| This thesis is based on the chemiluminescence principle and biological immune probe built aseries of high-sensitivity, high selectivity, high luminous efficiency ECL immunosensor. The ECLimmunosensor achieve highly sensitive detection of different target substances (methyl parathion,alpha-fetoprotein, HIV antibody) analysis. The ECL sensor of methyl parathion construction isbased on the methyl parathion molecules having a strong selective adsorption performance ofzirconium oxide nanoparticles. Alpha-fetoprotein and HIV antibody immune sensor is captured bythe magnetic nano-probe, a quantum dot labeled antibody signal tag immune sandwich complex isformed in vitro, using an external magnetic field to its separation and further modification to theelectrode surface constituting ECL immunosensor. Through in vitro immunization to form asandwich immune complex, and the use of magnetic separation technology immune complexseparation greatly simplify the preparation process of the immunosensor, and saves the time of thepreparation of the sensor, reducing the cost, and improve the detection sensitivity, in the clinicaldetection above expected in practical application.1. Enhanced electrochemiluminescence employed for the selective detection of methylparathion based on a zirconia nanoparticle film modified electrode.A simple, rapid and sensitive electrochemiluminescence (ECL) sensor was proposed for directmeasurements of methyl parathion (MP) based on the strong affinity of a nano zirconia particles(ZrO2NPs) modified film on the electrode to the phosphoric group. ZrO2NPs, which couldprovide a larger absorption area to immobilize organophosphorus, was firstly modified on theglassy carbon electrode surface to prepare the proposed ECL sensor (ZrO2/GC). Subsequently, theZrO2/GC electrode was scanned from–0.8to+0.6V to obtain the background signal at0.44V in aluminol/KCl solution. Then, a certain concentration of MP was added to an aqueous solution for240s, which was absorbed onto the ZrO2/GC electrode surface. Moreover, the MP absorbed on thesurface of the ZrO2/GC electrode enhanced the ECL signal of luminol in the luminol/KCl solution,which increased with the concentration of MP. As a result, a novel ECL sensor was obtained in aluminol/KCl solution. The MP was determined in the range of from3.8×10–11to3.8×10–6molL–1, with a low detection limit of1.27×10–11mol L–1(S/N=3). The proposed ECL sensor performance for MP detection will open a new field in the application of rapid and screen detectionof ultra-trace amounts of organ phosphorus pesticides (OPs) of vegetables used in farm markets.2. The sandwich-type electrochemiluminescence immunosensor for α-fetoprotein based onenrichment by Fe3O4-Au magnetic nano probes and signal amplification by CdS-Aucomposite nanoparticles labeled anti-AFP.A novel and sensitive sandwich-type electrochemiluminescence (ECL) immunosensor wasfabricated on a glassy carbon electrode (GCE) for ultra trace levels of-fetoprotein (AFP) basedon sandwich immunoreaction strategy by enrichment using magnetic capture probes and quantumdots coated with Au shell (CdS-Au) as the signal tag. The capture probe was prepared byimmobilizing the primary antibody of AFP (Ab1) on the core/shell Fe3O4-Au nanoparticles, whichwas first employed to capture AFP antigens to form Fe3O4-Au/Ab1/AFP complex from the serumafter incubation. The product can be separated from the background solution through the magneticseparation. Then the CdS-Au labeled secondary antibody (Ab2) as signal tag (CdS-Au/Ab2) wasconjugated successfully with Fe3O4-Au/Ab1/AFP complex to form a sandwich-typeimmunocomplex (Fe3O4-Au/Ab1/AFP/Ab2/CdS-Au), which can be further separated by anexternal magnetic field and produce ECL signals at a fixed voltage. The signal was proportional toa certain concentration range of AFP for quantification. Thus, an easy-to-use immunosensor withmagnetic probes and a quantum dots signal tag was obtained. The immunosensor performed at alevel of high sensitivity and a broad concentration range for AFP between0.0005and5.0ng mL1with a detection limit of0.2pg mL1. The use of magnetic probes was combined with pre-concentration and separation for trace levels of tumor markers in the serum. Due to theamplification of the signal tag, the immunosensor is highly sensitive, which can offer great promisefor rapid, simple, selective and cost-effective detection of effective biomonitoring for clinicalapplication.3. Design of sensitive biocompatible quantum-dots embedded in mesoporous silicamicrospheres for the quantitative immunoassay of HIV antibodies.A novel sandwich-type electrochemiluminescence (ECL) immunosensor was synthesized toenable the sensitive detection of HIV. This system incorporated mesoporous silica complexed withquantum dots (QDs) and nano-gold particles, which were assembled to enhance signal detection.Magnetic beads were prepared by immobilizing the secondary anti-IgG antibody. This was firstemployed to capture anti-HIV antibody (Ab) to form a Fe3O4/anti-IgG/Ab complex. A highloading and signal-enhanced nanocomposite (hereafter referred to as Au-mSiO2-CdTe) was used asa HIV antigen label. The Au-mSiO2-CdTe nanocomposite was conjugated to the Fe3O4/anti-IgG/Ab complex to form an immunocomplex (hereafter referred to as Fe3O4/anti-IgG/Ab/HIV/CdTe-mSiO2-Au). This complex could be further separated by an external magnetic field to produce ECL signals at a fixed voltage. Due to the large specific surface area, and porevolume of mesoporous silica, the loading of the CdTe QDs was markedly increased. Thus, theloaded QDs released a powerful chemiluminescent signal with a concordantly increased sensitivityof the immunosensor. In addition, the immunosensor was highly sensitive, and displayed a linearrange of responses for HIV antibody across a dilution range of1:1500through1:50. The thresholdlimit of detection of the immunosensor was found to be1:1500. We propose that theimmunosensor is highly sensitive and is thus a promising candidate in rapid, robust, and cost-effective biomonitoring applications in the clinical diagnostic laboratory. |
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