X-ray Microscopy Studies of Protein Adsorption on a Phase-Segregated Polystyrene/Polymethyl Methacrylate Surface. 1. Concentration and Exposure-Time Dependence for Albumin Adsorption

Abstract

X-ray photoemission electron microscopy using synchrotron radiation illumination has been used to measure the spatial distributions of albumin on a phase-segregated polystyrene/poly(methyl methacrylate) (PS/PMMA) polymer thin film following adsorption from unbuffered, deionized aqueous solutions under a range of solution concentrations and exposure times. Chemical mapping of the albumin, PS, and PMMA shows that the distribution of albumin on different adsorption sites (PS, PMMA, and the interface between the PS and PMMA domains) changes depending on the concentration of the albumin solution and the exposure time. The preferred sites of absorption at low concentration and short exposure are the PS/PMMA interfaces. Albumin shows a stronger preference for the PS domains than the PMMA domains. The exposure-time dependence suggests that a dynamic equilibrium between albumin in solution and adsorbed on PS domains is established in a shorter time than is required for equilibrating albumin between the solution and the PMMA domains. The explanation of these preferences in terms of possible adsorption mechanisms is discussed.

Modulation of Protein−Surface Interactions on Nanopatterned Polymer Films

“…[11][12][13][14][15][16][17] Previous reports have also explored the effect of a nanopattern on adsorption behavior. For example, the presence of chemical nanostripes with line widths close to that of individual proteins has been shown to induce proteins to preferentially adsorb with an orientation aligned with the nanopattern's anisotropy.…”

Using Intrinsic X-ray Absorption Spectral Differences To Identify and Map Peptides and Proteins

“…[1][2][3]16,17 The spectra of peptides and proteins on polymer surfaces is being examined by photoemission electron microscopy (X-PEEM). 4,18 These techniques compliment more common methods for mapping proteins such as laser scanning microscopy of fluorescent labeling proteins, 19 which has high specificity but limited spatial resolution, and immunoelectron microscopy, which has high spatial resolution but requires a chemically fixed sample. 20 The X-ray absorption spectra of proteins are quite distinct from that of other biological materials, especially at the C 1s edge.…”

Modulating Protein Adhesion and Conformation with Block Copolymer Surfaces

“…Measurements taken after 20 min indicate that at low concentrations the albumin will selectively absorb at the polymer interface, but at higher concentrations the absorption on the PMMA and PS components will increase ( Fig. 42.12) [115]. Similarly, at a given concentration, the albumin would start absorbing at the interface at the initial time point and at latter time points absorb on the PMMA and PS components.…”

“…Phase-separated mixtures of PMMA and PS were studied for protein adhesion using X-ray photoemission electron spectroscopy [113][114][115]. While not strictly a block copolymer, these mixture phase separate to form patterns that are similar to those found in block copolymers.…”