Poly(ethylene oxide) Grafted to Silicon Surfaces: Grafting Density and Protein Adsorption

Abstract

Poly(ethylene oxide) (PEO) polymer, in linear and star form, was covalently grafted to silicon surfaces, and the surfaces were tested for their ability to adsorb proteins. Linear PEG of molecular weight 3400, 10 000, and 20 000 g/mol and star PEO molecules were coupled via their terminal hydroxyl groups activated by tresyl chloride to aminosilane-treated silicon wafers. The amount of PEO coupled to the surface was varied by changing the concentration of the tresyl-PEO solution. The dry PEO thickness on the surface was measured using X-ray photoelectron spectroscopy (XPS) and ellipsometry, from which the grafting density was calculated. The PEO surfaces were exposed to solutions of each of three proteins: cytochrome-c, albumin, and fibronectin. The degree of adsorption of each protein was determined by XPS and ellipsometry and recorded as a function of PEO grafting density. All three proteins were found to reach zero adsorption at the highest grafting densities on all three PEG surfaces, which for all three PEG surfaces was a PEO content of 100 +/- 10 ng/cm2. On both star PEO surfaces, albumin and fibronectin decreased to zero adsorption at intermediate values of grafting density, whereas cytochrome-c continued to adsorb at all grafting densities, although with a decreasing trend. A physical model of the surface helped explain these protein adsorption results in terms of the spacing and degree of overlap of grafted PEO chains.

Construction of a densely poly(ethylene glycol)-chain-tethered surface and its performance

“…This is especially true regarding the versatile techniques for surface coating using PEG that have been developed since the 1980s to improve blood and bio-compatibility. Figure 1 summarizes several methods for the immobilization of PEG on substrate surfaces: PEG gels, 19,20,36 the physical and chemical immobilization of PEG 13,21,37 (so-called grafting-to method), the adsorption of block [22][23][24][25][26][27]38 and graft 27,28,39,40 copolymers, polymerization from the surface 41 (the so-called grafting-from method), the immobilization of star-shape polymers and micelles, [42][43][44] and other methods.…”

Improved Performances of Intraocular Lenses by Poly(ethylene glycol) Chemical Coatings

“…[22][23][24][25][26][27] The covalent grafting of PEG onto a variety of substrates, including silicon, 24,28 polyurethane-urea, 29 glass, 30,31 fluorinated ethylene-propylene copolymers, 32 and polysulfone membranes, 33 has been reported along with a quite satisfactory protein-repellent effect. It may be anticipated that the proteinrepellent properties of PEG would prevent an extracellular matrix from being formed and, thus, cells from adhering.…”

Hyperbranched aliphatic polyether polyols

“…Currently, PEG is frequently used for anti-biofouling surface coatings, 185 but the relatively low stability toward oxidation limits its application in biological systems. Polyglycerol as a highly biocompatible aliphatic polyether shows higher stability toward oxidation, 186 and self-assembled monolayers (SAMs) presenting oligo-or polyglycerols exhibit excellent protein resistance.…”