Label-free protein recognition using an aptamer-based impedance measurement assay

A novel aptamer-based biosensing assay for label-free protein detection and quantification by measuring the change in electrochemical impedance upon protein–aptamer complex formation was demonstrated. Our process starts with a self-assembly of the DNA aptamer on a microfabricated thin film gold electrode, followed by the recognition of the protein binding event via monitoring the interfacial electron transfer resistance with electrochemical impedance spectroscopy. The thrombin binding aptamer (TBA) has high binding affinity and specificity to its target protein and the impedance detection assay shows a reliable and sensitive quantification of thrombin with a detection range of four orders of magnitude and a detection limit of 0.1 nM.