Multiplexed electrochemical immunoassay using streptavidin/nanogold/carbon nanohorn as a signal tag to induce silver deposition

• Streptavidin functionalized nanogold/carbon nanohorn as a new common tracing tag is synthesized.
• This tag can recognize the biotinylated signal antibodies to perform multiplexed immunoassay.
• Coupling with the nanomaterial-promoted silver enhancement amplifies the signal and greatly improves the sensitivity of immunoassay.
• This method is simple and low-cost, and exhibits wide concentration range and acceptable, reproducibility, stability and accuracy.

An ultrasensitive multiplexed immunoassay method was developed by using streptavidin/nanogold/carbon nanohorn (SA/Au/CNH) as a novel signal tag to induce silver enhancement for signal amplification. The Au/CNH was prepared by in situ growth of nanogold on carboxylated CNH and functionalized with streptavidin. The SA/Au/CNH showed well dispersibility in physiological buffer and could sever as a common tracing tag to recognize biotinylated signal antibody. The immunosensor array was prepared on disposable screen-printed electrodes. Through sandwich-type immunoreaction and biotin-streptavidin affinity reaction, the SA/Au/CNH tag was captured on the immunoconjugates to induce silver deposition and amplify the electrochemical stripping signals. Using α-fetoprotein and carcinoembryonic antigen as model analytes, the proposed method showed wide linear ranges with the detection limits down to 0.024 pg mL−1 and 0.032 pg mL−1, respectively, and eliminated completely signal cross-talk between adjacent immunosensors. It provided a convenient, high-efficient and ultrasensitive electrochemical detection route for biological analytes, showing great potential in clinical application.

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