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Biomedical subjects

R Q Yu

Publications and source records attributed to R Q Yu.

At least 19 recordsLinked to original sources
PubMed2001

Renewable amperometric immunosensor for Schistosoma japonium antibody assay.

A renewable amperometric immunosensor has been proposed for the determination of Schistosoma japonium antibody (SjAb) in rabbit serum. A paraffin-graphite-Schistosoma japonium antigen (SjAg) biocomposite, which needs no additional curing, was directly used to construct the immunosensors. The analytical sample containing the desired SjAb was mixed with SjAb labeled with horseradish peroxidase (HRP) to form the incubation solution for the competitive binding assay. Amperometry was used to determine the amount of HRP fixed on the sensor surface, which was related to the content of desired SjAb. Assay conditions were optimized, including the selection of substrate, the loading of SjAg in the biocomposite, the amount of labeled SjAb in the incubation solution, the incubation time, and the temperature. Using o-aminophenol (o-AP) as a substrate, amperometric detection at -200 mV (vs SCE) resulted in a pseudolinear detection range of about 0.36 to 14 microg/mL, with a detection limit of 0.36 microg/mL. Rabbit serum samples with varying infection degrees were analyzed, and the results demonstrated that the concentration that is detectable in this system meets the demands of clinical analyses. A new surface on the immunosensor for use in another competitive assay can be obtained by removing the original one and polishing the surface.

Animals↗
PubMed2001

Synthesis of glycosylated porphyrins as neutral ionophores for a berberine-sensitive electrode.

For preparing a berberine-sensitive electrode, 5,10,15,20-tetrakis[2-(2,3,4,6-tetraacetyl-beta-D-glucopyranosyl)-1-O- phenyl]porphyrin (T(o-glu)PPH2) was synthesized from the reaction of pyrrole with ortho-acetylglycosylated benzaldehyde by Lindsay's method. The electrode based on T(o-glu)PPH2 with an optimized membrane composition exhibits Nernstian response to berberine in the concentration range 2.4 x 10(-7)-5.0 x 10(-3) mol L-1, with a pH range from 3.9 to 10.2, and a fast response time of 30 s. The electrode shows fair selectivity towards berberine with respect to common co-existing species. T(o-glu)PPH2 shows better potentiometric response characteristics comparing to chloro[5,10,15,20-tetrakis[2-(2,3,4,6-tetraacetyl-beta-D- glucopyranosyl)-1-O-phenyl]-porphinato]-manganese (MnT(o-glu)PPCl) and better selectivity towards berberine than tetraphenylporphyrin (TPPH2). The effect of the composition of the electrode membrane has been studied and the experimental conditions optimized. The contents of berberine in pharmaceutical tablets were determined by direct potentiometry and the results agreed with values obtained by the pharmacopoeia method.

Berberine↗
PubMed2001

Renewable amperometric immunosensor for complement 3 assay based on the sol-gel technique.

A renewable amperometric immunosensor based on the sol-gel technique has been constructed by dispersing graphite, complement 3 (C3) antiserum, and sol-gel at low temperature. The prepared immunosensor is rigid, porous, and has a renewable external surface. A competitive binding assay has been used to determine C3 in human serum with the aid of C3 labeled with horseradish peroxidase. The enzyme-labeled antigen can readily diffuse toward the encapsulated antibody, which retains its binding properties. The experimental conditions for the assay with the biocomposite, including the loading of C3 antiserum in the biocomposite, the amount of labeled C3 in incubation solution, incubation time, and temperature, have been optimized. Using C3 labeled with horseradish peroxidase, and o-AP as the substrate, amperometric detection at -150 mV (relative to the SCE) results in a linear detection range of 1.17-35.1 microg mL(-1), with a detection limit of 0.56 microg mL(-1). Serum samples have been assayed and the results demonstrate the feasibility of the proposed immunosensor for clinical analysis. The surface of the immunosensor can be renewed simply by polishing to obtain a fresh immunocomposite ready to use in a new competitive assay.

Biosensing Techniques↗
PubMed2001

Picric acid sensitive optode based on a fluorescence carrier covalently bound to membrane.

An acryloyl group was attached to fluorescein through the phenol hydroxyl group to make it photopolymerizable with 2-hydroxypropyl methacrylate and covalently immobilized on an optode glass surface modified with gamma-(methacryloxy)propyltrimethoxysilane. The optode system with a plastic-clad fused silica bifurcated fiber optic bundle shows satisfactory analytical performance characteristics for determining picric acid in terms of selectivity and reproducibility with a linear range from 8.0 x 10(-7) to 4.0 x 10(-3) mol L-1. The quenching mechanism was investigated. The optode membrane can be applied to the indirect determination of cinchonine drug and the results obtained were satisfactory.

Fiber Optic Technology↗
PubMed2001

Fluorescence spectral study of interaction of water-soluble metal complexes of Schiff-base and DNA.

The fluorescence spectral characteristics and the interaction of several water-soluble metal complexes of Schiff-base with DNA are described. Among the complexes tested, Mn-Schiff-base bound to DNA showed a marked decrease in the fluorescence intensity with a blue shift of the excitation and emission peaks. Some hypochromism in the UV absorption spectra was also observed. KI quenching and competitive binding to DNA between Mn-Schiff-base and ethidium bromide (EB) were studied in connection with other experimental observations to show that the interactive model between Mn-Schiff-base and DNA is an intercalative one. The pH and salt effect on the fluorescence properties was also investigated. The linear relationship between F/F0 and the concentration of calf thymus DNA covers 3.0 x 10(-6)-2 x 10(-4) mol L-1, which can be utilized for determining traces of calf thymus DNA with a detection limit of 8.0 x 10(-7) mol L-1 in base pairs.

DNA↗
PubMed2000

A novel ethacrynic acid sensor based on a lanthanide porphyrin complex in a PVC matrix.

Lanthanide porphyrin complexes synthesized by a solid state method were used to prepare a novel ethacrynic acid (EA) sensor. The sensor, based on pentane-2,4-dionato(meso-tetraphenylporphinato)terbium [TbTPP(acac)] with an optimized membrane composition, exhibits a Nernstian response to EA- ion in the concentration range 7.4 x 10(-6)-1.0 x 10(-1) mol l-1 with a pH range from 3.2 to 6.8 and a fast response time of 30 s. The electrode shows improved selectivity towards EA- ion with respect to common co-existing ions compared with the previously reported EA sensor. As electroactive materials, lanthanide porphyrin complexes show better potentiometric response characteristics than copper porphyrin complexes. The effect of solvent mediators and lipophilic ion additives was studied and the experimental conditions were optimized. The electrode was applied to the determination of EA in human urine samples with satisfactory results.

Electrochemistry↗
PubMed2000

Renewable amperometric immunosensor based on paraffin-graphite-transferrin antiserum biocomposite for transferrin assay.

A renewable electrochemical immunosensor was developed for the determination of transferrin in human serum. It is based on a paraffin-graphite-transferrin antiserum biocomposite, which needs no additional curing. A competitive binding assay was used to determine transferrin in human serum with the aid of transferrin labeled with horseradish peroxidase. The assay conditions were optimized, including the loading of transferrin antiserum in the biocomposite, the amount of labeled transferrin in the incubation solution, incubation time and temperature. Serum samples were analyzed and the results demonstrate that the concentration range of determination with this system meets the demands of clinical analysis. The surface of the immunosensor can be regenerated by simply polishing to obtain a fresh immunocomposite ready to be used in a new competitive assay.

Biosensing Techniques↗
PubMed2000

Bismetalloporphyrin-based ISE sensitive to fluoroborate.

Several mu-oxo-bismetalloporphyrin complexes were synthesized for preparing fluoroborate sensors. The electrode based on mu-oxo-bis[tetra(p-chlorophenyl)porphinatomanganese(III)] with an optimized membrane composition shows a potentiometric response towards fluoroborate ion over the concentration range from 4.3 x 10(-7) to 1.0 x 10(-1) mol l-1 with a Nernstian slope, a wide working pH range from 5.5 to 12.0 and a fast response time of 30 s. The electrode shows anti-Hofmeister selectivity towards BF4- with respect to common co-existing ions, which is an improvement over methods reported so far. As electroactive materials, several mu-oxo-bismetalloporphyrins with different substituents on the benzene rings were compared for potentiometric response characteristics. The interaction between BF4- and bismetalloporphyrin was investigated using UV/VIS spectrophotometry. The electrode was applied to the determination of fluoroborate in electroplating solutions.

Borates↗
PubMed2000

A PARAFAC algorithm using penalty diagonalization error (PDE) for three-way data array resolution.

A modified parallel factors analysis (PARAFAC) algorithm with the penalty diagnolization error (PDE) was developed. This algorithm can overcome the slow convergence problem of the traditional PARAFAC method and is insensitive to the number of components, i.e., it is much faster than PARAFAC and insensitive to overestimation of the dimensionality of the model. The characteristic performance was demonstrated by treating simulated and real excitation-emission fluorescence data for samples of naphthalene, 1-naphthol and 2-naphthol with satisfactory results.

Journal Article↗
PubMed1999

DNA binding studies of a solvatochromic fluorescence probe 3-methoxybenzanthrone.

A fluorescence probe of 3-methoxybenzanthrone (MBA) exhibits significant solvatochromic characteristics correlated with the polarity of solvents. The interaction of the solvatochromic fluorescence probe with calf thymus DNA (ct-DNA) has been investigated. In the presence of ct-DNA the fluorescence of MBA is strongly quenched with a blue-shift of emission peak and a hypochromism in absorption spectra. The absorption spectra, fluorescence quenching and fluorescence polarization experiments show that the MBA molecule as an intercalator is inserted into the base-stacking domain of the ct-DNA double helix, and the interaction of the nucleobases with the MBA molecule causes quenching of fluorescence and hypochromism in the absorption spectra. The intrinsic binding constant and the binding site number were determined to be 1.70 x 10(5) mol l-1 in base pairs and six, respectively. The I0/I versus [ct-DNA] plot shows linear relationship in the range covering 4.3 x 10(-7)-1.02 x 10(-4) mol l-1 in base pairs which can be used for ct-DNA determination. The limit of detection was found to be 4.3 x 10(-7) mol l-1 in base pairs (0.5 microgram ml-1).

Absorption↗
PubMed1998

Organic solvent induced quenching of porous silicon photoluminescence.

A comparison has been made for the quenching effect of three classes of organic solvents on the porous silicon photoluminescence, including hydrocarbons, solvents containing oxygen and nitrogen. Among them organoamines possess the strongest quenching effect. The experiments show that the solvent molecules interact synergistically with porous silicon and the main pathways include the surface hydrophobic interaction, dipole-dipole interaction and hole trapping, the later being the dominant pathway in quenching of porous silicon photoluminescence.

Hydrocarbons↗
PubMed1997

Fluorescence quenching of ethidium ion by porphyrin cations and quaternary ammonium surfactants in the presence of DNA.

Fluorescence quenching of free and DNA-bound ethidium bromide (EB) by a number of quaternary ammonium and other compounds was studied. For free EB or bound EB at lower DNA concentration the fluorescence quenching follows the Stern-Volmer equation and at higher DNA concentration follows an exponential model. At least at low quencher concentrations the quenching efficiency varies with DNA or NaCl concentrations and is about 100 times greater for bound than free EB. The quenching pathways may involve energy transfer and conformational loosening or distortion of the DNA helix in addition to possible electron transfer.

DNA↗
PubMed1997

Highly selective iodide poly(vinyl chloride) membrane electrode based on a nickel(II) tetraazaannulene macrocyclic complex.

A PVC membrane electrode based on a nickel(II) tetraazaannulene macrocyclic complex as the carrier is described. The electrode exhibits an anti-Hofmeister selectivity sequence with a preference for iodide at pH 3.0-4.0. It has a linear response to iodide from 8.0 x 10(-6) to 1 x 10(-1) mol dm-3 with a slope of -54.7 +/- 0.2 mV per decade (20 degrees C), a satisfactory reproducibility and a rapid response time. The pH dependence of the potential response is discussed. The response mechanism of the electrode was investigated by ac impedance, quartz crystal microbalance and spectroscopic techniques. The electrode can be used for the determination of iodide in drug preparations.

Heterocyclic Compounds↗
PubMed1997

[Clinical and experimental study on treatment of chronic hepatitis B with yanggan aoping mixture].

OBJECTIVE: To assess the efficacy of Yanggan Aoping Mixture (YGAPM) in treating hepatitis B. METHODS: Patients suffered from chronic hepatitis B were treated with YGAPM. Observe their short- and long-term efficacy and the change of serum hepatitis B virus marker. In experiment, the effect of YGAPM in treating rat's liver injury as well as HBV-infected tree shrew and duck HBV-infected ducks was observed. RESULTS: In 79 cases of chronic persistant hepatitis, the markedly effective rate was 60.76%, and follow-up studies on 40 cases, the further rasied to 70.00%. In 73 cases of chronic active hepatitis, the markedly effective rate was 60.27%, and further raised to 62.50% in 32 follow-up cases. In the treatment group, 85 (71.43%) of the 119 cases with HBeAg-positive turned to negative. Whereas in the control group, only 40 (44.94%) of 89 HBeAg-positive cases turned to negative, P < 0.01. Results of experimental study showed that negative conversion rate of tree shrew infected with HBV marker was raised, while infected duck blood with duck HBV DNA was inhibited. Those compared with the control group separately, the difference was remarkably significant. CONCLUSIONS: YGAPM is an effective drug in treating chronic hepatitis B, and it could effectively negative convert the HBV marker.

Adolescent↗
PubMed1996

A perfume odour-sensing system using an array of piezoelectric crystal sensors with plasticized PVC coatings.

Using PVC polymer as membrane matrix and di-n-octylphenyl phosphate (DOPP) as plasticizer, a piezoelectric crystal sensor (PCS) array with 12 adsorptive materials selected from 68 compounds by cluster analysis has been constructed as a perfume odour-sensing system. The frequency shift data obtained from the sensor array responding to four commercial perfume odours are first autoscaled and then treated by principal component analysis. The experimental results show that the plasticized PVC membrane PCS array provides improved performance of pattern recognition compared with the single adsorptive coating PCS array. The frequency shift response characteristics of these sensors have been investigated experimentally. The proposed sensor array has also been applied to the classification of commercial spirituous liquor, wine and soft drink samples, as well as aliphatic alcohol homologues and isomers.

Journal Article↗
PubMed1996

Polymer agglutination-based piezoelectric immunoassay for the determination of complement III.

A piezoelectric immunoassay technique, which is based on the detection of agglutination of antibody- or antigen-bearing polymer by an immunoreaction using a piezoelectric quartz crystal, has been developed for the determination of complement III (C3). Anti-C3 antibodies were physically adsorbed onto the carboxymethyl cellulose polymer by hydrogen bonds. The agglutination of the (anti-C3 antibody)-bearing polymer by immunoreaction caused a viscosity change of the solution, which could be monitored by a piezoelectric quartz crystal. The effect of experimental conditions such as the polymer concentration, the antibody dilution ratio and the reaction temperature on the frequency response were investigated. The linear ranges for C3 concentration determined by the end-point method and the initial rate method were 22.0-43.2 micrograms ml-1 and 22.0-49.1 micrograms ml-1, respectively. Other antigens presenting in serum did not interfere with the determination of C3. Analytical results of ten clinical specimens obtained using the developed technique were in satisfactory agreement with those given by the rate diffusion turbidimetry. With a simple regeneration method devised, the crystal can be used repeatedly with acceptable reproducibility.

Complement C3↗
PubMed1995

Piezoelectric immunosensor for the detection of immunoglobulin M.

A piezoelectric immunosensor has been developed for the determination of human IgM. The crystals are AT-cut and have a basic resonant frequency of 9 MHz. Immobilization of goat antihuman IgM antibodies to the crystals' surfaces was accomplished via a CNBr-activated copolymer coating of 2-hydroxyethyl methacrylate and methylmethacrylate. The IgM piezoelectric immunosensor can be used for the human IgM determination in the range 5-93 micrograms ml-1. The analytical results given by this approach were in satisfactory agreement with those given by the single radical immunodiffusion procedure. The sensitivity, specificity and reproducibility of this immunosensor were investigated. Further, the valent value of goat antihuman IgM antibody binding with human IgM antigen and the affinity constant of immunoreaction in this experimental system were studied. After washing with tetrahydrofuran, a crystal can be re-used 20 times without detectable loss of sensitivity.

Biosensing Techniques↗