AVS 47th International Symposium
    Biomaterial Interfaces Tuesday Sessions
       Session BI-TuM

Paper BI-TuM6
How to Make and Analyze Cross-linked Monolayers of Mytilus Edulis Foot Proteins (Mefp)

Tuesday, October 3, 2000, 10:00 am, Room 202

Session: Protein-Surface Interactions
Presenter: H. Elwing, Lab of Interface Biophysics, Sweden
Authors: H. Elwing, Lab of Interface Biophysics, Sweden
K. Mjorn, Lab of Interface Biophysics, Sweden
K. Uvdal, Linkoping University, Sweden
M. Fahlman, Linkoping University, Sweden
J Lausmaa, National Testing and Res. Institute, Sweden
F. Hook, Lab of Interface Biophysics, Sweden
Correspondent: Click to Email
The Mefp proteins are potential candidates as "tissue glues" in biomaterial applications. Several of the Mepf proteins contain high amounts of DOPA (dihydroxyphenylalanin). On oxidation to o-quinone the DOPA molecules become highly reactive and forms a base for cross-linking of the proteins in the byssus threads as well as binding to solid surfaces. We have developed an experimental model consisting of polar siliconoxide surfaces and apolar alkanethiol surfaces. On this surfaces we follow adsorption of purified Mefp-1 with the use of optical methods such as surface plasmon resonance (SPR) and high precision ellipsometry. Periodate induced crosslinking of the molecular layers is then followed by Quarts crystal microbalance (QCM-D) and ellipsometry. At apolar surfaces we found a reduction of layer thickness from about 20 nm to about 4 nm as well as a significant reduction of the viscoelastic properties of the protein layers as measured by QCM-D. On the other hand, adsorption of Mefp-1 on polar surfaces res ulted in a protein layer that was thin and dense from the beginning and cross-linking resulted only in significant small change of layer thickness and viscoelasticity of the mefp-1 layer. It was obvious that adsorption of Mefp-1 to polar surfaces significantly reduced the possibility of cross-linking most probably due to binding engagement of the DOPA side chains to the silicon oxide surface. We also made an analysis with photoelectron spectroscopy (XPS). High-resolution spectra at normal and glancing take off angles were obtained with a particular emphasis placed on the C 1s core level. Four distinct peaks were visible in the non-deconvoluted spectrum. Carbon-nitrogen and carbon-oxygen bonds were studied as a function of depth, crosslinking and the polarity of the substrate. Significant differences were found and is now subjected to a more detailed analysis together with data from time of flight secondary ion spectroscopy (TOF-SIMS).