AVS 47th International Symposium
    Biomaterial Interfaces Wednesday Sessions
       Session BI-WeP

Paper BI-WeP15
Soft X-ray Spectromicroscopy of Protein Adsorption on Polyurethanes

Wednesday, October 4, 2000, 11:00 am, Room Exhibit Hall C & D

Session: Poster Session
Presenter: C. Morin, McMaster University, Canada
Authors: C. Morin, McMaster University, Canada
A.P. Hitchcock, McMaster University, Canada
I.N. Koprinarov, McMaster University, Canada
R. Cornelius, McMaster University, Canada
J.L. Brash, McMaster University, Canada
Correspondent: Click to Email
New quantitative techniques for chemical microanalysis which allow detailed study of protein polymer interactions are required for biomaterial interface optimization. We are particularly interested in identification of possible preferences of first sites of protein attachment to polyurethane polymers used in blood contact medical applications. We are exploring Scanning Transmission X-Ray Microscopy (STXM) and Photoemission Electron Microscopy (PEEM) in this context. These techniques use near edge X-ray absorption spectroscopy (NEXAFS) for chemical identification. Both techniques have been used to map albumin and fibrinogen adsorbed on various polymer surfaces. As an example, STXM was used to study protein adsorption from a 0.1 mg/ml albumin solution onto a TDI-based, high-ether polyurethane film (~100 nm thick) which had submicron phase segregated regions of a highly aromatic polyisocyanate polyaddition product (PIPA) reinforcement material. Image sequences recorded throughout the C 1s and N 1s regions were used to generate composition maps by fitting the spectrum at each pixel to spectra of pure reference materials. The strong amide carbonyl resonance at 288.2 eV provides a sufficiently strong signature of protein to allow mapping down to monolayer levels even though the STXM results average over the full thickness of the polymer and protein sample. PEEM studies on similar materials provide greater surface sensitivity but are complicated by high sensitivity to topography as well as charging artefacts. Results from the two techniques will be compared to illustrate the strengths and weakness of these soft X-ray spectromicroscopy techniques when applied to biomaterials problems. X-ray microscopy is carried out at the Advanced Light Source (supported by DoE under contract DE-AC03-76SF00098), supported financially by NSERC (Canada).