Tetrahedral DNA Framework-Bridged Aptasensing Method for Ultrasensitive Determination of Cardiac Troponin I.

The development of a sensitive and accurate method for the determination of cardiac troponin I (cTnI), as an ideal biomarker of acute myocardial infarction (AMI), is critical for the early diagnosis of AMI. In this work, a tetrahedral DNA framework (TDF)-bridged aptasensing method was proposed for the ultrasensitive determination of cTnI via electrogenerated chemiluminescence (ECL) and fluorescence imaging methods, in which a specific anti-cTnI aptamer-tagged tetrahedral DNA framework (TDF-aptamer) was designed as a capture probe by incorporating a specific aptamer against cTnI within the three-dimensional TDF. The TDF-aptamer was modified onto a gold electrode surface through the Au-S bond, providing a specifically captured platform for cTnI with a 3D binding space at the nanoscale. One microsized signal probe (Ab2-biotin•SA@MB-Ru1) was synthesized by using magnetic Fe3O4 as carriers to load a large amount of ruthenium complex and a specific cTnI antibody. After the sandwich assay among the modified TDF-aptamer, cTnI, and the signal probe, both ECL and fluorescence signals were recorded for the cTnI assay with desirable selectivity and high sensitivity (linear range of 5 to 80 pg/mL using ECL intensity detection and 0.5 to 500 pg/mL using ECL and fluorescence imaging methods). This work demonstrated that the combination of the specific TDF-aptamer and microsized Ab2-biotin•SA@MB-Ru1 within the imaging method can enhance the specific recognition and detection sensitivity for cTnI, which is promising for AMI diagnosis.