One-pot synthesis of multidimensional conducting polymer nanotubes for superior performance field-effect transistor-type carcinoembryonic antigen biosensors

Abstract

Carcinoembryonic antigen (CEA), a glycoprotein, is a crucially important tumor marker due to its relation to carcinomas. An abnormal level of CEA in the serum is connected to a diagnosis of cancer. In this work, highly sensitive and selective field-effect transistor (FET) biosensors were fabricated to detect CEA, using aptamer-functionalized multidimensional conducting-polymer (3-carboxylate polypyrrole) nanotubes (Apt–C-PPy MNTs). The multidimensional system, C-PPy MNTs, is firstly produced by a solution based temperature controlled self-degradation method. The C-PPy MNTs are integrated with the CEA-binding aptamer immobilized on an interdigitated array electrode substrate by covalent bonding with amide groups (–CONH) to produce a FET-type biosensor transducer. The resulting C-PPy MNT-based FET sensors exhibit a rapid response in real time (<1 s) and ultrasensitivity toward CEA with a limit of detection of 1 fg mL⁻¹. This limit of detection is 2–3 orders of magnitude more sensitive than previous reports. The liquid-gated FET-type sensor showed specificity toward CEA in a mixed solution containing compounds found in similar proteins and biological signals. Additionally, a superior lifetime is demonstrated for the FET sensor, owing to the covalent bonding involved in the immobilization processes.