Tissue Plasminogen Activator-Porous Magnetic Nanorods for Targeted Thrombolytic Therapy after Ischemic Stroke

Purpose: Stroke is the 5th leading cause of death in the US. The only FDA-approved treatment is the intravenous administration of tissue plasminogen activator (tPA). However, due to tPA’s inability to lyse the clot fully, about 90% of these patients still live with speech or motor impediments. Moreover, the large dose of tPA administered increases the susceptibility to global tPA-mediated hemorrhage. Therefore, the purpose of the study was to increase tPA’s thrombolysis rate and reduce total tPA administered using a novel nanomaterial, tPA-loaded Fe3O4 nanorods (tPA-NRs). We hypothesize that tPA-NRs will be more successful at thrombolysis and minimize the off-target effects of tPA. Methods: Fe3O4 nanorods were fabricated by oblique angle deposition technique and loaded with tPA using glutaraldehyde as the cross-linker. To determine the thrombolysis efficiency of tPA-NRs in vitro, PE 50 catheters containing blood clots were used as the vascular thrombosis model to mimic in vivo thrombotic conditions. Such PE 50 catheters containing blood clots were placed vertically in the center of a rotating magnetic field and the blood clot lysis time was recorded. To examine the proposed approach in vivo, a FeCl3-induced distal middle cerebral artery occlusion (dMCAO) model was used. Animals will randomly be assigned to four groups and treated with tPA-NRs (1 mg/kg), NRs (1 mg/kg), tPA (10 mg/kg) or vehicle accordingly via internal carotid artery injection after ischemic stroke. A custom-made rotational magnetic field was applied above the head of mouse (near infarction region) during and after injection for 60 min, and the thrombolysis process was observed under microscope. Results: In vitro results demonstrated that tPA-NRs could achieve a mass loading ratio as high as 12.9% and the loaded tPA can be released when stimulated by an external rotating magnetic field. Furthermore, PE50-catheter thrombolysis results demonstrated that tPA-NRs had a significant enhancement of thrombolysis efficiency in comparison with high-dose tPA group (P In vivo results unequivocally showed that: 1) intra-arterial injection of tPA-NRs could target the site of the clot under magnetic guidance; 2) the mechanical force generated by the spinning of the tPA-NRs under the external rotational magnetic field could significantly decrease dMCA blood flow recanalization time from 85 min with high dose tPA (10 mg/kg) to 25 min with low dose tPA-NRs (1 mg/kg) (p Conclusions: In summary, this study provides a proof of concept for developing novel, biocompatible, magnetically guided tPA-NRs delivery system to enhance thrombolysis after ischemic stroke. This approach is significant in that it could not only revolutionize for the treatment of ischemic stroke but also have major impacts on treatments for other deadly thrombotic diseases such as myocardial infarction and pulmonary embolism.