An electrochemical immunosensor based on NH₂-MIL-88B/Ag@Ru composites for sensitive detection of cardiac troponin I

An electrochemical immunosensor was developed based on silver-ruthenium nanoparticles functionalized NH₂-MIL-88B (NH₂-MIL-88B/Ag@Ru) composites for sensitive detection of cardiac troponin I (cTnI). The NH₂-MIL-88B/Ag@Ru composites shows synergistic peroxidase-like activity with K_m values of 0.737 mM^- 1 for hydrogen peroxide (H₂O₂) and 0.55 mM^- 1 for 3,3',5,5'-tetramethylbiphenylamine (TMB). Additionally, the electrode surface is modified using a one-step electrodeposition reduction of graphene with chloroauric acid trihydrate (rGO-AuNPs) to increase the effective specific surface area and facilitate charge transfer. By integrating NH₂-MIL-88B/Ag@Ru composites as a signal amplification tracer and proportionally optimized rGO-AuNPs as the sensing platform, the resulting electrochemical immunosensor exhibits a wide linear detection range from 20 fg/mL to 200 ng/mL for cTnI, with a detection limit of 2.15 fg/mL. Furthermore, in a doxorubicin (DOX)-induced myocardial injury model, this sensor demonstrated excellent practicality paired with the PalmSens 4 portable analyzer. Detection results were consistent with commercial enzyme-linked immunosorbent assay (ELISA), and serum sample recoveries were excellent. This study provides a feasible strategy for the rapid and sensitive detection of cTnI, demonstrating potential for clinical application.