Anisotropic aptamer-modified DNA tetrahedra/MOF nanoprobes for enhanced colorimetric aptasensing of cardiac troponin I

Cardiac troponin I (cTnI), a principal biomarker of acute myocardial infarction, possesses superior cardiac specificity and can provide a long detection window for cardiac injury. Although the potential of cTnI as a cardiac biomarker is promising, sensitive and rapid detection of cTnI remains challenging. In this work, a novel colorimetric biosensor was developed for cTnI detection based on multifunctional hybrid nanoprobes coupled with triple-aptamer-modified tetrahedral DNA nanostructures (TAPT-TDNs). First, we evaluated the affinity of four TAPT-TDNs with three vertices modified by two kinds of aptamers in different proportions. The four TAPT-TDNs exhibited much better affinity than the single-stranded aptamer for cTnI, which was attributed to the fact that TAPT-TDNs could improve the capture efficiency of cTnI with excellent interface density and constant support. Second, the selected TAPT-TDNs with highest affinity were immobilized on Fe3O4-Au magnetic nanoparticles as capture probes (named Fe3O4-Au-TAPT-TDNs). TAPT-TDNs and HRP were both labeled on NH2-MIL-101(Fe) to form signaling probes (named MIL-101(Fe)-HRP-TAPT-TDNs). Then, with the help of capture probes and signaling probes, the target protein was recognized and captured to form capture probe-cTnI-signaling probe sandwich-like structures, causing a decrease in signaling probes in the supernatant with magnetic separation and eventually leading to a visual color change. This colorimetric aptasensor displays excellent analytical performance toward cTnI with a detection limit of 27 pg·mL−1. The anisotropic aptamer-mediated colorimetric sensor may serve as an alternative to conventional immunoassays for quick and accurate detection of cTnI in clinical samples.