Interaction of endothelial cells with plasma-polymer modified surfaces

Endothelialisation of implantable vascular grafts and stents is directed by the adsorbed protein layer. Chemical and mechanical cues sensed at the biomaterial surface by endothelial cells determine their attachment, survival and proliferation. Given the multiplicity of possible interactions we describe the novel application of live cell imaging, factorial analysis and single molecule imaging to investigate higher order interactions between surface chemistry and adsorbed proteins influencing endothelial cell (EC) adhesion dynamics. EC fates were tracked by time-lapse imaging of cell contact area on plasma polymer modified surfaces. The combinatorial effect of plasma polymer chemistry and adsorbed proteins was characterised by factorial experimental design and analysis. Single molecule imaging and counting was used for the first time to quantify binding of fluorescently labelled albumin to plasma polymerized surfaces: Modified glass surfaces with thin plasma polymer coatings rich in primary amine groups had a high affinity for albumin (-2, 650 molecules/iim2) while plasma polymer surfaces functionalised with hydroxyl groups had very low levels of albumin binding (22-30 molecules/ m2). Plasma polymer coatings rich in primary amine groups also promoted endothelial cell adhesion and was superior to tissue culture plastic. An interaction between albumin, heparin and fibronectin promoted adhesion to amine plasma polymer coated glass, while hydroxyl plasma polymer coated glass prevented EC attachment. Tracking cell-specific interactions with the adsorbed protein layer by time-lapse microscopy is more predictive of in vivo cellular responses to biomaterials compared to studies that only measure protein adsorption.