Urokinase-Conjugated Magnetite Nanoparticles as a Promising Drug Delivery System for Targeted Thrombolysis: Synthesis and Preclinical Evaluation.

Mortality and disabilities as outcomes of cardiovascular diseases are primarily related to blood clotting. Optimization of thrombolytic drugs is aimed at the prevention of side effects (in particular, bleeding) associated with a disbalance between coagulation and anticoagulation caused by systemically administered agents. Minimally invasive and efficient approaches to deliver the thrombolytic agent to the site of clot formation are needed. Herein, we report a novel nanocomposite prepared by heparin-mediated cross-linking of urokinase with magnetite nanoparticles (MNPs@uPA). We showed that heparin within the composition evoked no inhibitory effects on urokinase activity. Importantly, the magneto-control further increased the thrombolytic efficacy of the composition. Using our nanocomposition, we demonstrated efficient lysis of experimental clots in vitro and in animal vessels followed by complete restoration of blood flow. No sustained toxicity or hemorrhagic complications were registered in rats and rabbits after single bolus i.v. injection of therapeutic doses of MNPs@uPA. We conclude that MNPs@uPA is a prototype of easy-to-prepare, inexpensive, biocompatible, and noninvasive thrombolytic nanomedicines potentially useful in the treatment of blood clotting.

Thrombin@Fe3O4 nanoparticles for use as a hemostatic agent in internal bleeding.

Bleeding remains one of the main causes of premature mortality at present, with internal bleeding being the most dangerous case. In this paper, magnetic hemostatic nanoparticles are shown for the first time to assist in minimally invasive treatment of internal bleeding, implying the introduction directly into the circulatory system followed by localization in the bleeding zone due to the application of an external magnetic field. Nanoparticles were produced by entrapping human thrombin (THR) into a sol-gel derived magnetite matrix followed by grinding to sizes below 200 nm and subsequent colloidization. Prepared colloids show protrombotic activity and cause plasma coagulation in in vitro experiments. We also show here using a model blood vessel that the THR@ferria composite does not cause systematic thrombosis due to low activity, but being concentrated by an external magnetic field with simultaneous fibrinogen injection accelerates local hemostasis and stops the bleeding. For instance, a model vessel system with circulating blood at the puncture of the vessel wall and the application of a permanent magnetic field yielded a hemostasis time by a factor of 6.5 shorter than that observed for the control sample. Biocompatibility of composites was tested on HELF and HeLa cells and revealed no toxic effects.

Leach-proof magnetic thrombolytic nanoparticles and coatings of enhanced activity.

Despite the fact that magnetic thrombolytic composites is an emerging area, all known so far systems are based on the similar mechanism of action: thrombolytic enzyme releases from the magnetic carrier leaving non-active matrix, thus making the whole system active only for a limited period of time. Such systems often have very complex structure organization and composition, consisting of materials not approved for parenteral injection, making them poor candidates for real clinical trials and implementation. Here we report, for the first time, the production of thrombolytic magnetic composite material with non-releasing behavior and prolonged action. Obtained composite shows good thrombolytic activity, consists of fully biocompatible materials and could be applied as infinitely active thrombolytic coatings or magnetically-targetable thrombolytic agents.

Streptokinase@alumina nanoparticles as a promising thrombolytic colloid with prolonged action.

The present study is devoted to the development of a new class of thrombolytic systems - nanocolloids. A non-direct plasminogen activator, streptokinase, was entrapped in a sol-gel matrix based on boehmite nanoparticles used in medical practice as the most common vaccine adjuvant. It is shown that when the enzyme content in the composite is less than 10%, only minor release is observed, while thrombolytic properties are maintained at a relatively high level, demonstrating the prolonged effect. Based on the obtained composites, thrombolytic nanocolloids containing nanoparticles of less than 500 nm size and suitable for parenteral administration were produced. The thrombolytic properties were studied using the plasminogen activation tests, human plasma clots and a model thrombus made from a whole human blood. Based on the obtained results, the structure of the composites and the mechanism of their action are suggested.

Synthesis of Thrombolytic Sol-Gel Coatings: Toward Drug-Entrapped Vascular Grafts.

As is evident from numerous investigations, drug-eluting vascular grafts and stents have not solved the main problems associated with thrombosis and due to drug release only postpone their advance for a longer period. Here we point to a potential solution of this problem by developing thrombolytic sol-gel coatings which potentially could lead to drug-entrapped vascular grafts: urokinase-type plasminogen activator was entrapped within a porous alumina sol-gel film with a subsequent deposition on a polymer graft.