Blood response hydrophobic materials

The most widely studied synthetic polymers for blood contact applications are polyether urethane ureas ( Biomer (Ethicon)). These materials have been used in artificial hearts, as coatings for lead wires in pacemakers, have been used and are being considered for blood vessel prostheses. The success of these materials is believed to be due to preferential adsorption of albumin rather than globulin or fibrinogen which promote a clotting response. However, these materials are hydrophobic and questions of long-term effectiveness are unresolved. Particularly, these materials may shed emboli or may be susceptible to surface calcification. Thus, it may be desirable to have synthetic polymers which are hydrophilic and better resemble blood vessels [475]. 

Previous experience with polystyrene-type adsorbent materials (Amberhte XAD-4) in clinical hemoperfusion was characterized by significant bioincompatible responses such as complement activation and sharp drop of white blood cell (WBC) and platelet counts (neutropenia and thrombocytopenia). This was believed to be due to the hydrophobic nature of the polystyrene surface. Similar problems were also noted with activated carbon adsorbents. The biocompatibility of both materials needed to be improved by applying more hydrophilic polymers as surface... 

Polyurethanes, due in part to their flexibility and toughness, are perhaps the polymer of choice for ventricular assist devices and blood pumps. Consequently, they have received considerable interest as bloodcontacting materials. In nonhuman primates, those polyurethanes, such as Pellethane , which exhibit the most hydrophobic surface chemistry produce the least platelet consumption [12]. In dogs, early platelet interactions with polyurethanes vary considerably although relationships to polymer surface chemistry remain unclear [13]. Thus while polyurethanes are chemically versatile and possess many desirable mechanical properties, it is generally not possible to predict their biologic responses in humans. 

---