Development of an ingenious method for determination of Dynabeads protein A based on a giant magnetoimpedance sensor

A novel analytical method based on giant magnetoimpedance (GMI) effect is developed for quantitative determination of Dynabeads protein A (DPA). An integrated GMI sensor involving the sensing elements of NiFe/Cu/NiFe films is prepared by Micro-Electro-Mechanical-Systems (MEMS) technology. DPA with various concentrations are immobilized on Au film, and a GMI-based biosensing platform is established. The magnetic signals produced by DPA are sensed by the GMI sensing elements, and the GMI sensor provides a detection signal in the form of a magnetoimpedance change. We observed that the GMI ratio is greatly reduced at high frequencies due to the presence of DPA. The GMI sensor displays a linear range of 0.1–5 μg mL−1, and a low detection limit (90 Dynabeads) is achieved at f = 1.5 MHz. Therefore, this GMI-based analytical method may be useful for highly sensitive detection of biological markers in ultra-trace quantities.