Effect of carbon spacer length on the antibacterial properties of zwitterionic poly(sulfobetaine) type copolymeric brushes and their application in wound healing

Creating infection resistant polymer brushes possessing antiadhesive, bactericidal and cell-compatible features can be regarded as a promising approach to prevent biomaterial-associated infections. In this work, polysulfobetaine type zwitterionic homo- and copolymer brushes with varying spacer lengths (charge separation distance between zwitterions, n = 3, 6 or 12) were allowed to grow onto a tartaric acid based aliphatic polyester substrate using surface initiated atom transfer radical polymerization. All of the brush modified surfaces were thoroughly characterized and assessed for their anti-infective performances in vitro. Strikingly, a suitable copolymer composition, i.e., polyZ6-co-Z12 (50/50 copolymer of polysulfobetaine methacrylates with 6 and 12 spacer lengths), was observed to inhibit bacterial growth completely and its activity was sustained for a long time (>3 months). Surprisingly, its antibacterial effect was found to be bactericidal, as is evident from live-dead staining of residual dead bacterial cells that can be easily released by exposing the surface to salt solution, thereby regenerating the surface. However, all of the other copolymer as well as homopolymer brushes exhibited bacteriostatic behavior. An attempt was made to understand the peculiar behavior of this particular brush composition. Nevertheless, the biocidal and also protein repellent brush did not display any cytotoxicity towards human cells, making it an ideal substrate to be used as an infection resistant biomedical implant. Animal studies further confirmed that this particular copolymeric brush modified scaffold can be a promising anti-infective wound dressing material with rapid wound healing effects as compared to the unmodified scaffold.