Cu/Mn Double-Doped CeO2 Nanocomposites as Signal Tags and Signal Amplifiers for Sensitive Electrochemical Detection of Procalcitonin

Nanomaterials themselves as redox probes and nanocatalysts have many advantages for electrochemical biosensors. However, most nanomaterials with excellent catalytic activity cannot be directly used as redox probe to construct electrochemical biosensor because the redox signal of these nanomaterials can only be obtained in strong acid or alkali solution at high positive or negative potential, which greatly limits their applications in biologic assay. In this study, Cu/Mn double-doped CeO2 nanocomposite (CuMn-CeO2) was synthesized to use as signal tags and signal amplifiers for the construction of electrochemical immunosensor for sensitive assay of procalcitonin (PCT). Herein, CuMn-CeO2 not only possesses excellent catalytic activity toward H2O2 for signal amplification, but also can be directly used as redox probe for electrochemical signal readout achieved in neutral mild buffer solution at low positive potential. Importantly, since doping Cu, Mn into CeO2 lattice structure can generate extra oxygen vacancies, the redox and catalytic performance of obtained CuMn-CeO2 was much better than that of pure CeO2, which improves the performance of proposed immunosensor. Furthermore, CuMn-CeO2 can be implemented as a matrix for immobilizing amounts of secondary antibody anti-PCT by forming ester-like bridging between carboxylic groups of Ab2 and CeO2 without extra chemical modifications, which greatly simplifies the preparative steps. The prepared immunosensor exhibited a wide linear range of 0.1 pg mL–1 to 36.0 ng mL–1 with a low detection limit of 0.03 pg mL–1. This study implements nanomaterial themselves as redox probes and signal amplifiers and paves a new way for constructing electrochemical immunosensor.