▎ 摘　　要

A novel electrochemical biosensor was developed for ultrasensitive determination of testosterone from femtomolar to micromolar levels via electrochemical impedance spectroscopy (EIS) measurements. The sensor features a nanosized molecularly imprinted polymer (MIP) film that was electrochemically grafted on a graphene-oxide sheets modified electrode. The detection mechanism of this senor is explained via the change of the interfacial impedance that derived from the recognition of the target molecule. Due to the nanosheet structure as well as the high surface area of graphene-oxide, the sensitivity of the MIP sensor is enhanced remarkably. Under an optimized condition, a wide linear range from 1 fM to 1 mu m (1x10(-15)-1x10(-6) mol L-1) and a detection limit of 0.4 fM (4.0x10(-16) mol L-1) was obtained. This composite film presented a good selectivity over structurally similar steroid hormones, and a long term stability in room temperature for the detection of testosterone. Considering these advantages, the MIP/GO electrochemical biosensor could be a substitute of testosterone immunosensor, and may be further extended to the detection of other endogenous substances.