Formation of self-assembled monolayers by chemisorption of derivatives of oligo(ethylene glycol) of structure HS(CH2)11(OCH2CH2)mOH on gold

Abstract

This paper describes the preparation of oligo(ethylene glycol)-terminated alkanethiols having structure HS-(CH2)n(0CH2CH2)m0H (m = 3-7) and their use in the formation of self-assembled monolayers (SAMs) on gold. A combination of experimental evidence derived from X-ray photoelectron spectroscopy (XPS), measurement of contact angles, and ellipsometry implies substantial disorder in the oligo(ethylene glycol)-containing segment. The order in the -(CH2)ngroup is not defined by the available evidence. The SAMs are moderately hydrophilic: 0a(H2O) = 34-38°; 0r(H2O) = 22-25°. A study of monolayers containing mixtures of HS(CH2)nCH3 and HS(CH2)u(OCH2CH2)6OH suggests that the oligo(ethylene glycol) moieties are effective at preventing underlying methylene groups from influencing wetting by water. A limited study demonstrates that these oligo(ethylene glycol)-containing SAMs resist the adsorption of protein from solution and suggests that SAMs will be a useful model system for studying the adsorption of proteins onto organic surfaces.

Surface polyethylene glycol enhances substrate-mediated gene delivery by nonspecifically immobilized complexes

“…Our results are consistent with previous reports demonstrating that increasing the density of PEG groups decreases cell adhesion, due to the PEGylated surfaces' increased ability to resist protein adsorption [43][44][45][46]. Finally, we note that increasing the EG content in solution results in an associated increase in the number of EG groups within the monolayer [38]. However, the surface concentration of EG groups is likely less than the solution concentration.…”

“…2). The relatively high contact angles reported for EG-containing SAMs are consistent with an outer phase that exposes CH 2 groups to solution [38]. PEG, while known as a hydrophilic polymer, is truly amphiphilic, with both hydrophilic and hydrophobic components, and this combination of properties is a key to its biocompatibility [51].…”

“…However, the surface concentration of EG groups is likely less than the solution concentration. Studies with mixed solutions of alkanethiols have indicated that the EG content on the surface may be reduced 3-to 30-fold relative to the solution content [38].…”

“…We hypothesize that, rather than attach PEG to the complexes directly, its presence in a SAM could enhance substrate-mediated transfection by conveying the desired properties of PEG on gene delivery (reduced complex aggregation, complex size stability), and promote interactions between the complexes and cell membrane. SAMs presenting oligo(ethylene glycol) (EG) groups [38,39] have previously been used to resist protein adsorption according to the length of the EG chain and its percent composition within the monolayer [39,40], and are used here to modulate DNA complex adsorption for substrate-mediated gene delivery. In our studies, EG-terminated alkanethiols were incorporated into SAMs at concentrations that do not limit cell adhesion and combinations of EG-and COO − -terminated alkanethiols were examined for their ability to bind and release complexes and to subsequently support transfection.…”

Click Chemistry‐Based Functionalization on Non‐Oxidized Silicon Substrates

“…In this respect, the silicon substrates are commonly modified with oligo-or poly(ethylene glycol) (OEG or PEG), which are well-known antifouling and biocompatible materials. [63][64][65][66] Direct photoor thermal-mediated grafting of OEG-terminated alkenes onto an Si À H surface through Si À C bond formation has been reported. [67][68][69] As the OEG-alkenes (e.g., TMG-EG10 in Scheme 8) are hygroscopic and very likely to trap a trace amount of water that is reactive to the Si À H surface under UV irradiation, the photo-initiated grafting must be carried Scheme 7.…”