Detection of AFP with an ultra-sensitive giant magnetoimpedance biosensor

Detecting cancer biomarkers is important for early cancer diagnosis and ensuring timely medical checkups. A magnetic biosensor is one effective tool for sensitive detection of these biomarkers. Herein, we propose an ultra-sensitive magnetic biosensor system composed of an off-diagonal giant magnetoimpedance (GMI)sensor, a simple microfluidic chip and a Helmholtz coil. The GMI sensor was found to provide highly sensitive detection in an external magnetic field (H_ext)ranging from −1.2 Oe to 1.2 Oe with maximum sensitivity of 35 V/Oe. We investigated the sensitivity of the sensor system to detect magnetic beads (MBs)at different H_ext. Biodetection with the sensor system was conducted with immunoassays between MB-labeled antibody and AFP antigen immobilized on the glass substrate of the open chamber on the chip. The output signal of the sensor system exhibited a linear correlation with the concentration of AFP antigens from 100 fg/mL to 1 μg/mL and a lower limit of detection (LOD)of 100 fg/mL. This ultra-sensitive GMI biosensor provides a useful approach for detecting cancer biomarkers.