Formation of tetra(ethylene oxide) terminated Si - C linked monolayers and their derivatization with glycine: An example of a generic strategy for the immobilization of biomolecules on silicon

Till Böcking, Kristopher A. Kilian, Tracey Hanley, Suhrawardi Ilyas, Katharina Gaus, Michael Gal, J. Justin Gooding

Research output: Contribution to journalArticle

Abstract

Surface modification with oligo(ethylene oxide) functionalized monolayers terminated with reactive headgroups constitutes a powerful strategy to provide specific coupling of biomolecules with simultaneous protection from nonspecific adsorption on surfaces for the preparation of biorecognition interfaces. To date, oligo(ethylene oxide) functionalized monolayer-forming molecules which can be activated for attachment of biomolecules but which can selectively form monolayers onto hydrogen terminated silicon have yet to be developed. Here, self-assembled monolayers (SAMs) containing tetra(ethylene oxide) moieties protected with tert-butyl dimethylsilyl groups were formed by thermal hydrosilylation of alkenes with single-crystal Si(111)-H. The protection group was used to avoid side reactions with the hydride terminated silicon surface. Monolayer formation was carried out using solutions of the alkene in the high-boiling-point solvent 1,3,5-triethylbenzene. The protecting group was removed under very mild acidic conditions to yield a free hydroxyl functionality, a convenient surface moiety for coupling of biological entities via carbamate bond formation. The chemical composition and structure of the monolayers before and after deprotection were characterized by X-ray photoelectron spectroscopy (XPS) and X-ray reflectometry. To demonstrate the utility of this surface for covalent modification, two reagents were compared and contrasted for their ability to activate the surface hydroxyl groups for coupling of free amines, carbonyl diimidazole (GDI), and disuccinimidyl carbonate (DSC). Analysis of XP spectra before and after activation by GDI or DSC, and after subsequent reaction with glycine, provided quantitative information on the extent of activation and overall coupling efficiencies. GDI activated surfaces gave poor coupling yields under various conditions, whereas DSC mediated activation followed by aminolysis at neutral pH was found to be an efficient method for the immobilization of amines on tetra(ethylene oxide) modified surfaces.

Original languageEnglish (US)
Pages (from-to)10522-10529
Number of pages8
JournalLangmuir
Volume21
Issue number23
DOIs
StatePublished - Nov 8 2005

ASJC Scopus subject areas

  • Materials Science(all)
  • Condensed Matter Physics
  • Surfaces and Interfaces
  • Spectroscopy
  • Electrochemistry

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