A Survey of Structure−Property Relationships of Surfaces that Resist the Adsorption of Protein

Abstract

This paper describes the use of surface plasmon resonance (SPR) spectroscopy and self-assembled monolayers (SAMs) to determine the characteristics of functional groups that give surfaces the ability to resist the nonspecific adsorption of proteins from solution. Mixed SAMs presenting different functional groups were prepared for screening using a synthetic protocol based on the reaction of organic amines with a SAM terminated by interchain carboxylic anhydride groups. Surfaces that presented derivatives of oligo(sarcosine), N-acetylpiperazine, and permethylated sorbitol groups were particularly effective in resisting the adsorption of proteins. Incorporation of these groups into single-component SAMs resulted in surfaces that are comparable to (but slightly less good than) single-component SAMs that present oligo(ethylene glycol) in their ability to resist the adsorption of proteins. In the group of surfaces examined, those that resisted the adsorption of proteins had the following properties: they were hydrophilic; they contained groups that were hydrogen-bond acceptors but not hydrogen-bond donors; and they were overall electrically neutral.

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

“…These surfaces had previously resisted cell adhesion (Fig. 1), presumably through resisting protein adsorption [39,40]. However, adhesion studies on SAMs containing only EG alkanethiols (100% EG) with immobilized complexes or PEI alone demonstrate significant cell adhesion (Fig.…”

“…A SAM consisting of only EG groups (Fig. 1f) had no cells attached, which was expected due to the resistance of the surface to protein adsorption [39,40] that would be needed to support cellular adhesion. A complete elimination of cellular adhesion on SAMs containing 100% EG thiols indicates that the monolayers are robust.…”

“…Additionally, free PEI in the complex solution, which would be more abundant at an N/P of 25, could be binding to the SAM and changing the surface properties, eliminating differences between surfaces. Although these EG-modified SAMs have substantially reduced protein adsorption [39,40], presumably through steric stabilization and excluded volume, some adsorption of serum proteins does occur [47,48], and complexes may bind to these surfaces via similar mechanisms.…”

“…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.…”

Glycosylation Characterization of Human and Porcine Fibrinogen Proteins by Lectin-Binding Biophotonic Microarray Imaging

“…The technique uses the sensitivity of the light scattering properties of the gold nanoparticle localised surface plasmons to provide intensity changes observed in real time with a video camera. The gold nanoparticle array spots can be functionalised by self-assembling monolayers (SAMs) which carry a terminal carboxylic group (linker) for chemical modification and a terminal hydroxyl group (spacer), respectively [26][27] . The carboxylic group can be used to couple various different chemically modified sugars on the surface 28 .…”