title: Strongly stretched protein resistant poly(ethylene glycol) brushes prepared by grafting-to.
abstract: We present a new grafting-to method for resistant "non-fouling" poly(ethylene glycol) brushes, which is based on grafting of polymers with reactive end groups in 0.9 M Na2SO4 at room temperature. The grafting process, the resulting brushes, and the resistance toward biomolecular adsorption are investigated by surface plasmon resonance, quartz crystal microbalance, and atomic force microscopy. We determine both grafting density and thickness independently and use narrow molecular weight distributions which result in well-defined brushes. High density (e.g., 0.4 coils per nm(2) for 10 kDa) and thick (40 nm for 20 kDa) brushes are readily achieved that suppress adsorption from complete serum (10× dilution, exposure for 50 min) by up to 99% on gold (down to 4 ng/cm(2) protein coverage). The brushes outperform oligo(ethylene glycol) monolayers prepared on the same surfaces and analyzed in the same manner. The brush heights are in agreement with calculations based on a simple model similar to the de Gennes "strongly stretched" brush, where the height is proportional to molecular weight. This result has so far generally been considered to be possible only for brushes prepared by grafting-from. Our results are consistent with the theory that the brushes act as kinetic barriers rather than efficient prevention of adsorption at equilibrium. We suggest that the free energy barrier for passing the brush depends on both monomer concentration and thickness. The extraordinary simplicity of the method and good inert properties of the brushes should make our results widely applicable in biointerface science.
authors: †Department of Applied Physics, Chalmers University of Technology, 41296 Göteborg, Sweden.
authors: Gustav
authors: G
authors: Emilsson
authors: ‡Biozentrum and the Swiss Nanoscience Institute, University of Basel, 4056 Basel, Switzerland.
authors: Rafael L
authors: RL
authors: Schoch
authors: Laurent
authors: L
authors: Feuz
authors: †Department of Applied Physics, Chalmers University of Technology, 41296 Göteborg, Sweden.
authors: Fredrik
authors: F
authors: Höök
authors: ‡Biozentrum and the Swiss Nanoscience Institute, University of Basel, 4056 Basel, Switzerland.
authors: Roderick Y H
authors: RY
authors: Lim
authors: †Department of Applied Physics, Chalmers University of Technology, 41296 Göteborg, Sweden.
authors: Andreas B
authors: AB
authors: Dahlin
mesh_terms: D000327:Adsorption; D001672:Biocompatible Materials / Q000737:chemistry*; D001798:Blood Proteins / Q000737:chemistry*; D055119:Elastic Modulus; D008422:Materials Testing; D008970:Molecular Weight; D011092:Polyethylene Glycols / Q000737:chemistry*; D013314:Stress, Mechanical; D013718:Tensile Strength
chemical_list: D001672:Biocompatible Materials; D001798:Blood Proteins; D011092:Polyethylene Glycols
keywords: inert; poly(ethylene glycol); polymer brush; protein adsorption; strongly stretched