Giant magneto-resistance based immunoassay for the tumor marker carcinoembryonic antigen

We report on a giant magnetoresistance (GMR) based immunosensor for the carcinoembryonic antigen (CEA) labeled with superparamagnetic microparticles (Dynabeads). The GMR sensor contains 200 GMR strips and was fabricated by micro-electromechanical system (MEMS) technology. This system can detect Dynabeads in concentrations down to 10 nga <...mL(-1). Sandwich immunoassays were employed on the surface of a gold film modified with a self-assembled monolayer and using biotinylated secondary antibody against CEA and streptavidinylated Dynabeads. With DC magnetic fields in the range of 40 to 90 Oe, CEA can be detected with a detection limit as low as 10 pga <...mL(-1). Samples spiked with different concentrations of CEA can be distinguished clearly, and the method is deemed to be well suited for clinical use.