Developing innovative point-of-care electrochemical sensors empowered by cardiac troponin I-responsive nanocomposite materials

This study integrates dopamine (DA) electropolymerization, epitope imprinting, and nanomaterials (i.e., gold nanoparticles (AuNP) and graphene quantum dots (GQD)) to develop three distinct electrochemical sensors (DA-AuNP-MIP, DA-GQD-MIP, and DA-AuNP-GQD-MIP) for detecting cardiac troponin I (cTnI) with assessing their sensitivity, selectivity, and specificity profiles. The sensors exhibited high affinity for the target biomarker, enabling detection within a concentration range of 0.01-20 ng mL-1, with dissociation constants ranging from 2.7-69 pM. The successful fabrication of sensors was also confirmed through atomic force microscopy (AFM), scanning electron microscopy (SEM), fluorescence microscopy, contact angle measurements, cyclic voltammetry (CV), square wave voltammetry (SWV), and electrochemical impedance spectroscopy (EIS). The cTnI selectivity assessment of imprinted nanosensors compared to their non-imprinted counterparts at 0.01-2.5 ng mL-1 showed that the DA-AuNP-GQD-MIP sensor yielded a maximum imprinting factor of 5.9. A negligible cross-reactivity for DA-AuNP-MIP and DA-AuNP-GQD-MIP sensors was found against glucose, adenovirus epitope, another cTnI epitope, bovine serum albumin (BSA), transferrin, and neuron-specific enolase (NSE). Epitope specificity at various concentrations (10 - 60 nM), concentration-dependent cTnI detection in human serum (0.01 - 10 ng mL-1) and sensor recovery rates (0.1-10 ng mL-1) in human serum were determined with the best-performing sensor (i.e., DA-AuNP-GQD-MIP). The sensor demonstrated very high epitope specificity in comparison to another cTnI epitope as well as excellent detection performances in human serum studies. The newly engineered epitope-mediated electrochemical sensing platform showcases considerable potential for precise and straightforward diagnosis of coronary artery diseases, aiming to materialize a cost-effective Point-of-Care Testing (POCT) system.