Synergistic action sandwich-type aptasensor based on nanozymes and biological enzymes for ultrasensitive cardiac troponin I determination.

The fast and highly sensitive detection of cardiac troponin I (cTnI) is an efficient means of controlling myocardial infarction. In this study, a sandwich-type electrochemical aptasensor for cTnI determination is constructed using reduced graphene oxide-tetraethylene pentaamine (rGO-TEPA) based on Au metal ion-modified carbon nanotubes (CNTs) as the substrate nanocomposite and Co₃O₄ nanoparticles doped with AuPt bimetallic nanoparticles, horseradish peroxidase (HRP), hemoglobin (hemin), and aptamer 2 (Apt2) (Co₃O₄/AuPt/HRP/hemin/Apt2) as the signal probe. The synergistic catalysis of the Co₃O₄/AuPt nanozymes and HRP/hemin biological enzymes can catalyze the decomposition of H₂O₂. In the existence of the cTnI, the two aptamers bind specifically to the target, thereby affecting the electrochemical reaction. Under optimum conditions, the sandwich-type electrochemical aptasensor has a striking analytical behavior. The electrochemical redox signals linearly increase with the logarithm of the cTnI concentration in the range 0.1 ~ 1.0 × 10⁷ pg/mL with a limit of detection as low as 0.01 pg/mL. The aptasensor has good selectivity, repeatability, and stability. The recovery of the target analyte from  human serum samples is 99.1 ~ 101.8% and the relative standard deviation value of the enzyme-linked immunosorbent assay is less than 5%. This sandwich-type aptasensor can satisfy the requirements of actual sample detection and provide a new theoretical foundation and method for the clinical detection of cTnI.