Novel dual-sensitization electrochemiluminescence immunosensor using photopermeable Ru(bpy)32+-doped chitosan/SiO2 nanoparticles as labels and chitosan-decorated Nafion/MWNTs composites as enhancer

A novel dual-sensitization electrochemiluminescence (ECL) immunosensor for the detection of tumour protein prostate specific antigen (PSA) at trace level using Ru(bpy) 3 2+ -doped chitosan/SiO 2 nanoparticles (Ru(bpy) 3 2+ /chitosan/SiO 2 NPs) as the first signal enhancers was fabricated. Due to chitosan with excellent pore forming capacity, these nanoparticles possess porous structures and better photopermeability, and therefore have higher luminescence efficiencies compared with Ru(bpy) 3 2+ /SiO 2 NPs reported in previous publications. Conversely, chitosan with good biocompatibility and high hydrophilicity was electrochemically decorated onto a Nafion/multiwall carbon nanotubes (Nafion/MWNTs) modified electrode surface and used as the second sensitizing matrix to seize large amounts of prostate specific capture antibody (Ab 1 ). The chitosan-decorated Nafion/MWNTs composites exhibited a 5.5-times higher ECL intensity than the unadorned Nafion/MWNTs films. Also, without additional reagents, such as (3-aminopropyl)triethoxysilane (APTS), the one-step functionalized Ru(bpy) 3 2+ /chitosan/SiO 2 NPs provided a large number of active arms to connect with PSA-detected antibodies (Ab 2 ) through the amino groups in chitosan. After a sandwich immunoreaction, the PSA antigen and Ru(bpy) 3 2+ /chitosan/SiO 2 NPs-labelled Ab 2 were sequentially captured onto the Ab 1 /chitosan/Nafion/MWNTs-modified electrode surface. The ECL signal increases were linearly related to the PSA antigen concentrations and ranged from 0.01 pg·mLl −1 to 10.0 pg·mLl −1 . Under the optimized experimental conditions, the immunosensor displayed excellent sensitivity and selectivity. The detection limit was as low as 3.4 fg·mLl −1 , equivalent to, or better than, those of the reported ECL immunosensors for PSA.