Production of giant unilamellar vesicles and encapsulation of lyotropic nematic liquid crystals

Peng Bao,J Cliff Jones,Helen F Gleeson,Daniel A Paterson,Stephen D Evans,Sally A Peyman,Jonathan A T Sandoe,Richard J Bushby

doi:10.1039/d0sm01684e

Peng Bao, J Cliff Jones + Show 6 more

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https://doi.org/10.1039/d0sm01684e

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Abstract

We describe a modified microfluidic method for making Giant Unilamellar Vesicles (GUVs) via water/octanol-lipid/water double emulsion droplets. At a high enough lipid concentration we show that the de-wetting of the octanol from these droplets occurs spontaneously (off-chip) without the need to use shear to aid the de-wetting process. The resultant mixture of octanol droplets and GUVs can be separated by making use of the buoyancy of the octanol. A simpler microfluidic device and pump system can be employed and, because of the higher flow-rates and much higher rate of formation of the double emulsion droplets (∼1500 s-1 compared to up to ∼75 s-1), it is easier to make larger numbers of GUVs and larger volumes of solution. Because of the potential for using GUVs that incorporate lyotropic nematic liquid crystals in biosensors we have used this method to make GUVs that incorporate the nematic phases of sunset yellow and disodium chromoglycate. However, the phase behaviour of these lyotropic liquid crystals is quite sensitive to concentration and we found that there is an unexpected spread in the concentration of the contents of the GUVs obtained.

Highlights

IntroductionGiant Unilamellar Vesicles (GUVs) have many potential applications.[1,2,3,4,5,6,7,8] They are widely used as cell models (protocells)[9,10] and in studies in which the ultimate aim is to create artificial life.[10,11,12,13,14,15] As a result, many methods have been developed for their production and for encapsulating materials within them.[16,17,18,19,20,21] None of these methods are wholly problem-free[22] but microfluidic approaches probably offer most control
When 2 mg mLÀ1 lipid in octanol is used as the ‘oil’ phase the resultant droplets develop a prominent oil pocket on one side. In this case it seems that the inequalities (1)–(3) are not fully satisfied and that an element of shear, or of interaction with the walls of the channel is required to complete the de-wetting.[43]
One can envisage biomolecule detector systems being based on such Giant Unilamellar Vesicles (GUVs), which either make use of the switching of the anchoring of the LNLC between perpendicular and planar or which make use of phase changes in the lyotropic liquid crystal

Summary

Introduction

Giant Unilamellar Vesicles (GUVs) have many potential applications.[1,2,3,4,5,6,7,8] They are widely used as cell models (protocells)[9,10] and in studies in which the ultimate aim is to create artificial life.[10,11,12,13,14,15] As a result, many methods have been developed for their production and for encapsulating materials within them.[16,17,18,19,20,21] None of these methods are wholly problem-free[22] but microfluidic approaches probably offer most control. Microfluidics allows very small volumes of liquid to be brought together with high spatial and temporal accuracy and so it provides control of both size and uniformity in GUV production.[23,24,25,26,27,28,29] Flow-focussed microfluidic methods are based on the production of an intermediate ‘double emulsion’

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