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Guo H.,Tsinghua University | Zhou X.,Tsinghua University | Zhang Y.,Hebei Institute of Food Quality Supervision Inspection and Research | Gu C.,Tsinghua University | And 2 more authors.
RSC Advances | Year: 2016

Methods based on optical biosensors for the investigation of biomolecular interactions between high-affinity antibodies and antigens has advanced over the last years. In this study, experimental and data analysis protocols were developed to determine the rate and equilibrium constants by using multiplexed planar waveguide fluorescence immunosensor. Four different antibodies were used as models in the test system. Antigen-BSAs were immobilized on the sensor surface, and the binding of specific antibodies labeled with Cy5.5 under certain conditions was measured. Sets of binding curves obtained with different antibody concentrations were analyzed by using the numerical integration of differential rate equations and global fitting applying by the one to one reaction model. As a result, the kinetic rate constants (ka and kd) and affinity (KD) can be determined for each antibody interaction under identical conditions. An indirect competitive immunoassay simulation model is also presented in the paper and shows the relationship between detection response, initial concentration of antibody and affinity constant. By analyzing the results and fitted in the indirect competitive immunoassay model, the optimized concentration of antibody and working ranges for detection can be estimated. Thus, the application of waveguide fluorescence immunosensors for protein interaction analysis is a promising and high throughput tool for obtaining data on the binding behavior between antibodies and antigens, and support the optimization in immunoassay. © The Royal Society of Chemistry 2016. Source

Sun H.,Hebei University | Qi H.,Hebei University | Li H.,Hebei Institute of Food Quality Supervision Inspection and Research
Food Analytical Methods | Year: 2013

A rapid and effective method was developed in the first time for the determination of four sulfonamides (SAs) and their N4-acetylated metabolites in aquatic products using capillary electrophoresis with accelerated solvent extraction (ASE). The eight residues were extracted with acetonitrile at 70 °C under 10.3 MPa pressure and two static cycles with a static time of 5 min. The eight analytes can be baseline separated with 6 min. The standard curves for the determination of eight residues by the capillary electrophoretic method have good linearity (r 2 > 0.999). The method limits of quantification (LOQs) for N4-acetylsulfadiazine, sulfadiazine, sulfamerazine, sulfamethoxazole, sulfamethazine, N4-acetylsulfamethazine, N4-acetylsulfamerazine, and N4-acetylsulfamethoxazole in aquatic products were 26.4, 33.0, 33.0, 33.0, 39.6, 370, and 1,076 μg kg-1, respectively. Intra- and inter-day precision (RSD) were 0.4-2.2 % and 1.4-3.5 %, respectively. Their average recoveries with three spiked levels ranged from 83 % to 116 % with the RSDs less than 4 %. The proposed method provides a rapid and simple extraction procedure with high sensitivity and recoveries, and can permit routine detection of the studied SAs residues in aquatic products at the maximum residue level. © 2012 Springer Science+Business Media, LLC. Source

Ning Y.,State Key Laboratory of Food Science and Technology | Ning Y.,Jiangnan University | Li Q.,Hebei Institute of Food Quality Supervision Inspection and Research | Chen F.,Clemson University | And 4 more authors.
Bioresource Technology | Year: 2012

The effects of medium composition and culture conditions on the production of 6G-fructofuranosidase with value-added astaxanthin were investigated to reduce the capital cost of neo-fructooligosaccharides (neo-FOS) production by Xanthophyllomyces dendrorhous. The sucrose and corn steep liquor (CSL) were found to be the optimal carbon source and nitrogen source, respectively. CSL and initial pH were selected as the critical factors using Plackett-Burman design. Maximum 6G-fructofuranosidase 242.57U/mL with 5.23mg/L value-added astaxanthin was obtained at CSL 52.5mL/L and pH 7.89 by central composite design. Neo-FOS yield could reach 238.12g/L under the optimized medium conditions. Cost analysis suggested 66.3% of substrate cost was reduced compared with that before optimization. These results demonstrated that the optimized medium and culture conditions could significantly enhance the production of 6G-fructofuranosidase with value-added astaxanthin and remarkably decrease the substrate cost, which opened up possibilities to produce neo-FOS industrially. © 2011 Elsevier Ltd. Source

Sun H.-W.,Hebei University | Kang Z.-S.,Hebei University | Li H.,Hebei University | Li H.,Hebei Institute of Food Quality Supervision Inspection and Research
Fenxi Huaxue/ Chinese Journal of Analytical Chemistry | Year: 2010

A gel permeation chromatography-solid phase extraction-rapid resolution liquidchromatography-tandem mass spectrometry (GPC-SPE-RRLC-MS/MS) method was developed for the determination of 9 steroid hormone residues in beef tissue. The beef samples were enzymatically digested with β-glucuronidase/ arylsulfatase, and then extracted with tert-butyl methyl ether under ultrasonication incubation. Cleanup was carried out with GPC followed by a further HLB SPE. After C18 RRLC gradient elution separation withacetonitrile-0.1% aqueous formic acid as a mobile phase, the eluents were qualitatively and quantitatively determined under multireaction monitoring (MRM) scan type with tandemmass analyzer.The limit of quantification (LOQ) was 0.2-0.7 μg kg-1, andthe calibration curves showedgood linearity with correlation coefficients larger than 0.999. At the spiked levels of 0.2, 1.0 and 4.0 μg kg-1, the average recoveries were in the range of 81.4%-110%, and the relative standard deviations (RSDs) were in the range of 2.17%-9.82% (n = 7). The testresults of real sample showed this method is sensitive and accurate. The proposed methodwas used for the sensitive and accurate determination of 9 steroid hormone residues in high-fat and complex samples. Copyright © 2010. Source

Hao X.-J.,Tsinghua University | Hao X.-J.,Inner Mongolia University of Technology | Zhou X.-H.,Tsinghua University | Zhou X.-H.,Collaborative Innovation Center for Advanced Water Pollution Control Technology and Equipment | And 6 more authors.
Sensors and Actuators, B: Chemical | Year: 2014

A sensitive, simple and rapid detection of trace amounts of melamine in milk products was achieved in a reusable, portable optical sensor system based on the principle of immunoassay and evanescent wave-excited fluorescence. The evanescent wave fiber-optic immunosensor (EWFI) employed a single-multi mode fiber optic coupler for light excitation and collection of fluorescence generated from the fiber optic probe. A reusable immunosurface of fiber probe was established to allow the performance of more than 300 assay cycles. Each assay cycle was less than 15 min. The typical calibration curves of the EWFI obtained for melamine (MA) had a detection limit of 5.14 μg/L with the detectable working range from 12.62 to 284.18 μg/L when the concentration of Cy5.5-labeled antibody was 0.2 μg/mL. The cross-reactivity against the organic compounds structurally similar to MA was negligible. The recoveries of MA in all sorts of dairy products ranged from 86.1% to 106.5% with relative standard deviation values of less than 4%, confirming the application potential in the measurement of MA in reality. The immunoassay performance of the EWFI was also validated with respect to conventional LC-MS/MS and the correlation between methods was in good agreement with the coefficient variation of less than 20% for majority samples. © 2014 Elsevier B.V. Source

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