Three-dimensional electrochemical immunosensor for sensitive detection of carcinoembryonic antigen based on monolithic and macroporous graphene foam

• Immunosensor based on monolithic 3D graphene was prepared for the first time.
• 3D graphene was functionalized by in-situ polymerization of dopamine.
• Polydopamine layer imparts 3D graphene with well hydrophilicity and modifiability.
• Lectin grafted on polydopamine was used to immobilize sugar-protein labeled Ab.
• A wide detection range of 0.1–750.0 ng ml−1 was reached.

A high performance three-dimensional (3D) electrochemical immunosensor was developed for sensitive detection of the tumor biomarker, carcinoembryonic antigen (CEA). Monolithic and macroporous graphene foam grown by chemical vapor deposition (CVD) served as the scaffold of the free-standing 3D electrode. Immuno-recognition interface was fabricated via simple and non-covalent immobilization of antibody using lectin-mediated strategy. Briefly, the well-known lectin macromolecule (concanavalin A, Con A) monolayer was functionalized on 3D graphene (3D-G) using in-situ polymerized polydopamine as the linker. Then the widely used horseradish peroxidase (HRP)-labeled antibody (anti-CEA) in immunoassays was efficiently immobilized to demonstrate the recognition interface via the biospecific affinity of lectin with sugarprotein. The 3D immunosensor is able to detect CEA with a wide linear range (0.1–750.0 ng ml−1), low detection limit (~90 pg ml−1 at a signal-to-noise ratio of 3), and short incubation time (30 min). Furthermore, this biosensor was used for the detection of the CEA level in real serum samples.