Purpose and introduction Thromboembolic material producing large vessel occlusion of the cerebral arteries varies substantially in composition and these differences affect the ability of both intravenous thrombolysis and mechanical thrombectomy to achieve rapid arterial recanalization. The binding of targeted magnetic nanoparticles may offer a means of noninvasively determining clot composition. We hypothesize that binding of targeted magnetic nanoparticles to thrombus is measurable and varies with clot composition.
Materials and methods Thromboembolic material was extracted from 10 patients during emergent mechanical thrombectomy for large vessel occlusion in ICA, MCA, or basilar arteries. The nominal source of the thromboembolic material and time from onset to clot retrieval were recorded. Each sample was divided and sent both for standard histopathologic evaluation and for in vitro assessment by magnetic spectroscopy of nanoparticle Brownian rotation (MSB). The thromboembolic material was incubated in a solution of magnetic nanoparticles that had been coated with antibodies directed toward thrombin. Nanoparticle binding was measured using magnetic relaxometry.
Results All clots bound measurable quantities of the thrombin-directed magnetic nanoparticles. 2/10 of the samples were composed of >90% fibrin material. These two samples demonstrated much higher than expected nanoparticle binding. The other samples had proportions of thrombus that ranged from 50 to 60%. Among these samples there was a significant correlation between nanoparticle weight and RBC content (R2 = 0.70, p<0.04) and a lesser association between nanoparticle relaxation and RBC content (R2 = 0.49, p<0.12).
Discussion Thrombin-directed nanoparticles bound thrombin-rich thromboembolic material roughly in proportion to the RBC content, as expected, confirming an affinity of these particles for this component of the clot. However, samples consisting almost exclusively of fibrin bound even higher levels of the nanoparticles suggesting the presence of an additional binding mechanism.
Disclosures C. Eskey: None. W. Wells: None. D. Schartz: None. C. Jackson: None. J. Weaver: None.
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