Leukocyte interactions with surface modified biomaterials on in vitro flow conditions

Investigating the influence of modified biomaterials on leukocyte activation we used a dynamic model approaching flow conditions of extracorporeal circulation. Four different surface modifications (three heparin and one non-heparin coatings) were compared to each other and native control material, which is routinely used in cardiopulmonary bypass and extracorporeal circulation. Fresh human donor blood was heparinized and recirculated for 180 min in a tubing circuit with an integrated blood filter and a roller pump.Leukocyte number, differential blood analyses, elastase and anaphylatoxin C5a were determined to investigate the effects of blood/surface contact on leukocytes.Leukocyte stimulation was reduced in different amount compared to the control depending on the coating method. Heparin coatings showed a slight drop of monocyte and granulocyte percentage after 180 min of perfusion, whereas the control and the non-heparin modification induced a larger decrease. Elastase and C5a concentrations detected differences between the modifications themselves. C5a and elastase increased in each case in the course of the perfusion time.We conclude that heparin coatings induce less leukocyte activation than the native control material. The effect of biomaterials on leukocyte activation depends on the type of the coating method. It is shown that the flow model is suitable for investigations on leukocytes under hemodynamic flow conditions similar to those usual in clinical application.