cRGD Urokinase Liposomes for Thrombolysis in Rat Model of Acute Pulmonary Microthromboembolism.

Purpose: To study the thrombolytic effect and safety of cRGD urokinase liposomes (cRGD-UK-LIP) in rats with acute pulmonary microthromboembolism (APMTE), and explore the application value of echocardiography (ECHO) in animal models. Patients and Methods: Ninety-six SD rats were randomized into 6 groups (16/group): normal control, sham operation, APMTE, normal saline (NS), free urokinase (UK), cRGD-UK-LIP. Four groups (APMTE, NS, UK, cRGD-UK-LIP) of rats were injected with autologous thrombus to induce APMTE. Samples were injected into 3 groups (NS, UK, cRGD-UK-LIP) of rats after modeling. Echocardiography was used to assess right ventricle (RV) function and morphology in rats. Six rats in each group were randomly selected and pulmonary artery pressure (PAP) of them was measured through ECHO-guided transthoracic puncture. Finally, the rats were killed and their tissues were taken for pathological examination. Results: Compared with normal control or sham operation group, rats in APMTE group had enlarged RV, decreased RV function, increased PAP, and lung tissue of them showed postthromboembolic appearance. There was no significant difference between NS group and APMTE group. RV morphology and function of rats in the UK group and cRGD-UK-LIP group were better and vessels with residual thrombus in these 2 groups were less than APMTE group, especially in the cRGD-UK-LIP group. In terms of PAP, only cRGD-UK-LIP group was significantly lower than APMTE group. No hyperemia, bleeding and swelling were observed in heart, liver and kidney of rats in each group. Conclusion: A rat model of APMTE was successfully established. cRGD-UK-LIP has better thrombolytic effect than free urokinase and it is safe. Echocardiography is not merely an important way to evaluate the morphology and function of RV, transthoracic puncture measurement under the guidance of it can be an effective way to monitor PAP in animal models.

Near-infrared light-responsive liposomes for protein delivery: Towards bleeding-free photothermally-assisted thrombolysis.

Smart drug delivery systems represent state-of-the-art approaches for targeted therapy of life-threatening diseases such as cancer and cardiovascular diseases. Stimuli-responsive on-demand release of therapeutic agents at the diseased site can significantly limit serious adverse effects. In this study, we engineered a near-infrared (NIR) light-responsive liposomal gold nanorod-containing platform for on-demand delivery of proteins using a hybrid formulation of ultrasmall gold nanorods (AuNRs), thermosensitive phospholipid (DPPC) and non-ionic surfactant (Brij58). In light-triggered release optimization studies, 55.6% (± 4.8) of a FITC-labelled model protein, ovalbumin (MW 45 kDa) was released in 15 min upon NIR irradiation (785 nm, 1.35 W/cm2 for 5 min). This platform was then utilized to test on-demand delivery of urokinase-plasminogen activator (uPA) for bleeding-free photothermally-assisted thrombolysis, where the photothermal effect of AuNRs would synergize with the released uPA in clot lysis. Urokinase light-responsive liposomes showed 80.7% (± 4.5) lysis of an in vitro halo-clot model in 30 min following NIR irradiation (785 nm, 1.35 W/cm2 for 5 min) compared to 36.3% (± 4.4) and 15.5% (± 5.5) clot lysis from equivalent free uPA and non-irradiated liposomes respectively. These results show the potential of low-dose, site-specific thrombolysis via the combination of light-triggered delivery/release of uPA from liposomes combined with photothermal thrombolytic effects from gold nanorods. In conclusion, newly engineered, gold nanorod-based, NIR light-responsive liposomes represent a promising drug delivery system for site-directed, photothermally-stimulated therapeutic protein release.