorescent chemosensor for the immediate detection of Zn2+ and Mg2+ in acetonitrile was synthesized in this paper. The structure of 1o was determined by performing spectroscopy and elemental analysis. The presence of Zn2+ or Mg2+ made the chemosensor 1o showed an obvious "turn-on" fluorescent signal (bright yellow-green for Zn2+ and bright cyan for Mg2+ ). The fluorescent change caused by the 1:1 binding of 1o and Zn2+ or Mg2+ might be due to hindering the ESIPT process, which were bolstered by Benesi-Hildebrand analysis, Job's plot curves, 1 H NMR titration and mass spectrometry. The detection limits were acquired from the standard curve plots for Mg2+ ions at 44.6 nM and for Zn2+ ions at 14 nM. Based on the fluorescent behaviors, a logic gate was constructed with the emission intensity at 528/518 nm as output signal, the UV/vis lights, Mg2+ /Zn2+ and EDTA as input signals. Exogenous Zn2+ and Mg2+ fluorescent bioimaging were performed on Hela cells with 1o, indicating its potential application in biodiagnostic analysis. In particular, 1o was manufactured into test paper, and Zn2+ or Mg2+ can be conveniently, efficiently and qualitatively identified by the fluorescent color variation of the test strips.
Magnesium is essential for many cellular and physiological processes, including muscle contraction, neuronal activity and metabolism. Consequently, the blood Mg ²⁺ concentration is tightly regulated by balanced intestinal Mg ²⁺ absorption, renal Mg ²⁺ excretion and Mg ²⁺ storage in bone and soft tissues. In recent years, the development of novel transgenic animal models and the identification of Mendelian disorders has advanced our current insight in the molecular mechanisms of Mg ²⁺ reabsorption in the kidney. In the proximal tubule, Mg ²⁺ reabsorption is dependent on paracellular permeability by claudin-2/12. In the thick ascending limb of Henle's loop, claudin-16/19 provide a cation-selective pore for paracellular Mg ²⁺ reabsorption. The paracellular Mg ²⁺ reabsorption in this segment is regulated by the calcium-sensing receptor, PTH and mTOR signaling. In the distal convoluted tubule, the fine-tuning of Mg ²⁺ reabsorption takes place by transcellular Mg ²⁺ reabsorption via TRPM6/TRPM7 divalent cation channels. The activity of TRPM6/TRPM7 is dependent on hormonal regulation, metabolic activity and interacting proteins. Basolateral Mg ²⁺ extrusion is still poorly understood, but probably dependent on the Na ⁺ gradient. CNNM2 and SLC41A3 are the main candidates to act as Na ⁺ -Mg ²⁺ exchangers. Consequently, disturbances of basolateral Na ⁺ /K ⁺ transport indirectly result in impaired renal Mg ²⁺ reabsorption in the DCT. Altogether, this review aims to provide an overview of the molecular mechanisms of Mg ²⁺ reabsorption in the kidney, specifically focusing on transgenic mouse models and human hereditary disease.
A new N3O2 aza-crown macrocyclic ligand (L) bearing two fluorophore naphthalene moieties was synthesized and characterized by IR, 1H and 13C NMR, DEPt-135, HSQCGP, microanalysis as well as mass spectrometry....
Nanorobots hold great promise for integrated drug delivery systems that are responsive to molecular triggers. Herein, we successfully developed an automatic smart bionanorobot that has transport capability and recognizes and removes zinc ions from poisoned cells based on nanoscale polyhedral oligomeric silsesquioxane molecules. This intelligent bionanorobot can easily move inside and outside the cell and find zinc ions owing to its highly selective recognition to zinc ions and high cell permeability, especially the well-combined high penetration and strong binding energy. More importantly, it was also found that this intelligent bionanorobot can restore round HeLa cells to a normal fusiform cell morphology following high-concentration zinc treatment and does not interfere with cell proliferation and division. It was also shown by in vivo experiments that the bionanorobot can inhibit persistent enlargement of the liver caused by zinc ion poisoning.
The magnesium (Mg²⁺) ion is the second most abundant intracellular cation after potassium, and it is involved in a variety of biological processes and physiological functions. Because of the different effects which are dependent on Mg²⁺ ion concentration, it is critical to monitor Mg²⁺ ion levels in biological systems. Here, we report the hydrothermal synthesis of photoluminescent N-doped carbon dots (NCDs) using 4-Hydroxybenzaldehyde and 1, 2, 4, 5-benzenetetramine tetrahydrochloride as carbon and nitrogen sources, respectively. The as-synthesized NCDs demonstrated excitation dependent photoluminescence (PL) with a quantum yield of 16.2%. Because of water dispersibility and chelating functional groups, NCDs were used for highly selective detection of Mg²⁺ ions using ratiometric PL enhancement with a detection limit of 60 μM. Following that, based on highly biocompatibility and sensing of Mg²⁺ ions in aqueous solutions, NCDs were employed as photoluminescent probe to detect the Mg²⁺ ions of mammalian cell lines such as J774, HeLa, and Hek293T, which is most likely due to effective complex formation between NCDs and the intracellular Mg²⁺ ions. As far as we could possibly know, this is the first report of aqueous solution dispersed carbon dots for intracellular sensing and imaging of Mg²⁺ ions based solely on an increase in NCDs PL intensity.
Pancreatic cancer is highly malignant with a poor prognosis. Gemcitabine-based chemotherapy is the first-line treatment for pancreatic cancer; however, its clinical outcomes remain unsatisfactory due to drug resistance and side effects. In this study, we developed and characterized a novel polyhedral oligomeric silsesquioxane (POSS)-based nanoplatform (GEM-POSS-SQ), where the photothermal agent squaraine (SQ) and chemotherapeutic drug gemcitabine (GEM) were grafted into POSS via an efficient click chemistry method for combination therapy. The resultant GEM-POSS-SQ nanoparticles (NPs) effectively eliminated the aggregation of SQ and enhanced the photothermal performance in vitro and in vivo. Cell viability and apoptosis assays showed that GEM-POSS-SQ NPs exhibited a significant synergistic chemo-photothermal effect, especially in chemoresistant PANC-1 pancreatic cancer cells. Confocal laser scanning microscopy revealed near infrared (NIR)-triggered cell membrane disruption and GEM-mediated nuclear damage caused by GEM-POSS-SQ NPs. Intratumoral application of GEM-POSS-SQ NPs under NIR irradiation greatly inhibited tumor growth in PANC-1 tumor-bearing mice, with a higher proportion of TUNEL-positive cells and a lower proportion of Ki-67-positive cells observed in isolated tumor tissue. Importantly, no noticeable side effects were observed in the mice. The as-prepared GEM-POSS-SQ nanoparticles can serve as an alternative strategy to fight pancreatic cancer and can also be exploited to treat other cancers.
As a chalcone‐based fluorescent turn‐on chemosensor to Mg2+ and Cd2+, SBOD (sodium (E)‐2‐(3‐(5‐bromothiophen‐2‐yl)‐3‐oxoprop‐1‐en‐1‐yl)‐4,6‐dichlorophenolate) was designed and synthesized. SBOD detected selectively Mg2+ and Cd2+ through effective fluorescence increase. Detection limits of SBOD for Mg2+ and Cd2+ were calculated to be 3.8 μM and 2.9 μM. The binding modes of SBOD for Mg2+ and Cd2+ were determined to be 1:1 by ESI‐MS and Job plot. Association mechanisms of SBOD to Mg2+ and Cd2+ were illustrated by ESI‐MS, UV‐vis and fluorescent spectroscopy and calculations.
The metal cations, Al³⁺ and Mg²⁺, could affect human health and cell biological processes. Their fast and selective detection using one probe remains a challenge. A novel fluorescence probe, N'-((1-hydroxynaphthalen-2-yl)methylene)isoquinoline-3-carbohydrazide (NHMI), was developed for selectively monitoring Al³⁺ and Mg²⁺. The probe NHMI showed a distinctive “turn-on” fluorescence signal towards Al³⁺ and Mg²⁺ (cyan for Al³⁺ with 2556-folds enhancement and yellow for Mg²⁺ with 88-folds enhancement), which is quite distinct from other metal cations and allows for naked-eye detection. This interesting response was attributed to the influence of PET, ESIPT process and CHEF effect, when Al³⁺ or Mg²⁺ chelated with NHMI. Furthermore, the fluorescence titration experiments manifested that the detection limit of probe NHMI for Al³⁺/Mg²⁺ was as low as 1.20×10–8 M and 7.69×10–8 M, respectively. The formed complexes NHMI-Al³⁺ and NHMI-Mg²⁺ were analyzed by Job's plot, ESI-MS, ¹H-NMR and FT-IR. The coordination pockets and fluorescence mechanisms of two metal complexes were explored by density functional theory calculation. Moreover, NHMI showed low cytotoxicity and good cell permeability. Fluorescence bioimaging of Al³⁺/Mg²⁺ in MCF-7 cells with NHMI indicated its potential application in biological diagnostics analysis.
The kidneys play a crucial role in maintaining calcium (Ca ²⁺ ) and magnesium (Mg ²⁺ ) homeostasis by regulating these minerals' reabsorption. In the thick ascending limb of Henle's loop (TAL), Ca ²⁺ and Mg ²⁺ are reabsorbed through the tight junctions by a shared paracellular pathway formed by claudin-16 and claudin-19. Hypercalcemia activates the Ca ²⁺ -sensing receptor (CaSR) in the TAL, causing upregulation of the pore-blocking claudin-14 (CLDN14) that reduces Ca ²⁺ and Mg ²⁺ reabsorption from this segment. Additionally, a high Mg ²⁺ diet is known to increase both urinary Mg ²⁺ and Ca ²⁺ excretion. Since Mg ²⁺ may also activate the CaSR, we aimed to investigate whether CaSR-dependent increases in CLDN14 expression also regulate urinary Mg ²⁺ excretion in response to hypermagnesemia. Here we show that a Mg ²⁺ -enriched diet increased urinary Mg ²⁺ and Ca ²⁺ excretion in mice, however this occurred without detectable changes in renal CLDN14 expression. The administration of a high Mg ²⁺ diet to Cldn14 -/- mice did not cause more pronounced hypermagnesemia nor significantly alter urinary Mg ²⁺ excretion. Finally, in vitro evaluation of CaSR-driven Cldn14 promoter activity in response to increasing Mg ²⁺ concentrations revealed that Cldn14 expression only increases at supraphysiological extracellular Mg ²⁺ levels. Together, these results suggest that CLDN14 is not involved in regulating extracellular Mg ²⁺ balance following high dietary Mg ²⁺ intake.
Chemotherapy mostly functions as a carrier for direct drug delivery to the tumor, which may induce secondary damage to healthy tissue cells around the tumor. To avoid this side effect, using multifunctional drugs with high cell permeability during chemotherapy is crucial to achieve significant antitumor efficacy. In this study, polyhedral oligomeric silsesquioxane-based multifunctional organic–inorganic hybrid molecules with potential for recognition, imaging, and treatment were designed and successfully synthesized through a facile and efficient one-pot reaction process. The structure and properties of the synthesized multifunctional molecules were characterized by Fourier transform infrared spectroscopy, nuclear magnetic resonance spectroscopy, mass spectrometry, fluorescence spectroscopy, cytotoxicity assay, surface tension testing, cell compatibility testing, hematoxylin and eosin staining, as well as in vivo and in vitro studies. The results demonstrated that these multifunctional molecules can be effectively used for delivering precisely-targeted imaging and therapeutic agents and exhibited considerable cell permeability, The excellent synergy between high permeability and precise targeting results in multifunctional molecules with superior diagnostic performance.
Maleic anhydride is often used as a modifier to improve the thermal performance of the material due to its unique structure and properties. However, in order to meet higher demands, it is often imperative to have better heat resistance and thermal stability. Currently, the traditional method is physically blend inorganic nanoparticles to further improve thermal performance. Unfortunately, inorganic nanoparticles have a fatal problem in that they are not uniformly dispersed in the system, which severely limits their application. Here, we used organic–inorganic molecule, MAPOSS (methyl methacrylate‐based cage oligomeric silsesquioxane), to chemically modify the copolymer. And considering the unique structure of MAPOSS, we used two monomers with different polarities to study its influence on the thermal properties of the copolymerization system (MMA‐MAH‐MAPOSS and ST‐MAH‐MAPOSS), and discussed the interaction mechanism, respectively. As a result, MAPOSS introduced can not only be evenly distributed in the polymerization system via chemical bonding and physical interactions but also effectively improve the thermal stability and high‐temperature resistance of the polymers. Thereinto, the Tg of MMA‐MAH copolymer is increased to above 130°C, and the carbon residue rate is up to 7.3%. The carbon residue rate is increased to 15.6% without affecting the Tg of the ST‐MAH copolymer.
As magnesium ions have been considered as one of the most important cations for many physiological and pathological functions since the past century, selective and specific detection of magnesium ions with chemosensors has drawn great interest and became essential in biomedical and biological studies. Herein, we report on highly fluorescent boron doped carbon dots (BCDs) that are synthesized from catechol as carbon source and naphthalene boronic acid as the boron source by a simple solvothermal method. The obtained BCDs exhibited violet luminescence with quantum yield of 39.4 %, which is higher than any previous report. For the first time, the as-prepared BCDs were explored for highly selective and sensitive detection of Mg2+ ion over Ca2+ ion. This method is based on a fluorescence property resulting from the strong complex formed between Mg2+ and BCDs, with limit of detection (LOD) of about 39 µM, which is much less than the concentration range of intracellular Mg2+ ion in mammalian cells (0.5-0.7 mM). Remarkably, the BCDs can be effectively reusable upon gradual addition of EDTA to the BCDs-Mg2+ complex. The oxygen moieties on the BCDs surfaces are probable active binding sites towards Mg2+ ions for enhancing the fluorescence. Therefore, BCDs could be useful for the detection of Mg2+ ions without using expensive instruments and materials. To the best of our knowledge, this is the first report on detection of magnesium ion using carbon dots.
A new fluorescent schiff base chemosensor (H2L) was prepared for the sensitive and selective sensing of Mg²⁺ ions based on multiple mechanisms. H2L is a weak fluorescent (f = 0.031) due to PET process and CN isomerization. Upon addition of Mg²⁺, the complex [MgL] was formed and a remarkable fluorescence enhancement (f = 0.182) was produced. H2L had no such significant effect on the fluorescence in the presence of metal ions, such as Na⁺, Ag⁺, K⁺, Ca²⁺, Mg²⁺, Hg²⁺, Mn²⁺, Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺, Cd²⁺, Pb²⁺, Cr³⁺, Fe³⁺, and In³⁺. The satisfactory linear relationship was observed between the added concentrations of Mg²⁺ and the fluorescence intensity of H2L. The detection limit was 3.04 × 10⁻⁹ M with a rapid response time. Chemical inputs of Mg²⁺ and Fe³⁺ ions satisfy the conditions of INHIBIT molecular logic gate.
A solvent-dependent fluorescent probe QC for the dual detection of Mg²⁺ ion and Zn²⁺ ion has been constructed based on a Schiff base compound, in which 8-hydroxyquinoline served as not only a fluorophore but also a recognition group. Among the various tested metal ions, this probe exhibited high sensitivity and good selectivity toward Mg²⁺ ion in acetonitrile and Zn²⁺ ion in EtOH-H2O (9:1, v/v), respectively. With the treatment of Mg²⁺ ion or Zn²⁺ ion, 1:2 complex was formed between QC and Mg²⁺ ion, which inhibited the PET processes caused by the lone pair electrons from the nitrogen atom of the -C = N group and the nitrogen atom of quinoline moiety, resulting in the fluorescence enhancement for Mg²⁺ ion. Whereas a 1:1 complex was formed between QC and Zn²⁺ ion, which inhibited the PET process only caused by the lone pair electrons from the nitrogen atom of the -C = N group, resulting in the fluorescence enhancement at a shorter wavelength. The detection limit was calculated as low as 6.28 × 10⁻⁸ M for Mg²⁺ ion and 2.36 × 10⁻⁷ M for Zn²⁺ ion. DFT analysis further supported this concept to design the probe.
A fluorescent probe was rational designed and prepared to distinguish Mg²⁺ ion from Ca²⁺ ion, in which 8-hydroxyquinoline acted as not only a fluorophore but also a recognition group. Notably, this probe QB (8-hydroxyquinoline-5-benzothiazole) shows two fluorescence response modes for highly selective detection of Mg²⁺ ion, namely fluorescence ratiometric mode and turn-on mode, which can be realized by controlling the excitation wavelength at 356 nm or 425 nm. After the addition of Mg²⁺ ion, the color of the QB solution changed from colorless to yellow, which can be easily found by naked eye. All experimental results suggested that probe QB has a high selectivity toward Mg²⁺ ion in the presence of other cations. Its detection limit for Mg²⁺ ion was estimated as low as 0.142 μM, and this value was far lower than the intracellular concentration (0.5–1.2 mM). The detection mechanism was proposed further by the experiment of ¹H NMR titration and theoretical calculation. More significantly, this probe was successfully used to detect Mg²⁺ ion in brine samples as a quantitative method, and was also applied to detecting and imaging Mg²⁺ ion in living cells, indicating its great application value in practical use for the detection of Mg²⁺ ion.
The rapid, simple and reliable identification of heavy metal ions has attracted increasing attention of researchers. This work constructed a fluorescent sensor array by using 4 kinds of polymer templated silver nanoclusters (Ag NCs) as the sensing elements. This sensor array can be used for identifying 7 kinds of heavy metal ions including Pb²⁺, Fe³⁺, Cu²⁺, Cd²⁺, Cr³⁺, Co²⁺ and Ni²⁺. The fluorescence intensity ratios of Ag NCs after and before adding metal ions were applied as the output signals. We used principal component analysis (PCA) to reduce the dimensions of data variables and obtained a PCA scatter plot that could clearly distinguish every kind of 7 metal ions. This sensor array had a good performance when the ions concentration was in the range of 15-800 μM at pH of 7. The sensor array could also clearly discriminate these 7 heavy metal ions spiked in tap water. The Ag NCs-based sensor array could also be used as a fluorescence lifetime sensor array for the discrimination of metal ions. Taken all together, the developed sensor array holds great promise for practical analysis in the environment.
A novel dual-mode colorimetric and fluorescent probe was designed and synthesized based on the reaction of 1,10-phenanthroline and 8- hydroxyquinoline, 5-(1H-imidazole [4,5-f] [1,10]phenanthrolin-2-yl)quinolin-8-ol (PHQ), for detection of Mg²⁺ ion. The probe was characterized by FT-IR, UV–Vis and ¹H NMR techniques. The PHQ sensor displays outstanding sensitivity and selectivity toward Mg²⁺ over other cations via fluorescence quenching at 300 nm and color change from colorless to yellow. A very important aspect of the presented ligand is its very high fluorescence efficiency over individual precursors 1,10-phenantroline and 8-hudroxyquinoline. Addition of Mg²⁺ ion to PHQ led to a color change with a significant bathochromic shift in the λmax of the absorption band and made naked eye detection possible. The experimental results as performed by Job's method revealed a 2:1 stoichiometry of PHQ/Mg²⁺ ratio. The sensor exhibited high selectivity and sensitivity toward Mg²⁺ ions in the presence of adverse anions and cations and the detection limit was found to be 33 nM ¹H NMR and quantum calculations DFT and TDDFT were used to determine the type of interactions between the PHQ and Mg²⁺.
An innovative strategy of adjusting the molecular polarity of organics is applied for multifunctional simultaneous ions detection. It involved the use of 4-bromo-2-hydroxyben Rhodamine B hydrazide (RHBr) as a colorimetric and fluorescent multifunctional chemosensor. Briefly, it was designed and prepared via integrating 4-bromo-2-hydroxybenzaldehyde with Rhodamine B hydrazide, and Rhodamine B as fluorophore group, CO, -CHN and -OH groups as reaction site, Br atom as electro n-withdrawing group. On the basis of theoretical calculation under Gaussian 09 software suit, RHBr could exclusively recognize Cu2+, Al3+ and Ca2+. This was also experimentally confirmed by the different turn-on colorimetric and fluorescent signals. For example the selective detection of Cu2+ ion in DMSO/H2O (1/1 = v/v, 10.0 mM HEPES pH 7.0) with the "naked-eye" when the color changed from colorless to pink, Al3+ with "turn-on" strong orange-red fluorescence and Ca2+ with strong green fluorescence in EtOH/H2O (v/v = 95/5). Under the optimized conditions, all the ions could be detected at a very low concentrations (1.7 × 10-7 M, 1.0 × 10-8 M, 2.8 × 10-7 M for Cu2+, Al3+, and Ca2+, respectively). In addition, the "in situ" formed RHBr-Al3+ was used to recognize l-phenylalanine (LPA) with a "turn-off" fluorescence ranging from 0.03-10.0 μM with the low detection concetration of 3.0 × 10-7 M. The sensing mechanisms of RHBr toward three metal ions and the ensemble RHBr-Al3+ toward the l-phenylalanine (LPA) were further investigated in detail. Practical application experiments further proved that RHBr had good cell permeability and could be utilized to detect Al3+ and Ca2+, and the complexes of RHBr-Al3+ could be applied to detect l-phenylalanine (LPA) in the living cells and zebrafishes, respectively.
The magnesium ion (Mg²⁺) is an essential cation to maintain proper cellular activities. To visualize the dynamics and functions of Mg²⁺, there is a great need for the development of Mg²⁺-selective fluorescent probes. However, conventional Mg²⁺ fluorescent probes are falling behind in low selectivity and poor fluorescence color variation. In this report, to make available a distinct color window for multicolor imaging, we designed and synthesized highly Mg²⁺-selective and near-infrared (NIR) fluorescent probes, the KMG-500 series consisting of a charged μ-diketone as a selective binding site for Mg²⁺ and a Si-rhodamine residue as the NIR fluorophore, which showed photoinduced electron transfer (PeT)-type OFF-ON response to the concentration of Mg²⁺. Two types of KMG-500 series probes, tetramethyl substituted Si-rhodamine KMG-501 and tetraethyl substituted Si-rhodamine KMG-502, were synthesized for the evaluation of cell permeability. For intracellular application, the membrane-permeable acetoxymethyl derivative KMG-501 (KMG-501AM) was synthesized and allowed to stably stain cultured rat hippocampal neurons during imaging of intracellular Mg²⁺. On the other hand, KMG-502 was cell membrane permeable without AM modification, preventing the probe from staying inside cells during imaging. KMG-501 distributed mainly in the cytoplasm and partially localized in lysosomes and mitochondria in cultured rat hippocampal neurons. Mg²⁺ increase in response to the FCCP uncoupler inducing depolarization of the mitochondrial inner membrane potential was detected in the KMG-501 stained neurons. For the first time, KMG-501 succeeded in imaging intracellular Mg²⁺ dynamics with NIR fluorescence. Moreover, it allows to simultaneously visualize changes in Mg²⁺ and ATP concentration and also mitochondrial inner membrane potential and their interactions. This probe is expected to be a strong tool for multicolor imaging of intracellular Mg²⁺.
Fluorescent sensors with selectivity and sensitivity to metal ions are an active field in supramolecular chemistry for biochemical, analytical, and environmental problems. Mg2+ is one of the most abundant divalent ions in the cell, and it plays a critical role in many biological processes. Coumarin‐based sensors are widely used as desirable fluorophore and binding moieties showing a remarkable sensitivity and fluorometric enhancement for Mg2+. In this work, density functional theory/multireference configuration interaction (DFT/MRCI) calculations were performed in order to understand the sensing behavior of the organic fluorescent sensor 7‐hydroxy‐4‐methyl‐8‐((2‐(pyridin‐2‐yl)hydrazono)methyl)‐2H‐chromen‐2‐one (PyHC) in ethanol to solvated Mg2+ ions. The computed optical properties reproduce well‐reported experimental data. Our results suggest that after photoexcitation of the free PyHC, a photo‐induced electron transfer (PET) mechanism may compete with the fluorescence decay to the ground state. In contrast, this PET channel is no longer available in the complex with Mg2+ making the emissive decay more efficient. © 2019 Wiley Periodicals, Inc. Hybrid semiempiricalDFT/MRCI calculations were employed to investigate the electronic structure and fluorescing turn‐on mechanism of a coumarin‐Shiff dye upon binding to Mg2+ ions.
Vanilinyl-piconilyl hydrazide dyad Schiff base (HVPh) is structurally characterized by single crystal X-Ray diffraction data. The molecule exhibits intense green fluorescence in solid state and serves as solvent tuned dual detector to Mg2+ and Al3+ and secondary sensor to HF2-. Mg2+ impart yellow emission at 522 nm (LOD, 45 nM) in DMSO while intense blue emission for Al3+ in pure water at 460 nm (LOD, 7.4 nM) is observed. The probe forms 1:1 complex with Al3+, and 1:2 complex with Mg2+ and the composition of complexes are established by NMR, Mass and FTIR spectral data. The study of anion sensitivity of the complexes shows that the HF2- efficiently quenches the emission of the complexes and the LOD are far below the WHO recommended data (Mg2+, 200 mM; Al3+, 7.41 mM; F-, 3.68 M). A recovery study has been performed to check the practical applicability of the probe using drinking water supplied by Kolkata Municipality Corporation in the Jadavpur University campus. Molecular INHIBIT logic gate has also been constructed by the sensor. DFT and TDDFT computation technique is used to explain the experimental findings.
A new dual functional turn-on chemosensor, (2-hydroxy-5-methyl-1,3-phenylene)bis(methanylylidene)bis(isoquinoline-1-carbohydrazide) (HL), has been developed, which could highly selectively discriminate Mg²⁺ and Zn²⁺ in different solvent systems. The chemosensor HL exhibits rapid visual turn-on fluorescent enhancing recognition toward Mg²⁺/Zn²⁺, which are not interfered by other cations, especially for respective congeners Ca²⁺/Cd²⁺. The remarkable fluorescent enhancement (71-fold or 11-fold) were observed after adding Mg²⁺ in acetonitrile or Zn²⁺ in DMF-H2O solvent systems. Additionally such a solvent medium-controlled platform could achieve quantitative determination of Mg²⁺ and Zn²⁺ quantitation with low detection limits of 2.97 × 10–8 M and 3.07 × 10–7 M, respectively. Further the turn-on fluorescent sensing mechanism is also investigated by ¹H NMR spectra, FT-IR and ESI-MS spectra. Density functional theory (DFT) calculations derive optimized geometries of HL and its complexes. Notably, non-toxic HL also can be successfully applied as a visual probe for practical determination of Mg²⁺/Zn²⁺ in MCF-7 cells, Zebrafish larvae, syrup and water samples, which might provide extensive application in biological and medicine field.
A multi-ion fluorescent probe for Mg²⁺/Zn²⁺, 7-methoxychromone-3-carbaldehyde-(3’,4’,5’-tris(benzyloxy) benzoyl) hydrazone (L), based on a novel chromone-dendron Schiff base was designed and synthesized. The simultaneous detection of Mg²⁺ and Zn²⁺ was realized by regulating solvent: L showed excellent selectivity and high sensitivity toward Mg²⁺ in ethanol and Zn²⁺ in aqueous solution. The clear binding mode and corresponding turn-on mechanism (PET) were elucidated in this paper.
The development of efficient analytical procedures for the selective detection of magnesium is an important analytical task, since this element is one of the most abundant metals in cells and plays an essential role in a plenty of cellular processes. Magnesium misbalance has been related to several pathologies and diseases both in plants and animals, as far as in humans, but the number of suitable methods for magnesium detection especially in life sample and biological environments is scarce. Chemical sensors, due to their high reliability, simplicity of handling and instrumentation, fast and real-time in situ and on site analysis are promising candidates for magnesium analysis and represent an attractive alternative to the standard instrumental methods. Here the recent achievements in the development of chemical sensors for magnesium ions detection over the last decade are reviewed. The working principles and the main types of sensors applied are described. Focus is placed on the optical sensors and multisensory systems applications for magnesium assessment in different media. Further, a critical outlook on the employment of multisensory approach in comparison to single selective sensors application in biological samples is presented. Graphical abstract 2
A new fluorescent sensor, 5-methyl-1H-pyrazole-3-carboxylic acid (6-methoxy-naphthalen-2-ylmethylene)-hydrazide (PYN), composed of a naphthalene group as the fluorogenic unit and a pyrazole carbohydrazide as the binding unit for metal ions has been designed and synthesized. The sensor shows excellent selectivity and sensitivity with a fluorescence enhancement towards Zn²⁺ and Mg²⁺ over other cations in aqueous acetonitrile solution. Turn-on fluorescent enhancements (FE) as high as ∼49 fold and ∼41 fold in mixed media for Zn²⁺ and, Mg²⁺ respectively were noticed. The signal enhancement of the sensor is based on chelation-enhanced fluorescence (CHEF) effect of PYN-Zn²⁺/Mg²⁺ with the inhibition of the photoinduced electron transfer (PET) effect. Moreover, the Job's plot established 1 : 1 stoichiometry of the complex formation between PYN and Zn²⁺ or Mg²⁺ ions. The limit of detection for Zn²⁺ and Mg²⁺ is as low as 2.2 × 10⁻⁷ M and 3.9 × 10⁻⁷ M respectively. PYN exhibited a second mode of selectivity for Zn²⁺ as it displaces Mg²⁺ from the PYN-Mg²⁺ complex. Density Functional Theory (DFT) calculations have been performed in order to show the structure and electronic properties of PYN and its complexes [PYN-Zn²⁺/Mg²⁺]. Cell imaging experiments confirmed that PYN can be used for monitoring intracellular Zn²⁺ and Mg²⁺ levels in living cells in vitro.
Thymol (2-isopropyl-5-methylphenol), the major constituent of ajwain, is a naturally occurring monoterpene phenol having antioxidant, anti-inflammatory and antimicrobial activities. Herein, we report 4-hydroxy-5-isopropyl-2 methylisophthalaldehyde (DFT) derived from thymol and its derivatives as selective fluorescent chemosensors for Mg2+ in aqueous medium. These probes can selectively detect Mg2+ ion and efficiently images intracellular free Mg2+ in living RAW 264.7 and HeLa cells under fluorescence microscope without any interference from common metal ions. Density Function Theory studies strongly support the experimental facts.
In this study, a novel fluorescein-derived Schiff-base ligand bearing a chromone moiety which was called 6-Hydroxy-3-formylchromone fluorescein hydrazone (1) has been designed, synthesized and evaluated as a Mg2+ “turn on” fluorescent probe. This probe 1 exhibited high selectivity and sensitivity towards Mg2+ over other important metal ions investigated, and the remarkable enhancement in fluorescence emission centered at 504 nm was observed in the presence of Mg2+, which was attributed to the ring-opening process of the fluorescein fluorophore in probe 1 upon complexation of 1 with Mg2+. Furthermore, the “turn on” response of this probe 1 to Mg2+ was nearly completed within 3 min, which indicated that this probe 1 could be utilized to sense and monitor Mg2+ for real-time detection.
Magnesium is abundant in biological systems and an important divalent cation in the human body. Mg2+ helps mediate cellular energy metabolism, ribosomal and membrane integrity. Additionally Mg2+ modulates the activity of several membrane transport and signal transduction systems. Despite its importance however, little is known about the molecular mechanisms of Mg2+ transport and homeostasis in mammals. In mammals the amount of Mg2+ absorption is about the same as the amount of Mg2+ excretion in urine. Additionally, when total Mg2+ intake is deficient, the kidney is capable of reabsorbing all filtered Mg2+. This balance between intake and excretion indicates that the kidney plays a principal role in maintenance of total body Mg2+ homeostasis. Within the kidney, Mg2+ filtered by the glomerulus is handled in different ways along the nephron. About 10-20% of Mg2+ is reabsorbed by the proximal tubule. the bulk of Mg2+ (about 50-70%) is reabsorbed by the cortical thick ascending limb of the loop of Henle. In this region, Mg2+ moves across the epithelium through the paracellular pathway, driven by the positive lumenal transepithelial voltage. A recently cloned human gene, paracellin-1 was shown to encode a protein localized to the tight junctions of the cortical thick ascending limb and is thought to mediate Mg2+ transport via the paracellular space of this epithelium. The distal convoluted tubule reabsorbs the remaining 5-10% of filtered Mg2+. This segment seems to play an important role in determining final urinary excretion, since there is no evidence for significant Mg2+ absorption beyond the distal tubule. Although many renal Mg2+ transport activities have been characterized, no Mg2+ transporter cDNAs have been cloned from mammalian tissues. Recent research has certainly expanded our knowledge of Mg2+ transport in kidney; but details of the transport processes and the mechanisms by which they control Mg2+ excretion must await cloning of renal Mg2+ transporters and/or channels. Such information would provide new concepts in our understanding of renal Mg2+ handling.
The body maintains Mg(2+) homeostasis by renal and intestinal (re)absorption. However, the molecular mechanisms that mediate transepithelial Mg(2+) transport are largely unknown. Transient receptor potential melastatin 6 (TRPM6) was recently identified and shown to function in active epithelial Mg(2+) transport in intestine and kidney. To define the relationship between Mg(2+) status and TRPM6 expression, we used two models of hypomagnesemia: 1) C57BL/6J mice fed a mildly or severely Mg(2+)-deficient diet, and 2) mice selected for either low (MgL) or high (MgH) erythrocyte and plasma Mg(2+) status. In addition, the mice were subjected to a severely Mg(2+)-deficient diet. Our results show that C57BL/6J mice fed a severely Mg(2+)-deficient diet developed hypomagnesemia and hypomagnesuria and showed increased TRPM6 expression in kidney and intestine. When fed a Mg(2+)-adequate diet, MgL mice presented hypomagnesemia and hypermagnesuria, and lower kidney and intestinal TRPM6 expression, compared with MgH mice. A severely Mg(2+)-deficient diet led to hypomagnesemia and hypomagnesuria in both strains. Furthermore, this diet induced kidney TRPM6 expression in MgL mice, but not in MgH mice. In conclusion, as shown in C57BL/6J mice, dietary Mg(2+)-restriction results in increased Mg(2+) (re)absorption, which is correlated with increased TRPM6 expression. In MgL and MgH mice, the inherited Mg(2+) status is linked to different TRPM6 expression. The MgL and MgH mice respond differently to a low-Mg(2+) diet with regard to TRPM6 expression in the kidney, consistent with genetic factors contributing to the regulation of cellular Mg(2+) levels. Further studies of these mice strains could improve our understanding of the genetics of Mg(2+) homeostasis.