Molecule Detection and Manipulation by Magnetic Carriers

Hubert Brückl1, Jörg Schotter1, Monika Brzeska1, Günter Reiss1, P. B. Kamp2, Anke Becker2, and Alfred Pühler2

1Department of Physics and 2Department of Biology, University of Bielefeld, Universitätsstr. 25, D-33615 Bielefeld, Germany




Functionalized magnetic carriers like commercially available magnetite beads provide two unique advantages for biochip systems. Used as labels of biomolecules they can be detected by highly sensitive magnetoresistive sensors, which are based on the new effects of giant magnetoresistance or tunnelling magnetoresistance. On the other hand, biomolecules attached to magnetic carriers can be manipulated by external magnetic fields. Therefore, both manipulation and detection of single molecules can be done electronically (i.e. easily) on a chip. We demonstrate on-chip manipulation of paramagnetic carriers by conducting lines which are patterned on a Si wafer and embedded in Si oxide. The two-dimensional positioning of molecules is possible in this way. In addition to the manipulating system, magnetoresistive sensors can be incorporated on the chip which are capable to detect single carriers or respectively single molecules. The detection capability is demonstrated with single-stranded DNA from salmon sperm on large scaled sensors. A linear response is found in dependence of the carrier coverage. The sensitivity exceeds the optical fluorescent methods.