Salt-Responsive Switchable Block Copolymer Brushes with Antibacterial and Antifouling Properties.

A strategy for multifunctional biosurfaces exploiting multiblock copolymers and the antipolyelectrolyte effect is reported. Combining a polyzwitterionic/antifouling and a polycationic/antibacterial block with a central anchoring block for attachment to titanium oxide surfaces affords surface coatings that exhibit antifouling properties against proteins and allow for surface regeneration by clearing adhering proteins by employing a salt washing step. The surfaces also kill bacteria by contact killing, which is aided by a nonfouling block. The synthesis of block copolymers of 4-vinyl pyridine (VP), dimethyl 4-vinylbenzyl phosphonate (DMVBP), and 4-vinylbenzyltrimethyl ammonium chloride (TMA) is achieved on the multigram scale via RAFT polymerization with good end group retention and narrow dispersities. By polymer analogous reactions, poly(4-vinyl pyridinium propane sulfonate-block-4-vinylbenzyl phosphonic acid-block-4-vinylbenzyl trimethylammonium chloride) (P(VSP-b-PA-b-TMA)) is obtained. The antifouling properties against the model protein pepsin and the salt-induced surface regeneration are shown in surface plasmon resonance (SPR) experiments, while independently the antibacterial and antifouling properties of coated titanium substrates are successfully tested in preliminary microbiological assays against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli). This strategy may contribute to the development of long-term effective antibacterial implant surface coatings to suppress biomedical device-associated infections.