Flow-induced detachment of adherent platelets from fibrinogen-coated surface

Abstract

A study of the shear forces under which adherent platelets of different morphologies can be detached from surfaces was carried out using a newly designed tapered flow chamber, which covered the entire shear range of physiological circulation. Platelets that naturally settled on a fibrinogen-coated surface were exposed to shear flow and were subsequently processed for scanning electron microscopic observation. We found that 1) the density of platelets remaining after flow exposure decreased with local shear stress, 2) adherent platelets of different morphologies withstood different levels of shear stress: most round cells and 40% of the cells that had a few short pseudopods were detached at < 10 dyn/cm2, whereas most spread cells could withstand 50 dyn/cm2, 3) pulsatile flow was more effective in removing adherent platelets than equivalent steady flow, 4) cytochalasin D and colchicine retarded platelet shape change and made them more easily detached by shear forces, and 5) metabolic energy-depleted platelets spread readily and formed shear-resistant clumps. Our observations indicated that adherent platelets of different morphologies on a fibrinogen-coated surface could withstand different levels of flow shear stress.

Experimental Study of Fibrin/Fibrin-Specific Molecular Interactions Using a Sphere/Plane Adhesion Model

“…In addition, the procedure for fibrin immobilization used a silane coupling agent associated with polyglutaraldehyde. Thus, in contrast to meshworks prepared by spraying or adsorption of fibrinogen (17,11,18), where immobilization of fibrinogen takes place by nonspecific physisorption resulting in conformational changes (48,49), the conformation of fibrinogen was preseved as indicated by immunological studies (25,29), and a firm attachment through covalent interactions was obtained.…”

“…This simplified approach has been followed recently by three different teams (16)(17)(18). However, their studies have been focused mainly on biochemical aspects.…”

Obstacles in Haemocompatibility Testing

“…However, when the flow was further increased to simulate the conditions of coronary arteries at 3.2 N/m 2 , platelet numbers at hydrophilic surfaces were significantly reduced as compared with hydrophobic surfaces [167]. These results strongly suggest detachment of platelets from hydrophilic surfaces, which can be explained by the small contact area of platelets [168]. Furthermore, the platelets attached to hydrophilic surfaces remain spherical and thus experience higher shear forces.…”

“…In contrast, platelets on hydrophobic materials can withstand high shear forces due to strong contact and complete spreading of platelets. When examined with scanning electron microscopy, the platelets on hydrophobic surfaces were indeed more extended like a pancake than on similar material with hydrophilic characteristics [168]. It can be concluded that under conditions of arterial flow, especially at hydrophilic surfaces, less platelets adhere after 15 min due to detachment [169].…”

Computational Model of Device-Induced Thrombosis and Thromboembolism

“…Further, the embolization of single platelets has been reported to be a strong function of surface chemistry and shear rate. 27,49 Thus, for this model, an exponential single-platelet embolization term was included. Thrombus embolization is also well documented and has been shown 19 to be cyclic and significant.…”