Berlin 2005 – wissenschaftliches Programm
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MA: Magnetismus
MA 11: FV-internes Symposium ”Applied Magnetism” (Organizers: R. Hilzinger, H. Huneus, J. Wecker)
MA 11.1: Hauptvortrag
Samstag, 5. März 2005, 09:00–09:30, TU H1028
Magnetoresistive biochips and magnetic field assisted hybridization — •Paulo P. Freitas — INESC-MN, Lisbon Portugal
Magnetoresistive biochips use arrays of magnetoresistive sensors to detect the presence of magnetically labelled biomolecules-the targets (DNA, proteins, antibodies) hybridized to immobilized complementary probes. Magnetic labels consist of non-remanent paramagnetic or superparamagnetic particles (typically FeOx based) with dimensions from µm size down to 50nm in diameter. New generations of ferromagnetic particles with dimensions down to 10nm are also being investigated. Different types of magnetoresistive sensors have been used, GMR multilayers, spin valves, and planar Hall sensors. Low resistance magnetic tunnel junctions, with improved S/N ratio start to be considered. Sensor design, detection geometry and electronics must take into account the required minimum particle concentration to be detected (single label) and the dynamic range (maximum number of labels to be detected). At the moment, and for DNA, c-DNA experiments at our lab using spin-valve based biochips, the detection limit has been pushed to 10ftmole/cm2 using 250nm FeOx labels. Recently, biomolecular hybridization rates were strongly enhanced by sweeping target biomolecules over the immobilized probes using a combination of AC and DC magnetic fields. Hybridization now takes place in few minutes in comparison with several hours in a diffusion controlled process.