Vapor-based hybrid grafting of heparin-like coating for dialysis membranes with enhanced hemocompatibility

Heparin is commonly used to improve the hemocompatibility of biomaterials, but high doses of heparin may cause significant side effect in clinical applications. Thus, heparin-mimicking surfaces have been urgently explored to reduce the use of heparin. In this work, heparin-like coating was deposited on polylactide (PLA) dialysis membranes using one-step hybrid grafting of a carboxyl-enriched poly(methacrylic acid) (pMAA) coating via initiated chemical vapor deposition (iCVD). The hybrid grafting was conducted by depositing a prime layer of poly(methacrylic acid-co-ethylene glycol dimethacrylate) (p(MAA-co-EGDMA)) copolymer followed by immediate in situ grafting of a pMAA homopolymer layer. The grafting parameters were systematically studied to obtain the maximum grafting density of pMAA. The resulting membrane with maximized surface functionality shows strong hydrophilicity with a water contact angle of 33° without affecting its permeability, excellent suppression of platelet adhesion and deformation, and significantly lengthened clotting time (APTT, TT, and PT prolonged to 308.4 s, 31.0 s, and 31.9 s, respectively). The substantially enhanced hemocompatibility is attributed to the abundant carboxyl groups achieved by hybrid grafting, which effectively disrupts the coagulation cascade. This facile iCVD grafting method can be a promising candidate for improving the hemocompatibility of biomaterials, such as dialysis membranes, catheters, and implants.