Interference-free aptasensor for the sensitive determination of cardiac troponin I: Towards rapid diagnosis of myocardial infarction

Acute myocardial infarction (AMI) is a leading cause of mortality. Human cardiac troponin I (cTnI) is used as the biomarker for AMI diagnosis. Several assays have been demonstrated for screening cTnI. However, they usually suffer from analytical interference due to the presence of macrotroponin (an immunoglobulin-bound complex) and cardiac troponin T (cTnT) in the sample. This work presents a new sensitive, and selective aptasensor for the interference-free electrochemical determination of cTnI in biological fluids. The sensor is comprised of a screen-printed electrode that is modified with dendritic gold nanostructures and cTnI-specific electroactive aptamer for screening the biomarker by square wave voltammetry (SWV) within 10 min. The new aptasensor demonstrated high sensitivity over the concentration range 0.04 - 50 ng. mL -1 [limit of quantification (LOQ) = 0.04 ng. mL⁻¹ and limit of detection (LOD) = 0.012 ng. mL -1 ]. The sensor showed excellent selectivity towards cTnI over cTnT, macrotroponin, and cTnI antibody molecules. For point-of-care (POC) screening, the aptasensor was integrated with an ultra-compact potentiostat in a lab-on-a-phone assembly and used to determine the biomarker in human serum samples from the Royal College of Pathologists of Australasia Quality Assurance Program (RCPA QAP). The cTnI quantification by the new aptasensor was in excellent agreement with the samples median concentrations that were reported by reference immunoassay method (R 2 = 0.99). These results warrant a large-scale clinical validation trial of this new POC diagnostic for cTnI.