Engineered endothelium-mimicking antithrombotic surfaces via combination of nitric oxide-generation with fibrinolysis strategies

Thrombosis associated with implants can severely impact therapeutic outcomes and lead to increased morbidity and mortality. Thus, developing blood-contacting materials with superior anticoagulant properties is essential to prevent and mitigate device-related thrombosis. Herein, we propose a novel single-molecule multi-functional strategy for creating blood-compatible surfaces. The synthesized azide-modified Cu-DOTA-(Lys)3 molecule, which possesses both NO release and fibrinolysis functions, was immobilized on material surfaces via click chemistry. Due to the specificity, rapidity, and completeness of click chemistry, the firmly grafted Cu-DOTA-(Lys)3 endows the modified material with excellent antithrombotic properties of vascular endothelium and thrombolytic properties of fibrinolytic system. This surface effectively prevented thrombus formation in both in vitro and in vivo experiments, owing to the synergistic effect of anticoagulation and thrombolysis. Moreover, the modified material maintained its functional efficacy after one month of PBS immersion, demonstrating excellent stability. Overall, this single-molecule multifunctional strategy may become a promising surface engineering technique for blood-contacting materials.

Multistage Anticoagulant Surfaces: A Synergistic Combination of Protein Resistance, Fibrinolysis, and Endothelialization

Anticoagulant surface modification of blood-contacting materials has been shown to be effective in preventing thrombosis and reducing the dose of anticoagulant drugs that patients take. However, commercially available anticoagulant coatings, that is, both bioinert and bioactive coatings, are typically based on a single anticoagulation strategy. This puts the anticoagulation function of the coating at risk of failure during long-term use. Considering the several pathways of the human coagulation system, the synergy of multiple anticoagulation theories may provide separate, targeted effects at different stages of thrombosis. Based on this presumption, in this work, negatively charged poly(sodium p-styrenesulfonate-co-oligo(ethylene glycol) methyl ether methacrylate) and positively charged poly(lysine-co-1-adamantan-1-ylmethyl methacrylate) were synthesized to construct matrix layers on the substrate by electrostatic layer-by-layer self-assembly (LBL). Amino-functionalized β-cyclodextrin (β-CD-PEI) was subsequently immobilized on the surface by host-guest interactions, and heparin was grafted. By adjusting the content of poly(oligo(ethylene glycol) methyl ether methacrylate) (POEGMA), the interactions between modified surfaces and plasma proteins/cells were regulated. This multistage anticoagulant surface exhibits inertness at the initial stage of implantation, resisting nonspecific protein adsorption (POEGMA). When coagulation reactions occur, heparin exerts its active anticoagulant function in a timely manner, blocking the pathway of thrombosis. If thrombus formation is inevitable, lysine can play a fibrinolytic role in dissolving fibrin clots. Finally, during implantation, endothelial cells continue to adhere and proliferate on the surface, forming an endothelial layer, which meets the blood compatibility requirements. This method provides a new approach to construct a multistage anticoagulant surface for blood-contacting materials.

A hemocompatible polyurethane surface having dual fibrinolytic and nitric oxide generating functions

Thrombus formation remains a serious problem in developing blood compatible materials. Despite continuous, intensive efforts over many years to prepare surfaces that prevent clotting, such surfaces have not been achieved; indeed it seems that surface-induced clotting is inevitable. An alternative approach is to accept that clotting will occur and to design surfaces so that small, nascent clots will be lysed before they can cause harm. The generation of plasmin, as in the fibrinolytic system, may be adopted for this purpose. The vascular endothelium (the inner surface of intact blood vessels) releases nitric oxide (NO) on a continuous basis. NO protects against platelet activation and aggregation, and also has an anti-proliferative effect on smooth muscle cells (SMCs). Based on these two important functions of the vascular system, the approach of constructing a fibrinolytic surface that generates NO is developed in the present work. Poly(oligo(ethylene glycol) methyl ether methacrylate-co-6-amino-2-(2-methacylamido)-hexanoic acid) (poly(OEGMA-co-LysMA)) was attached to a vinyl-functionalized polyurethane (PU) surface by graft polymerization giving a surface (PU-POL) with protein-resistant properties (via poly(OEGMA)) and clot lysing properties (via poly(LysMA)). Selenocystamine, which catalyzes S-nitrosothiol decomposition to generate NO in the vasculature, was then immobilized on the PU-POL surface via covalent attachment. A dual functioning surface with fibrinolytic activity (lysis of nascent clots) and NO releasing ability (inhibition of platelet adhesion and SMC adhesion as well as proliferation) was thereby constructed.

Blood compatible materials: state of the art

Devices that function in contact with blood are ubiquitous in clinical medicine and biotechnology. These devices include vascular grafts, coronary stents, heart valves, catheters, hemodialysers, heart-lung bypass systems and many others. Blood contact generally leads to thrombosis (among other adverse outcomes), and no material has yet been developed which remains thrombus-free indefinitely and in all situations: extracorporeally, in the venous circulation and in the arterial circulation. In this article knowledge on blood-material interactions and "thromboresistant" materials is reviewed. Current approaches to the development of thromboresistant materials are discussed including surface passivation; incorporation and/or release of anticoagulants, antiplatelet agents and thrombolytic agents; and mimicry of the vascular endothelium.