Photometric aptasensor using biofunctionalized photonic crystal slabs

We present a biosensor using a photonic crystal slab (PCS) surface-functionalized with aptamers (thus aptasensor) and a label-free photometric detection scheme. Resonances in the optical transmission spectrum of the PCS are highly sensitive to mass changes on the surface of the PCS. We align the resonance´s spectral position to the falling edge of a light emitting diode´s (LED) spectrum and use two crossed polarization filters before and after the PCS. Thus, we may detect a molecular binding process on the surface of the PCS with a simple photometric intensity measurement. Using a CMOS camera, we determine the signal and reference intensity at different positions on the PCS. The functionality of this aptasensor is demonstrated by applying a 125 nM thrombin-solution to the PCS bio-functionalized with anti-thrombin aptamers. A significant signal was obtained and the reaction kinetic was observed.