IUVSTA 15th International Vacuum Congress (IVC-15), AVS 48th International Symposium (AVS-48), 11th International Conference on Solid Surfaces (ICSS-11)
    Biomaterials Tuesday Sessions
       Session BI-TuA

Invited Paper BI-TuA1
Surface Forces and Coating Properties Involved in Protein Repellency

Tuesday, October 30, 2001, 2:00 pm, Room 102

Session: Non Fouling Surfaces and Theoretical Concepts
Presenter: H.J. Griesser, CSIRO, Molecular Science, Australia
Authors: P. Kingshott, CSIRO, Molecular Science, Australia
H. Thissen, CSIRO, Molecular Science, Australia
L. Meagher, CSIRO, Molecular Science, Australia
P. Hamilton-Brown, CSIRO, Molecular Science, Australia
H.J. Griesser, CSIRO, Molecular Science, Australia
Correspondent: Click to Email
PEO coatings have attracted much interest as non-fouling coatings. However, literature data show varying extents of reduction in protein adsorption with PEO coatings prepared in various ways, and use of techniques that may not always have been sufficiently sensitive to support claims of non-fouling (as opposed to low-fouling). We have immobilized PEG chains of different lengths onto surfaces with different densities of pinning groups and at room temperature as well as under cloud point conditions to study how these parameters affects macromolecular conformations and protein resistance. We have also investigated the limits of detection of adsorbed proteins on the 'best' coatings by the sensitive surface analytical methos XPS, ToF-SSIMS and MALDI. Cell colonization was found to be totally inhibited and this could be attributed to the inability of fibronectin and vitronectin to adsorb to the coating. Using a laser ablation technique, patterns were then created of cell-adhesive islands within a PEO-coated surface area. It was shown that the cells recognized edges with high precision. Finally, surface force curves were acquired using a colloid-modified AFM tip in order to probe for the interfacial forces that contribute to incomplete or complete protein repellency. Our PEO coatings differ markedly in structure and some properties from oligo-EO coatings prepared by SAM methodology, yet give analogous results in terms of resistance to fouling. Based on this and data with polysaccharides (Hartley et al, this meeting) we speculate that protein resistance does not require a 'magic' chemistry or a fully extended 'brush' structure; a highly hydrated coating that possesses a repulsive surface force due to steric-entropic-osmotic effects on compression, of sufficient magnitude and range to screen attractive van der Waals and electrostatic forces emanating from the substrate, is sufficient. The chemical composition may not matter as long as the coating is well hydrated and of a minimal thickness, and protein repellency may solely be a result of appropriate physico-chemical properties. Moreover, charge neutrality is required, as negatively charged coatings such as hyaluronan are effective only against some fouling situations. For insance our PEO coatings are neutral and screen substrate charges, thus repelling proteins of both charge signs.