title: Symmetric pH-dependent swelling and antibacterial properties of chitosan brushes.
abstract: Charged polymer brushes grafted to surfaces are of great interest for antibacterial, biosensor, nanofluidic, and drug delivery applications. In this paper, chitosans with quaternary ammonium salts, CH-Q, were immobilized on silicon oxide and characterized by in situ quartz-crystal microbalance with dissipation, QCM-D, and in situ spectroscopic ellipsometry, SE. Both methods showed that the hydrated film exhibited a minimum thickness of ~40 nm near pH 5 that increased strongly (up to ~80 nm) at lower and higher pH. This symmetric swelling is surprising because CH-Q is a cationic polymer. The CH-Q grafted layer was stable for pH values from 3 to 8 and exhibited rapid, reversible swelling and contraction upon varying pH. The CH-Q layer also reduced S. aureus colonization by a factor of ~30× compared to bare silicon oxide and an amine terminated silane grafted to silicon oxide. This antibacterial characteristic of CH-Q is attributed to the quaternary ammonium salts and the flexible polymer brush.
authors: Institute of Medicine and Engineering, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA.
authors: Hyun-Su
authors: HS
authors: Lee
authors: David M
authors: DM
authors: Eckmann
authors: Daeyeon
authors: D
authors: Lee
authors: Noreen J
authors: NJ
authors: Hickok
authors: Russell J
authors: RJ
authors: Composto
mesh_terms: D000900:Anti-Bacterial Agents / Q000737:chemistry*; D002240:Carbohydrate Sequence; D048271:Chitosan / Q000737:chemistry*; D004852:Epoxy Compounds / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D008958:Models, Molecular; D008969:Molecular Sequence Data; D000644:Quaternary Ammonium Compounds / Q000737:chemistry; D012822:Silicon Dioxide / Q000737:chemistry; D012995:Solubility; D013499:Surface Properties; D014867:Water / Q000737:chemistry
chemical_list: D000900:Anti-Bacterial Agents; D004852:Epoxy Compounds; D000644:Quaternary Ammonium Compounds; D014867:Water; D012822:Silicon Dioxide; D048271:Chitosan