Study On Ultrasensitive Electrochemiluminescence Immunosensors Constructed By Nanocomposites

Electrochemiluminescence (ECL) is achieved by applying a certain voltage to stimulate the reaction of the products or some components in the system to produce an optical radiation. As a combination product of electrochemistry and chemiluminescence, it is a useful and available detection tool due to the merits of high sensitivity, rapid detection, wide dynamic concentration response ranges. With their rapid development, nanomaterials have been widely applied in biosensor because of their large specific surface area, good biocompatibility and so on. In particular, the nanocomposites combined with perylene anhydrides have important theoretical significance and practical application value in ECL biosensors.Part1Amplified electrochemiluminescent immunosensing using apoferritin-templated poly(etherimide) nanoparticles as co-reactant for intection of HCGIn this study, the new Ru(bpy)32+/PEI system is based on the in-situ releasing of the effective co-reactant of PEI from the protein cage of apoferritin for signal amplification. At first, CNTs were decorated with3,4,9,10-perylene tetracarboxylic acid (PTCA) was employed as carriers for immobilization of streptavidin (SA) and Ab2. Then the biotin-modified apoferritin-templated PEI nanoparticles (bio-Apo-PEI) were covalently bound to SA on the surface of CNT carriers to form the Ab2bioconjugates (bio-Apo-PEI/SA/Ab2/CNTs). For this proposed immunosensor, graphene and carbon nanotubes which were dispersed in Nafion solution were modified on the bare glass carbon electrode. Subsequently, Ru(bpy)32+was assembled onto the modified electrode surface by electronic adsorption. And then, AuNPs were assembled onto the modified electrode, which could further improve the ECL intensity and be favorable for the adsorption of antibody. The as-proposed ECL immunosensor exhibited sensitive response on the detection of HCG. A linear concentration range of5.0×10-4to2.0×102mIU/mL with a detection limit of0.17μIU/mL (S/N=3) was observed. The immunosensor would extend the applications in the field of immunoassays.Part2Reagentless electrochemiluminescent detection of protein biomarker using Graphene-based magnetic nano probes and poly-L-lysine as co-reactantIn the work, we constructed a reagentless ECL immunosensor using magnetic graphene as Ru(bpy)32+and secondary antibody immobilization matrix. First, with L-lysine electrodeposited on the bare glass electrode surface, gold nanoparticles was electrodeposited on the modified electrode, which could further improve the ECL intensity and be favorable for the immobilized total triiodothyronine antibody (anti-T3), and then bind the antigen analytes. Fe3O4@GO labeled with Ru(bpy)32+and secondary antibody could be captured onto the electrode surface by a sandwich immunoassay protocol. In this work, the poly-lysine containing primary and secondary amino can act as co-reactant of Ru(bpy)32+to amplify the ECL signal and improve the detection sensitivity.. The ECL intensity decreased linearly with the T3concentrations in the range from0.1pg/mL to10ng/mL with a detection limit of0.03pg/mL. This strategy avoids the addition of the co-reactant to the electrolyte and significantly simplifies the immunoassay procedure, shortens the analytical time, and thus provides a new promising platform for clinical immunoassay.Part3Ultrasensitive APE-1mmunosensing based on self-enhanced electrochemiluminescence of a novel Ru (Ⅱ) complexIn this work, an alternative "signal on" immunosensor for ultrasensitive detection of APE-1was designed utilizing the self-enhanced electrochemiluminescence (ECL) of a novel Ru (II) complex functionalized coil-like nanocomposite as signal labels. In order to achieve the high sensitivity, the aromatic compound of3,4,9,10-perylene tetracarboxylic acid (PTCA) was bind to PEI-Ru(II), acting as enhancer and linker for subsequent assembly on the carbon nanotubes (CNTs). Then the CNTs were used as nano-carries for PTCA-PEI-Ru(Ⅱ) loading via π-π stacking to obtain the coil-like PTCA-PEI-Ru(II)/CNTs composite. Furthermore, the PTCA-PEI-Ru(II)/CNTs could induce the hollow gold nanoparticles (HGNPs) assembling on the surface via residual-NH2groups of PTCA-PEI-Ru(II). The HGNPs decorated coil-like PTCA-PEI-Ru(II)/CNTs composite showed uniform size distribution, good stability and significant ECL intensity, and could easily serve as a tracing tag to label detection antibody (Ab2). Au nanoparticles (AuNPs) were electrodeposited to the surface of the glass carbon electrode (GCE), with enhanced surface area and good biocompatibility to capture primary antibody (Abl) and then bind the antigen analyte. The measurement was based on a sandwich immunoassay method. The experimental results demonstrated that the proposed immunosensor exhibited sensitive and stable response for the detection of APE-1, ranging from1fg/mL to1pg/mL with a limit of detection down to0.3fg/mL (S/N=3).