Blood compatibility, surface design

Blood-compatible polymer materials are required to inhibit both platelet adhesion and coagulation just as the endothelial on the polymer surface. It is known that there are many investigations in the design and the synthesis of socalled antithrombogenic materials. The immobilization of biologically active substances such as heparin [74, 75], urokinase [76], and prostaglandins [77-81] is one of the practical approaches. 

In vitro flow systems such as flow cells and recirculating flow tubes are usually of short duration, minutes to hours, and thus may not adequately assess blood component interactions with test materials. Flow is an important parameter that must be designed into each test model utilized for hematocompatibiUty. In additions, in vitro, ex vivo, and in vivo test systems must also consider and, if possible, evaluate the extent of thromboembo-lization that is present. In the past, dean test surfaces have been considered blood compatible when, in fact, significant thrombus formation has occurred with thromboembolization under flow leading to the so-called dean surface and interpretation of blood compatibility. Nonadherence of blood components does not necessarily imply hematocompatibiUty. 

Sagnella S, Mai-Ngam K. Chitosan based surfactant polymers designed to improve blood compatibility on biomaterials. Colloids SurfB Biointerfaces May 2005 42(2) 147-55. Wang Y, Hong Q, Chen Y, et al. Surface properties of polyurethanes modified by bioactive polysaccharide-based polyelectrolyte multilayers. Colloids Surf B Biointerfaces December 2012 100 77-83. 

The surface property of these materials can be divided into three general categories 1) smooth, nonpermeable, 2) porous or rough, and 3) biolized. Among the various factors to be considered for candidate materials, the two most important are mechanical durability and blood compatibility, particularly antithrombogenicity This paper will present an historical review of plastic materials used for the fabrication of blood pumps, with the emphasis on antithrombogenicity not only in relation to the material itself, but also with respect to its design and fabrication. 

Nyilas (51) has similarly studied these differences in surface chemical composition. More importantly, he has shown significant differences in the Lee-White clotting time and prothrombin time for the air side versus the substrate side. The air-facing side demonstrated superior blood compatibility compared to the substrate side. For this reason fabrication regimens are usually designed so that blood contacting surfaces are from the air side. This is easily accomplished by at least one additional coating of the blood contact surfaces after they are removed from the mold. 

New concepts for making blood compatible polymer materials have been proposed based on the characteristics of natural phospholipid molecules in plasma. It was considered that if a polymer surface possesses a phospholipid-like structure, a large amount of natural phospholipids in plasma can be adsorbed on the surface by their self-assembling character. Based on this idea, a methacrylate monomer with a phospholipid polar group, 2-methacryloyloxy ethyl phosphorylcholine (MFC), was designed and synthesized The polymers, composed of MFC and various alkyl methacrylates (as shown in Fig. 1) or styrene derivatives were prepared and their blood compatibility carefully evaluated ". Flatelet adhesion and activation were significantly suppressed on the surface of the MFC polymers when the MFC composition was above 30 mol%. These excellent... 

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