A New Electrochemiluminescence Immunoassay Based on Magnetic Microbeads as Carrier of Labels

An ultrasensitive ectrochemiluminescense (ECL) immunoassay was proposed by using magnetic microbeads as the carrier of ECL labels for ECL signal amplification. First, polyclonal antibody (pcAb) of abrin was immobilized on a microplate. Then, abrin was bound to pcAb. Next, biotinylated monoclonal antibody (mcAb) was conjugated to abrin, yielding the sandwich immunocomplex on the plate. After that, Ru(bpy)32+ labeled magnetic microbeads were conjugated on the plate through specific biotin-streptavidin interaction. Finally, Ru(bpy)32+ labeled magnetic microbeads were released from the plate, and ECL of Ru(bpy)32+ was measured for abrin determination. A logarithmic linear relationship between ECL intensity and abrin concentration in the range of 2–200 ng L−1 was obtained. The linear regression equation was lgY = 1.295lgX + 0.201 (R = 0.995, n = 7, p < 0.0001), and the detection limit was 2 ng L−1. This new approach holds great promise for highly sensitive detection of target proteins in various fields such as biodiagnostics, environmental monitoring and biodefense.