Nanoscale Platelet Formation by Monounsaturated and Saturated Sophorolipids under Basic pH Conditions

Cuvier, Anne-Sophie; Babonneau, Florence; Berton, Jan; Stevens, Christian V.; Fadda, G. C.; Péhau‐Arnaudet, Gérard; Griel, Patrick Le; Prévost, Sylvain; Pérez, Javier; Baccile, Niki

doi:10.1002/chem.201502933

Cited by 32 publications

(57 citation statements)

References 66 publications

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“…Against this hypothesis, one should highlight the fact that the platelet aggregates disappear with lowering pH, as shown by the diminishing low-q signal between pH 12 and pH 10 on the SL-C18:0 sample in Figure 4. However, that signal is related to large (several micrometers) platelet aggregates and not to a single platelet, as shown in ref 38. On the contrary, other arguments support the second hypothesis.…”

Section: Langmuirmentioning

confidence: 84%

Self-Assembly Mechanism of pH-Responsive Glycolipids: Micelles, Fibers, Vesicles, and Bilayers

et al. 2016

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A set of four structurally related glycolipids are described: two of them have one glucose unit connected to either stearic or oleic acid, and two other ones have a diglucose headgroup (sophorose) similarly connected to either stearic or oleic acid. The self-assembly properties of these compounds, poorly known, are important to know due to their use in various fields of application from cleaning to cosmetics to medical. At basic pH, they all form mainly small micellar aggregates. At acidic pH, the oleic and stearic derivatives of the monoglucose form, respectively, vesicles and bilayer, while the same derivatives of the sophorose headgroup form micelles and twisted ribbons. We use pH-resolved in situ small angle X-ray scattering (SAXS) under synchrotron radiation to characterize the pH-dependent mechanism of evolution from micelles to the more complex aggregates at acidic pH. By pointing out the importance of the COO − /COOH ratio, the melting temperature, T m , of the lipid moieties, hydration of the glycosidic headgroup, the packing parameter, membrane rigidity, and edge stabilization, we are now able to draw a precise picture of the full self-assembly mechanism. This work is a didactical illustration of the complexity of the self-assembly process of a stimuli-responsive amphiphile during which many concomitant parameters play a key role at different stages of the process.

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Section: Langmuirmentioning

confidence: 84%

Self-Assembly Mechanism of pH-Responsive Glycolipids: Micelles, Fibers, Vesicles, and Bilayers

et al. 2016

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“…58 Acidic monounsaturated sophorolipids form ellipsoidal micelles in water in a very broad pH range (from pH 11 to pH 3), 59 although at basic pH, formation of nanoplatelets is also observed. 60 We also reported the micellar structure and their surface charge induced by pH. 61,62 The same molecules were also reported to form giant ribbons.…”

Section: Introductionmentioning

confidence: 88%

“…All solutions were clear except for the 50.11 solution, which was slightly turbid, the reason for which has been reported elsewhere. 60 …”

Section: Preparation Of Solutionsmentioning

confidence: 99%

“…56,[60][61][62] For pH o 5, sophorolipids form neutral spheroidal micelles, 61 while for 5 o pH o 7, micelles interact with one another due to negative charge coming from the partial deprotonation of the carboxylic acid. 61,62 Finally, for pH 4 8, small spheroidal micelles and platelets to some extent are detected using combined SAXS and cryo-TEM.…”

Section: Effect Of Ph On Sophorolipid Surface Assemblymentioning

confidence: 99%

“…61,62 Finally, for pH 4 8, small spheroidal micelles and platelets to some extent are detected using combined SAXS and cryo-TEM. 60 In some cases, acidic sophorolipids form twisted ribbons under acidic pH conditions. 55,58 However, this was not the case for the compound used in the present study, which only formed a stable micellar solution.…”

Section: Effect Of Ph On Sophorolipid Surface Assemblymentioning

confidence: 99%

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Surface-induced assembly of sophorolipids

Peyre

Hamraoui

Faustini

et al. 2017

Phys. Chem. Chem. Phys.

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The surface self-assembly properties of acidic sophorolipids, a bolaform microbial glycolipids with pHresponsive properties in solution, were studied based on the chemical nature of the support and pH of the solution. Sophorolipids generally form micelles in water but formation of morphologies like platelets and twisted fibers depending on pH have also been reported. The surface self-assembly was achieved using dip-coating on three different substrates namely gold, silicon(111) and TiO 2 anatase. Deposition conditions (dip-coating withdrawal speed, relative humidity, temperature) were tested, and it was found that optimum self-assembly occurred at a withdrawal speed of 1 mm s À1 , T of 25 1C and relative humidity of 25%. The local structure of the sophorolipid films was characterized by Atomic Force Microscopy, while Scanning Electron Microscopy was used to characterize the spatial homogeneity. We also attempted to correlate dispersive, electron donor and electron attractor surface energy components, using Good-Van Oss's approach, and the behavior of sophorolipids. We found that when the surface energy is dominated by dispersive components, sophorolipids spontaneously assemble into entangled needles at all pH values (4, 6 and 11). However, when the surface energy is dominated by electronic components, pH has a strong influence on the surface self-assembly. We could discriminate three major organizations: homogeneous layer, isolated aggregates and a two-dimensional network similar to block copolymer surface self-assembly.

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Micelles versus Ribbons: How Congeners Drive the Self‐Assembly of Acidic Sophorolipid Biosurfactants

et al. 2017

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Sophorolipids (SLs), a class of microbially derived biosurfactants, are reported by different research groups to have different self-assembled structures (either micelles or giant ribbons) under the same conditions. Here we explore the reasons behind these contradictory results and attribute these differences to the role of specific congeners that are present in minute quantities. We show that a sample composed of a majority of oleic acid (C18:1) sophorolipid in the presence of only 0.5 % (or more) of congeners with stearic acid (C18:0) or linoleic acid (C18:2) results in the formation of micelles that are stable over long periods of time. Conversely, the presence of only 10 to 15 % of congeners with a stearic acid chain gives fibrillar structures instead of micelles. To study the mechanisms responsible, oleic acid SLs devoid of any other congeners were prepared. Very interestingly, this sample can self-assemble into either micelles or fibers depending on minute modifications to the self-assembly conditions. The findings are supported by light scattering, small-angle X-ray scattering, transmission electron microscopy under cryogenic conditions, high-pressure liquid chromatography, and NMR spectroscopy.

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Nanoscale Platelet Formation by Monounsaturated and Saturated Sophorolipids under Basic pH Conditions

Cited by 32 publications

References 66 publications

Self-Assembly Mechanism of pH-Responsive Glycolipids: Micelles, Fibers, Vesicles, and Bilayers

Self-Assembly Mechanism of pH-Responsive Glycolipids: Micelles, Fibers, Vesicles, and Bilayers

Surface-induced assembly of sophorolipids

Micelles versus Ribbons: How Congeners Drive the Self‐Assembly of Acidic Sophorolipid Biosurfactants

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