▎ 摘　　要

The authors describe an electrochemical immunoassay for ultrasensitive determination of the Mycobacterium tuberculosis (MTb) secretory protein MPT64 which is an antigen for early diagnosis of infection with MTb. Protein G was used to immobilize antibodies against MPT64 on a gold electrode. Graphene oxide with its large surface area was used as a carrier to anchor magnetite (Fe3O4) and platinum (Pt) nanoparticles. The nanocomposite of type GO@Fe3O4@Pt was used as a signal reporter with excellent catalytic activity and recyclability. The nanocomposite exhibits peroxidase-like activity for hydrogen peroxide, best at -0.25V (vs. Ag/AgCl). It works over a wide range of pH values (2-10) and temperatures (25-65 degrees C). Further signal amplification strategy was accomplished by rolling circle amplification. This voltammetric assay has a linear response to the logarithm of MPT64 concentration in therange from 5.0fgmL(-1) to 1.0ngmL(-1) and a detection limit of 0.34fgmL(-1) (at asignal to noise ratioof 3, forn=10). The assay can be completed within 4h. It was successfully applied to the determination of MPT64 in spiked serum samples. Conceivably, the assay has a large potential in providing laboratory evidence for rapid diagnosis of MTb infection.