Enhanced Resistance of Zwitterionic Hydrogels against Marine Fouling Using a Zwitterionic Photo Cross-Linker

Polyzwitterions have great potential as fouling-resistant materials for biomedical and environmental products, in particular, in the form of hydrogel coatings. While typically these are soft materials, for many applications it is also necessary to achieve sufficient mechanical stability. This may be accomplished by high degrees of cross-linking, which, however, will impair the overall hydrophilicity of the gels for the commonly used hydrophobic cross-linkers. To mitigate this dilemma, a zwitterionic methacrylate monomer was developed that contains a benzophenone moiety as a photo-cross-linkable unit and a hydrophilic zwitterionic sulfobetaine moiety. Copolymers of the standard sulfobetaine methacrylate 3-[N-(2'-methacryloyloxyethyl)-N,N-dimethylammonio] propane-1-sulfonate (SPe) with contents of the new photo cross-linker of up to about 50 mol % were realized, and their films were photocured and analyzed. Subsequently, the resistance against the nonspecific adsorption of model proteins was determined in laboratory assays by surface plasmon resonance spectroscopy. Moreover, the attachment of marine fouling organisms was investigated in laboratory assays under dynamic conditions as well as in short-term field exposures in the sea. Copolymers with sufficiently high cross-linker contents of about 30 mol % were able to maintain a high hydration capability and to substantially reduce marine biofouling even in field tests in the ocean.