A new method for continuous measurement of platelet adhesion under flow conditions

Platelet adhesion to the subendothelial tissue or biomaterial surface is an initial step in the formation of the hemostatic plug or thrombus. To clarify the mechanism of platelet adhesion in vivo, a simple and reproducible method for quantitation of platelet adhesion under flow conditions is required. In this study, a mechanical device for continuous recording of platelet adhesion under flow conditions using a quartz crystal microbalance was developed, an extremely sensitive sensor capable of measuring mass changes in the nanogram range. The relationship between surface mass change (ΔW) and resonant frequency change (Δf) for piezoelectric crystals is given by the Sauerbrey equation: Δf = f(O²)ΔW/NAπ (f(O); fundamental frequency (5MHz) A; the area of quartz plate undergoing oscillation N; frequency constant for AT-cut quartz crystal π; density of quartz crystal). Although the perfusion of buffer solution alone or addition of washed red cell suspension (Ht 30%) and formaldehyde-fixed platelets have no effect on Δf, addition of washed platelets in the presence of red cells caused an increase in Δf. To confirm that the increase in Δf results from platelet adhesion to the material surface, adherent and subsequently aggregated platelets were visualized by fluorescence microscopy using fluorescein-isothiocyanate labeled antiplatelet membrane glycoprotein Ib monoclonal antibody. There was a good correlation between the increase in Δf and the extent of platelet adhesion and subsequent aggregation. These results may indicate that this newly developed apparatus will be helpful for continuous measurement of platelet adhesion.