Bacterial anti-adhesive and pH-induced antibacterial agent releasing ultra-thin films of zwitterionic copolymer micelles

We report on preparation of substrates with dual function coatings, i.e. bacterial anti-adhesive and antibacterial agent releasing polymer films of zwitterionic block copolymer micelles (BCMs). BCMs were obtained by pH-induced self-assembly of poly[3-dimethyl (methacryloyloxyethyl) ammonium propane sulfonate-b-2-(diisopropylamino)ethyl methacrylate] (beta PDMA-b-PDPA), resulting in BCMs with zwitterionic beta PDMA-coronae and pH-responsive PDPA-core. These zwitterionic BCMs were then used as building blocks to construct mono- and multi-layer films. We found that the number of layers in the film was critical for the anti-adhesive property and 3-layer films were the most anti-adhesive against a model Gram-positive bacterium, Staphylococcus aureus. Antibacterial activity could be introduced to the films by loading Triclosan into beta PDMA-b-PDPA micelles. Triclosan containing films were effective against Triclosan-sensitive Staphylococcus aureus specifically at moderately acidic conditions due to pH induced disintegration of the micellar core blocks and release of Triclosan from the surface. Three layer films also exhibited anti-adhesive property at physiological pH against a model Gram-negative bacterium, Escherichia coli. At moderately acidic pH, the coatings showed a contact antibacterial effect against an isolate of Escherichia coli with low sensitivity to Triclosan only when micellar cores were loaded with Triclosan. Such dual function films can be promising to combat biofouling at the non homogeneous and/or defective parts of an anti-adhesive coating. Moreover, considering the moderately acidic conditions around an infection site, these multilayers can be advantageous due to their property of pH-induced antibacterial agent release.