Application of differential phase detection for sensitivity improvement in surface plasmon resonance sensors

Surface plasmon resonance (SPR) is an effective tool for quantitative detection of binding reaction between biomolecules. Currently SPR sensors are mainly based on measuring the angular shift associated with biomolecular adhesion. In fact it has been shown that the phase jump across the SPR dip is very steep, and consequently better sensitivity may be achieved by measuring the optical phase. In this presentation, we report interferometric techniques we have developed in our laboratory for achieving SPR phase detection. We also demonstrate that the incorporation of differential phase detection can further improve the performance of SPR biosensors. Currently the experimental sensitivity of our differential phase setup is 5.48/spl times/10/sup -8/ refractive index unit (RIU), which is three times better than that reported from conventional angular systems.