Flow-Induced Vesicle Translocation through a Narrow Slit─Transit Time Scaling Relations

The translocation of soft objects like transferosomes and vesicles through splenic interendothelial slits is a major factor in vesicular transdermal delivery system for enhanced drug permeation or disease progression and also plays a critical role in microfluidic devices used for separation purposes. Using extensive Molecular Dynamics simulations, we study the pressure-driven flow-induced translocation of a loaded vesicle through a narrow rectangular slit whereby the hydrodynamic interactions in the channel are taken into account by means of multiparticle collision dynamics (MPCD). Considering vesicles of different size M, moving in a stream induced by a constant body force F, we demonstrate that the transit time τ of the vesicle passing through a slit with half-width H scales as τ ∝ MF^-1H^-2, confirming earlier theoretical predictions. The scaling regime is bounded from below by a critical force F_min^jam ∝ H^-1, at which the vesicle gets stuck in the pore, while beyond a significantly larger force the transit time τ becomes independent of the slit width. For growing concentration ϕ of filler particles inside the vesicle as well as with the increase in attraction between the fillers one observes an increase of the vesicle surface area and of the surface tension leading to a significant increase of the passing time τ as well.