A dual-mode label-free electrochemical immunosensor for ultrasensitive detection of procalcitonin based on g-C3N4-NiCo2S4-CNTs-Ag NPs

Abstract

Herein, a label-free electrochemical immunosensor based on differential pulse voltammetry (DPV) and amperometric i–t curve (i–t) dual-mode analysis is proposed for early quantitative detection of procalcitonin (PCT). Due to the advantages of high chemical stability and biocompatibility, graphite carbon nitride (g-C₃N₄) was adopted as a high-capacity sensing interface to carry signal indicators. As an effective indicator of chronoamperometry, nickel cobalt sulfide (NiCo₂S₄) was uniformly dispersed on the surface of g-C₃N₄ through in-situ hydrothermal synthesis, which not only promotes the activation of bimetallic activity, but also effectively prevents the aggregation of NiCo₂S₄. At the same time, in order to establish a dual-mode analysis platform to improve accuracy and sensitivity, highly conductive carbon nanotubes (CNTs) were hybridized with composite materials to load Ag nanoparticles (Ag NPs), which have excellent oxidizing properties and are used as indicators of DPV. On account of this advanced sensing strategy, a wide linear response (DPV: 0.05 ng mL⁻¹–50 ng mL⁻¹ and i–t: 1.00 pg mL⁻¹–10.00 ng mL⁻¹) and a low detection limit (DPV: 16.70 pg mL⁻¹ and i–t: 0.33 pg mL⁻¹) are demonstrated. The immunosensor synthesized by this method has good stability and sensitivity, which could be applied in clinical diagnosis and treatment.