Novel triple-layer nanofibrous composite membranes with high gas-selectivity for efficient blood oxygenation

Abstract

Oxygenation membranes, as the central component of extracorporeal membrane oxygenation (ECMO), faced the challenge of simultaneously achieving high gas permselectivity and hemocompatibility. Herein, we designed an integrated triple-layer Janus composite membrane with excellent comprehensive performance experiencing reverse-interfacial polymerization (R-IP) twice and then zwitterionic modification. The hydrophobic polyvinylidene fluoride (PVDF) nanofibrous substrate functioned as a plasma-leakage barrier while providing a low-resistance pathway for gas permeance. The middle selective polyamide layer (SPA) consisted of an ultrathin auxiliary PA layer (APA) using low concentrations of organic trimesoyl chloride (TMC) and aqueous polyethyleneimine (PEI) solutions (by first R-IP), and a dense PA layer (DPA) using high concentration solutions (second R-IP) for achieving high CO₂/O₂ permselectivity and a rich amino surface. The initial APA layer could seal most macropores of the nanofibrous substrate effectively and provide a relatively smooth interface, facilitating uniform loading and diffusion of organic phase for fabricating compact DPA layer in second R-IP. The top hydrophilic zwitterionic layer would be formed by N-methylation of abundant unreacted amino groups from residual PEI and subsequent quaternization with 3-bromopropionic acid (3-BPA) to generate carboxybetaine zwitterionic structures on the SPA layer for improving the hemocompatibility. The resultant triple-layer Janus composite membrane exhibited adequate gas permeance (O2 permeance of 131.5 GPU and CO2 permeance of 1578.6 GPU) and high CO2/O2 selectivity of ~12.2. The zwitterionic surface concurrently enhanced membrane hydrophilicity, giving excellent resistance to thrombus formation and plasma leakage. This work successfully integrated an asymmetric Janus structure into oxygenation membranes, demonstrating the application potential in ECMO.