Figure 1. Schematic illustration of the ratiometric E-AB sensor for prion detection.

The assay uses the target protein (prion protein) as a mediator to regulate the competitive host-guest interaction between β-CD and the redox probes. However, other proteins could not interact with MB-tagged prion aptamer (MB-Apt), resulting in the unsuccessful formation of protein biogate and thus the displacement of MB by FCA. Based on the ratio between the oxidation peak current of MB (I_MB) and that of FCA (I_FCA), prion was detected sensitively and selectively.