| AVS 63rd International Symposium & Exhibition | |
| Nanometer-scale Science and Technology | Thursday Sessions |
| Session NS+BI-ThA |
| Session: | Applied Nanoscale Microscopy Techniques/Biomaterial Interfaces – New Advances |
| Presenter: | Michael Taylor, The University of Nottingham, UK |
| Authors: | M. Taylor, The University of Nottingham, UK M.R. Alexander, The University of Nottingham, UK M. Zelzer, National Physical Laboratory, UK |
| Correspondent: | Click to Email |
Over the last decade the beneficial properties of hydrogels as artificial cell culture supports have been extensively investigated1. Certain synthetic hydrogels have been proposed to be similar in composition and structure to the native extracellular matrix of the stem cell niche, their in vivo cell habitat, which is a powerful component in controlling stem cell fate2. The stem cell differentiation pathway taken is influenced by a number of factors. When culturing cells within or upon hydrogels this choice can be strongly dependent on the underlying 3D hydrogel chemistry which strongly influences hydrogel-cell interactions3. The interrelationship between hydrogel chemistry and that of biomolecules in controlling cellular response ideally requires analysis methods to characterise the chemistry without labels and often in 3D. Time-of-flight secondary ion mass spectrometry (ToF SIMS) has the potential to be utilised for through thickness characterisation of hydrogels. The frozen-hydrated sample format is well suited to minimise changes associated with dehydration or the chemical complexity of ‘fixation’, a challenging aspect in vacuum analysis conditions4. Frost formation can occur in the ambient atmosphere preventing ready depth profiling of the frozen hydrogels5. We develop a simple method to remove this frost by blowing with gas prior to entry into the instrument which is shown to produce remarkably good profiles on a poly(2-hydroxyethyl methacrylate) (pHEMA) hydrogel film where a model protein, lysozyme, is incorporated to demonstrate how biomolecule distribution within hydrogels can be determined. A comparison of lysozyme incorporation is made between the situation where the protein is present in the polymer dip coating solution and lysozyme is a component of the incubation medium. It is shown that protonated water clusters H(H2O)n+ where n=5-11 that are indicative of ice are detected through the entire thickness of the pHEMA and the lysozyme distribution through the pHEMA hydrogel films can be determined using the intensity of characteristic fragment secondary ions. We also expand the developed methodology to X-Ray Photoelectron Spectroscopy (XPS) for through thickness analysis of the similar pHEMA / lysozyme hydrogels, and show that lysozyme distribution can be quantitatively mapped in hydrogels.