Bacterial anti-adhesive properties of a monolayer of zwitterionic block copolymer micelles

We report on bacterial anti-adhesive properties of a monolayer of block copolymer micelles (BCMs) with zwitterionic coronae and pH-responsive cores. BCMs were obtained by pH-induced self-assembly of selectively betainized poly[3-dimethyl (methacryloyloxyethyl) ammonium propane sulfonate-b-2-(diisopropylamino)ethyl methacrylate] (βPDMA-b-PDPA) in aqueous solution above neutral pH. Monolayer films were self-assembled at pH 7.5 when βPDMA-b-PDPA was in the micellar form. Bacterial anti-adhesive properties of the zwitterionic micellar coatings were examined against S. aureus through: i) a macroscopic test based on viable cell counting; ii) direct microscopic visualization of adherent bacteria by live/dead staining and iii) crystal violet staining to evaluate surface adherent biomass. 95% reduction in cell adhesion was observed by microscopy indicating the anti-adhesive properties of βPDMA-b-PDPA micellar monolayer. Results obtained from the viable cell count assay and crystal violet staining showed similar trends and were in good agreement with the microscopy results. Such coatings are promising to impart both anti-adhesive and antimicrobial properties to a surface due to bacterial anti-adhesive properties of zwitterionic coronae and the potential of pH-responsive cores to release antimicrobial agents.