Sandwich-type electrochemiluminescence immunosensor based on Ru-silica@Au composite nanoparticles labeled anti-AFP

A simple and sensitive sandwich-type electrochemiluminescence immunosensor for α-1-fetoprotein (AFP) on a gold nanoparticles (nano-Au) modified glassy carbon electrode (GCE) was developed by using Ru-silica (Ru(bpy)₃²⁺-doped silica) doped Au (Ru-silica@Au) composite as labels. The primary antibody, anti-AFP was first immobilized on the gold nanoparticles modified electrode due to the covalent conjugation, then the antigen and the Ru-silica@Au composite nanoparticles labeled secondary antibody was conjugated successively to form a sandwich-type immunocomplex through the specific interaction. The surfaces of Ru-silica nanoparticles were modified via the assemble of Au nanoparticles. The prepared Ru-silica@Au composite nanoparticles own the large surface area, good biocompatibility and highly effective electrochemiluminescence properties. The morphologies of the Ru-silica@Au composite nanoparticles were investigated by using transmission electronic microscope (TEM). The Ru-silica@Au composite nanoparticles labeled anti-AFP/AFP/bovine serum albumin (BSA)/anti-AFP/nano-Au modified GCE electrode was evaluated by means of cyclic voltammetry (CV) and electrogenerated chemiluminescence (ECL). The immunosensor performed high sensitivity and wide liner for detection AFP in the range of 0.05-50 ng/mL and the limit detection was 0.03 ng/mL (defined as S/N = 3).