Real time observation of platelet adhesion to opaque biomaterial surfaces under shear flow conditions

We developed a new system which enables direct observation of platelet adhe sion on opaque biomaterials under shear flow conditions, by combining a thi n quartz cone which produces laminar shear flows, with an upright epifluore scence microscope which visualizes stained platelets through the rotating c one. This is the first report on the observation of platelets adhered to op aque biomaterials in real time under shear flow conditions. The direct obse rvation of platelet adhesion to expanded polytetrafluoroethylene (ePTFE) as an opaque biomaterial revealed that the kinetics of platelet adhesion to e PTFE depended greatly on shear stresses, showing that the shear stress of 5 .0 dyne/cm(2) induced higher adhesiveness of platelets to ePTFE than that o f either 0.1 or 15 dyne/cm(2). The observation also showed a difference in platelet adhesiveness among ePTFEs with different fibril lengths-0, 3.2, 18 , and 35 mu m-indicating that ePTFEs with shorter fibril length had lower a dhesiveness of platelets under a shear stress of 5.0 dyne/cm(2). It is indi spensable for analyzing the phenomena of platelet adhesion to opaque biomat erials to observe in real-time rolling, adhesion, and detachment of platele ts under shear stresses without disturbing shear flow conditions. The resul ts showed that the mechanical and optical design of the system could serve this purpose. (C) 1999 John Wiley & Sons, Inc.