Decreased tissue factor expression with increased CD11b upregulation on elastin-based biomaterial coatings

Elastin-like polypeptide (ELP) coatings have been shown to have non-thrombogenic properties both in vitro and in vivo. In this work, we expand our understanding of this phenomenon by investigating the interaction of these coatings with leukocytes. Citrated whole blood was exposed to a shear rate of 300 s^-1 for 2 hours at 37 °C on ELP1- and ELP4-coated polyethylene terephthalate (Mylar™) surfaces in a cone and plate device. Scanning electron microscopy and flow cytometry were used to measure leukocyte activation and platelet-leukocyte aggregation in response to the ELP1 and ELP4 coatings on the surface and in the bulk, respectively. Surface analysis showed little leukocyte activity on the surface of uncoated positive controls. Both the tissue factor (TF) expression (indicative of leukocyte activation) and CD61 expression (indicative of platelet-leukocyte aggregates), in the bulk were decreased by 40% and 20%, respectively, with the ELP coating of Mylar™, while a two- to three-fold increase in CD11b upregulation (indicative of leukocyte activation) for ELP1 and ELP4 was determined. Two of three bulk markers indicated that ELP-coated Mylar™ decreased the leukocyte response compared to the uncoated Mylar™, while the third, CD11b, indicated an increase in leukocyte response to the ELP coatings.