OC 47.2 - Development of an assay to quantify tranexamic acid levels in plasma

Background: Fibrinolysis, the degradation of fibrin clots, is initiated by the cleavage of the zymogen plasminogen into active plasmin. Unfortunately, dysregulations in fibrinolysis during vascular trauma can result in bleeds that puts patients at risk of exsanguination. In these cases, tranexamic acid (TXA), which inhibits fibrinolysis mainly by blocking the binding of plasminogen with fibrin. Despite its widespread usage, there has yet to be a point-of-care test (POCT) that can readily monitor TXA levels in biological fluids.

Aims: Here, we propose an assay to quantify TXA concentrations in plasma.

Methods: This FRET-based assay uses a fluorescently labeled plasminogen variant (S741C) that binds to fibrin degradation products (FDPs) labelled with a fluorescence quencher. Binding of the fluorescent plasminogen with the quencher-labeled FDPs leads to diminished fluorescence signal. The presence of TXA causes dissociation of plasminogen from FDPs, which leads to the recovery of fluorescence signal in a TXA dose-dependent manner.

Results: This new assay was able to demonstrate dose-dependence between 1 and 100 µM of TXA in plasma. The intraassay and interassay variabilities were determined to be 5.7% and 3.0%, respectively. When tested for measuring known levels of TXA added to plasma samples, the ratio between measured and expected TXA concentration as determined by the slope of the plot was 1.0151.

Conclusion(s): Our study demonstrates a novel fluorescence-based assay that can quantify TXA concentrations in plasma samples within minutes, thus demonstrating its viability to become a rapid POCT with clinical implications.