Protein Adsorption on Well-Characterized Polyethylene Oxide Brushes on Gold: Dependence on Molecular Weight and Grafting Density

Abstract

The adsorption of lysozyme protein was measured ex situ on well-characterized gold surfaces coated by end-tethered polyethylene oxide brushes of various molecular weights and controlled grafting densities. The adsorbed amount of protein for different molecular weight brushes was found to collapse onto one master curve when plotted against brush coverage. We interpret this relationship in terms of a model involving site-blocking of the adsorption of proteins at the substrate and discuss the role of the physical attraction of PEO segments to gold. We account for our observation of a simple exponential relationship between protein adsorption and normalized brush coverage with a simple protein adsorption model. In contrast to other studies in similar systems, we do not observe protein adsorption on brushes at high grafting density, and we suggest that this discrepancy may be due to the solubility effects of salt upon the brushes, influencing their protein binding affinity, in the limit of high grafting density and high brush volume fraction.

Structure and Stability of PEG‐ and Mixed PEG‐Layer‐Coated Nanoparticles at High Particle Concentrations Studied In Situ by Small‐Angle X‐Ray Scattering

“…In contrast, at high grafting densities, the polymer chains are forced into a stretched, so‐called brush conformation to minimize polymer–polymer contacts and to maximize polymer–solvent contacts. In the case of PEGylated materials, it has been shown that these conformations critically affect the immune response and the protein adsorption in general . The grafting density and structure of the polymer layer, or more generally ligand layer, also dictate the chemical and colloidal stability of NPs .…”

Quantum dot surface engineering: Toward inert fluorophores with compact size and bright, stable emission

“…Likewise increased rigidity of the coating by chain-chain interactions driven by hydrogen bonds can enhance protein fouling [260]. While these findings indicate a tradeoff between chemical stability and anti-fouling characteristics, others have not detected an upper limit for PEG packing density for minimizing fouling [261]. …”

Mode of lysozyme protein adsorption at end-tethered polyethylene oxide brushes on gold surfaces determined by neutron reflectivity

“…We were able to accurately control the grafting of these brushes over the range of grafting at which PEO brushes become protein resistive using a concentrated homopolymer solution. In further work we showed that the adsorbed amount of protein at these surfaces follows an exponential decay with brush coverage [20]. We interpreted this relationship with a simple model that accounts for protein adsorption on the gold substrate in the primary position on areas not covered by polymer brush due to lateral fluctuations in the grafting of PEO chains.…”

“…It has been found that adsorbed amount of protein at end-tethered PEO surfaces is dependent upon the grafting density and molecular weight of the chains, with variation between studies believed to be due to various factors such as distal chemistry or brush-substrate interactions. In previous work by the authors, Taylor and Jones, it was found that the adsorb amount of lysozyme protein at PEO brushes on gold decreases with increasing coverage, implying that PEO polymers essentially block the adsorption of protein at the substrate-brush interface [20]. The exact position of adsorbed protein at end-tethered polyethylene oxide brushes has long been a mystery and is of significant importance in understanding the antifouling properties of such surfaces.…”

“…1. Further studies have also stressed the importance of lateral fluctuations in surface coverage of polymer, and suggest that protein adsorption can mainly be accounted by primary adsorption upon bald spots where polymer is not present [20,35].…”