A reagentless electrochemical immunosensor based on probe immobilization and the layer-by-layer assembly technique for sensitive detection of tumor markers

Facile electrochemical methods for highly sensitive detection of tumor markers provide great advances in early clinical diagnosis of cancer and public health protection. Herein, a reagentless electrochemical immunosensing platform was developed for sensitive immunoassay of tumor biomarkers based on surface-confined probes and the layer-by-layer assembly technique. Ferrocene grafted cationic polymer polyethyleneimine (PEI-Fc) was modified on chemically reduced graphene oxide (rGO) to form a redoxactive and positively charged PEI-Fc-G nanocomposite. Through the layer-by-layer electrostatic assembly technique, the positively charged PEI-Fc-G and negatively charged anionic polyelectrolyte sodium-p-styrene (PSS) were alternately assembled on a negatively charged Au electrode. Based on the biospecific binding of lectin and sugarprotein, the concanavalin A (Con A) lectin monolayer served as the linker to immobilize sugarprotein (horseradish peroxidase, HRP) labeled anti-CEA antibody (HRP-Ab) on the surface of the (PEI-Fc-G/PSS)(n)/PEI multilayer substrate. With carcinoembryonic antigen (CEA) being the model tumor biomarker, the as-prepared immunosensor presented high selectivity and good stability for sensitive and reagentless detection of CEA with a wide range of 0.1 ng mL(-1) to 120 ng mL(-1) (R-2 = 0.9963) and a detection limit as low as 60 pg mL(-1) at a signal/noise ratio of 3. The proposed immunosensor might serve as a versatile platform for reliable cancer diagnostics clinical and biochemical analysis.