Antithrombotic coating with sheltered positive charges prevents contact activation by controlling factor XII–biointerface binding

Antithrombotic surfaces that prevent coagulation activation without interfering with haemostasis are required for blood-contacting devices. Such materials would restrain device-induced thrombogenesis and decrease the need for anticoagulant use, thereby reducing unwanted bleeding. Here, by optimizing the interactions with coagulation factor XII rather than preventing its surface adsorption, we develop a substrate-independent antithrombotic polymeric coating with sheltered positive charges. The antithrombic properties of the coating were demonstrated in vitro with human blood and in vivo using a carotid artery–jugular vein shunt model in rabbits. The coating exhibits a strong interaction with factor XII, but results in a low reciprocal activation of the contact pathway that triggers clot formation. These findings contradict the prevailing strategy of designing antithrombotic materials through protein-repelling surfaces. Overall, the polymeric coating we describe can benefit most blood-contacting devices and is a useful engineering guideline for designing surfaces with improved antithrombotic properties.