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Biomolecule-bound Mg2+ species, particularly polyphosphate complexes, represent a large and dynamic fraction of the total cellular magnesium that is essential for cellular function but remains invisible to most indicators. Here we report a new family of Eu(III)-based indicators, the MagQEu family, functionalized with a 4-oxo-4H-quinolizine-3-carboxylic acid metal recognition group/sensitization antenna for turn-on, luminescence-based detection of biologically relevant Mg2+ species. [ABSTRACT FROM AUTHOR]

Biomolecule-bound Mg2+ species, particularly polyphosphate complexes, represent a large and dynamic fraction of the total cellular magnesium that is essential for cellular function but remains invisible to most indicators. Here we report a new family of Eu(III)-based indicators, the MagQEu family, functionalized with a 4-oxo-4H-quinolizine-3-carboxylic acid metal recognition group/sensitization antenna for turn-on, luminescence-based detection of biologically relevant Mg2+ species. [ABSTRACT FROM AUTHOR]

In this work, we employed target-driven assembly of a Mg2+-dependent DNAzyme to develop an ultrasensitive electrochemical biosensor for the simultaneous detection of miRNA-21 and miRNA-141. The target miRNAs could hybridize with two partial DNAzymes, facilitating the formation of a stable and active Mg2+-dependent DNAzyme. With the help of the Mg2+ cofactor, the DNAzyme could circularly cleave the ferrocene (Fc) or methylene blue (MB) labelled hairpin probes and release Fc and MB labels from the electrode surface, which could significantly amplify the current suppression to achieve multiple detection of small amounts of miRNA-21 and miRNA-141. This electrochemical biosensor showed high sensitivity and selectivity for the simultaneous detection of miRNA-21 and miRNA-141. Furthermore, the proposed method was also successfully applied for the determination of miRNA-21 and miRNA-141 from diluted serum samples. Overall, the proposed sensor showed several considerable advantages including simple preparation, high sensitivity, and enzyme-free signal amplification. Therefore, the proposed electrochemical biosensor could be used as a highly efficient amplification strategy for simultaneous detection of various miRNA biomarkers in bioanalysis and clinical diagnostics. [ABSTRACT FROM AUTHOR]

Most fluorescent indicators for Mg2+ suffer from poor selectivity against other divalent cations, especially Ca2+, thus do not provide reliable information on cellular Mg2+ concentrations in processes in which such metals are involved. We report a new set of highly selective fluorescent indicators based on alkoxystyryl-functionalized BODIPY fluorophores decorated with a 4-oxo-4H-quinolizine-3-carboxylic acid metal binding moiety. The new sensors, MagQ1 and MagQ2, display absorption and emission maxima above 600 nm, with a 29-fold fluorescence enhancement and good quantum yields (Φ ＞ 0.3) upon coordination of Mg2+ in aqueous buffer. Fluorescence response to Mg2+ is not affected by the presence of competing divalent cations typically present in the cellular milieu, and displays minimal pH dependence in the physiologically relevant range. The choice of alkoxy groups decorating the styryl BODIPY core does not influence the basic photophysical and metal binding properties of the compounds, but has a marked effect on their intracellular retention and thus in their applicability for detection of cellular Mg2+ by fluorescence imaging. In particular, we demonstrate the utility of a triethyleneglycol (TEG) functionalization tactic that endows MagQ2 with superior cellular retention in live cells by reducing active extrusion through organic anion transporters, which are thought to cause fast leakage of typical anionic dyes. With enhanced retention and excellent photophysical properties, MagQ2 can be applied in the detection of cellular Mg2+ influx without interference of high concentrations of Ca2+ akin to those involved in signaling. [ABSTRACT FROM AUTHOR]

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

Biomolecule-bound Mg 2+ species, particularly polyphosphate complexes, represent a large and dynamic fraction of the total cellular magnesium that is essential for cellular function but remains invisible to most indicators. Here we report a new family of Eu(III)-based indicators, the MagQEu family, functionalized with a 4-oxo-4 H -quinolizine-3-carboxylic acid metal recognition group/sensitization antenna for turn-on, luminescence-based detection of biologically relevant Mg 2+ species.

Most fluorescent indicators for Mg 2+ suffer from poor selectivity against other divalent cations, especially Ca 2+ , thus do not provide reliable information on cellular Mg 2+ concentrations in processes in which such metals are involved. We report a new set of highly selective fluorescent indicators based on alkoxystyryl-functionalized BODIPY fluorophores decorated with a 4-oxo-4 H -quinolizine-3-carboxylic acid metal binding moiety. The new sensors, MagQ1 and MagQ2 , display absorption and emission maxima above 600 nm, with a 29-fold fluorescence enhancement and good quantum yields (Φ > 0.3) upon coordination of Mg 2+ in aqueous buffer. Fluorescence response to Mg 2+ is not affected by the presence of competing divalent cations typically present in the cellular milieu, and displays minimal pH dependence in the physiologically relevant range. The choice of alkoxy groups decorating the styryl BODIPY core does not influence the basic photophysical and metal binding properties of the compounds, but has a marked effect on their intracellular retention and thus in their applicability for detection of cellular Mg 2+ by fluorescence imaging. In particular, we demonstrate the utility of a triethyleneglycol (TEG) functionalization tactic that endows MagQ2 with superior cellular retention in live cells by reducing active extrusion through organic anion transporters, which are thought to cause fast leakage of typical anionic dyes. With enhanced retention and excellent photophysical properties, MagQ2 can be applied in the detection of cellular Mg 2+ influx without interference of high concentrations of Ca 2+ akin to those involved in signaling., Competing Interests: Conflicts of interest There are no conflicts to declare.

Fluorescent sensors with low-energy excitation are in great demand for the study of cellular Mg 2+ by fluorescence miscroscopy, but to date they remain scarce. Addressing this gap, we report herein a new set of molecular fluorescent sensors for the detection of Mg 2+ based on an o-aminophenol-N,N,O-triacetic acid (APTRA) metal-recognition moiety combined with two different BODIPY fluorophores. The new sensors, MagB1 and MagB2, display absorption and emission maxima in the visible range and respond to Mg 2+ in aqueous buffer with large fluorescence enhancements. MagB2, a red-emitting fluorescent indicator based on a styryl-BODIPY, displays superior metal selectivity and optical properties compared to its green emitting counterpart, MagB1. With an excellent 58-fold fluorescence turn-on and Mg 2+ dissociation constant in tune with physiological concentrations of the cation (low millimolar range), MagB2 enables visualization of changes in intracellular levels of free Mg 2+ in live cells with no significant interference from basal levels of Ca 2+ , the most common competitor.

A new dinuclear Ru(II) polypyridyl complex, [(bpy)2 Ru(H2 bpip)Ru(bpy)2 ](4+) (RuH2 bpip, bpy=2,2-bipyridine, H2 bpip=2,6-pyridyl(imidazo[4,5-f][1,10]phenanthroline), was developed to act as a one- and two-photon luminescent probe for biological Cu(2+) detection. This Ru(II) complex shows a significant two-photon absorption cross section (400 GM) and displays a remarkable one- and two-photon luminescence switch in the presence of Cu(2+) ions. Importantly, RuH2 bpip can selectively recognise Cu(2+) in aqueous media in the presence of other abundant cellular cations (such as Na(+) , K(+) , Mg(2+) , and Ca(2+) ), trace metal ions in organisms (such as Zn(2+) , Ag(+) , Fe(3+) , Fe(2+) , Ni(2+) , Mn(2+) , and Co(2+) ), prevalent toxic metal ions in the environment (such as Cd(2+) , Hg(2+) , and Cr(3+) ), and amino acids, with high sensitivity (detection limit≤3.33×10(-8)  M) and a rapid response time (≤15 s). The biological applications of RuH2 bpip were also evaluated and it was found to exhibit low cytotoxicity, good water solubility, and membrane permeability; RuH2 bpip was, therefore, employed as a sensing probe for the detection of Cu(2+) in living cells and zebrafish., (Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)