In my lab, we have developed a sensitive in-vitro immunoassay technique based on biofunctionalized magnetic nanoparticles (BMNs) and magneto-optical Faraday effect. As the BMNs react with the biotarget, BMNs aggregate to form the bigger magnetic clusters and induce the change of Faraday angle which can be used to quantify the amount of biotarget. The measurement process of the magneto-optical Faraday effect immunoassay system is very simple and does not require the redundant washing steps like Enzyme-linked immunosorbent assay (ELISA). With respect to other optical immunoassay method using fluorescence, the background influence from the reagent is almost zero in the Faraday immunoassay system because the magneto-optical Faraday effect for most biomaterials is too weak to be detected under a small magnetic field. We have demonstrated that the detection limits of 0.53 ng/mL for c-reactive protein and 10 pg/mL for tau protein were achieved by using the Faraday immunoassay system. We showed that Faraday immunoassay system is a potential and promising tool for the early diagnosis of diseases.

Magneto-optical Faraday Effect, Magnetic Nanoparticle, Magneto-Plasmonic Nanoparticle, Surface Plasmon Resonance, Immunoassay