Microfluidic Paper-Based Analytical Devices (μPADs) and Micro Total Analysis Systems (μTAS): Development, Applications and Future Trends

Microfluidic paper-based analytical devices and micro total analysis systems are relatively new group of analytical tools, capable of analyzing complex biochemical samples containing macromolecules, proteins, nucleic acids, toxins, cells or pathogens. Within one analytical run, fluidic manipulations like transportation, sorting, mixing or separation are available. Recently, microfluidic devices are a subject of extensive research, mostly for fast and non-expensive biochemical analysis but also for screening of medical samples and forensic diagnostics. They are used for neurotransmitter detection, cancer diagnosis and treatment, cell and tissue culture growth and amplification, drug discovery and determination, detection and identification of microorganisms. This review summarizes development history, basic fabrication methods, applications and also future development trends for production of such devices.     

Microfluidic fluorescence in situ hybridization and flow cytometry (μFlowFISH)

We describe an integrated microfluidic device (μFlowFISH) capable of performing 16S rRNA fluorescence in situ hybridization (FISH) followed by flow cytometric detection for identifying bacteria in natural microbial communities. The device was used for detection of species involved in bioremediation of Cr(vi) and other metals in groundwater samples from a highly-contaminated environmental site (Hanford, WA, USA). The μFlowFISH seamlessly integrates two components: a hybridization chamber formed between two photopolymerized membranes, where cells and probes are electrophoretically loaded, incubated and washed, and a downstream cross structure for electrokinetically focusing cells into a single-file flow for flow cytometry analysis. The device is capable of analyzing a wide variety of bacteria including aerobic, facultative and anaerobic bacteria and was initially tested and validated using cultured microbes, including Escherichia coli, as well as two strains isolated from Hanford site: Desulfovibrio vulgaris strain RCH1, and Pseudomonas sp.strain RCH2 that are involved in Cr(vi) reduction and immobilization. Combined labeling and detection efficiencies of 74-97% were observed in experiments with simple mixtures of cultured cells, confirming specific labeling. Results obtained were in excellent agreement with those obtained by conventional flow cytometry confirming the accuracy of μFlowFISH. Finally, the device was used for analyzing water samples collected on different dates from the Hanford site. We were able to monitor the numbers of Pseudomonas sp. with only 100-200 cells loaded into the microchip. The μFlowFISH approach provides an automated platform for quantitative detection of microbial cells from complex samples, and is ideally suited for analysis of precious samples with low cell numbers such as those found at extreme environmental niches, bioremediation sites, and the human microbiome.     

Improvement on Simultaneous Determination of Cr(III) and Cr(VI) by Capillary Electrophoresis and Chemiluminescence Detection

Chromiumexistsindifferentoxidationstatesingroundwater,industrialwastewater,seawater,andsoilofourenvironment1,2.Chromium(III)isanessentialtraceelementforhumans,requiredforthemaintenanceofnormalglucose,cholesterol,andfattyacidmetabolism.Ontheotherhand,watersolublechromium(VI),intheformCr2O72-orCrO42-,ishighlyirritatingandtoxictohumansandanimals3.Itsacutetoxiceffectsincludeanimmediatecardiovascularshockandlatereffectsonkidney,liver,andblood-formingorgans.Therefore,itisnecessaryforriskassessme…     

Study on Conductivity Detection for Capillary Electrophoresis──Design of a new type of miniature conductance cell

IntroductionSineHjerenintroduceditinl967,capillaryelectrophoresis(CE)hasbecomeapowerfulanalyticaltool.Becauseithasidealdetectionlimits,smallsampleintIoductionandhighseparationefficiency,CEhasbeenappliedinmanyareasincludingchemistry,biology,medicineandenvironmentalscience,etc.InCEtechnique,owingtoextremelysmallsampleintroductionandverythincapillaries,thedetectorsmustpossessthefeaturesofhigh-sensitivity,high-reso1ution,rapidresponseandon-line.Forthisreason,developingdetectivemethodsisaveryim…     

Spectroscopic Properties of a Biologically Relevant [Fe2(μ-O)2] Diamond Core Motif with a Short Iron-Iron Distance

Diiron cofactors in enzymes perform diverse challenging transformations. The structures of high valent intermediates ( Q in methane monooxygenase and X in ribonucleotide reductase) are debated since Fe−Fe distances of 2.5–3.4 Å were attributed to “open” or “closed” cores with bridging or terminal oxido groups. We report the crystallographic and spectroscopic characterization of a Fe^III₂(μ-O)₂ complex ( 2 ) with tetrahedral (4C) centres and short Fe−Fe distance (2.52 Å), persisting in organic solutions. 2 shows a large Fe K-pre-edge intensity, which is caused by the pronounced asymmetry at the T_D Fe^III centres due to the short Fe−μ−O bonds. A ≈2.5 Å Fe−Fe distance is unlikely for six-coordinate sites in Q or X , but for a Fe₂(μ-O)₂ core containing four-coordinate (or by possible extension five-coordinate) iron centres there may be enough flexibility to accommodate a particularly short Fe−Fe separation with intense pre-edge transition. This finding may broaden the scope of models considered for the structure of high-valent diiron intermediates formed upon O₂ activation in biology.     

Studies on Nucleophilic Ring-Opning Reaction of Ethylene Epoxide by (μ - CH,S )(μ-IMIgS ) Fea (CO)a——Syntheais and Crystal Structure of (μ-Methylthio)- (μ- R -Hydroxylethylthio)hexacarbonyldiiron

A new type of Fe-S complex (C), (μ -CH3S) (μ-HOCH2CH2S) Fe2(CO)6which contains μ-β-hydroxyethyl, has been synthesized in high yield through ring-opening reaction of ethylene epoxide under uncleophilic attack of active complex (A), (μ-CH3S)(μ-IMgS) Fe2(CO)6, followed byan alcoholysis of the intermediate (B). The crystal structure of (C)was determined by an X-ray diffraction technique. The crystal belongs to monoclinic system with space group of C2/c. Cell parameters a= 15.784(3), b = 22.172(3), c=9.774(2)A, β=119.53(2)°, V=2976.3A. Dc = 1.SOg cm-3 , Z=8, F(000)=1616 and final R=0.077.     

Synthesis and Structure of a Novel Mg6 Cluster Molecule Mg6(μ3-OH)2(μ3-Br)2(μ-Br)8(THF)8

A novel Mg₆ cluster molecule with the formula of Mg₆( ₃-OH)₂( ₃-Br)₂(-Br)₈(THF)₈ (1) has been isolated in 38% yield from a reaction of the Grignard reagent, 2-naphthyl-Mg-Br with BBr₃ in THF. The structure of 1, determined by a single-crystal X-ray diffraction analysis, contains two Mg₃ triangles linked together by two bridging bromide ligands. Within each Mg₃ triangle, one hydroxide and one bromide ligand function as triply bridging ligands capping both sides of the Mg₃ triangle. The coordination geometry around each Mg(II) ion is approximately octahedral. NMR studies revealed that compound 1 is highly fluxional in solution.     

Detection of Hydrogen Peroxide in River Water via a Microplate Luminescence Assay with Time-Resolved (“Gated”) Detection

Hydrogen peroxide (HP) in river water was determined using the highly luminescent Eu³⁺-tetracycline hydrogen peroxide (EuTc-HP) complex. A 15-fold increase in luminescence intensity of Eu³⁺-tetracycline (EuTc) is observed at 616nm after formation of EuTc-HP. In order to eliminate interferences by other fluorescent substances that exist in river water, a time-resolved scheme is employed: EuTc-HP has a main decay time of 61µs, while background fluorescence decays within a few ns. Thus, by performing measurements after a delay time of typically 30µs, the signal becomes highly specific for EuTc-HP. Under optimized conditions (pH 7 in MOPS buffer), the calibration curve for the determination of HP was linear over the range of 2 to 160µmolL^–1. The limit of detection is 1.1µmolL^–1 HP. An average recovery of 99.5% was obtained for measurements of river water samples spiked with HP. The relative standard deviation of less than 2% indicates the high accuracy and precision of the method.     

Synthesis and characterisation of hexanuclear ruthenium clusters containing a μ4-nitrene ligand. Crystal structures of [Ru6(CO)15(μ-CO)2(μ4NH)(μ-OMe)μ3-η2-N(H)C(O)OMe] and [Ru6(CO)16(μ-CO)2(μ4-NH)(μ-OMe)(μ-NCO)]

Two hexaruthenium carbonyl clusters [Ru₆(CO)₁₅(μ-CO)₂(μ₄-NH) (μ-OMe){μ₃-η²-N(H)C(O)OMe}] and [Ru₆(CO)₁₆(μ-CO)₂-(μ₄-NH)(μ-OMe)(μ-NCO)]2 have been isolated from the pyrolysis of H₂Ru₃(CO))₉NOCH₃, and single-crystal X-ray structure analysis shows that both 1 and 2 have a square planar arrangement of four ruthenium atoms capped by a μ₄-nitrene ligand, with two additional ruthenium atoms bridging two opposite RuRu edges of the square base to form a ‘boat’ form metal framework.     

Large tunneling effect on the hydrogen transfer in bis(μ-oxo)dicopper enzyme: a theoretical study

Type-III copper-containing enzymes have dicopper centers in their active sites and exhibit a novel capacity for activating aliphatic C-H bonds in various substrates by taking molecular oxygen. Dicopper enzyme models developed by Tolman and co-workers reveal exceptionally large kinetic isotope effects (KIEs) for the hydrogen transfer process, indicating a significant tunneling effect. In this work, we demonstrate that variational transition state theory allows accurate prediction of the KIEs and Arrhenius parameters for such model systems. This includes multidimensional tunneling based on state-of-the-art quantum-mechanical calculations of the minimum-energy path (MEP). The computational model of bis(μ-oxo)dicopper enzyme consists of 70 atoms, resulting in a 204-dimensional potential energy surface. The calculated values of E(a)(H) - E(a)(D), A(H)/A(D), and the KIE at 233 K are -1.86 kcal/mol, 0.51, and 28.1, respectively, for the isopropyl ligand system. These values agree very well with experimental values within the limits of experimental error. For the representative tunneling path (RTP) at 233 K, the pre- and post-tunneling configurations are 3.3 kcal/mol below the adiabatic energy maximum, where the hydrogen travels 0.54 ? by tunneling. We found that tunneling is very efficient for hydrogen transfer and that the RTP is very different from the MEP. It is mainly heavy atoms that move as the reaction proceeds from the reactant complex to the pretunneling configuration, and the hydrogen atom suddenly hops at that point.     

Synthesis,Crystal Structure and Catalytic Activity of a Hexa-μ-chloro-tetrakis-(1-triphenylmethyltriazole)-μ4-oxo-tetracopper(Ⅱ)

A new Cu(Ⅱ) complex,[Cu_4Cl_6O(1-TrTz)_4]where 1-Tr Tz is 1-trityl-1H-[1,2,4]triazole,was synthesized by the reaction of 1-trityl-1H-[1,2,4]triazole with two hydrated cupric chlorides,and its structure was characterized by X-ray single-crystal diffraction.[Cu_4Cl_6O(1-TrTz)_4]is of monoclinic system,space group P21/c,a=12.5024(13),b=26.400(3),c=28.588(3)?,β=112.807(4)°,V=8698.1(16)?~3,Z=4,ρ_(calc)=1.411 g/cm~3,μ=1.265 mm~(–1),F(000)=3772,the final R=0.1293 and w R=0.3644 for 55774 observed reflections (I2s(I)),R(all data)=0.1972,w R(all data)=0.3989,completeness to theta of 25.242 is 99.9%and GOF=1.103.In the structure of[Cu_4Cl_6O(1-TrTz)_4],the central O atom is tetrahedral and is coordinated with four Cu atoms.The distance between copper and oxygen bond is 1.909(6)?.In addition,the catalytic property of this complex was investigated and it could effectively catalyze the Ullmann coupling reaction of various (hetero)aryl chlorides with azoles.     

Chemical Synthesis Studies on Pb Zr Alkoxides: A New Pb-Zr Structural Type,Pb3Zr7(μ4-O)4 (μ3-O)4(μ-O2CCH3) 8(μ-OiPr)6(Oi Pr)4

The compound [Pb₃Zr₇(₄-O)₄ (₃-O)₄(O₂CCH₃)₈ (OPrⁱ)₁₀] has been isolated from a reaction mixture containing known Pb-Zr and Pb-Ti complexes and characterised by ²⁰⁷Pb and ¹ H NMR and IR spectroscopy. The compound crystallises in the space group P with a = 13.778(4) Å, b = 21.916(5) Å, c = 27.768(10) Å; = 86.52(3)°, = 87.68(3)°, = 72.72(2)° V 7989(4) ų, Z = 4, R = 0.0973. A Pb-Zr alkoxide complex containing acetylacetone has also been synthesised using PbO as a reagent having the composition [Pb₂Zr₄(O)₂ (OⁱPr)₆(OⁿPr)₈ (acac)₂] allocated on the basis of MW, mass spectral and ¹H NMR data.     

Development of a N-acetyl-β-D-glucosaminidase (NAG) assay on a centrifugal lab-on-a-compact-disc (Lab-CD) platform

A centrifugal microfluidic platform, which is also known as lab-on-a-compact-disc (Lab-CD), was developed for use as a urinary N-acetyl-β-D-glucosaminidase (NAG) activity assay. In this work, Lab-CD design, centrifugal operations and analytical procedures were established. Automated liquid handling on Lab-CD processes, such as fluid transport, sample metering, mixing, and fluorescence detection are accomplished using a portable Lab-CD system. The linearity of the NAG assay using 4-methylumbelliferyl-N-acetyl-β-D-glucosaminide (4-MU-GlcNAc) was found to be acceptable in the range of 2.5 to 20 U L(-1); the relative standard deviations for the fluorescence intensity of eight samples (7.5 U L(-1)) was 6.4%. Clinical diagnostics is one of the most promising applications for Lab-CD technologies. All the benefits of miniaturization, such as reduced sample requirement, reduced reagent consumption and automation, are realized in this investigation.     

Co-complexation of Lithium Gallates on the Titanium Molecular Oxide {[Ti(η(5)-C(5)Me(5))(μ-O)}(3)(μ(3)-CH)

Amide and lithium aryloxide gallates [Li(+){RGaPh(3)}(-)] (R = NMe(2), O-2,6-Me(2)C(6)H(3)) react with the μ(3)-alkylidyne oxoderivative ligand [{Ti(η(5)-C(5)Me(5))(μ-O)}(3)(μ(3)-CH)] (1) to afford the gallium-lithium-titanium cubane complexes [{Ph(3)Ga(μ-R)Li}{Ti(η(5)-C(5)Me(5))(μ-O)}(3)(μ(3)-CH)] [R = NMe(2) (3), O-2,6-Me(2)C(6)H(3) (4)]. The same complexes can be obtained by treatment of the [Ph(3)Ga(μ(3)-O)(3){Ti(η(5)-C(5)Me(5))}(3)(μ(3)-CH)] (2) adduct with the corresponding lithium amide or aryloxide, respectively. Complex 3 evolves with formation of 5 as a solvent-separated ion pair constituted by the lithium dicubane cationic species [Li{(μ(3)-O)(3)Ti(3)(η(5)-C(5)Me(5))(3)(μ(3)-CH)}(2)](+) together with the anionic [(GaPh(3))(2)(μ-NMe(2))](-) unit. On the other hand, the reaction of 1 with Li(p-MeC(6)H(4)) and GaPh(3) leads to the complex [Li{(μ(3)-O)(3)Ti(3)(η(5)-C(5)Me(5))(3)(μ(3)-CH)}(2)][GaLi(p-MeC(6)H(4))(2)Ph(3)] (6). X-ray diffraction studies were performed on 1, 2, 4, and 5, while trials to obtain crystals of 6 led to characterization of [Li{(μ(3)-O)(3)Ti(3)(η(5)-C(5)Me(5))(3)(μ(3)-CH)}(2)][PhLi(μ-C(6)H(5))(2)Ga(p-MeC(6)H(4))Ph] 6a.     

The effects of redox-inactive metal ions on the activation of dioxygen: isolation and characterization of a heterobimetallic complex containing a Mn(III)-(μ-OH)-Ca(II) core

Rate enhancements for the reduction of dioxygen by a Mn(II) complex were observed in the presence of redox-inactive group 2 metal ions. The rate changes were correlated with an increase in the Lewis acidity of the group 2 metal ions. These studies led to the isolation of heterobimetallic complexes containing Mn(III)-(μ-OH)-M(II) cores (M(II) = Ca(II), Ba(II)) in which the hydroxo oxygen atom is derived from O(2). This type of core structure has relevance to the oxygen-evolving complex within photosystem II.     

Synthesis, Structure and Properties of a Copper Complex Cu2(μ-PhCOO)2(μ-CH3COO)2(CH3OH)2

The title complex Cu2(μ-PhCOO)2(μ-CH3COO)2(CH3OH)2 1(C20H24Cu2O10, Mr=structure was determined by X-ray diffraction method. Complex 1 belongs to orthorhombic, space group Pbca with a = 13.083(6), b = 8.078(4), c = 21.566(2)(A), V = 2279(2) (A)3, Z = 4, Dc= 1.607g/cm3, F(000) = 1128,μ(MoKa) = 1.918 mm-1, the final R = 0.0506 and wR = 0.1382. Each Cu(Ⅱ)ion is coordinated by five oxygen atoms from two benzoic acids, two acetic acids and one methanol molecule in a slightly distorted square pyramidal environment. The title molecules construct a 2-D complex 1 displays strong emissions. IR and TG-DTA studies are also presented.     

A New Preparation of Mo2(CO)8(μ-PPh2)2 and W2(CO)8(μ-PPh2)2 by a Phosphorus-Carbon Bond Cleavage Reaction. Crystal Structure of a New Polymorph of Mo2(CO)8(μ-PPh2)2

A new synthesis of Mo₂(CO)₈(-PPh₂)₂ and W₂(CO)₈(-PPh₂)₂ by the reaction of molybdenum and tungsten hexacarbonyls with a tetraazamacrocyclic ligand containing —CH₂PPh₂ side chains, comprising cleavage of the phosphorus-methylene bond has been performed. The complexes have been investigated by magnetic and spectroscopic measurements and by single-crystal structure analyses. The structural characterization of a new polymorph of Mo₂(CO)₈(-PPh₂)₂ has been described.