Abstract 18726: Thrombin-Inhibiting Nanoparticles Prevent Growth of Fibrin Clots by Inhibiting and Adhering to Clot-Bound Thrombin
Introduction: Sustained and localized prevention of clotting via thrombin inhibition could provide efficient care without significant bleeding effects for clinical scenarios including angioplasty, myocardial infarction, microangiopathy, and acute kidney injury. Thrombin-inhibiting perfluorocarbon nanoparticles (PFC NPs) carrying the direct inhibitors bivalirudin (BVR) and PPACK have demonstrated minimal bleeding effects with inhibition of and binding at sites of acute thrombosis in mouse and rabbit models. Here, we demonstrate that thrombin-inhibiting PFC NPs inhibit clot-bound thrombin and seal clots against further growth when exposed to plasma.
Methods and Results: In solution, BVR, PPACK, BVR NPs, and PPACK NPs demonstrated concentration-dependent inhibition of Fibrinopeptide A (FPA) production by thrombin, as evaluated by ELISA. FPA ELISA for human plasma exposed to human fibrin clots demonstrated that BVR, PPACK, BVR NPs, and PPACK NPs inhibited thrombin bound in fibrin clots to the same extent as in solution.
Fibrin clots were incubated with non-targeted NPs, BVR NPs, or PPACK NPs. 19F MRI at 12T demonstrated that BVR and PPACK NPs specifically bind to clots (figure 1A).
Clots treated with BVR, PPACK, BVR NPs, PPACK NPs, or saline, were submerged in human plasma and imaged sequentially over one hour in T2-weighted 1H MRI at 12T. Clots treated with saline, BVR, or PPACK grew in volume when exposed to plasma, adding loose fibrin gel. Clots treated with BVR or PPACK NPs did not grow significantly (figure 1B-E).
Conclusions: Thrombin-inhibiting PFC NPs have previously been shown to specifically bind to sites of acute thrombotic injury. Data presented herein show that PPACK and BVR NPs inhibit activity of clot-bound thrombin and specifically bind to fibrin clots derived from human plasma. PPACK and BVR NPs bound on the surface of fibrin clots prevent further clot growth on exposure to plasma.
- © 2013 by American Heart Association, Inc.