Anti-biofilm surfaces from mixed dopamine-modified polymer brushes： synergistic role of cationic and zwitterionic chains to resist Staphyloccocus aureus
Infections resulting from bacteria attachment and the biofilm formation on the medical implants are giving rise to a severe problem for medical devices safety. Development of antibacterial materials that integrate bactericidal and antifouling properties is a promising approach to prevent biomaterial-associated infections. In this work, two types of dopamine-modified polymers, dopamine-terminated quaternary ammonium salts polymer (D-PQAs) with various lengths of N-alkyl chain (D-PQA4C, D-PQA8C, D-PQA12C, respectively) and dopamine-terminated poly(sulfobetaine methacrylate) (D-PSBMA), are synthesized by atom transfer radical polymerization (ATRP). Mixed polymer brushes of D-PQAs and D-PSBMA with various ratios are well integrated onto the surface of silicon wafer by a facile mussel-inspired adhesion. We demonstrate that the synergistic antibacterial effect depends on both the ratio of two components and their surface structures of mixed polymer brushes originated from interaction between the D-PQAs and D-PSBMA. The N-alkyl chain length of D-PQAs could influence the distribution and orientation of the alkyl chain on the mixed polymer brushes. A chart of antibacterial efficiency for the mixed polymer brushes is obtained to reveal the synergistic role of cationic and zwitterionic chains to resist S.aureus. The dominant amount of antifouling D-PSBMA with the minor amount of bactericidal D-PQAs with short N-alkyl chain length will facilitate the synergistic antibacterial effect. The selected polymer brushes (PSBMA/PQA4C-10%, PSBMA/PQA4C-30%, and PSBMA/PQA8C-10%) can effectively prevent biofilm formation of S. aureus for a long time while having good biocompatibility. Our present work may provide a universal design rule for the preparation of anti-biofilm and biocompatible surfaces for biomedical applications.