An aptamer-based protein biosensor by detecting the amplified impedance signal

A label-free electrochemical impedance based protein biosensor was introduced by using aptamer as recognition tool. Our sensing protocol utilizes the affinity interaction between the thrombin and the self-assembled DNA aptamer on gold electrode. This specific interaction increases the electrode interfacial electronic transfer resistance. The resistance signal is then "amplified" by using guanidine hydrochloride to denature the captured thrombin for increasing the hydrated radius of the thrombin, consequently blocking the electron transfer from solution to electrode. The sensor sensitivity is improved using this strategy and as low as 1.0 x 10(-14) mol L-1 thrombin (enzymatic activity 10 U/mg) can be detected out.