One Renewable and Magnetic Electrochemiluminescence Immunosenor Based on Tris(2,2’-bipyridine) ruthenium(II) Modified Magnetic Composite Nanoparticles Labeled Anti-AFP

A renewable and magnetic electrochemiluminescence (ECL) immunosensor for alpha-fetoprotein (AFP) was fabricated by using RuL-MWNTs (Tris(2,2’-bipyridine) ruthenium(II) complex immobilized on multiwall carbon nanotubes through π-π stacking function between the carbon aromatic systems) doped Au ([email protected]) composite as labels. Polyelectrolyte poly(dimethyldiallylammonium chloride) (PDDA) was employed to covered on the surfaces of RuL-MWNTs which made it have positive electric charge and can absorb negative colloid Au nanoparticles to fabricate [email protected] through electric attraction. The primary antibody, anti-AFP was first immobilized on the Fe3O4(core)/gold(shell) nanoparticles (Fe3O4@Au, GMP) as probes. Then the antigen and the [email protected] composite nanoparticles labeled Ru(bpy)32+-conjuged secondary antibody ([email protected]~RuLAb2) were combined successively to form [email protected]~RuLAb2/AFP/anti-AFP-GMP sandwich-type immunocomplexes through the specific interaction. The resulting magnetic sandwich immune complexes can be absorbed on the planar screen printed carbon electrode (SPCE) due to the external magnetic field added on the bottom of it. The magnetic sandwich complexes can be easily washed away from the surface of SPCE when the magnetic field was removed which made the immunosensor reusable. The prepared [email protected] composite nanoparticles own large surface area, good biocompatibility and highly effective ECL properties. The morphologies of the [email protected] and its antibody labeled composite nanoparticles were characterized by transmission electronic microscope (TEM). The sensor performed high sensitivity and wide liner for detection AFP in the range of 0.01-50 ng·mL–1 and the limit detection was 3 pg·mL-1 (defined as S/N=3). Furthermore the sandwich immunocomplexes can be performed the rapid separation from the unbound secondary antibody quickly by magnetic field. So the immunosensor can simultaneously realize separation, enrichment and determination, with high sensitivity, which would be valuable for clinical immunoassay for AFP in human serum.