Site-directed dual bioprobes inducing single-step nano-sandwich assay for the detection of cardiac troponin I

Bioreceptor functionalized metallic nano-colloids have been identified as effective nanobioprobes to realize the detection of an analyte based on a common phenomenon of salt-induced aggregation. In marked contrast to this, we describe a nano-sandwich assay integrating the novel match-pair of aptamer and peptide functionalized gold nanoparticles. The site-directed biomolecular interaction of high affinity aptamer and peptide bioreceptors directed towards distinct sites of cardiac biomarker troponin I; this was found to form a nano-sandwich assay in a peculiar manner. The gold nanoconjugates interact with specific and distant regions of troponin Ito result in collision of probes upon target identification. In the presence of TnI, both nanobioprobes bind at their respective sites forming a nano-sandwich pair providing a visual color change from red to blue. Thus, the presence of target TnI itself causes instant agglomeration in just a single-step without addition of any external aggregator. The assay imparts 100% specificity and 90% sensitivity in a dynamic concentration range of 0.1-500 ng/mL troponin I with detection limit as low as 0.084 ng/mL. The applicability of the assay has been validated in clinical samples of acute myocardial infarction patients thus establishing a promising point-of-care detection of TnI.

Automated summary

This article describes a novel nano-sandwich assay using aptamer and peptide functionalized gold nanoparticles for the detection of the cardiac biomarker troponin I. The assay achieves 100% specificity and 90% sensitivity, with a detection limit as low as 0.084 ng/mL, making it promising for point-of-care detection of TnI.