Steady-state multiplicity in receptor-mediated colloidal adhesion

Biological adhesion is frequently mediated by specific binding between macromolecular bonds. Reconstituting molecules onto colloids allows recreation of bioadhesion in cell-free systems. We have used adhesive dynamics, a numerical simulation of binding interactions at adhesive interfaces, to explore the dynamics of colloidal adhesion to complementary surfaces mediated by biomolecules under hydrodynamic flow. In our model system, we show clearly that for certain parameter combinations multiple steady states in the particle velocity will be observed. In these regimes of multiplicity, static incubation predisposes particles to a firmly bound state (of zero velocity) while perfused particles are observed to detach (and reach the hydrodynamic velocity) at an identical level of applied force. Our calculations indicate that adhesion multiplicity is most probable for adhesion receptors with slow thermal dissociation rates and large reactive compliance (sensitivity to applied force). We examine how additional model parameters, including bond density, association rate, molecular elasticity, and force, alter the existence of bistable adhesion states and suggest an experimental protocol where this phenomenon could be observed.