SiO₂ Nanoparticle-based Electrochemiluminescence Signal Amplification For Ru（bpy）₃Cl₂ And Its High-sensitive Immunoassay

In this paper, the electrochemiluminescence(ECL) signal amplification system of Ru(bpy)32+ was established and its application in quantitative detection for hepatitis B surface antigen(HBs Ag) was studied based on the carrier of Si O2 nanoparticles. Besides,in order to improve the reproducibility and simplicity for ECL detection, a new-type flow cell was made and its properties were investigated.In virtue of the unique property of β-cyclodextrin(β-CD), it was applied to ECL signal amplification for Ru(bpy)32+. Ru(bpy)32+could interact with β-CD to form the supermolecular inclusion(β-CD-Ru). In the preparation of Si O2 nanoparticles with St?ber method, β-CD-Ru could dope inside to get the nanoparticles β-CD-Ru@Si O2. ECL intensity of the prepared nanoparticles got an enhancement. But after amino-functionalization by3-aminopropyl)triethoxysilane(APTES), as a result of the electron hindrance of silane layer, ECL intensity of the as-obtained nanoparticles β-CD-Ru@Si O2-APTES decreased remarkably as well as its stability. Consequently, it cannot be further applied to the high-sensitive analysis of bio-labeling.The strong ECL nanoparticles have been prepared based on the anionic polyelectrolyte sodium polyacrylate(PAA)-ECL enhancement for Ru(bpy)32+, which were loaded by the carrier of Si O2 nanoparticle. There were two kinks of Ru(bpy)32+for the as-prepared nanoparticles PAA-Ru@Si O2/[PAA???Ru&Nafion???Ru], namely, the doped one and the exchanged one. The former was loaded inside the ECL nanoparticles by doping in a form of ion-pair macromolecules PAA-Ru, and the corresponding ECL was enhanced about 2 times owing to the increase of the doping amount of Ru(bpy)32+. The latter was loaded on the surface of the ECL nanoparticles by ion exchanging with the PAA-doped Nafion membrane. Based on an obvious increase of the exchangeable ion on the membrane surface, ECL intensity of the exchanged Ru(bpy)32+ was enhanced about 3 times. At thesame time, ECL intensity of the doped Ru(bpy)32+ was further enhanced 15 times, since PAA in the doped membrane could obviously enhance electron transfer for the internally-doped Ru(bpy)32+ to the working electrode. Furthermore, the labeling of antibodies could be easily realized by the as-prepared nanoparticles based on hydrophobic regions of Nafion and then a high sensitive ECL immunoassay for HBs Ag was developed.The linear range was between 1 and 100 pg m L-1(R2= 0.9912). The detection limit was low to 0.11 pg m L-1(signal-to-noise ratio = 3). Good precision of ECL measurement and feasibility in human serum have been found. Such immunoassay had a potential in quantitative determination of HBs Ag at a ultra-low concentration level for early clinical diagnosis.