Aging of plasma treated surfaces and their effects on platelet adhesion and activation

Improving hemocompatibility of blood connecting devices is one of the key issues in biomaterial science. To prevent and study the effects of platelet adhesion and activation on polyethylene terephthalate (PET), a highly non-equilibrium oxygen plasma was used. Surface analyzing techniques confirmed that incorporation of oxygen functional groups, achieved by treatment with oxygen plasma, changed the surface character of PET from hydrophobic to hydrophilic. Moreover, plasma modifies the surface morphology and increases surface roughness of PET. It was shown that such surface modification has a significant effect on platelet adhesion and activation. Even a short exposure of PET surface to highly non-equilibrium plasma reduced adhesion and activation of platelets mainly through oxygen surface functionalization. However effects of plasma treatment diminish with time and many oxygen functional groups are lost from the surface within 3 h of aging. It was shown that aging of plasma treated PET is highly affected by the storage conditions. Thus the main objective of our work was to study these aging effects on platelet adhesion after storage of PET in the air, in deionized water and in phosphate buffered saline. According to the surface analysis, the samples stored in the air showed the least aging effects, as they contained the lowest number of adhered platelets.