Fluorescence immunoassay using triangular carbon dots for detection of the cardiac marker Troponin T in acute myocardial infarction

A cardiac immunosensor was developed to detect heart attacks (myocardial infarctions) at an early stage. This technique, utilizing carboxylic functionalized triangular carbon dots (caf-TCDs) combined with an antibody anti-cardiac Troponin T (anti-cTnT), proved to be a quick and sensitive method for detecting cardiac troponin T (cTnT) in both buffer solutions and biological fluids such as serum. The antibody for cardiac Troponin T (cTnT) was chemically linked to amphiphilic caf-TCDs using a carbodiimide coupling reaction. Exfoliated graphene oxide (GO) sheets effectively bind to anti-cTnT labeled caf-TCDs on their surface, resulting in a non-radiative energy transfer process where the fluorescence is suppressed. This interaction between caf-TCDs and GO follows a nonlinear and increasing Stern-Volmer relationship, indicating a combination of static and dynamic quenching. When antigen (cTnT) is present, the interaction between antibodies (anti-cTnT) and the cTnT molecules hinders the energy transfer process. This interaction also affects the positioning of the nano-couple and causes the detachment of CDs from the GO surface. As a result, the energy transfer process is impeded, leading to the restoration of fluorescence intensity. The sensor exhibits high specificity and low sensitivity to non-specific antigens. It shows a linear reaction to cTnT in the range of 0.05–50 ng mL^-1, with a detection limit of 0.046 ng mL^-1. Therefore, the anti-cTnT-caf-TCD/GO sensor offers a potential platform for detecting cTnT with increased sensitivity.