Coagulation Factor XIII-Binding Aptamers as Bivalent Ligands Targeting Fibrin and Activated Platelets in the Thrombus

Thromboembolic diseases are commonly associated with thrombus-induced ischemia and tissue damage; identification of the location of the thrombus, or thrombus-targeting, may facilitate diagnosis and target therapy. We hypothesized that aptamers with high affinity and specificity for coagulation factor XIII (FXIII) can serve as thrombus-targeting probes. With systematic evolution of ligands by exponential enrichment technology and semi-activated FXIII (FXIII’) as the target, guanine-rich FXIII’-binding aptamers (FAs; 76 nt) were selected from a library of single-stranded DNA. Next generation sequencing identified FAs with the highest frequency; bio-layer interferometry revealed a dissociation constant (Kd) from 0.7 to 2.5 nM. Truncation with preservation of a conserved region based on entropy analysis resulted in three truncated FAs (FATs; 41-47 nt) that exhibited 4-fold signal in binding to activated vs. resting platelets, as determined by flowcytometry. In addition, FAT2 exhibited up to 4.2-fold binding of that from scrambled ssDNA to platelet/fibrin clot or whole blood clot in vitro, suggesting binding to both activated plateltes and fibrin. FAT2 also exhibited targeting effects in a microcirculatory thrombosis model in mice. Nevertheless, FATs induced no effect on blood coagulation, as determined by thromboelastometry. In conclusion, FXIII-binding aptamers are potentially amenable to thrombus targeting in theranostic application of thromboembolic diseases. To development FXIII-targeting aptamer for thrombus imaging