Platelet activation biomaterials

The in vitro study of the hemocompatibility of biomaterials requires the consideration of many parameters, static or dynamic contact, flow rate, wall shear rate, form of biomaterial to be tested, pathway to consider (platelet adhesion, platelet activation, complement activation, contact phase activation etc..) and duration of contact(39). It has previously been demonstrated t t hemodynamic circumstances play a significant role in determining localization, growth and fiagmentation of thrombi and platelet adhesion in vivo, and that flow rate controls platelet transport to a surface and their adhesion (40). This evidence is siqtpoited by observed differences in platelet activity predominance in venous and arterial flow (41). Qearly, defining the blood compatibility of a material is a conqrromise between a number of these factors. 

The suitable materials for the above mentioned domains are polymers, metals and ceramics. Among these, polymers play an important role. Even the polymers have a lot of remarkable properties that could be used in biomaterials design, the interaction between these artificial materials and tissues and blood could create serious medical problems such as clot formation, activating of platelets, and occlusion of tubes for dialysis or vascular grafts. In the last few years, novel techniques of synthesis have been used to correlate desirable chemical, physical and biological properties of biomaterials. 

Biomaterial with immobilized prostaglandins show excellent antithrombotic effects by inhibition platelet aggregation [77-81]. However, some of the prostaglandins are too unstable to use. In our study, a stable and biologically active prostacyclin derivative TRK-100 (shown in Scheme 10) was used. 

Dr. Thomas Chandy is a research associate in the Division of Chemical Engineering Material Sciences, Biomedical Engineering Institute and Interventional Cardiology Laboratories at the University of Minnesota. He has over two decades research experience at Sri Chlia Tvunal Institute for Medical Sciences Technology, Trivandrum, India, in the area of biomaterial surface engineering and blood biomaterial interactions. More recently. Dr. Chandy and Dr. Rao have focused their research on platelet biomaterial interactiorrs and development of assist devices for cardiovascular applications. They continue to be active in this newly evolving area of research. 

A similar series of experiments concerned a blend of a terpolymer of PVC with a cationic elastomer, containing or not ionically bound heparin. Perfusion with washed platelet suspensions, under conditions excluding thrombin generation from plasma, demonstrated the activation of platelets by heparin 3U), as reflected in a parallel increase in platelet deposition and RTG secretion (Table V). The perfusion system thus offers a simple means of in vitro screening of biomaterials for short term interactions with platelets and plasma proteins. 

In spite of the desirable characteristics of the biomaterials used in the heart valve prostheses, problems with thrombo-embolic complications are significant with implanted valves and patients with mechanical valves are under long-term anticoagulant therapy. The mechanical stresses induced by the flow of blood across the valve prostheses have been finked to the lysis and activation of fornied elements of blood (red blood cells, white blood cells, and platelets) resulting in the deposition of thrombi in regions with... 

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