Characterization of Biomaterials by Soft X-Ray Spectromicroscopy

Abstract

Synchrotron-based soft X-ray spectromicroscopy techniques are emerging as useful tools to characterize potentially biocompatible materials and to probe protein interactions with model biomaterial surfaces. Simultaneous quantitative chemical analysis of the near surface region of the candidate biomaterial, and adsorbed proteins, peptides or other biological species can be obtained at high spatial resolution via scanning transmission X-ray microscopy (STXM) and X-ray photoemission electron microscopy (X-PEEM). Both techniques use near-edge X-ray absorption fine structure (NEXAFS) spectral contrast for chemical identification and quantitation. The capabilities of STXM and X-PEEM for the analysis of biomaterials are reviewed and illustrated by three recent studies: (1) characterization of hydrophobic surfaces, including adsorption of fibrinogen (Fg) or human serum albumin (HSA) to hydrophobic polymeric thin films, (2) studies of HSA adsorption to biodegradable or potentially biocompatible polymers, and (3) studies of biomaterials under fully hydrated conditions. Other recent applications of STXM and X-PEEM to biomaterials are also reviewed.

Soft X-ray spectromicroscopy and ptychography

“…If an insulating organic film is sufficiently thin (in my experience, below 50 nm), there is sufficient electrical transport to a conductive substrate that the surface field is stable and imaging and spectromicroscopy can be performed. This mode has been used to study polymer thin films [45] as well as protein and peptide interactions with polymeric biomaterials [46]. In situations where the insulating material is too thick it is still possible to successfully perform XPEEM spectromicroscopy if the surface is modified to supply a lateral conducting metal layer with a region thinned to a few nm to enable electron escape from the underlying sample of interest [47].…”

“…SPEM provides the power and clarity of XPS for surface analysis. XPEEM is finding many useful applications in the area of thin film and surface analysis, as well as biomaterials [46] and biomineralization [47]. STXM is perhaps the most versatile of the four methods since it has been used to study a very wide range of sample types and processes, including picosecond magnetization dynamics [32].…”

Neutron and X‐Ray Techniques for Biological and Biomaterials Studies

“…In the buffer case due to the combination of the red PS and the blue Fg signal the PS phase exhibits a pink color (19 ± 5% Fg detected) while the PMMA domain significantly less protein is found (9 ± 5% Fg). Upon adhesion from water the protein adhesion is almost reversed: on the PS domains no protein is found while for PMMA 19 ± 5% Fg were found 173…”

STXM Characterization of PEM Fuel Cell Catalyst Layers

“…Soft X-ray scanning transmission microscopy (STXM) is a novel synchrotron based technique which is proving to be a very powerful tool for imaging and quantitative spatially resolved chemical mapping of soft materials such as polymers and biomaterials (3)(4)(5)(6). Recently it has been applied for analysis of the fuel cell MEA components (7)(8)(9)(10)(11).…”