An InSb-based magnetoresistive biosensor using Fe₃O₄ nanoparticles (Sensors and Actuators B: Chemical)

   A magnetoresistive biosensor was demonstrated using an InSb-based semiconductor channel. The Fe3O4 nanoparticle was linked with a target antigen via a capture antibody in the reagent, and a detection antibody immobilized on an InSb channel was shown to selectively bind to the antigen-capture antibody-nanoparticle complex. The detected magnetic nanoparticles produced a stray magnetic field that induced a change in the resistance of the channel due to the Lorentz force. The antigen concentration was pro-portional to the number of nanoparticles attached to the sensor surface, and hence could be determined by measuring the magnetoresistance level of the sensing channel. This antigen-antibody reaction sensor was shown to detect an extremely small amount of liver cancer antigen, at a concentration as low as 1 pg/ml. The systematic tests we carried out also confirmed the good selectivity and reusability of this biosensor.