The influence of surface roughness on the damage of von Willebrand Factor under shear flow condition

Despite technological advances in mechanical circulatory support devices to treat end-stage heart failure, blood damage induced by non-physiological shear stress in operation often triggered clinical hemocompatibility complications. The loss of high molecular weight von Willebrand Factor (HMW-VWF) has been considered as an essential cause of gastrointestinal bleeding. In addition to the mechanics factors, interface factors may also affect blood damage, especially the surface characteristics. In this study, the effect of surface roughness on VWF damage under flow condition was investigated. A roller pump circulation experimental platform with a roughness embedded sample chamber was constructed to provide blood shearing flow condition. VWF molecular weight analysis, VWF antigen (VWF-Ag) concentration assay, and VWF ristocetin cofactor activity (VWF-Rico) assay were performed on the sheared blood samples. These variables are the main functional indicators of VWF. It was found that the surface roughness induced VWF damage is mainly caused by the loss of HMW-VWF rather than reducing the total amount of VWF. The threshold value of surface roughness for a rapid increase in the degradation of HMW-VWF under low flow rate was obtained between Ra 0.4 and 0.6 μm, which was smaller than the threshold for hemolysis. Our findings indicated that VWF is more sensitive to the interface factor of surface roughness than red blood cells, thus has a higher requirement for blood pump design. It could provide reference for the material design and processing in developing mechanical circulatory support devices.