Background: Current antiplatelet therapies remain ineffective for a large percentage of the population, while presenting significant risks for bleeding. We explore a novel way to inhibit arterial thrombus formation. Theoretically, a negative charge may influence the tertiary structure of von Willebrand Factor (vWF) to favor the globular configuration by biophysical means without the use of platelet inactivating drugs.

Aims: We tested this hypothesis experimentally for charged nanoparticles (CNP) to inhibit arterial thrombus formation in a microfluidic thrombosis assay (MTA).

Methods: We employed the MTA for efficacy screening of CNP size, surface charge, and blood concentration with polystyrene particles. Occlusion time (OT) in the MTA is measured as the time from first blood contact with the stenosis to the time of the initial maximum mass balance reading. An assessment of platelet surface coverage in the microfluidic was also performed. An effective particle was also assessed for its effects on hemostasis in a murine tail-bleeding model.

Results: The results of the MTA showed that CNP significantly extend occlusion time, with a maximum effect found at approximately 1.8 x 10¹¹ CNP/mL of blood (Figure 1). The observed dosing profile was unusual in that higher doses resulted in less effect. The CNP decreased the rate of platelet adhesion and the total amount of platelet surface coverage, indicating that clots form slower and are potentially weaker than clots under normal conditions. Preliminary murine studies show no significant increase in bleeding due to CNP (Figure 2).

Conclusions: This study effectively demonstrates a new therapeutic for reducing acute arterial thrombosis based on preventing the shear elongation of circulating vWF. The effect is seen in multiple particles of differing size and charge, with a non-sigmoid dose-response curve, illustrating the non-pharmacologic mechanism of anti-thrombosis. CNP may be an inexpensive alternative to current antithrombotic agents without the inherent bleeding side-effects.

[The CNP significantly retarded thrombus formation as quantified by (A) occlusion time and (B) platelet-calcein staining (1.8 x 1011 nanoparticles/mL).]

[CNP vs. PBS in a murine tail bleeding model found no difference in bleeding, indicating that CNP do not significantly impact hemostatic function.]

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ISTH Congress Abstracts - https://abstracts.isth.org/abstract/antithrombotic-therapy-by-charged-nanoparticles/