Polymer-based membrane filters are emerging materials used in various fields such as water treatment, energy production, food processing, as well as pharmaceutical industry and biomedicine. However, despite their high mechanical strength and chemical resistance, synthetic membranes have significant drawbacks in terms of biocompatibility and advanced functionality. Biofunctionalization is a promising way to introduce novel bioinspired materials. Immobilization of biomolecules such as proteins offers numerous advantages, e.g., prevention of contamination, improved stability or biocompatibility. For instance, bovine serum albumin (BSA) has been used to improve blood compatibility by reducing haemolysis, or to adsorb toxins in the treatment of liver diseases. Covalent coupling allows very strong binding and thus prevents delamination. However, the commonly used chemical coupling methods have significant drawbacks such as multistep reactions, expensive or toxic chemicals, long reaction times, or harsh conditions.

In this study, BSA was covalently attached to polyvinylidene fluoride (PVDF) flat sheet membranes using a one-step, clean and fast electron beam process. The membrane is impregnated with an aqueous solution containing small or large biomolecules. Irradiation with an electron beam leads to activation of the polymer substrate and solute molecules. Reactive species rapidly form covalent bonds, resulting in a permanent modification. The mechanism behind this polymer surface functionalization was recently reported, i.e., radiation-induced graft immobilization (RIGI). By using a design of experiments (DoE) approach, BSA protein coverage of up to 1300 mg/m² was achieved, which is one of the highest values reported to date. Furthermore, this reagent-free method allows the reuse of impregnation solution at least five times without reducing the grafting yield. Overall, an efficiency 230-times higher than best literature values was calculated for this promising processing technology.

This method eventually enables the development of innovative materials applying a variety of exciting biomolecules such as antimicrobial peptides, photoactive molecules, or biocatalytically active enzymes.