Direct immunomagnetic detection of low abundance cardiac biomarker by aptamer DNA nanocomplex

An early and rapid diagnosis of acute myocardial infraction (MI) by serum biomarker quantification is vital for boosting up treatment efficacy and survival rate; however, it still remains challenging due to ultralow biomarkers content and the emergent nature of the disease. In view of these challenges, a single-step target capturing method for cardiac Troponin I (cTnI), the major cardiac biomarker of MI, was developed. The detection of target cTnI was performed by coupling the capture antibody modified magnetic silica nanoparticle (mSiO2) and an aptamer-based DNA nanostructure produced by hybridization chain reaction (aptHCR). cTnI in sample was first directly captured by mSiO2 and aptHCR in 30 min. The as formed nanocomplex was then labelled by a customized DNA turn on fluorescent dye SPM. By reading the strengthened fluorescent signal using total internal reflection fluorescence microscope (TIRFM), the detection platform has accomplished an impressive LOD of 8.5 fM with high specificity towards cTnI. The advantages of the short immunoreaction time (30 min) and the pre-treatment free property of the method have addressed the urgent diagnostic requirements of MI. The detection platform offers a potential solution to tackle insufficient sensitivity and tedious turnaround time of clinically approved assays for cTnI detection.