Construction of thrombus-targeted microbubbles carrying tissue plasminogen activator and their in vitro thrombolysis efficacy: a primary research.

Thrombosis is the common mechanism of various diseases of heart and vasculature and their major morbility and mortality. An efficient, safe and easy thrombolysis method is needed. We tried to develop a new type of ultrasound microbubbles carrying thrombolytics and simultaneously targeting to thrombus, which could bind with thrombus specifically and release the encapsulated drug locally under the ultrasound exposure. Microbubbles carrying tissue plasminogen activator (tPA) and Arg-Gly-Asp-Ser tetrapeptide (RGDS) were prepared by lyopyilization. Their properties were detected, including morphology, particle size, surface potential and pH. The results showed that the microbubbles were suitable for intravenous injection. The envelope rate of tPA, detected by ELISA, was (81.12 +/- 2.44%), and the conjugate rate of RGDS, detected by flow cytometer, was (94.49 +/- 6.19%). The tPA encapsulated in microbubbles kept fibrinolysis activity under the conditions of both natural releasing and ultrasound exposure, checked by agarose fibrin plate process. The contrast-enhanced ultrasonography (CEU) in rabbit liver showed that they were good for enhanced ultrasound imaging. The in vitro thrombolysis of the microbubbles to the blood clots from healthy human was detected with a mimical flowing model propelled by peristaltic pump. The drug-loaded microbubbles plus ultrasound irradiation got higher thrombolysis with the lowest dosage. The tPA-loaded microbubbles targeting to thrombus can be prepared by lyopyilization, which will bring out a novel way for the targeting drug-released thrombolysis therapy.