Covalently functionalized graphene oxide with 2-aminoanthraquinone for construction of a ratiometric electrochemical biosensor toward cardiac troponin I quantification.

Cardiac troponin I (cTnI) represents a highly specific biomarker for the detection of myocardial infarction. To meet the demand for accurate detection of cTnI, a ratiometric electrochemical biosensor based on graphene oxide-2-aminoanthraquinone (GO-AQ) and iron-based metal-organic frameworks‑gold nanoparticles (FeMOFs-Au NPs) was developed. GO possesses a large specific surface area and favorable biocompatibility, serving as an ideal carrier for subsequent antibody immobilization. Diazotized AQ was anchored onto the surface of GO via covalent bonds to generate stable electrochemical redox signals. Owing to their stable framework structure, FeMOFs can produce inherent and stable electrochemical redox peaks. The in-situ growth of Au NPs greatly enhances the conductivity of MOFs and accelerates interfacial electron transfer. With the self-calibration mechanism, the developed sensor could detect cTnI concentrations ranging from 0.001 to 100 ng mL-1, and limit of detection was determined to be 0.36 pg mL-1. Benefiting from superior signal stability, the sensor exhibited excellent intra-batch and inter-batch reproducibility. For practical samples, the sensor showed good recovery rates (99.92%-107.8%) and could distinguish patients from healthy individuals. The detection performance of the ratiometric sensor is significantly superior to that of single-signal modes, and the obtained results are highly consistent with those measured by commercial method.