University of North Florida
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Stuart Chalk, Ph.D.
Department of Chemistry
University of North Florida
Phone: 1-904-620-1938
Fax: 1-904-620-3535
Email: schalk@unf.edu
Website: @unf

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Huangxian Ju

Abbrev:
Ju, H.X.
Other Names:
Address:
Department of Chemistry, State Key Laboratory of Coordination Chemistry, Institute of Analytical Science, Nanjing University, Nanjing 210093, China
Phone:
+86-25-359-3593
Fax:
+86-25-359-3593

Citations 14

"Flow Injection Chemiluminescence Analysis For Highly Sensitive Determination Of Noscapine"
J. Photochem. Photobio. A 2004 Volume 162, Issue 2-3 Pages 457-462
Yafeng Zhuang, Xilan Cai, Junsheng Yu and Huangxian Ju

Abstract: Noscapine is an antitussive drug and possesses potent antitumor activity. This work establishes a highly sensitive method for its determination by flow injection chemiluminescence (CL) technique. This method is based on its strong sensitizing effect on the weak CL reaction between sulfite and acidic permanganate. The mechanism for the sensitizing process is proposed on the basis of fluorescence and CL spectra. Under optimal experimental conditions, the CL response is proportional to the concentration of noscapine over the range of 2.0 x 10^-8 to 2.0 x 10^-6 mol/l with a correlation coefficient of 0.9998 and a detection limit of 8.0 x 10^-9 mol/l (3s). The relative standard deviation for 11 repetitive determinations of 5.0 x 10^-7 mol/l noscapine is 1.2%. Most of metal ions and some alkaloids such as morphine, codeine and heroin do not interfere with the determination. The interference of coexisted papaverine in the opium can be eliminated by the dilution of sample solution. The method has been satisfactorily used for the determination of noscapine in synthesized samples.

"Flow-injection Chemiluminescent Immunoassay For α-fetoprotein Based On Epoxysilane Modified Glass Microbeads"
J. Immunol. Methods 2006 Volume 312, Issue 1-2 Pages 61-67
Zhifeng Fu, Chen Hao, Xiaoqing Fei and Huangxian Ju

Abstract: A flow-injection chemiluminescent immunoassay system based on a novel transparent immunoaffinity reactor is proposed for the quantitation of α-fetoprotein. The reactor prepared with α-fetoprotein immobilized epoxysilane modified glass microbeads was used as an immunosensor for chemiluminescent detection. With a non-competitive immunoassay format, the proposed immunosensor system is a low cost, flexible and rapid assay for α-fetoprotein. After an off-line incubation of the analyte α-fetoprotein with horseradish peroxidase-labeled α-fetoprotein antibody as enzyme tracer, the mixture was injected into the reactor, which led to trapping of the free enzyme tracer by the reactor. The trapped enzyme tracer was detected by the p-iodophenol-luminol-H2O2 chemiluminescence system. Under optimal conditions, the decrease in chemiluminescence intensity was proportional to the α-fetoprotein concentration in the range of 5.0-100 ng/ml with a detection limit of 2.7 ng/ml at a signal/noise ratio of 3. The immunosensor system showed an acceptable reproducibility and stability. Clinical serum samples were assayed with this method and the results were in acceptable agreement with those obtained from immunoradiometric assay.

"Flow Injection Immunoassay For Carcinoembryonic Antigen Combined With Time-resolved Fluorometric Detection"
J. Immunol. Methods 2005 Volume 305, Issue 2 Pages 120-127
Feng Yan, Jiannong Zhou, Jiehua Lin, Huangxian Ju and Xiaoya Hu

Abstract: Time-resolved fluorescence has been developed for immunoassay to obtain higher sensitivity than usual immunoassays. In this paper, a simple, sensitive and specific method was developed for immunoassay of serum carcinoembryonic antigen (CEA) by combining time-resolved fluoroimmunoassay (TRFIA) and flow injection analysis. Based on a sandwich immunoassay format, a monoclonal antibody immobilized immunoaffinity column inserted in a flow system was used for immunoreactions. The cleaved solution was collected after the reaction between the immunocomplex in the immunoaffinity column and the enhancement solution that was used to cleave the Eu-labels from the immunocomplex, and then detected by time-resolved fluorescence. Serum CEA could be detected in the linear range from 2.5 to 100 ng/ml with a correlation coefficient of 0.997 and the detection limit of 1.0 ng/ml. Twenty human serum samples detected by this method were in good agreement with the results obtained by the electrochemiluminescence immunoassay. This method could be further developed for fast practical clinical detection of serum CEA levels. © 2005 Elsevier B.V. All rights reserved.

"Chemiluminescent Immunosensor For CA19-9 Based On Antigen Immobilization On A Cross-linked Chitosan Membrane"
J. Immunol. Methods 2004 Volume 291, Issue 1-2 Pages 165-174
Jiehua Lin, Feng Yan, Xiaoya Hu and Huangxian Ju

Abstract: A novel chemiluminescent immunosensor for carbohydrate antigen 19-9 (CA19-9) based on the immobilization of CA19-9 on the cross-linked chitosan membrane was developed. The different membranes were characterized by atomic force microscopy (AFM) and infrared spectrum, respectively. Based on a noncompetitive immunoassay format, this proposed chemiluminescent immunosensor enabled a low-cost, flexible and rapid determination for CA19-9 in combination with flow injection analysis (FIA). After an off-line incubation of the analyte CA19-9 with horseradish peroxidase (HRP)-labeled anti-CA19-9, the mixture was injected into the immunosensor, which led to the trapping of free HRP-labeled anti-CA19-9 by the immobilized antigen in the immunosensor. The trapped HRP-labeled antibody was detected by chemiluminescence due to its catalytic activity following the reaction of luminol and H2O2. Under optimal conditions, the decreased chemiluminescent signal of the immunosensor was proportional to the CA19-9 concentration in the range of 2.0-25 U/ml with a detection limit of 1.0 U/ml. The immunosensor showed an acceptable accuracy and good reproducibility. The results of 20 human serum samples detected by this method were in acceptable agreement with those obtained by immunoradiometric assay. The proposed immunosensor provided a new promising tool for practical clinical detection of the serum CA19-9 level.

"Chemiluminescence Sensor For The Determination Of Hydroxylamine By Electrostatically Immobilizing Luminol And Periodate"
Chem. Res. Chin. Univ. 2003 Volume 19, Issue 2 Pages 155-159
ZHANG Si-chun, ZHOU Guo-jun, JU Huang-xian

Abstract: A novel chemiluminescence (CL) sensor, which can he used for hydroxylamine determination in combination with flow injection analysis, was developed by electrostatically immobilizing luminol and periodate on an-ion-exchange resin respectively. Hydroxylamine was sensed by its enhancing effect on the weak CL reaction between luminol and periodate. which were eluted from the ion exchange column. The response of the sensor to hydroxylamine was linear in the concentration range of 8.0 x 10^-8 - 2.0 x 10^-6 mol/L with a detection limit of 4.0 x 10^-8 mol/L hydroxylamine (3s). The relative standard deviation (RSD) was 2.0% for 9 repetitive determinations at a hydroxylamine concentration of 5.0 x 10^-7 mol/L. The sensor could be reused for over 400 times with a good reproducibility and was used to determine hydroxylamine in wastewater.

"Noncompetitive Enzyme Immunoassay For Carcinoembryonic Antigen By Flow Injection Chemiluminescence"
Clin. Chim. Acta 2004 Volume 341, Issue 1-2 Pages 109-115
Jiehua Lin, Feng Yan and Huangxian Ju

Abstract: Background: Recently, many automated immunoassay analyzers have been developed for carcinoembryonic antigen (CEA) to overcome the shortcomings in traditional immunoassay methods that are time-consuming and labor-intensive. Flow injection immunoassay (FIIA) has been increasingly applied to laboratory medicine due to its ease in automation, rapid speed and reproducible results. It is important to develop a FIIA method for CEA determination. Methods: Based on a noncompetitive immunoassay format, a CEA-immobilized immunoaffinity column inserted in the flow system was used to trap the unbound horseradish peroxidase (HRP)-labeled antibody after an off-line incubation of CEA and HRP-labeled anti-CEA. The trapped enzyme conjugate was detected by injecting substrates to produce an enhanced chemiluminescence (CL). Results: The linear range for CEA was 1.0-25 ng/ml with a correlation coefficient of 0.997 and a detection limit of 0.5 ng/ml. The sampling and chemiluminescence detection time for one sample was 5 min after a preincubation procedure of 25 min. Twenty five human serum samples detected by this method were in good agreement with the results obtained by immunoradiometric assay (IRMA). Conclusions: This method could be used for rapid analysis of CEA and potentially other antigens.

"Flow Injection Chemiluminescence Sensor For The Determination Of Gallic Acid By Immobilizing Luminol And Periodate On Anion-exchange Resin"
Chin. J. Chem. 2002 Volume 20, Issue 10 Pages 1049-1054
ZHANG, Si-Chun, ZHOU, Guo-Jun, JU, Huang-Xian

Abstract: A novel chemiluminescence (CL) sensor for the determination of gallic acid combined with flow injection analysis was developed by electrostatically immobilizing luminol and periodate on anion-exchange resins respectively. Gallic acid was sensed by its enhancing effect on the weak CL reaction between luminol. and periodate, which were eluted from the ion exchange column. The possible reaction mechanism of the CL system was suggested and discussed. The response of the sensor to gallic acid concentration was linear over the range of 8.0 x 10^-9-1.0 x 10^-6 mol/L with a detection limit of 6.5 x 10^-9 mol/L (3s). The relative standard deviation (RSD) for 7 repetitive determinations of gallic add (1.0 x 10^-7 mol/L) was 1.8%. The sensor could be used for over 400 times determination with a good reproducibility.

"Binding Of Acetylcholinesterase To Multiwall Carbon Nanotube-cross-linked Chitosan Composite For Flow-injection Amperometric Detection Of An Organophosphorous Insecticide"
Chem. Eur. J. 2006 Volume 12, Issue 4 Pages 1074-1080
Vivek Babu Kandimalla, Dr., Huangxian Ju, Prof.

Abstract: A novel method for immobilization of acetylcholinesterase (AChE) by binding covalently to a cross-linked chitosan-multiwall carbon nanotube (MWNT) composite is described. In addition a sensitive, fast, cheap and automatizable flow injection detection of an organophosphorous insecticide was developed. The MWNTs were homogeneously distributed in the chitosan membrane which showed a homogeneous porous structure. The immobilized AChE could catalyze the hydrolysis of acetylthiocholine with a KMapp value of 177 ?M to form thiocholine, which was then oxidized to produce detectable signal in a linear range of 1.0-500 ?M and fast response. MWNTs could catalyze the electrooxidation of thiocholine, thus increasing detection sensitivity. Based on the inhibition of an organophosphorous insecticide on the enzymatic activity of AChE, using Sulfotep as a model compound, the conditions for the flow-injection detection of the insecticide were optimized. Both biocompatibility of chitosan and inherent conductive properties of MWNTs favored the detection of the insecticide from 1.5 to 80 ?M along with good stability and reproducibility. 95% reactivation from inhibited AChE could be regenerated by using 2-pyridinealdoxime methiodide within 15 min for 15 times. The detection of Sulfotep samples exhibited satisfactory results. The proposed flow-injection analysis device can be applied to automated determination and characterization of enzyme inhibitors.

"A Disposable Electrochemical Immunosensor For Flow Injection Immunoassay Of Carcinoembryonic Antigen"
Biosens. Bioelectron. 2006 Volume 22, Issue 1 Pages 102-108
Jie Wu, Jinhai Tang, Zong Dai, Feng Yan, Huangxian Ju and Nabil El Murr

Abstract: A new simple immunoassay method for carcinoembryonic antigen (CEA) detection using a disposable immunosensor coupled with a flow injection system was developed. The immunosensor was prepared by coating CEA/colloid Au/chitosan membrane at a screen-printed carbon electrode (SPCE). Using a competitive immunoassay format, the immunosensor inserted in the flow system with an injection of sample and horseradish peroxidase (HRP)-labeled CEA antibody was used to trap the labeled antibody at room temperature for 35 min. The current response obtained from the labeled HRP to thionine-H2O2 system decreased proportionally to the CEA concentration in the range of 0.50-25 ng/ml with a correlation coefficient of 0.9981 and a detection limit of 0.22 ng/ml (S/N = 3). The immunoassay system could automatically control the incubation, washing and current measurement steps with good stability and acceptable accuracy. Thus, the proposed method proved its potential use in clinical immunoassay of CEA. © 2005 Elsevier B.V. All rights reserved.

"Amperometric Biosensor For Hydrogen Peroxide Based On Ferrocene-bovine Serum Albumin And Multiwall Carbon Nanotube Modified Ormosil Composite"
Biosens. Bioelectron. 2006 Volume 21, Issue 8 Pages 1529-1535
Vijay Shyam Tripathi, Vivek Babu Kandimalla and Huangxian Ju

Abstract: A novel amperometric biosensor for hydrogen peroxide (H2O2) was developed by entrapping horseradish peroxidase (HRP) in a new ormosil composite doped with ferrocene monocarboxylic acid-bovine serum albumin conjugate and multiwall carbon nanotubes (MWNTs). The ormosil was prepared using 3-(aminopropyl)triethoxysilane and 2-(3,4 epoxycyclohexyl)-ethyltrimethoxy silane as monomers. The encapsulated conjugate showed excellent electrochemistry and acted as an electron transfer mediator. The presence of MWNTs improved the conductivity of the composite film. This matrix showed a biocompatible microenvironment for retaining the native activity of the entrapped HRP and a very low mass transport barrier to the substrate, which provided a fast amperometric response to H2O2. The proposed H2O2 biosensor exhibited a linear range of 0.02-4.0 mM with a detection limit of 5.0 µM (S/N = 3) and a value of 2.0 mM. It could be used for flow injection analysis of hydrogen peroxide with a linear range from 0.02 to 4.5 mM, sensitivity of 0.042 µA/mM and analytical time of 20 s per sample. This biosensor possessed good analytical performance and storage stability.

"Glucose Sensor For Flow Injection Analysis Of Serum Glucose Based On Immobilization Of Glucose Oxidase In Titania Sol-gel Membrane"
Biosens. Bioelectron. 2003 Volume 19, Issue 4 Pages 401-409
Jiuhong Yu, Songqin Liu and Huangxian Ju

Abstract: A novel amperometric glucose sensor was constructed by immobilizing glucose oxidase (GOD) in a titania sol-gel film, which was prepared with a vapor deposition method. The sol-gel film was uniform, porous and showed a very low mass transport barrier and a regular dense distribution of GOD. Titania sol-gel matrix retained the native structure and activity of entrapped enzyme and prevented the cracking of conventional sol-gel glasses and the leaking of enzyme out of the film. With ferrocenium as a mediator the glucose sensor exhibited a fast response, a wide linear range from 0.07 to 15 mM. It showed a good accuracy and high sensitivity as 7.2 µA cm-2 mM 1. The general interferences coexisted in blood except ascorbic acid did not affect glucose determination, and coating Nafion film on the sol-gel film could eliminate the interference from ascorbic acid. The serum glucose determination results obtained with a flow injection analysis (FIA) system showed an acceptable accuracy, a good reproducibility and stability and indicated the sensor could be used in FIA determination of glucose. The vapor deposition method could fabricate glucose sensor in batches with a very small amount of enzyme.
Glucose

"Flow-Injection Chemiluminescence Determination Of Papaverine Using Cerium(IV)-Sulfite System"
Anal. Lett. 2004 Volume 37, Issue 1 Pages 143-155
Sichun Zhang; Yafeng Zhuang; Huangxian Ju

Abstract: A sensitizing effect of papaverine on the weak chemiluminescence (CL) reaction of sulfite with acidic cerium(IV) is studied. In papaverine and cerium(IV) solution, the increase in the fluorescent intensity of cerium(III) at 360 nm with an increasing time indicates a slow oxidation of papaverine by acidic cerium(IV). This reaction results in the formation of intermediate radical of papaverine, which enhanced the CL emission of sulfite-cerium(IV) system. Based on this finding, a flow injection (CL) method is proposed for the determination of papaverine. The CL intensity is proportional to the concentration of papaverine from 1.0 x 10^-7 to 1.0 x 10^-5 M with a correlation coefficient of 0.9991. The detection limit is 8.7 x 10^-8 M (3?). The relative standard deviation for seven independent determinations of 1.0 x 10^-6 M papaverine is 2.0%. The proposed method has been satisfactorily used for the determination of papaverine in pharmaceutical preparations and biological fluids.

"β-Cyclodextrin Sensitized Chemiluminescence Of Hemoglobin-hydrogen Peroxide-carbonate And Its Analytical Application"
Anal. Chim. Acta 2003 Volume 475, Issue 1-2 Pages 163-170
Sichun Zhang and Huangxian Ju

Abstract: The weak chemiluminescence (CL) from the reaction of hemoglobin (Hb) with hydrogen peroxide in an aqueous carbonate solution was significantly enhanced in the presence of β-cyclodextrin (β-CD). The mechanism was discussed by examining CL emission spectrum and the effect of various free radical scavengers on CL emission intensity. The β-CD could form encapsulation complex with heme, which was dissociated from Hb in alkaline medium. The formed complex showed better catalytic activity than free heme thus resulting in an enhanced CL emission intensity. A flow injection CL method for the determination of Hb ranging from 2.0 x 10^-9 to 1.0 x 10^-5 g mL-1 was developed with β-CD as a sensitizer. The detection limit (3s) for Hb was 1.2 x 10^-9 g mL-1 (1.9 x 10^-11 mol l-1) and the relative standard deviation (RSD) for seven independent detections of 1.0 x 10^-7 g mL-1 Hb was 2.4%. Since metal ions could not form complex with β-CD, this method showed a good selectivity. The proposed method was used for the determination of Hb in human blood and serum.

"Noncompetitive Enzyme Immunoassay For α-Fetoprotein Using Flow Injection Chemiluminescence"
Appl. Biochem. Biotechnol. 2004 Volume 117, Issue 2 Pages 93-102
Lin, Jiehua; Yan, Feng; Ju, Huangxian

Abstract: A novel, direct noncompetitive flow injection enzyme immunoassay for ?-fetoprotein (AFP) was developed by enhanced chemiluminescence detection. The method was based on off-line incubation of AFP and horseradish peroxidase (HRP)-labeled anti-AFP, and then trapping of the unbound enzyme conjugate by an immunoaffinity column filled with AFP-modified Sepharose. The immunocomplex formed in incubation passed through the column and then was directly detected by a post-column chemiluminescence technique. The optimal conditions for the immunoassay procedure and chemiluminescence detection were established. At a 1:10 dilution of enzyme conjugate solution, the linear range for chemiluminescence detection of AFP was from 2.0 to 75 ng/mL with a correlation coefficient of 0.993 and a coefficient of variation of 2.67% at 30 ng/mL. The detection limit was 0.5 ng/mL. This method was flexible, sensitive, and rapid. The immunoaffinity column of 200 µL could be repeatedly used 100 times without a single decrease. The whole assay time including the preincubation step was only 30 min for one sample.