Numerical simulation of intracellular drug delivery via rapid squeezing

Abstract

Intracellular drug delivery by rapid squeezing is one of the most recent and simple cell membrane disruption-mediated drug encapsulation approaches. In this method, cell membranes are perforated in a microfluidic setup due to rapid cell deformation during squeezing through constricted channels. While squeezing-based drug loading has been successful in loading drug molecules into various cell types, such as immune cells, cancer cells, and other primary cells, there is so far no comprehensive understanding of the pore opening mechanism on the cell membrane and the systematic analysis on how different channel geometries and squeezing speed influence drug loading. This article aims to develop a three-dimensional computational model to study the intracellular delivery for compound cells squeezing through microfluidic channels. The Lattice Boltzmann method, as the flow solver, integrated with a spring-connected network via frictional coupling, is employed to capture compound capsule dynamics over fast squeezing. The pore size is proportional to the local areal strain of triangular patches on the compound cell through mathematical correlations derived from molecular dynamics and coarse-grained molecular dynamics simulations. We quantify the drug concentration inside the cell cytoplasm by introducing a new mathematical model for passive diffusion after squeezing. Compared to the existing models, the proposed model does not have any empirical parameters that depend on operating conditions and device geometry. Since the compound cell model is new, it is validated by simulating a nucleated cell under a simple shear flow at different capillary numbers and comparing the results with other numerical models reported in literature. The cell deformation during squeezing is also compared with the pattern found from our compound cell squeezing experiment. Afterward, compound cell squeezing is modeled for different cell squeezing velocities, constriction lengths, and constriction widths. We reported the instantaneous cell center velocity, variations of axial and vertical cell dimensions, cell porosity, and normalized drug concentration to shed light on the underlying physics in fast squeezing-based drug delivery. Consistent with experimental findings in the literature, the numerical results confirm that constriction width reduction, constriction length enlargement, and average cell velocity promote intracellular drug delivery. The results show that the existence of the nucleus increases cell porosity and loaded drug concentration after squeezing. Given geometrical parameters and cell average velocity, the maximum porosity is achieved at three different locations: constriction entrance, constriction middle part, and outside the constriction. Our numerical results provide reasonable justifications for experimental findings on the influences of constriction geometry and cell velocity on the performance of cell-squeezing delivery. We expect this model can help design and optimize squeezing-based cargo delivery.

Development of a microfluidic cell transfection device into gene-edited CAR T cell manufacturing workflow

“…We designed devices with 10, 20, and 40 μm wide ridge, with the understanding that ridge width affects both the flow resistance as well as the imposed shear force acting on cells. 38 Although there was no statistical significance associated with the differences, the 10 μm-ridge device results in 14% higher delivery percentage compared with the other two designs (45.3 ± 2.5% compared with 31.5 ± 14.8% and 21.9 ± 13.0%) (Fig. 3A).…”

“…It is noted that this finding is in contrast with the optimal parameter in mechanoporation devices that rely on shear force, in which longer constrictions result in higher delivery efficiency. 23,38 This possibly reflects a difference in the underlying delivery mechanism. In a shear force mechanoporation device, cell membrane and cortex are weakened from frictional force between cells and sidewalls in the constriction, positively correlating with the permeability of the cell membrane.…”

“…In a shear force mechanoporation device, cell membrane and cortex are weakened from frictional force between cells and sidewalls in the constriction, positively correlating with the permeability of the cell membrane. 38 The VECT device relies on volume exchange arising from intracellular pressure build-up during compression. 21 In this model, the primary contributing factor is strain rate with shear-based mechanisms of more minor effect.…”

A computational study of cell membrane damage and intracellular delivery in a cross-slot microchannel

“…Specifically, the comprehensive model takes into account the recovery of the membrane damage, on a time scale of several minutes. With the model, the group considered the intracellular drug delivery by rapid squeezing in a constricted channel, 26 and various other problems such as haemoglobin release from red blood cells. 24,26 Luo and Bai 28 considered the release of a diffusive solute from an elastic microcapsule flowing through a constricted channel.…”

Coarse-grained molecular simulation of extracellular vesicle squeezing for drug loading

“…The developed model was used to study the deformation of EVs due to squeezing, pore formation, and drug loading through the transient pores. Unlike the stain-based pore formation model, 52 the pore formation process is simulated explicitly through coarse-grained molecular dynamics coupled with a lattice-Boltzmann flow solver, yet with large dimensional and time scales far beyond the reach of traditional molecular dynamics simulations. A novel approach for predicting pore formation and drug loading through the EV is presented by studying the effects of various squeezing parameters.…”