Near-infrared chromogenic sensing of organotin species by a cyclopalladated azo dye.

A simple cyclopalladated complex of 4-(2-thiazolylazo)resorcinol showed a specific red-to-green colour change upon addition of organotin species in the acetonitrile-water medium.

A colorimetric and fluorescent merocyanine-based probe for biological thiols.

A new "dual-mode" chromogenic and fluorescent turn-on probe (2) for the selective sensing of biological thiols is reported. In MeOH-H(2)O cosolvent at physiological pH 7.40 (MeOH-H(2)O = 3:7), biological thiols cleave the 2,4-dinitrobenzenesulfonyl group to release the chromo- and fluorophore merocyanine (3).

Enhanced fluorescence sensing of hydroxylated organotins by a boronic acid-linked Schiff base.

A simple Schiff base, 2-(2',4'-dihydroxybenzylidene)aminobenzeneboronic acid, was found to show a fluorescence enhancement in the presence of hydroxylated organotins in aqueous solution.

Pb(4)Br(11)(3-) cluster as a fluorescent indicator for micro water content in aprotic organic solvents.

Micro water content in aprotic solvents can be conveniently determined from the Stokes' shift value of the fluorescent anionic Pb(4)Br(11)(3-) cluster in situ formed in the test solvents.

A novel Hg2+ selective ratiometric fluorescent chemodosimeter based on an intramolecular FRET mechanism.

A irreversible Hg2+ selective ratiometric fluorescence probe FR, a fluorescein fluorophore linked to a rhodamine B hydrazide by a thiourea spacer, was designed and synthesized. The developed probe FR exhibited great ratiometric fluorescence enhancement and remarkable yellow-magenta color change toward Hg2+ with excellent selectivity in aqueous acetone solution, and the ratiometric fluorescence response to Hg2+ was not interfered by other metal cations including Fe3+, Co2+, Ni2+, Cr3+, Zn2+, Pb2+, Cd2+, Ca2+, Mg2+, Ba2+ and Mn2+. The linear range and the detection limit of this supposed ratiometric fluorescence method for Hg2+ were 0.0-10.0x10(-6) and 5x10(-8) M, respectively.

Fluorogenic and chromogenic rhodamine spirolactam based probe for nitric oxide by spiro ring opening reaction.

A new fluorogenic and chromogenic probe rhodamine B spirolactam (1) was developed that in aqueous solutions exhibited a highly selective and sensitive "turn-on" type spectral response toward NO detection following a NO-induced spiro-ring opening reaction in 1.

Rhodamine thiospirolactone. Highly selective and sensitive reversible sensing of Hg(II).

A novel rhodamine thiospirolactone chemosensor was found to develop prominent absorbance and fluorescence enhancements in the presence of Hg(2+) in aqueous solution and this was suggested to result from the thiospiro ring opening induced by Hg(2+) binding.

Colorimetric detection of fluoride in an aqueous solution using Zr(IV)-EDTA complex and a novel hemicyanine dye.

A new highly sensitive and selective colorimetric method for fluoride determination in water is described. The novel reagent used is a hemicyanine dye (HC), which forms a stable complex with Zr-EDTA, the fluoride-binding site, through the hydroxyl groups. The hemicyanine-chelating Zr-EDTA complex (HC-Zr-EDTA) is ready to react with fluoride ion to release HC. This result in remarkable color change of the sensing solutions from red (lambda(max)=513nm) to yellow (lambda(max)=427nm) at pH 4.40. When applied to the colorimetric determination of fluoride ions, a linear range from 3.0x10(-6) to 5.0x10(-5)mol/L and a detection limit of 2.8x10(-6)mol/L with a correlation coefficient of 0.9993 can be achieved under the optimized conditions. Because of the specific affinity of fluorides for the [Zr-EDTA], there is little interference by other ions. This method has been successfully applied to the determination of fluorides in toothpaste samples.

Switching the recognition preference of rhodamine B spirolactam by replacing one atom: design of rhodamine B thiohydrazide for recognition of Hg(II) in aqueous solution.

A new chemosensor based on rhodamine B thiohydrazide is described. Chemosensor B was found to show a reversible dual chromo- and fluorogenic response toward Hg2+ in aqueous solution in a highly selective and sensitive manner. This was suggested to result from the coordination of Hg2+ at the N, S binding sites in B to open its spiro ring.

A cyclometalated palladium-azo complex as a differential chromogenic probe for amino acids in aqueous solution.

Solutions of a cyclometalated palladium-azo complex exhibited differential UV-Vis absorption spectra in the presence of alpha-amino acids with different side chain groups.

Preparation of pH-sensitive polymer by thermal initiation polymerization and its application in fluorescence immunoassay.

A fluorescence immunoassay for human IgG (Ag) was developed using a pH-sensitive polymer prepared by thermal initiation or redox initiation polymerization as a carrier. In the competitive immunoassay, appropriate quantity of Ag was immobilized on the polymer and the standard Ag (or sample) solution, and a constant amount of fluorescein isothiocyanate labeled goat anti-human IgG antibody (Ab-FITC) was added. Immobilized Ag and the standard (or sample) Ag competed for binding to the Ab-FITC in 37 degrees C in homogeneous format. After changing the pH to separate the polymer-immune complex precipitate, it was re-dissolved and determined by fluorescence method. The results showed that the immobilization efficiency, immunological reaction activities of immobilized Ag and phase transition pH range were improved as Ag was immobilized by thermal initiation instead of redox initiation polymerization. Under optimum conditions, the calibration graphs for the Ag in both methods, thermal initiation and redox initiation, were linear over the concentration range of 0.0-1000ngmL(-1), with detection limits 8 (thermal initiation) and 12ngmL(-1) (redox initiation), respectively. Moreover, some pH-sensitive polymer prepared only in organic solvent or under high temperature could also be used as an immunoreaction carrier by thermal initiation polymerization. Thermal initiation polymerization was a better immobilization mode.

A lanthanide hybrid cluster as a selective optical chemosensor for phosphate-containing anions in aqueous solution.

An europium-chelating [2Fe-2S] cluster was used to assemble an optical molecular chemosensor highly selective for phosphate-containing anions. Phosphate, pyrophosphate, AMP, ADP, ATP, DNA and RNA were well distinguished by UV/V is absorption or fluorescence studies.

Silica-hemin composite nanoparticles as new biocatalyst to highly sensitive determination of glucose in human serum.

The preparation and utilization of a novel composite silica-hemin nanoparticles (CSHNs) as mimetic peroxidase are reported in this article. Experimental results showed that the composite nanoparticles had unique advantages over free hemin molecules in good stability and highly catalytic activity. By employing these nanoparticles as biocatalyst, we developed a new spectrofluorometric method for the determination of trace level glucose. The calibration graph for glucose was linear over the range 4.0 x 10(-7) mol/L - 7.0 x 10(-5) mol/L, with a detection limit of 1.0 x 10(-7) mol/L. The proposed method has been successfully applied to the determination of glucose in serum samples and offers the advantages of being rapid, stable, sensitive, and renewable.

Colorimetric recognition of different enzymology-concerning transition metals based on a hybrid cluster complex.

A hybrid cluster complex, formed by chelating a chromogenic ligand to a [2Fe-2S] cluster, sensitively exhibited differential colorimetric responses towards Hg2+, Cd2+, Cr3+, Pb2, Sn2+, Cu2+, Zn2+, Fe3+ and Co2+ in water at physiological pH. Speciation of some of these metal elements, such as Cr(III) and Sn(IV), was also studied by UV/Vis absorption.

Species-differentiable sensing of phosphate-containing anions in neutral aqueous solution based on coordinatively unsaturated lanthanide complex probes.

A new chromogenic/fluorogenic molecular probe was developed for highly selective and species-differentiable detection of phosphate-containing anions in neutral aqueous solution. The coordinatively unsaturated lanthanide complex, made from Eu(III) ion and 2-[(8-hydroxy-5-sulfo-7-quinoline)azo]-1,8-dihydroxy-3,6-naphthalene disulfonic acid, changed its conformation when binding to the incoming target anions, which resulted in differential absorption or fluorescence responses. It was demonstrated that not only phosphate and pyrophosphate but also DNA and RNA could be clearly distinguished by visible absorption or fluorescence spectra. Also, differential responses in absorption spectra were observed when AMP, ADP, and ATP were added into the sensing system. Selective quantitation of these phosphate-containing anions in aqueous solutions, therefore, can be easily available. DNA and RNA were distinguished by different colors and independent fluorescence emissions due to their intrinsic differences in beta-D-ribose residues. Simultaneous or independent quantitation of DNA and RNA in a mixture sample, therefore, is possible without pretreatment with nuclease. Furthermore, the influence from the base selectivity can be eliminated by the use of the probe. The detection limits of phosphate and 5'-ATP in neutral water were 6.0 x 10(-7) and 9.0 x 10(-7)M, respectively, by the UV/Vis spectrophotometric method; the detection limits were 12.3 ng/mL for DNA by fluorimetry and 2.3mg/L for RNA by UV/Vis spectrophotometry.

Determination of nucleic acids by near-infrared fluorescence quenching of hydrophobic thiacyanine dye in the presence of Triton X-100.

A near-infrared (near-IR) fluorescence quenching method was developed for the determination of nucleic acids in aqueous solution by using a cationic heptamethylene thiacyanine as a probe. The near-IR cationic cyanine showed maximum excitation and emission wavelengths at 800 and 825 nm, respectively, in the presence of Triton X-100; the fluorescence of the cyanine could be greatly quenched by DNA. The calibration graphs were linear over the range of 10-400 ng/mL for CT (calf thymus) DNA and over the range 5-400 ng/mL for FS (fish sperm) DNA under optimal conditions. The corresponding detection limits were 5.2 ng/mL for CT DNA and 2.5 ng/mL for FS DNA. The relative standard deviation (n = 8) was 3.1% for 75 ng/mL CT DNA and 2.2% for 75 ng/mL FS DNA, respectively. Preliminary research showed that the fluorescence quenching might be ascribed to the formation of dye aggregate facilitated by DNA.

Porphyrin hybrid complex ([2Fe-2S]2TPPS) as a catalyst for determination of hydrogen peroxide.

A new promising mimetic enzyme, a [2Fe-2S] cluster-porphyrin hybrid complex ([2Fe-2S]2TPPS), has been synthesized and applied to the determination of hydrogen peroxide. Under the optimum condition, the calibration graph has a linear range of 8.0 x 10(-8) - 1.0 x 10(6) mol/l H2O2 with a detection limit (3sigma, N = 9) of 5.3 x 10(-9) mol/l.

Molecularly imprinted sol-gel nanotubes membrane for biochemical separations.

In this study, we report a simple procedure for applying molecular imprinting functional groups to the inner surfaces of the template-synthesized sol-gel nanotubes for chemical separation of estrone. The silica nanotubes were synthesized within the pores of nanopore alumina template membranes using a sol-gel method by simultaneous hydrolysis of a silica monomer-imprinted molecule complex and tetraethoxysilane (TEOS). A covalent imprinting strategy was employed by generating a sacrificial spacer through the reaction of the isocyanate group of 3-(triethoxysilyl)propyl isocyanate and a phenol moiety of estrone to form a thermally cleavable urethane bond. This allowed us to remove the imprinted estrone by simple thermal reaction and to simultaneously introduce functional groups into the cavity formed by the silica nanotubes. Experiments indicated that estrone could be bound selectively by such an approach and have a binding affinity of 864 +/- 137 (n = 3).

Magnetite-containing spherical silica nanoparticles for biocatalysis and bioseparations.

The simultaneous entrapment of biological macromolecules and nanostructured silica-coated magnetite in sol-gel materials using a reverse-micelle technique leads to a bioactive, mechanically stable, nanometer-sized, and magnetically separable particles. These spherical particles have a typical diameter of 53 +/- 4 nm, a large surface area of 330 m(2)/g, an average pore diameter of 1.5 nm, a total pore volume of 1.427 cm(3)/g and a saturated magnetization (M(S)) of 3.2 emu/g. Peroxidase entrapped in these particles shows Michaelis-Mentan kinetics and high activity. The catalytic reaction will take place immediately after adding these particles to the reaction solution. These enzyme entrapping particles catalysts can be easily separated from the reaction mixture by simply using an external magnetic field. Experiments have proved that these catalysts have a long-term stability toward temperature and pH change, as compared to free enzyme molecules. To further prove the application of this novel magnetic biomaterial in analytical chemistry, a magnetic-separation immunoassay system was also developed for the quantitative determination of gentamicin. The calibration for gentamicin has a working range of 200-4000 ng/mL, with a detection limit of 160 ng/mL, which is close to that of the fluorescent polarization immunoassay (FPIA) using the same reactants.

Fluorescence enhancement method for the determination of nucleic acids using cationic cyanine as a fluorescence probe.

A fluorescence enhancement method with a cationic cyanine as a probe was developed for the determination of nucleic acids. Under the experimental conditions, the fluorescence enhancement of cyanine (lambda(ex)/lambda(em)= 524/591.5 nm) was observed in the presence of DNA. The calibration graphs were linear over the range of 0.01-15 microg mL(-1) for both calf thymus DNA (CT DNA) and fish sperm DNA (FS DNA). The limits of detection were 0.005 and 0.007 microg mL(-1) for CT DNA and FS DNA, respectively. The method was applied to the determination of DNA in synthetic and real samples and satisfactory results were obtained. A possible fluorescence enhancement mechanism was also studied.