Disposable immunosensor array for ultrasensitive detection of tumor markers using glucose oxidase-functionalized silica nanosphere tags

An ultrasensitive multiplexed electrochemical immunoassay method was developed for the detection of tumor markers by combining a newly designed trace tag and a disposable immunosensor array. The array was prepared by immobilizing capture antibodies on gold nanoparticles which were assembled on carbon nanotubes-chitosan modified screen-printed carbon electrodes. The trace tag was prepared by loading signal antibodies and high-content glucose oxidase on amino-functionalized silica nanosphere. With a sandwich-type immunoassay format, ultrahigh sensitivity was achieved by the enzymatic signal amplification with ferrocenecarboxylic acid as electron transfer mediator and the accelerated electron transfer by carbon nanotubes. Using carcinoembryonic antigen and a-fetoprotein as model analytes, this method showed wide linear ranges with the detection limits down to 3.2 and 4.0 pg/mL, respectively. The proposed immunosensor array exhibited acceptable stability and reproducibility. The assay results of serum samples were in acceptable agreement with the reference values. This method excluded completely the effect of dissolved oxygen and showed potential application for multianalyte determination in clinical diagnostics. (C) 2011 Elsevier B.V. All rights reserved.