Protein-coated surfaces, platelet adhesion

Several investigators (9, 21, 22) have found that foreign surfaces, when exposed to blood, adsorb plasma proteins. Since platelet adhesion to the surface is the first observable event occurring in clotting on foreign surfaces, and since platelets are known to participate in hemostasis and coagulation, the indication is that platelet adhesion onto the plasma protein-coated surface plays a major role in the in vivo initiation of thrombus formation on foreign surfaces. 

Aspects of Platelet Adhesion to Protein-Coated Surfaces... 

The work to be discussed here deals with platelet adhesion to protein coated surfaces. The protein coating, the cells on the surface and the moving fluid adjacent to the surface may be viewed as a system of interacting components. Flow is an important feature of this system since it brings new protein and cells to the system, augments the transport of cells to the surface and can cause the detachment of adherent cells. Each component of the system may influence the conditions of the other components. The variation of the surface concentrations of proteins on a solid substrate continues to be studied and remains a key area of interest. However, the action of immobilized cells on the substrate needs to be examined more carefully as well as their contribution of secreted substances to the fluid phase adjacent to the substrate and to the substrate protein itself Red cells, platelets and white cells may also adhere and detach from the substrate changing its make-up by yet another mechanism. 

HoUow fibers are widely used for filtration, utilizing the semipermeable nature of their capillary walls. In the medical industry, hollow fiber bioreactors are often made from cellulose and synthetic polymers. Cellulose acetate and cuprammonium rayon are the widely used ceUulose-based hollow fibers, while synthetic hollow fibers are often made from polysulfone, polyamide, and polyacrylonitrile. Modifications can be made to these materials to improve their functions by using polymers based on phospholipid, a substance found in the human cell membrane. 2-methaCTyloyloxyethyl phosphoryl-choline (MPC) is a methacrylate monomer with a phospholipid polar group. When MPC-based copolymers are used as additives for polysulfone, protein adsorption and platelet adhesion can be effectively reduced, thereby improving blood compatibility. Cellulose acetate hollow fiber membranes can also be modified with MPC-based copolymers by means of blending or surface coating to obtain improved permeability. 

One possible objection to the comparison of protein adsorption on flat surfaces with platelet adhesion and activation in polymer-coated bead columns is raised by the work of Vroman et al. (28) who showed that protein adsorption onto surfaces from plasma in narrow... 

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