Surface modifications of polypropylene membranes used for blood filtration

The surface of two commercial meltblown polypropylene (PP) membranes, used for the filtration of blood products, were modified by wet chemistry treatments (carbodiimide, tosyl chloride and trihalogeno-triazines) in the case of the oxygen-plasma treated membrane (O₂-PP), and by photochemistry using molecular clips in the case of the native PP membrane. The most efficient technique uses trifluoro-triazine reagent for the activation of both hydroxyl- and carboxyl-functions of O₂-PP. It enables the fixation of amine-terminated molecules with high degrees of derivatization (∼700 pmol/cm²), without inducing modification of the membrane morphology nor cytotoxicity. Only a weak decrease of surface hydrophilicity was measured after the treatments and steam-sterilization. This method was applied for the grafting of peptides (Gly-Gly-Gly-Gly-Gly, Gly-Arg-Gly-Asp-Ser, home-made modified Leu-Asp-Val) on O₂-PP membranes incorporated into multi-layer filter devices. These modified filters showed improved properties of leukocyte depletion in blood filtration experiments, principally due to the wetting properties of the membranes.