Immunosensor based on carbon nanotube/manganese dioxide electrochemical tags

• An electrochemical signal amplification scheme involving CNT–MnO2 tags is proposed.
• A highly competitive LOD of 40 pg mL−1 is achieved.
• Measurements in plasma samples were successfully demonstrated.

This article reports on carbon nanotube/manganese dioxide (CNT–MnO2) composites as electrochemical tags for non-enzymatic signal amplification in immunosensing. The synthesized CNT–MnO2 composites showed good electrochemical activity, electrical conductivity and stability. The electrochemical signal of CNT–MnO2 composites coated glassy carbon electrode (GCE) increased by nearly two orders of magnitude compared to bare GCE in hydrogen peroxide (H2O2) environment. CNT–MnO2 composite was subsequently validated as electrochemical tags for sensitive detection of α-fetoprotein (AFP), a tumor marker for diagnosing hepatocellular carcinoma. The electrochemical immunosensor demonstrated a linear response on a log-scale for AFP concentrations ranging from 0.2 to 100 ng mL−1. The limit of detection (LOD) was estimated to be 40 pg mL−1 (S/N = 3) in PBS buffer. Further measurements using AFP spiked plasma samples revealed the applicability of fabricated CNT–MnO2 composites for clinical and diagnostic applications.

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