Magnetoresistive sensors and magnetic nanoparticles for biotechnology

Magnetoresistive biosensors use a new detection method for molecular recognition reactions based on two recently developed techniques and devices: Magnetic markers and XMR sensors, where XMR means either giant magnetoresistance (GMR) or tunneling magnetoresistance (TMR). The markers are specifically attached to the target molecules, and their magnetic stray field is picked up by an embedded magnetoresistive sensor as a change of the electrical resistance. Compared to established, e.g., fluorescent, detection methods, magnetic biosensors have a number of advantages, including low molecular detection limits, flexibility, and the direct availability of an electronic signal suitable for further automated analysis. This makes them a promising choice for the detection units of future widespread and easy-to-use lab-on-a-chip systems or biochips. In this article, we discuss recent advances in this field and compare possible approaches toward single molecule detection.