Shear‐induced intracellular loading of cells with molecules by controlled microfluidics

Abstract

This study tested the hypothesis that controlled flow through microchannels can cause shear-induced intracellular loading of cells with molecules. The overall goal was to design a simple device to expose cells to fluid shear stress and thereby increase plasma membrane permeability. DU145 prostate cancer cells were exposed to fluid shear stress in the presence of fluorescent cell-impermeant molecules by using a cone-and-plate shearing device or high-velocity flow through microchannels. Using a syringe pump, cell suspensions were flowed through microchannels of 50 -300 μm diameter drilled through Mylar® sheets using an excimer laser. As quantified by flow cytometry, intracellular uptake and loss of viability correlated with the average shear stress. Optimal results were observed when exposing the cells to high shear stress for short durations in conical channels, which yielded uptake to over one third of cells while maintaining viability at approximately 80%. This method was capable of loading cells with molecules including calcein (0.62 kDa), large molecule weight dextrans (150 -2000 kDa), and bovine serum albumin (66 kDa). These results supported the hypothesis that shearinduced intracellular uptake could be generated by flow of cell suspensions through microchannels and further led to the design of a simple, inexpensive, and effective device to deliver molecules into cells. Such a device could benefit biological research and the biotechnology industry.

In vitro and ex vivo strategies for intracellular delivery

“…4c) 55 , cone-plate viscometers, devices for generating a determinable shear force over a surface, have also been shown to transiently permeabilize apical membranes in cell monolayers 56 . Such observations inspired the design of microfluidic devices to expose cells to shear forces proportional to flow velocity through 50-300 micron tapered microchannels 57 . Although an interesting concept, reproducibly controlling fluid shear forces at this scale has generally proven difficult.…”

The Mechanics of Traumatic Brain Injury: A Review of What We Know and What We Need to Know for Reducing Its Societal Burden

“…With the clear need for coupling mechanical input into functional consequences, work in the past decade has responded and provided more direct insight into the mechanisms that cause the resulting functional changes. Motivated by the early work using physical models and finite element simulations, several investigators developed microscope-based systems to study directly the relationship between the mechanical deformation and resultant biochemical signaling [183][184][185][186][187][188][189]. As a result, we now know that both neural and glial cells respond to mechanical deformation, that synaptically localized receptors are uniquely mechanosensitive, show immediate alterations in their physiological properties, and changes occur across both excitatory and inhibitory neurons [190][191][192][193][194][195].…”

A vector-free microfluidic platform for intracellular delivery

“…This method was developed with the aim of delivering almost any macromolecule of interest to almost any cell type, at high throughput. Although scrape loading and shear-based delivery methods have been demonstrated previously, they are unsuitable for some applications due to low viability and/or delivery efficiency (30)(31)(32). However, such injury/diffusion-based delivery methods do have the advantage of high throughput (compared with microinjection) and independence from exogenous materials or fields.…”