Assessment of the efficacy of tissue factor pathway inhibitor (TFPI) immobilized on glass slides to inhibit factor Xa under flow conditions

The purpose of the present study was to assess the efficacy of tissue factor pathway inhibitor (TFPI) immobilized on glass slides to inhibit factor Xa (FXa) under well defined flow conditions. Employing a parallel plate flow chamber, FXa was perfused over TFPI coated or uncoated glass slides. Wall shear rates of 50, 100, 400, and 1200 s^-1 were tested and the effluent was collected and assayed for FXa. Experiments were also carried out to determine the retention of adsorbed TFPI on the glass surfaces. FXa flux was calculated for the various shear rates used during the apparent steady state regime. There was a significant difference between these flux values in the untreated versus TFPI treated glass slides at all the shear rates (p<0.05). Increasing, the mass of adsorbed TFPI also significantly increased this inhibition. There was no measurable loss of adsorbed TFPI from the glass slides for all the conditions studied.