Blood platelet adhesion to protein studied by on-line acoustic wave sensor

The attachment of blood platelets to the surface of bare and protein-coated thickness-shear mode acoustic wave devices operating in a flow-through con figuration has been studied. Platelets in washed form bind to the gold elec trodes of such sensors, but the resulting frequency shifts are far less tha n predicted by the conventional mass-based model of device operation. Adher ence to albumin and various types of collagen can be produced by on-line in troduction of protein or by a pre-coating strategy. Differences in attachme nt of platelets to collagen types I and IV and the Horm variety can be dete cted. Platelets attached to collagen yield an interesting delayed, but reve rsible signal on exposure to a flowing medium of low pH. Scanning electron microscopy of sensor surfaces at various time points in this experiment rev eals that originally intact platelets are eventually destroyed by the high acidity of the medium. The reversible frequency is attributed to the presen ce of removable platelet granular components at the sensor-liquid interface .