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

Abstract

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.

Ultrasound-Mediated Drug Delivery for Cardiovascular Disease

“…Culp et al [200] and Xie et al [201] both demonstrated that GP IIb/IIIa targeted microbubbles exposed to US expedite lysis more than non-targeted microbubbles in vivo. Hua et al [202] demonstrated similar results in vitro using microbubbles conjugated to a tetrapeptide for targeting activated platelets. Fibrin can be targeted by conjugating an inactive portion of rt-PA to the drug delivery vesicle.…”

“…Platelets, which exist in high concentrations on the surface of thrombi, can be targeted by conjugating a glycoprotein (GP) IIb/IIIa receptor inhibitor to the delivery vesicle [200][201][202][203][204]. Investigations implementing this targeting strategy show enhanced thrombolysis in the presence of a thrombolytic and targeted microbubbles exposed to US.…”

Liposomes in Diagnosis and Treatment of Cardiovascular Disorders

“…Following a 50% t-Pa entrapment into eliP, ex vivo porcine clots treated with tPa-loaded echogenic liposomes were lysed with an effect similar to treatment with free t-Pa. 36 t-Pa can also be delivered as a PeGylated anionic gelatin complex 37 or in microbubbles with the arg-Gly-asp-ser (rGds) tetrapeptide as a targeting agent. 38 in both cases, after iv injection in a rabbit model, t-Pa was released from the nano-sized delivery complex when exposed to ultrasound.…”

Removing vascular obstructions: a challenge, yet an opportunity for interventional microdevices

“…Moreover, in recent studies, plasminogen activators were encapsulated into echogenic liposomes (G. J. Shaw et al 2009) and thrombustargeted microbubbles (Hua et al 2010) whose shell is destroyed by US; such a strategy permits to further enhance the local character of the removal therapy. Potential for such combined strategies is further discussed in Section 5.…”