Molecular Detection with Magnetic Labels and Magnetoresistive Sensors

For future lab-on-a-chip devices, compact and inexpensive detection units are required that directly translate the abundance of certain biomolecules into an electronic signal. By detecting specifically bound magnetic labels with magnetoresistive sensors, a versatile platform can be designed that fulfils those requirements and even enables on-chip manipulation of biomolecules by suitable magnetic gradient fields. Here, we present sensitive recognition of different types of magnetic labels by magnetoresistive sensors based both on giant magnetoresistance (GMR) and tunneling magnetoresistance (TMR). Hybridization experiments show that our prototype magnetoresistive biosensor can detect complex DNA with a length of one thousand base pairs down to a concentration of 24 pM. A direct comparison of our magnetoresistive and a standard fluorescent detection method clearly shows the advantage and competitiveness of our approach.