Rheological Droplet Interface Bilayers (rheo-DIBs): Probing the Unstirred Water Layer Effect on Membrane Permeability via Spinning Disk Induced Shear Stress

Stuart Haylock,Anthony J Flemming,Oscar Ces,Guido Bolognesi,Nathan E Barlow,Laura M C Barter,Nicholas J Brooks

doi:10.1038/s41598-017-17883-0

Abstract

A new rheological droplet interface bilayer (rheo-DIB) device is presented as a tool to apply shear stress on biological lipid membranes. Despite their exciting potential for affecting high-throughput membrane translocation studies, permeability assays conducted using DIBs have neglected the effect of the unstirred water layer (UWL). However as demonstrated in this study, neglecting this phenomenon can cause significant underestimates in membrane permeability measurements which in turn limits their ability to predict key processes such as drug translocation rates across lipid membranes. With the use of the rheo-DIB chip, the effective bilayer permeability can be modulated by applying shear stress to the droplet interfaces, inducing flow parallel to the DIB membranes. By analysing the relation between the effective membrane permeability and the applied stress, both the intrinsic membrane permeability and UWL thickness can be determined for the first time using this model membrane approach, thereby unlocking the potential of DIBs for undertaking diffusion assays. The results are also validated with numerical simulations.

Highlights

Droplet interface bilayers (DIB)[1,2] are model lipid membranes which are formed upon contact of two lipid monolayers at the interface of water droplets immersed in a second immiscible phase (Fig. 1a)
As indicated by the rheo-DIB permeability assay, it is clear that the unstirred effective permeability is ca. 55% lower than the intrinsic membrane permeability value for the specific case of resorufin permeability in μL scale DIBs
We have shown that this application can be applied in a high throughput manner, where we have measured the permeability of various lipids, and have shown the unstirred water layer (UWL) can often obscure permeability data that is not performed in stirred conditions

Summary

Introduction

Droplet interface bilayers (DIB)[1,2] are model lipid membranes which are formed upon contact of two lipid monolayers at the interface of water droplets immersed in a second immiscible phase (Fig. 1a). Sketch gradient on opposing (c) of sides a species concentration profile across C+ and C−, where a parallel fluid flow a lipid in the bilayer membrane with a concentration bulk solution develops a laminar boundary layer at the interface. This fluid dynamic boundary layer affects the bilayer C−b) and the diffusional UWL thickness δd± as a function of fluid velocity uz(y) in the concentrations

Methods

Results

Conclusion