Effect of interlamellar interactions on shear induced multilamellar vesicle formation

Abstract

Shear-induced multilamellar vesicle (MLV) formation has been studied by coupling the small-angle neutron scattering (SANS) technique with neutron spin echo (NSE) spectroscopy. A 10% mass fraction of the nonionic surfactant pentaethylene glycol dodecyl ether (CE) in water was selected as a model system for studying weak inter-lamellar interactions. These interactions are controlled either by adding an anionic surfactant, sodium dodecyl sulfate, or an antagonistic salt, rubidium tetraphenylborate. Increasing the charge density in the bilayer induces an enhanced ordering of the lamellar structure. The charge density dependence of the membrane bending modulus was determined by NSE and showed an increasing trend with charge. This behavior is well explained by a classical theoretical model. By considering the Caillé parameters calculated from the SANS data, the layer compressibility modulus B¯ is estimated and the nature of the dominant inter-lamellar interaction is determined. Shear flow induces MLV formation around a shear rate of 10 s, when a small amount of charge is included in the membrane. The flow-induced layer undulations are in-phase between neighboring layers when the inter-lamellar interaction is sufficiently strong. Under these conditions, MLV formation can occur without significantly changing the inter-lamellar spacing. On the other hand, in the case of weak inter-lamellar interactions, the flow-induced undulations are not in-phase, and greater steric repulsion leads to an increase in the inter-lamellar spacing with shear rate. In this case, MLV formation occurs as the amplitude of the undulations gets larger and the steric interaction leads to in-phase undulations between neighboring membranes.

Effect of salt on the lamellar Lα-to-MLV transformation in SDS/octanol/water under microfluidic flow

“…If B cannot be measured by ancillary techniques, model estimations can be made, assuming electrostatic or steric interactions between adjacent membranes. 11,13 The intermembrane potential for charged planes can be obtained from the one-dimensional Poisson-Boltzmann equation, as 13 B PB = πk B T d 2l B (d − δ ) 3 (3)…”

“…This L α to MLV transformation 21 has been extensively studied using different shear fields, stress and rates, using various model systems (non-ionic, 22-24 cationic 25,26 and anionic 27,28 ) alongside the effect of added co-surfactants 18,29 and salt. 13,19 Zilman and Granek 4 have proposed a theoretical model that estimates the critical shear required for the transformation in terms of the membrane properties (d and κ) and flow geometry, although experimental evidence appears unclear, with increasing membrane bending rigidity resulting in both higher 13,30 or lower critical shear rates. 31 To date, only a few studies have examined the coupling between L α membrane elastic properties and their flow response.…”

“…31 To date, only a few studies have examined the coupling between L α membrane elastic properties and their flow response. 13,30,31 Here, we consider the effect of varying NaCl content on the model anionic SDS/octanol/water system in the L α phase, building upon previous work on the flow-induced MLV phase transformation of the 2% NaCl system investigated by rheometry 28,[32][33][34] and microfluidics. 35,36 We first report on the effect of NaCl under quiescent conditions using SANS, viscometry and electrophoretic measurements (conductivity and zeta potential) to quantify and distinguish the effect of charge to the membrane elastic properties.…”

Lamellar-to-MLV transformation in SDS/octanol/brine examined by microfluidic-SANS and polarised microscopy

“…5,19 Experimentally, the formation of MLVs has been described by the emergence of intermediate multilamellar cylinder (MLC) phase [20][21][22] in continuous shear flow or a direct emergence of MLVs with oscillatory flows. 4 Numerous experimental reports have considered the effect of shear field, stress and rate, on various model systems (nonionic, 4,21,23,24 cationic 25,26 and anionic 27,28 ), the effect of added co-surfactants 3,29 and salt, 30,31 and the effect of oscillatory shear flows. 4,28,32 Predominant analytical techniques include rheology, 33,34 scattering, 21,22,34,35 optical microscopy 35,36 and 2 H NMR.…”

Shear-Induced Transformation of Polymer-Rich Lamellar Phases to Micron-Sized Vesicles

“…This is caused by suppression of the bilayer undulations . Another approach is the use of specifically tailored diblock copolymers in an aqueous solution where both blocks have the correct geometry, which is needed for the formation of MLVs. , In 2017, Kawabata et al studied the interlamellar interactions by adding salts with high charge density and bulky salts . Recently, Kuczera et al have found that the transition of a lamellar phase containing C 10 E 3 and water is also possible using large-amplitude oscillating shear .…”