A novel self-enhanced electrochemiluminescence immunosensor based on hollow Ru-SiO2@PEI nanoparticles for NSE analysis

Abstract 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.