Ratiometric electrochemical immunosensor for the detection of procalcitonin based on the ratios of SiO2-Fc-COOH-Au and UiO-66-TB complexes.

Procalcitonin (PCT) as a disease marker is of great significance in the early diagnosis of septicemia and pyemia. Biosensor have good prospects for analysis and detection of disease markers, but developing highly sensitive detection methods for detecting PCT remains a daunting task. In this paper, we develop a ratiometric electrochemical immunosensor with Au NPs modified SiO2-Fc-COOH complex as matrix and UiO-66 loaded with Toluidine blue (TB) as a marker for quantitative detection of procalcitonin (PCT). The SiO2 modified by APTES not only has a large specific surface area but also contains abundant amino groups, which can be connected to the electrochemical probe of ferrocenecarboxylic acid (Fc-COOH). UiO-66 has the advantages of large specific surface area, high porosity and adjustable structure, which can adsorb toluidine blue electrochemical probe through electrostatic attraction. Measurement and analysis of the prepared immunosensor by Differential Pulse Voltammetry (DPV) show that the oxidation peak currents of Fc-COOH and TB appear at potentials of 0.30 V and -0.30 V respectively. As the PCT concentration increases, the oxidation peak current of TB increases and the oxidation peak current of Fc-COOH decreases. The ratios (ΔI=ΔITB/ΔIFc-COOH) between the double signals could show a certain linear relationship with the concentration of the PCT within a certain range. Under optimal conditions, the linear range of detection obtained by the immunosensor was 1 pg/mL-100 ng/mL and the detection limit was 0.3 pg/mL. In this work, the developed ratiometric electrochemical immunosensor not only provides a simple, reliable and sensitive strategy for quantitative detection of PCT but also provides a useful method for clinical detection of other disease markers.