Drift and fluctuating motion of artificial platelet during adhesion process near the wall

To obtain long trajectories including lateral motion, we built a travelling stage of microscope for tracking particles moving through flow channel and estimated the lateral motion which contributes to NWE and adhesion. We employed recombinant Glycoprotein Ib alpha conjugated latex beads (rGPIbalpha-LB) as platelet substitute. These particles were observed at wall shear rate (WSR) of 200, 500, and 1000 /s with hematocrit of 0 and 40% of washed red blood cells in rectangular flow channel which had vWf surface. We tracked the particle as Lagrangian method and separated the trajectory of particle with drift and fluctuating motion, and investigated quantitatively the motion which contributes to NWE and adhesion to the wall surface. Trajectories of rGPIbalpha-LB were tracked from obtained movies. Then lateral gradient which reflects a drift motion of the particle toward the wall and dispersion coefficient which reflects a fluctuating motion of the particle were calculated. The rGPIbalpha-LB moved only along axial direction with 0% hematocrit. As hematocrit increases, rGPIbalpha-LB moved toward near the wall (about 0.9R) and the position was similar to that of NWE in previous studies. The dispersion coefficient increased near the wall and as WSR and hematocrit increased. In the near wall region, adhered particles showed significantly a tendency toward the wall and high fluctuating motion compared with non-contact particles. We concluded the particle which has drift motion toward the wall with high fluctuating motion induced by the presence of RBC and high shear contributes to interact to the wall surface and adhesion from NWE region.