RESUMO
In order to determine procalcitonin, a sandwich-type ratiometic electrochemical immunosensor was developed by differential pulse voltammetry (DPV). Due to high chemical stability and good biocompatibility, graphitic carbon nitride (g-C3N4) could be used as feasible supporter to carry silver nanoparticles (Ag NPs) with an obvious oxidative peak (measured typically at + 0.3 V vs. SCE). Ag NPs loaded onto g-C3N4 were not only beneficial to prevent the agglomeration of Ag NPs, but also favorable to improve the electron transfer velocity of g-C3N4. Moreover, the g-C3N4-Ag NPs as the matrix could immobilize primary antibody by Ag-N bond. Nile blue A (NBA), an excellent redox probe based on the redox reaction with two-electrons, provides a current signal at - 0.38 V (vs. SCE). Zr-based metal organic framework (UiO-67), an ideal framework material with large specific surface area and high porosity, could absorb the substantial water-soluble NBA by electrostatic adsorption. The UiO-67 modified by NBA (NBA-UiO-67) owned admirable biocompatibility and was a qualifying marker to load the secondary antibody. For the immunosensor, the current ratio of NBA to Ag NPs (INBA/IAg NPs) was increased as the concentrations of PCT increased. Under the optimum conditions, the linear range of the immunosensor was 0.005 to 50 ng/mL; the detection limit was 1.67 pg/mL (S/N = 3), which reflected the excellent analytical performance of the sensor. The proposed immunosensor strategy is a simple and dependable platform, with great application potential in biometric analysis.