title: Protein adsorption on and swelling of polyelectrolyte brushes: A simultaneous ellipsometry-quartz crystal microbalance study.
abstract: With a coupled spectroscopic ellipsometry-quartz crystal microbalance with dissipation (QCM-D) experimental setup, quantitative information can be obtained about the amount of buffer components (water molecules and ions) coupled to a poly(acrylic acid) (PAA) brush surface in swelling and protein adsorption processes. PAA Guiselin brushes with more than one anchoring point per single polymer chain were prepared. For the swollen brushes a high amount of buffer was found to be coupled to the brush-solution interface in addition to the content of buffer inside the brush layer. Upon adsorption of bovine serum albumin the further incorporation of buffer molecules into the protein-brush layer was monitored at overall electrostatic attractive conditions [below the protein isolectric poimt (IEP)] and electrostatic repulsive conditions (above the protein IEP), and the shear viscosity of the combined polymer-protein layer was evaluated from QCM-D data. For adsorption at the "wrong side" of the IEP an incorporation of excess buffer molecules was observed, indicating an adjustment of charges in the combined polymer-protein layer. Desorption of protein at pH 7.6 led to a very high stretching of the polymer-protein layer with additional incorporation of high amounts of buffer, reflecting the increase of negative charges on the protein molecules at this elevated pH.
authors.affiliation: Leibniz Institute of Polymer Research Dresden, Hohe Str. 6, 1069 Dresden, Germany.
authors.forename: Eva
authors.initials: E
authors.lastname: Bittrich
authors.forename: Keith Brian
authors.initials: KB
authors.lastname: Rodenhausen
authors.forename: Klaus-Jochen
authors.initials: KJ
authors.lastname: Eichhorn
authors.forename: Tino
authors.initials: T
authors.lastname: Hofmann
authors.forename: Mathias
authors.initials: M
authors.lastname: Schubert
authors.forename: Manfred
authors.initials: M
authors.lastname: Stamm
authors.forename: Petra
authors.initials: P
authors.lastname: Uhlmann
mesh_terms: D000180:Acrylic Resins / Q000737:chemistry*; D000327:Adsorption; D000818:Animals; D002417:Cattle; D006863:Hydrogen-Ion Concentration; D007526:Isoelectric Point; D008968:Molecular Conformation; D009994:Osmolar Concentration; D011506:Proteins / Q000737:chemistry*; D058525:Quartz Crystal Microbalance Techniques; D012031:Refractometry; D012710:Serum Albumin, Bovine / Q000737:chemistry; D013057:Spectrum Analysis / Q000379:methods*; D013499:Surface Properties; D014783:Viscosity
chemical_list: D000180:Acrylic Resins; D011506:Proteins; D012710:Serum Albumin, Bovine; C006903:carbopol 940