Research And Application Of Electrochemiluminescence Biosensors Based On Amplification Effect By Nanocomposites

Electrochemiluminescence(also named electrogenerated chemiluminescence, ECL) is a process that chemically generated species at electrode surfaces undergo electron-transfer reactions to that emit light from excited states. ECL has been widely used in the fileds, including environmental pollution detection, pharmaceutical analysis, immunoassay, and aptasensor-based detection due to the features superior to other analytical methods, such as rapid determination, lowcost, wide range and high sensitivity and so on. Nanocomposites contain different components, the performance of which was different, which can produce a strong mutual coupling effect. Thus nanocomposites can not only exhibite the performance of itself, but also emerge other new features, which have a great potential application in the fileds, such as research and development of new functional materials, environmental protection and pollution treatment, the utilization of new energy, and biochemical medicine. Recently, nanocomposites were always employed as a signal amplification strategy to achieve the detection of disease markers, proteins, and heavy metal ions with high sensitivity, which has been widely used in the construction of biosensors. In this paper, different microstructures of metal namoparticles were employed as the substrate, and ECL and nanocomposites were combined to construct the biosensors with high sensitivity:(1) In this study, with the assistance of ethylenediamine, Au NDs were prepared on ITO electrode using low-potential synthesis, with the superior properties, such as the larger surface area, excellent conductivity. The silver/zinc oxide(Ag/ZnO) with coupled structure was preparedby one-pot method, which could catalyze the reduction of ECL coreactant, H2O2. With Pb2+-specific deoxyribozyme, the Ag/ZnO coupled structure was closed to the surface of the electrode to catalyze part of H2O2, leading to a decrease of the ECL intensity. In addition, thesimple and sensitive DNA sensor could be applied for the determination of Pb2+ in lake water and human serum samples, respectively.(2) In this study, the graphene-modified porous Au-paper working electrode(GR/Au-PWE) with excellent conductivity was prepared successfully to immobilize the capture probe. The calcium carbonate/carboxymethyl chitosan(CaCO3/CMC) hybrid microspheres were prepared using the precipitation of calcium carbonate in an aqueous solution containing CMC. Using the solid-state matrix to control the nucleation and migration ofthe reduced silver atoms, luminescent silver nanoparticles(AgNPs) were successfully synthesized in glycine matrix by thermal reduction of silver ions. The CaCO3/CMC@AgNPs composites were prepared and employed as an ECL label. Taking advantage of dual-amplification effects, the DNA sensor could quantitatively detect the target DNA, and performed excellent selectivity.(3) In this study, the nanoporous gold(NPG) was easily prepared using a selective dissolution of silver from silver/gold alloy in nitric acid. The as-prepared ECL aptasensor consisted of two main components: an ECL substrate, amino group functionalized Ru(bpy)32+-doped silica(Ru-silica), and an ECL intensity switch. The ECL intensity switch contains two probes, which was split from one aptamer. The experimental results demonstrated that the ssDNA1/ATP/ssDNA2 sandwich composites layer could be formed when ATP was present, leading to the quenching of Ru(bpy)32+. Under optimal conditions, the ECL aptasensor could detect ATP quantitatively.(4) In this study, the nanoporous gold(NPG) was also easily preparedusing a selective dissolution of silver from silver/gold alloy in nitric acid. Due to the electrostatic interactions between citrate-capped gold nanoparticles(AuNPs) and Ru(bpy)32+ in aqueous medium, the Ru(bpy)32+-AuNPs(Ru-AuNPs) aggregates was successfully prepared. Then the Ru-AuNPs composite was assembled with functionalized graphene nanosheets(GR)(Ru-AuNPs/GR) with large surface area, good biocompatibility and electronic conductivity, which was employed as an ECL label. The ECL immunosensor not only exhibited high sensitivity, good reproducibility, satisfied regeneration and selectivity, but also could be an alternative for other analyte determination.