Interaction of Platelets with Model Surfaces III: Platelet Reaction with Synthetic Polymers

Blood/material surface interactions have been studied by passing citrated whole blood over beads in a column and examining the resultant activation of platelets and coagulation factors. Examination of many polymer and some crystalline surfaces indicates that platelet adhesion occurs with all surfaces except after pretreatment with albumin in some instances. Induction of the platelet release reaction and platelet adhesion vary from one surface to another and are not well correlated. The release reaction in response to some but not all surfaces can be blocked by pretreatment of blood with aspirin in vivo and indomethacin in vitro. PRP exhibits less activation than whole blood, but varying the hematocrit of whole blood from 23 to 53% does not change surface reactivity.

Of the materials studied, polyethylacrylate (PEA) and polymethylacrylate (PMA) appear least reactive. Certain materials, e.g. polystyrene and polyvinylacetate, exhibit variable surface reactivity with different blood samples, while others, e.g. pyrolytic carbon and PMA, produce a uniform response. A general trend appears to be less surface reactivity with decreasing glass transition temperature. Chemical modification of polymers and production of copolymers has been undertaken to define the nature of reactive sites. For example, acrylonitrile and aminomethylacrylate copolymers of PMA exhibit more reactivity than PMA.

Sepharose 4B (4% agarose gel beads) appears essentially non-reactive. However, Sepharose with covalently bound heparin promotes extensive platelet adhesion. Pretreatment of this surface with increasing amounts of plasma, but not albumin, produces decreasing surface reactivity.