Carbon Nanotubes Activate Blood Platelets by Inducing Extracellular Ca²⁺ Influx Sensitive to Calcium Entry Inhibitors

To elucidate a mechanism of prothrombotic effects of carbon nanotubes (CNTs), we report here that multiwalled CNTs activate blood platelets by inducing extracellular Ca(2+) influx that could be inhibited by calcium channel blockers SKF 96365 and 2-APB. We also demonstrate platelet aggregating activity of different single-walled and multiwalled CNTs. In addition, we show that CNT-induced platelet activation is associated with a marked release of platelet membrane microparticles positive for the granular secretion markers CD62P and CD63.