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

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.

Highly sensitive VOC detectors using insect olfactory receptors reconstituted into lipid bilayers

“…When N 2 gas flow was initiated, the microbeads began to circulate (movie S2), clearly indicating that the droplet was mixed by the gas flow; shear stress was likely applied to the gas-liquid interface. This phenomenon is similar to that in a previous study that demonstrated droplet mixing caused by shear stress between oil and an aqueous droplet ( 13 ). We used particle image velocimetry (PIV) to analyze the microfluidic flow ( Fig.…”

Chiral lipid bilayers are enantioselectively permeable

“…We demonstrated the feasibility of measuring small molecule permeability in DIBs using a series of fluorescent dye standards. Dyes are an ideal testbed because that are directly detectable and have known membrane permeation coefficients, such as the highly membrane-permeable resorufin 25 and rhodamine 110 (R110), and membrane-impermeable carboxylic acids 5(6)- carboxytetramethylrhodamine (cTMR) and 5(6)-carboxyfluorescein (cFAM). 26 Raw droplet fluorescence traces showed membrane-permeable resorufin readily transporting from donor to receiver droplets with increasing incubation time ( Supplementary Fig.…”

Evaporation-induced monolayer compression improves droplet interface bilayer formation using unsaturated lipids

“…Interestingly, nearly all studies on DOPC DIBs have utilized microfluidic environments and droplet volumes less than 100 nl to achieve consistent DIB formation (see Table S1 in the supplementary material). In a recent exception, 19 Barlow et al reported stable DIB formation between large, 900 nl DOPC-coated droplets, though only after more than 40 min of incubation in oil.…”