A sandwich-type electrochemical immunosensor for cardiac troponin I based on β-cyclodextrin functionalized 3D graphene incorporated with Ag nanoclusters

Abstract

Cardiac troponin I (cTnI) detection plays a critical role in the early diagnosis of acute myocardial infarction (AMI). In this study, a sandwich-type electrochemical immunosensor was developed for ultrasensitive quantification of cardiac troponin I (cTnI). The sensor platform utilized silver nanoclusters (AgNCs) incorporated with $\beta$-cyclodextrin functionalized 3D porous graphene ($\beta$-CD@3DG-AgNCs) to enhance electrical conductivity and primary antibody (Ab${}_1$) immobilization. For signal amplification, ferrocenecarboxylic acid combined with $\beta$-CD@3DG ($\beta$-CD@3DG-Fc-COOH) was employed as the signal probe, which demonstrated excellent secondary antibody (Ab${}_2$) capture capability. The synthesized nanomaterials were characterized using SEM, TEM, FTIR spectroscopy, X-ray Photoelectron Spectroscopy (XPS) and Thermo-Gravimetric Analysis (TGA). The electrochemical performance of the surface-modified electrodes was systematically investigated through cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Under optimized conditions, differential pulse voltammetry (DPV) revealed that the developed sensor exhibited an extensive linear response range (100 fg mL⁻¹–100 ng mL⁻¹) for cTnI quantification, with an exceptionally low detection limit of 45.5 fg mL⁻¹. The recovery rate ranging from 97.39% to 102.83% was achieved in human serum analysis, suggesting the potential applicability of this immunosensor for clinical diagnosis.