Electro-magnetic biosensor for binding force measurements on ligand–receptor complexes

We report on the development of a high-sensitivity biosensor combining an electrical detection of microbead labelled analytes with a magnetic system for binding strength measurements. The new sensor technology allows the determination of specific binding forces between analyte and the corresponding capture molecules (e.g. proteins, antibodies, DNA). The sensor chip comprises many biochemically functionalised ultramicroelectrodes to which one end of the ligand–receptor pairs is attached. By labelling the other end of these molecular pairs with superparamagnetic microparticles, a magnetically generated force can be applied to the molecular bonds and an unbinding can be induced. This unbinding event is electrochemically detected. With knowledge of the applied force, the binding force can be determined. We present such binding force measurements on the system NeutrAvidin–biotin and on the antibody–antigen system monoclonal anti-BSA and BSA. Because the sensor system allows a binding strength determination at several individual molecular pairs simultaneously, it seems promising that a fast investigation of environmental conditions on ligand–receptor interaction will be possible in the future.