Nanogold‐Enriched Carbon Nanohorn Label for Sensitive Electrochemical Detection of Biomarker on a Disposable Immunosensor

A novel nanogold‐enriched carbon nanohorn structure (nanoAu/CNH) was designed as a trace tag for highly efficient electrochemical detection of tumor marker using a disposable immunosensor. The nanoAu/CNH was synthesized by one‐pot in situ growth of nanogold on carboxylated single‐walled CNH. The labeling of signal antibody was performed via the inherent interaction between protein and nanogold. The disposable immunosensor was constructed by covalently cross‐linking capture antibody on chitosan modified screen‐printed carbon electrode. With a sandwich format, the nanoAu/CNH labeled antibody was conjugated on the immunosensor for electrochemical measurement of tumor marker by electrooxidizing the nanoAu at +1.3 V and then cathodic potential scan in 0.1 M HCl. Using α‐fetoprotein as model target, the proposed immunoassay showed acceptable precision and wide linear range from 0.1 pg mL−1 to 1 ng mL−1 with a detection limit of 0.07 pg mL−1. The new nanoAu/CNH label as well as the disposable immunosensor showed possessed potential application in point‐of‐care testing.