(190p) Ultrasound Triggered Synergistic Thrombolysis Using Tpa Loaded Microbubbles for the Treatment of Acute Ischemic Stroke

It is estimated that every 10 seconds a person dies from stroke, which makes stroke one of the leading causes of death and disability worldwide and 87% of the strokes are ischemic. Tissue plasminogen activator (tPA) is the only FDA approved drug for its treatment, but its use is constrained because of its narrow therapeutic window, hemorrhagic complications and its selective efficacy. We have fabricated tPA loaded microbubbles coated with 1,2-dibehenoyl-sn-glycero-3-phosphocholine (DBPC) and 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-[methoxy(polyethylene glycol)-2000] (DSPE-PEG2000) with sulfur hexafluoride (SF₆) as the gas core, to improve the efficacy and safety of tPA, as well as use the acoustic properties of microbubbles to have a synergistic thrombolytic effect in the treatment of ischemic stroke. We prepared the lipid coated microbubbles using coaxial electrohydrodynamic atomization (CEHDA) with SF₆ saturated PBS as the collecting medium. Particle size, surface charge and pH, which are crucial parameters for intravenous administration, were evaluated. The bioactivity of the encapsulated tPA was also measured. Furthermore, we evaluated the effectiveness of the fabricated tPA loaded microbubbles as a potential intervention for ischemic stroke in an in-vitro sheep clot model. Its thrombolytic efficacy was studied using a flow model propelled by a peristaltic pump to mimic the blood flow in humans. The tPA loaded microbubbles were injected into the sheep blood clots in the silicon tubes, housed in a water bath maintained at 37áµ’C. Ultrasound of 2MHz was applied using a transcranial doppler (TCD) through a human temporal bone onto the thrombus placed in the silicon tubes. The weight of the blood clot was measured before and after the experiment. It was found that the particle size was less than 8µm and was stable for more than 9 hours. Using CEHDA, tPA retained almost 80% of its activity. Our in-vitro results showed that tPA loaded microbubbles on insonation, caused higher thrombolytic efficiency of 20%, than free tPA and co-administration of tPA and microbubbles with or without ultrasound. This ultrasound responsive theranostic system could be potentially used in the treatment of ischemic stroke.