AVS 46th International Symposium
    Biomaterial Interfaces Group Tuesday Sessions
       Session BI-TuP

Paper BI-TuP4
Soft X-ray Spectromicroscopy Studies of Protein-Polymer Interactions

Tuesday, October 26, 1999, 5:30 pm, Room 4C

Session: Poster Session
Presenter: A.P. Hitchcock, McMaster University, Canada
Authors: A.P. Hitchcock, McMaster University, Canada
T. Tyliszczak, McMaster University, Canada
Y.M. Heng, McMaster University, Canada
R. Cornelius, McMaster University, Canada
J.L. Brash, McMaster University, Canada
H.W. Ade, North Carolina State University
Correspondent: Click to Email
Soft X-ray microscopy and micro-spectroscopy has considerable potential for characterizing the interaction of biological molecules with the surfaces of polymers used for biomaterials applications such as blood contact. We are exploring the use of scanning transmission X-ray microscopy (STXM) and various surface-sensitive X-ray microscopies - photoelectron emission microscopy (PEEM), scanning photoelectron microscopy (SPEM), and electron yield detection in STXM - for characterizing phase segregation at surfaces of polymers used for biomaterials applications, and for investigating specificity of cell and protein interactions with polymer surfaces. Transmission mode (STXM) has been used to study multilayer albumin adsorption on a polyurethane thin film which had micron-scale phase segregation. C 1s and N 1s STXM images and spectra recorded before and after protein exposure demonstrate that C 1s absorption spectroscopy differentiates protein, hard segment (urea), and soft segment (polyether) polyurethane signals and can locate proteins relative to an underlying phase segregated polymer. The strong C 1s -> @pi@*(C=O) excitation at 288.3 eV was found to be sufficiently well separated from the spectral features of the underlying polyurethane that considerable sensitivity to protein is achieved. The results clearly demonstrate that NEXAFS microscopy is relevant to biomaterials problems and that spatial segregation of protein does occur on phase separated polymers. Results to date suggest that albumin prefers the aromatic hard segment rather than the aliphatic soft segment regions of polyurethanes. The status of efforts to develop surface sensitive detection using total electron yield in STXM will also be discussed. X-ray microscopy is carried out at the Advanced Light Source (supported by DoE under contract DE-AC03-76SF00098), supported financially by NSERC (Canada).