Thrombocytes adhesiveness

The most important parameters to characterize blood compatibility are thrombocyte adhesion and thrombocyte number. In contact with a foreign body platelets tend to adhere similarly as in the case of an external injury. For this reason materials which show strong platelet adhesion as a consequence of their contact with a foreign body or provoke a decrease in the munber of blood platelets are considered as thrombogenic [94]. The decrease in the quantity of blood leucocytes after contact with a foreign body is a sign of a cellular immunore-sponse of the biological system toward the biomaterial. 

A number of polymer surface parameters, e.g. surface free energy and surface charge, are responsible for blood interaction phenomena. Regarding the correlation of hydrophilidty and thrombocyte adhesion, Ikada et al. determined a maximum of thrombocyte adhesion for a contact angle region between 60 and 80° [95]. Van Wachem et al. showed that the best blood compatibility of polymer blends is achieved for moderate wettability [96]. The influence of polar and dispersive components of the surface tension on blood compatibility was described by Kaelble and Coleman [97,98]. They found that polymers with high dispersive (y ) and low polar components (yP) of surface tension show better blood compatibility than polymers with low dispersive interactions. Furthermore, a nega-... 

Fig. 18. SEM micrographs of the thrombocyte adhesion on poly(ether sulfone) (PES) HEMA-grafted PES (HEMA-PES) and the negative control polyetherurethane (PUR), magnification x600...

Haematologic In a placebo-controlled, single-blind cross-over study of 3-day cycles separated by washout periods of at least 12 days in 30 healthy individuals, the interaction on antithrombotic effect between acetylsalicylic acid (ASA) and nsNSAIDs (including naproxen 500 mg twice daily, ibuprofen 600 mg daily, meloxicam 15 mg daily and etoricoxib 90 mg daily) taken 2h before ASA (320 mg) was evaluated. Ibuprofen and naproxen inhibited ASA s antithrombocyte effect below the nonresponse threshold. Etoricoxib and meloxicam did not cause relevant changes in ASA thrombocyte inhibition. Naproxen had an inherent weak thrombocyte inhibitory action below the ASA response threshold. This study showed that COX-1 affinity determines the pharmacodynamic interaction between NSAIDs and ASA on the main fxmctions of the thrombocyte adhesion and aggregation. Ibuprofen and also naproxen inhibited ASA s thrombocyte effect... 

The endothelial cells of the intima fulfil a host of tasks the endothelial layer is responsible for the transport of materials from the blood through the production of nitric oxide and the associated vasodilation it regulates blood pressure in addition, it has antithrombotic properties by preventing excessive adhesion of thrombocytes and leukocytes. 

Comparable with red blood cells, desialylation of platelets leads to a rapid removal from the circulation (Choi et al. 1972, Greenberg et al. 1979). Despite contradictory results (Nurden and Caen 1976, Gartner et al. 1977, Patschke et al. 1977), there are valid indications that membrane-bound sialic acid does play an important role in the adhesion and aggregation of thrombocytes. (For further details see section IV, Blood Clotting.)... 

---