Plasmonic biosensor schemes with thermo-responsive hydrogel binding matrix

We propose a new approach for surface plasmon-enhanced fluorescence spectroscopy (SPFS) biosensor with efficient collecting of molecular analytes from a sample at the sensor surface. It is based on a responsive hydrogel binding matrix that is tethered on a metallic sensor surface and that can reversibly swell and collapse upon triggering by an external stimulus. The swelling is associated with a rapid uptake of an aqueous sample into the matrix and subsequent selective binding of a specific analyte to the catcher molecules anchored to the matrix. Upon the collapse the gel, the sample fluid is expelled and the captured analyte is compacted in close proximity to the sensor surface where large field enhancement occurs. We pursue this approach by using an indium tin oxide (ITO) microheater with surface plasmon-supporting metallic layer and thermo-responsive poly(N-isopropylacrylamide) (PNIPAAm) hydrogel on the top. The NIPAAm-based gel can be functionalized with catcher molecules and we show that the developed setup enables rapid cycling of its swelling / collapsing state by temperature modulation around 32 °C.