Study On Sandwich-type Electrochemiluminescence Immunosensors Constructed By Composite Nanoparticles

Electrochemiluminescence (ECL), the generation of an optical signal triggered by an electrochemical reaction. ECL has recently become an important and valuable detection method and been applied in many fields due to its inherent advantages such as high sensitivity, high selectivity, very low background signal, simple instrumentation and low cost. ECL immunosensor, the combination of very sensitve ECL detections with extremely selective biological recognition pattern immunoassays. Thus the development of a highly sensitive immunosensor has been an important task. Recently, nanoparticles have often been used in constructing immunosensors. Particularly, composite nanoparticles played a very important role in developing highly sensitive immunosensor due to its unique physical and chemical properties.Part 1 Sandwich-type Electrochemiluminescence Immunosensor Based on Ru-silica@Au composite nanoparticles labeled anti AFPRu(bpy)32+ has been immobilized on the electrode in many ways, the Ru-silica (Ru(bpy)32+-doped silica) nanocomposite has been fixed on the electrode surface, Ru(bpy)32+ could be more stable, The Ru-silica nanocomposite with a high ECL signal, the large surface area, good biocompatibility. Therefore, The Ru-silica nanocomposite was considered as a good modified material. In this work, Ru-silica doped Au (Ru-silica@Au) composite Ru-silica@Au composite nanoparticles were prepared, the composite could combine the advantages of Ru-silica and gold nanoparticles, The Ru-silica@Au composite nanoparticles were used to label the second antibody, a high sensitivity electroluminescence immunosensor was constructed with sandwich-type method. The primary antibody, anti-AFP was first immobilized on the gold nanoparticles modified electrode due to the covalent conjugation, then the antigen and the Ru-silica@Au composite nanoparticles labeled secondary antibody was conjugated successively to form a sandwich-type immunocomplex through the specific interaction. Accordingly, through the ECL response of Ru-silica and tripropylamine (TPA), a strong ECL signal was obtained and an amplification analysis of protein reaction was achieved, which led to an increase of the immunosensor sensitivity. In the optimal experimental conditions, The immunosensor performed high sensitivity and wide liner for detection AFP in the range of 0.05-80 ng/mL and the limit detection was 0.03 ng/mL.Part 2 Electrochemiluminescence Immunosensor Based on DMBA labeled anti AFP4-(Dimethylamino)butyric acid (DMBA) is the other coreaction reagent of Ru(bpy)32+, has a certain amount of amino and carboxyl groups, could be used to adsorb biological molecules. A sandwich-type electrochemiluminescence (ECL) immunosensor was constructed by using DMBA label secondary antibody. Firstly, CS-Ru-silica composite nanoparticles were modified on the glassy carbon electrode (GCE). Subsequently, Au nanoparticles were immobilized on the surface of the electrode to immoblize anti-AFP. Later, the electrode was incubated with antigen of AFP and then reacted with the secondary antibody which was labeled DMBA. Accordingly, through the ECL response of Ru-silica and DMBA, a strong ECL signal was obtained. Moreover, high biocompatibility and low cost. Under optimal condition, the proposed immunosensor exhibited a good behavior for detection AFP in the range of 0.025-80 ng/mL,and the limit detection was 8.3 pg/mL (defined as S/N=3).Part 3 Au/CdTe composite nanoparticles Labeling for Electrochemiluminesence Detection of HCGSemiconductor nanomaterials (or quantum dots) have been extensively developed because of its unique fluorescence characteristics and good biocompatibility. In this study, Human chorionic gonadotropin (HCG) was used as the analyte, a highly sensitive sandwich-type ECL immunosensor based on CdTe/Au composite nanoparticles was developed. The CdTe/Au composite nanoparticles were prepared in this experimental, was used to label anti-HCG, The CdTe/Au composite nanoparticles not only provided a large surface areas and biocompatibe environment for adsorption of biomolecules, but also exhibited high ECL intensity and good conductivity. The modified electrodes were evaluated by means of cyclic voltammetry (CV) and electrogenerated chemiluminescence (ECL). Under the optimal conditions, a linear relationship between the ECL intensity and HCG concentration was obtained in the range of 0.02 mIU/mL to 50 mIU/mL with a detection limit of 0.0067 mIU/mL (S/N=3). This approach offered obvious advantages of simple, high sensitivity and good selectivity, which possessed great potential for protein detection in clinical laboratory.