Cerium oxide-triggered ‘one-to-many’ catalytic cycling strategy for in situ amplified electronic signal of low-abundance protein

Abstract

Multifunctionalized thionine-modified cerium oxide (Thi–CeO₂) nanostructures with redox ability and catalytic activity were designed as the bionanolabels for in situ amplified electronic signal of low-abundance protein (carcinoembryonic antigen, CEA, used as a model) based on a cerium oxide-triggered ‘one-to-many’ catalytic cycling strategy. Initially, the carried CeO₂ nanoparticles autocatalytically hydrolyzed the phosphate ester bond of L-ascorbic acid 2-phosphate (AAP) to produce a new reactant (L-ascorbic acid, AA), then the generated AA was electrochemically oxidized by the assembled thionine on the Thi–CeO₂, and the resultant product was then reduced back to AA by the added tris(2-carboxyethy)phosphine (TCEP). The catalytic cycling could be re-triggered by the thionine and TCEP, resulting in amplification of the electrochemical signal. Under the optimized conditions, the electrochemical immunosensor exhibited a wide linear range of 0.1 pg mL⁻¹ to 80 ng mL⁻¹ with a low detection limit of 0.08 pg mL⁻¹ CEA at the 3σ_blank level. In addition, the methodology was evaluated for the analysis of clinical serum samples, and was in good accordance with values obtained using the commercialized enzyme-linked immunosorbent assay (ELISA) method.