Improving Hemocompatibility of Membranes for Extracorporeal Membrane Oxygenators by Grafting Nonthrombogenic Polymer Brushes

Abstract

Nonthrombogenic modifications of membranes for extracorporeal membrane oxygenators (ECMOs) are of key interest. The absence of hemocompatibility of these membranes and the need of anticoagulation of patients result in severe and potentially life-threatening complications during ECMO treatment. To address the lack of hemocompatibility of the membrane, surface modifications are developed, which act as barriers to protein adsorption on the membrane and, in this way, prevent activation of the coagulation cascade. The modifications are based on nonionic and zwitterionic polymer brushes grafted directly from poly(4-methyl-1-pentene) (TPX) membranes via single electron transfer-living radical polymerization. Notably, this work introduces the first example of well-controlled surface-initiated radical polymerization of zwitterionic brushes. The antifouling layers markedly increase the recalcification time (a proxy of initiation of coagulation) compared to bare TPX membranes. Furthermore, platelet and leukocyte adhesion is drastically decreased, rendering the ECMO membranes hemocompatible.

Current Understanding of How Extracorporeal Membrane Oxygenators Activate Haemostasis and Other Blood Components

“…Current developments to further reduce protein fouling include the coating of high density hydrophilic molecules, which bind high amounts of water, and to include polymers with branch chains to stop conformational changes to the adsorbed proteins, known as polymer brushes (25, 26). Obstals et al have described the development of an polymer brush coated surface for ECMO, which significantly decreased coagulation, platelet, and leucocyte activation ex vivo (27). At present, these are not used clinically due to difficulties in the polymerisation process.…”

Controlled Surface Adhesion of Macrophages via Patterned Antifouling Polymer Brushes

“…The initiator, 11–(trichlorosilyl)undecyl 2‐bromo‐2‐methylpropanoate, was selected because of its ability to form well‐organized and stable monolayers on different substrates. [ 60 ] The polymer brushes were grafted from the initiator layer using surface‐initiated atom transfer radical polymerization (SI‐ATRP). This type of polymerization provides living end groups which are crucial for successful grafting of the top block.…”

Evaluating Whole Blood Clotting in vitro on Biomaterial Surfaces

“…Many published methods to investigate the anti-thrombogenic properties of biomaterials focus on studying the early stages of blood clotting, such as protein adsorption, and platelet adhesion and activation. Although they are important to understand the interaction between blood and the implant surface, these studies do not provide significant information about the overall coagulation process (Damodaran et al, 2013;Simon-Walker et al, 2018;Obstals et al, 2018).…”