APPLICATION OF FLUID MECHANIC AND KINETIC-MODELS TO CHARACTERIZE MAMMALIAN-CELL DETACHMENT IN A RADIAL-FLOW CHAMBER

The strength of adhesion and dynamics of detachment of murine 3T3 fibr oblasts from self-assembled monolayers were measured in a radial-flow chamber (RFC) by applying models for fluid mechanics, adhesion strengt h probability distributions, and detachment kinetics. Four models for predicting fluid mechanics in a RFC were compared to evaluate the accu racy of each model and the significance of inlet effects. Analysis of these models indicated an outer region at large radial positions consi stent with creeping flow, an intermediate region influenced by inertia l dampening, and an inner region dominated by entrance effects from th e axially-oriented inlet. In accompanying experiments patterns of the fraction of cells resisting detachment were constructed for individual surfaces as a function of the applied shear stress and evaluated by c omparison with integrals of both a normal and a log-normal distributio n function. The two functions were equally appropriate, yielding simil ar estimates of the mean strength of adhesion. Further, varying the Re ynolds number in the inlet, Re-d, between 630 and 1480 (corresponding to volumetric flow rates between 0.9 and 2.1 mL/s) did not affect the mean strength of adhesion. For these same experiments, analysis of the dynamics of detachment revealed three temporal phases: 1) rapid detac hment of cells at the onset of flow, consistent with a first-order hom ogeneous kinetic model; 2) time-dependent rate of detachment during th e first 30 sec. of exposure to hydrodynamic shear, consistent with the first-order heterogeneous kinetic model proposed by Dickinson and Coo per (1995); and 3) negligible detachment, indicative of pseudo-steady state after 60 sec. of flow. Our results provide rigorous guidelines f or the measurement of adhesive interactions between mammalian cells an d prospective biomaterial surfaces using a RFC. (C) 1997 John Wiley & Sons, Inc.