Polymers of intrinsic microporosity (PIMs) with immobilized carbonic anhydrase (CA) for extracorporeal membrane oxygenation

Abstract

Extracorporeal membrane oxygenation (ECMO) is widely used to save patients with severe respiratory failure. Although the mainstream ECMO membrane material poly(4-methyl-1-pentene) (PMP) provides excellent gas permeability, its hydrophobicity leads to thrombosis during clinical application. Recently, polymers of intrinsic microporosity (PIMs), characterized by high fractional free volume, have emerged as promising alternatives due to their superior permeability and convenient chemical modification. In our previous research, two modified PIM-1 (a typical PIM) membranes, amidoxime-functionalized (AO-PIM-1) and carboxyl/amide-functionalized (C-PIM-1), demonstrated enhanced hemocompatibility and gas-exchange performance. Nevertheless, effective CO₂ removal remains challenging since CO₂ predominantly exists as bicarbonate (HCO₃⁻) ions in blood. Physiologically, carbonic anhydrase (CA) in alveoli could catalyze the conversion of HCO₃⁻ to CO₂. Inspired by this natural mechanism, in this study, CA was immobilized onto PIM-1 membranes via 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride (EDC)/N-hydroxy succinimide (NHS) coupling. Different grafting conditions including grafting methods and types of PIM-1 substrates were explored. AO-PIM-1 showed optimal enzyme immobilization efficiency (78.35%), of which the immobilized CA retained 89.03% of initial activity after 14 days (versus 39.7% for free CA). ECMO simulation tests confirmed significantly enhanced CO₂ removal due to CA catalytic activity. This study provides a promising approach to developing advanced ECMO membranes, addressing current bottlenecks in membrane oxygenator technology, as well as offers a reference for grafting enzymes onto PIMs.