A novel self-enhanced electrochemiluminescence immunosensor based on hollow Ru-SiO(2)@PEI nanoparticles for NSE analysis

Poly(ethylenimine) (PEI) and Ru(bpy)(3)(2+)-doped silica (Ru-SiO(2)) nanoparticles were simply mixed together to prepare a novel self-enhanced electrochemiluminescence (ECL) composite of Ru-SiO(2)@PEI. The hollow Ru-SiO(2)@PEI nanoparticles were used to build an ECL immunosensor for the analysis of neuron specific enolase (NSE). PEI not only assembled on the surface of Ru-SiO(2) nanoparticles through the electrostatic interaction to act as co-reactant for Ru(bpy)(3)(2+) ECL, but also provided alkaline condition to etch the Ru-SiO(2) nanoparticles to form the hollow Ru-SiO(2)@PEI nanoparticles with porous shell. The unique structure of the Ru-SiO(2)@PEI nanoparticles loaded both a large amount of Ru(bpy)(3)(2+) and its co-reactant PEI at the same time, which shortened the electron-transfer distance, thereby greatly enhanced the luminous efficiency and amplified the ECL signal. The developed immunosensor showed a wide linear range from 1.0 × 10(−11) to 1.0 × 10(−5) mg mL(−1) with a low detection limit of 1.0 × 10(−11) mg mL(−1) for NSE. When the immunosensor was used for the determination of NSE in clinical human serum, the results were comparable with those obtained by using enzyme-linked immunosorbent assay (ELISA) method. The proposed method provides a promising alternative for NSE analysis in clinical samples.