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.