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Instruments / Technical Area	Publication Details	Published
B21-High Throughput SAXS	Palmitic acid sophorolipid biosurfactant: from self-assembled fibrillar network (SAFiN) to hydrogels with fast recovery Niki Baccile , Ghazi Ben Messaoud , Patrick Le Griel , Nathan Cowieson , Javier Perez , Robin Geys , Marilyn De Graeve , Sophie L. K. W. Roelants , Wim Soetaert Philosophical Transactions Of The Royal Society A: Mathematical, Physical And Engineering Sciences 379 DOI: 10.1098/rsta.2020.0343 Diamond Proposal Number(s): [23247] Show Abstract ▼ Abstract: Nanofibres are an interesting phase into which amphiphilic molecules can self-assemble. Described for a large number of synthetic lipids, they were seldom reported for natural lipids like microbial amphiphiles, known as biosurfactants. In this work, we show that the palmitic acid congener of sophorolipids (SLC16:0), one of the most studied families of biosurfactants, spontaneously forms a self-assembled fibre network (SAFiN) at pH below 6 through a pH jump process. pH-resolved in situ small-angle X-ray scattering (SAXS) shows a continuous micelle-to-fibre transition, characterized by an enhanced core–shell contrast between pH 9 and pH 7 and micellar fusion into a flat membrane between pH 7 and pH 6, approximately. Below pH 6, homogeneous, infinitely long nanofibres form by peeling off the membranes. Eventually, the nanofibre network spontaneously forms a thixotropic hydrogel with fast recovery rates after applying an oscillatory strain amplitude out of the linear viscoelastic regime: after being submitted to strain amplitudes during 5 min, the hydrogel recovers about 80% and 100% of its initial elastic modulus after, respectively, 20 s and 10 min. Finally, the strength of the hydrogel depends on the medium's final pH, with an elastic modulus fivefold higher at pH 3 than at pH 6.	Sep 2021
B21-High Throughput SAXS	Synthesis of multilamellar walls vesicles polyelectrolyte surfactant complexes from pH-stimulated phase transition using microbial biosurfactants C. Seyrig , P. Le Griel , N. Cowieson , J. Perez , N. Baccile Journal Of Colloid And Interface Science DOI: 10.1016/j.jcis.2020.07.021 Diamond Proposal Number(s): [23247] Show Abstract ▼ Abstract: Multilamellar wall vesicles (MLWV) are an interest class of polyelectrolyte-surfactant complexes (PESCs) for the wide applications ranging from house-care to biomedical products. If MLWV are generally obtained by a polyelectrolyte-driven vesicle agglutination under pseudo-equilibrium conditions, the resulting phase is often a mixture of more than one structure. In this work, we show that MLWV can be massively and reproductively prepared from a recently developed method involving a pH-stimulated phase transition from a complex coacervate phase (Co). We employ a biobased pH-sensitive microbial glucolipid biosurfactant in the presence of a natural, or synthetic, polyamine (chitosan, poly-L-Lysine, polyethylene imine, polyallylamine). In situ small angle X-ray scattering (SAXS) and cryogenic transmission electron microscopy (cryo-TEM) show a systematic isostructural and isodimensional transition from the Co to the MLWV phase, while optical microscopy under polarized light experiments and cryo-TEM reveal a massive, virtually quantitative, presence of MLWV. Finally, the multilamellar wall structure is not perturbed by filtration and sonication, two typical methods employed to control size distribution in vesicles. In summary, this work highlights a new, robust, non-equilibrium phase-change method to develop biobased multilamellar wall vesicles, promising soft colloids with applications in the field of personal care, cosmetics and pharmaceutics among many others.	Jul 2020
B21-High Throughput SAXS	Stimuli-induced nonequilibrium phase transitions in polyelectrolyte–surfactant complex coacervates Chloe Seyrig , Gertrude Kignelman , Wim Thielemans , Patrick Le Griel , Nathan Cowieson , Javier Perez , Niki Baccile Langmuir DOI: 10.1021/acs.langmuir.0c01177 Diamond Proposal Number(s): [23247] Show Abstract ▼ Abstract: Polyelectrolyte–surfactant complexes (PESCs) are important soft colloids with applications in the fields of personal care, cosmetics, pharmaceutics, and much more. If their phase diagrams have long been studied under pseudoequilibrium conditions, and often inside the micellar or vesicular regions, understanding the effect of nonequilibrium conditions, applied at phase boundaries, on the structure of PESCs generates an increasing interest. In this work we cross the micelle–vesicle and micelle–fiber phase boundaries in an isocompositional surfactant–polyelectrolyte aqueous system through a continuous and rapid variation of pH. We employ two microbial glycolipid biosurfactants in the presence of polyamines, both systems being characterized by their responsiveness to pH. We show that complex coacervates (Co) are always formed in the micellar region of both glycolipids’ phase diagram and that their phase behavior drives the PESC stability and structure. However, for glycolipid forming single-wall vesicles, we observe an isostructural and isodimensional transition between complex coacervates and a multilamellar walls vesicle (MLWV) phase. For the fiber-forming glycolipid, on the contrary, the complex coacervate disassembles into free polyelectrolyte coexisting with the equilibrium fiber phase. Last but not least, this work also demonstrates the use of microbial glycolipid biosurfactants in the development of sustainable PESCs.	Jul 2020

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