Application of the magnetoimpedance to biosensors

A prototype of a giant magnetoimpedance (GMI) biosensor was designed and tested using an amorphous ribbon. The GMI response was measured with a suspension containing a CM01N/9077 bead from Bangs Laboratories. This bead was coated with streptavidin so that it could be used as biomolecular label with a specific antibody. The GMI change caused by the presence of the specific antibody was measured with a prototype biosensor designed with a measuring cell containing an amorphous CoFeBSi ribbon. The GMI was measured in a range of current frequencies from 0.1 to 10 MHz and at intensities of Irms = 5 mA. Commercial Bangs Laboratories beads were supplied as a suspension in phosphate-buffered saline. A maximum difference of 5% in the GMI ratio measured with and without magnetic beads was obtained at a frequency of 1 MHz and Irms = 5 mA. As some potential applications for the GMI biosensor and further directions, a magnetoimpedance biosensor for detecting the presence of magnetic nanoparticles after introducing a protein on the surface of the sensor has been developed and tested for a model system by using human P21 protein (antibody and antigen) and nonspecific magnetic nanoparticles.