Magnetoresistive biosensors based on active guiding of magnetic particles towards the sensing zone

Magnetoresistive biosensors, using superparamagnetic particles as a label, have shown to be promising candidates for highly sensitive biosensors. One challenging task remains a further increase of their sensitivity. In the past, most research groups have realized this by increasing the sensitivity of the sensor. In this letter, we present a novel detection mechanism for these biosensors that increases their sensitivity by releasing specifically bound magnetic particles followed by their active guiding towards the sensing zone. For this, we first bind particles specifically to the sensor surface using a sandwich assay. In a following step, we release these particles by breaking the biomolecular bonds using a biochemical regeneration solution. Finally, the particles are repositioned to that location that gives rise to a theoretical maximum signal. Experimentally, a sudden increase in the sensor signal is observed during the latter step, which demonstrates the enhancement technique.