| AVS 55th International Symposium & Exhibition | |
| Synchrotron-based Spectroscopy and Spectro-Microscopy Topical Conference | Tuesday Sessions |
| Session SY+SS+BI-TuA |
| Session: | Synchrotron-based Spectroscopy and Spectro-Microscopy |
| Presenter: | A.P. Hitchcock, McMaster University, Canada |
| Authors: | A.P. Hitchcock, McMaster University, Canada B.O. Leung, McMaster University, Canada J.L. Brash, McMaster University, Canada R. Cornelius, McMaster University, Canada A. Scholl, Lawrence Berkeley National Laboratory A. Doran, Lawrence Berkeley National Laboratory |
| Correspondent: | Click to Email |
The biocompatibility of a material is dependent on its surface characteristics and how they affect the protein layer which forms upon initial contact with blood or tissue since those proteins mediate subsequent cellular responses. Chemical, mechanical and spatial characteristics are known to play a role in controlling initial protein adsorption. Thus direct measurements of adsorption preferences on structured biomaterials are highly relevant to optimization of biocompatibility. We are using synchrotron based X-ray PhotoEmission Electron Microscopy (X-PEEM) and Scanning Transmission X-ray Microscopy (STXM) to study preferential adsorption of proteins (human serum albumin (HSA), fibrinogen (Fg)) and peptides (sub-6, a cationic antimicrobial) to several phase segregated polymer blend surfaces – PS/PMMA1,2 and PS/PLA. The X-ray absorption contrast is sufficient to identify and quantify the polymer and protein/peptide components, and peptides can be differentiated from proteins.3 Single or competitive adsorption is carried out under controlled concentrations, pH, buffer, temperature and exposure times. All of these factors affect adsorption. Image sequences measured in the C 1s, N 1s and O 1s regions are analyzed by pixel-by-pixel spectral fitting to reference spectra. The resulting component maps are placed on quantitative thickness scales, either intrinsically in STXM (when reference spectra are provided on quantitative linear absorbance scales), or by normalizing total signal to a 10 nm measured sampling depth in PEEM. For adsorption on PS/PMMA, under all conditions there is a strong preference to adsorb at the domain interphases, which are thermodynamically favored since both hydrophobic and hydrophilic interactions can be satisfied. Otherwise, HSA and Fg have a preference for PS over PMMA. When sub-6 and HSA are co-adsorbed at neutral pH, there is evidence that the site distribution is controlled by preferential adsorption of a solution complex.4 Under basic conditions (pH=11) this complex is unstable and the preferential adsorption becomes similar to that seen when each component is adsorbed independently.
1 C. Morin et al., J Electron Spec, 137 (2004) 785.
2 L. Li et al., J Phys Chem B 110 (2006) 16763, ibid, 112 (2008) 2150
3 J. Stewart-Ornstein et al., J. Phys. Chem. B 111 (2007) 7691
4 B.O. Leung et al., Biointerphases 2008, submitted.