Platelet PhysiologyBlood platelets interact with a variety of soluble agonists such as epinephrine (EPI), adenosine diphosphate (ADP), thrombin, and thromboxane (TXA2) and many cell matrix components, including collagen, laminin, fibronectin, and von Willebrand factor and biomaterials used for construction of invasive medical devices [21???26].