An X‐ray Spectromicroscopy Study of Albumin Adsorption to Crosslinked Polyethylene Oxide Films

Abstract

Polyethylene oxide (PEO) is a hydrophilic polymer commonly used in biomedical applications to reduce protein adsorption [1] or improve biocompatibility. [2] The effectiveness of PEO for reducing protein adsorption to surfaces likely arises from its molecular conformation in aqueous solution, with repulsive forces developed at certain separation distances resulting in a steric repulsion effect. [3][4][5][6][7] Furthermore, PEO density, chain length, conformation, lack of charge, and its interactions with water are known to affect protein resistance. [8][9][10][11] Since PEO is soluble in water, techniques such as g, [12] UV [13,14] and electron irradiation [15] have been employed to crosslink the PEO chains to prevent mass loss upon protein exposure. UV-initiated crosslinking of PEO with pentaerythritol triacrylate (PETA) or other radical crosslinkers [16] is becoming increasingly popular, since PEO can be crosslinked in both solution and solid state. [17,18] The inclusion of PETA to form crosslinked PEO has been used in biomedical applications such as hydrogels [19] and micelles [20] for drug delivery, or to form chemically patterned surfaces for cell studies. [21] However, to our knowledge, the effect of PETA crosslinker on the biocompatibility of PEO-based materials has not been systematically investigated.In this study, we use synchrotron-based X-ray photoemission electron microscopy (X-PEEM) for surface characterization of thin PEO films containing variable levels of PETA crosslinker. We then investigate the effect of the PETA on the adsorption of human serum albumin (HSA) to these surfaces. Previously, we used X-PEEM to study HSA adsorption to phase segregated polystyrene (PS)-poly(methyl methacrylate) (PMMA) [22][23][24][25][26] or PS-polylactide (PLA) [27] thin films. This study is part of an on-going effort to use X-PEEM and other techniques to obtain detailed information on the interfacial interactions of proteins by measuring the distribution of specific proteins over well-characterized, chemically segregated surfaces at high spatial resolution.

Ultrahigh-spatial-resolution chemical and magnetic imaging by laser-based photoemission electron microscopy

“…Because of its elemental, chemical, and spin-structure specificity, it is used by researchers from a variety of disciplines for composition mapping and analysis. [1][2][3][4] The spatial resolution of PEEM depends on the spherical-and chromatic-aberration coefficients of the electron lens. [5][6][7][8] Because the photoexcited primary and secondary electrons exhibit a broad energy distribution, the effect of chromatic aberration on the formation of the image is significant in the case of XPEEM.…”

Characterization of Biomaterials by Soft X-Ray Spectromicroscopy

“…PEO was blended with 1.5, 5 and 10 wt % PETA and spun cast onto Si(111) at 4000 rpm for 40 s. The films were then exposed to 0.05 mg/mL HSA for 20 min before vigorous washing and analysis with X-PEEM [ 33 ]. This study found that PETA is a surface active molecule.…”

“…It was found that PETA segregated to the substrate-air surface. Furthermore, HSA adsorption increased with increasing PETA concentration, showing that the protein resistance of PEO was reduced with increasing concentrations of PETA crosslinker [ 33 ].…”

Neutron and X‐Ray Techniques for Biological and Biomaterials Studies

“…Beside techniques like staining (e.g., dyes, radioactive), antibody binding, surface plasmon resonance (or techniques the like), contact angle measurements, FTIR, and AFM again X‐ray spectroscopy is a useful tool [e.g., X‐ray photoelectron spectroscopy (XPS). To obtain high spatial resolution with high element specificity also for the lighter but biologically relevant atoms (mainly the Cs1 spectrum) synchrotron X‐ray spectroscopy (e.g., scanning transmission X‐ray microscopy (STXM) and X‐ray photoemission electron microscopy (X‐PEEM)170, 171) is the method of choice. Use is made of the near‐edge X‐ray absorption fine structure (NEXAFS) which gives contrast for the identification of the chemical element and its bonding state.…”