Interaction Forces and Morphology of a Protein-Resistant Poly(ethylene glycol) Layer

Abstract

The molecular interactions on a protein-resistant surface coated with low-molecular-weight poly(ethylene glycol) (PEG) copolymer brushes are investigated using the extended surface forces apparatus. The observed interaction force is predominantly repulsive and nearly elastic. The chains are extended with respect to the Flory radius, which is in agreement with qualitative predictions of scaling theory. Comparison with theory allows the determination of relevant quantities such as brush length and adsorbed mass. Based on these results, we propose a molecular model for the adsorbed copolymer morphology. Surface-force isotherms measured at high resolution allow distinctive structural forces to be detected, suggesting the existence of a weak equilibrium network between poly(ethylene glycol) and water--a finding in accordance with the remarkable solution properties of PEG. The occurrence of a fine structure is interpreted as a water-induced restriction of the polymer's conformational space. This restriction is highly relevant for the phenomenon of PEG protein resistance. Protein adsorption requires conformational transitions, both in the protein as well as in the PEG layer, which are energetically and kinetically unfavorable.

An RGD-restricted substrate interface is sufficient for the adhesion, growth and cartilage forming capacity of human chondrocytes

“…(Pasche et al, 2003) This protein resistant effect can be attributed to the architecture of the PEG brush. (Heuberger et al, 2005) Indeed, on PEG and RDG (scrambled cell adhesion sequence), HAC attached to a very limited extent and mostly remained suspended in the culture medium as clusters. The fact that on these bio-inactive surfaces cell attachment was not completely abolished could be explained by small local defects in the PLL-g-PEG or PLLg-PEG/PEG-RDG-layer, which likely permitted limited serum adsorption.…”

Macrotribological Studies of Poly(L-lysine)-graft-Poly(ethylene glycol) in Aqueous Glycerol Mixtures

“…There have been several studies, both theoretical [3] and experimental [4,5] that have investigated the origin of frictional forces between contacting brushes at different shear rates. For water-soluble polymer brushes in aqueous environments, the presence of bound (or 'hydration') water surrounding the polymer chains can result in structural forces between the hydrated brushes [6]. Strongly hydrated polymers, together with a continuous rapid exchange of bound water with other free water molecules, keep the surfaces separated while maintaining a high fluidity at the brush-brush interface at high compressions, thus leading to a very low coefficient of friction [7,8].…”

Behavior of Polyethylene Glycol Molecules at an Oscillating Solid-Liquid Interface

“…The cell and QCM system were shielded by a grounded aluminum plate. The gold electrodes of the QCM were rinsed with piranha solution H 2 SO 4 : H 2 O 2 30 3:1 prior to impedance measurements. For measurements in PEG solutions, the cell temperature was set to 25 0.1 .…”