Laboratoire d’analyse et d’architecture des systèmes
L.RECOULES, A.MIGAOU, X.DOLLAT, G.THOUAND, A.M.GUE, A.BOUKABACHE
MILE, I2C, Nantes
Revue Scientifique : Analytical and Bioanalytical Chemistry, Vol.410, N°4, pp.1189-1190, Novembre 2018 , N° 18378
L.J.HOLT, O.HALLATSCHEK, M.DELARUE
New York, Berkeley, MILE
Ouvrage (contribution) : Microfluidics in Cell Biology Part B: Microfluidics in Single Cells, N°ISBN 978-0-12-814282-0, Vol.147231, Octobre 2018, 215p. , N° 18315
Cells need to act upon the elastic extracellular matrix and against steric constraints when proliferating in a confined environment, leading to the build-up, at the population level, of a compressive, growth-induced, mechanical stress. Compressive mechanical stresses are ubiquitous to any cell population growing in a spatially-constrained environment, such as microbes or most solid tumors. They remain understudied, in particular in microbial populations, due to the lack of tools available to researchers. Here, we present various mechano-chemostats: microfluidic devices developed to study microbes under pressure. A mechano-chemostat permits researchers to control the intensity of growth-induced pressure through the control of cell confinement, while keeping cells in a defined chemical environment. These versatile devices enable the interrogation of physiological parameters influenced by mechanical compression at the single cell level and set a standard for the study of growth-induced compressive stress.
R.TICHAUER, G.FAVRE, S.CABANTOUS, G.LANDA, A.HEMERYCK, M.BRUT
M3, ICR, CRCT-INSERM
Revue Scientifique : Biophysical Journal, Vol.115, N°8, pp.1417-1430, Octobre 2018, doi 10.1016/j.bpj.2018.07.042 , N° 18306
Point mutations in p21ras are associated with ∼30% of human tumors by disrupting its GTP hydrolysis cycle, which is critical to its molecular switch function in cellular signaling pathways. In this work, we investigate the impact of Gln 61 substitutions in the structure of the p21N-ras active site and particularly focus on water reorganization around GTP, which appears to be crucial to evaluate favorable and unfavorable hydration sites for hydrolysis. The NRas-GTP complex is analyzed using a hybrid quantum mechanics/molecular mechanics approach, treating for the first time to our knowledge transient water molecules at the ab initio level and leading to results that account for the electrostatic coupling between the protein complex and the solvent. We show that for the wild-type protein, water molecules are found around the GTP γ-phosphate group, forming an arch extended from residues 12 to 35. Two density peaks are observed, supporting previous results that suggest the presence of two water molecules in the active site, one in the vicinity of residue 35 and a second one stabilized by hydrogen bonds formed with nitrogen backbone atoms of residues 12 and 60. The structural changes observed in NRas Gln 61 mutants result in the drastic delocalization of water molecules that we discuss. In mutants Q61H and Q61K, for which water distribution is overlocalized next to residue 60, the second density peak supports the hypothesis of a second water molecule. We also conclude that Gly 60 indirectly participates in GTP hydrolysis by correctly positioning transient water molecules in the protein complex and that Gln 61 has an indirect steric effect in stabilizing the preorganized catalytic site.
T.CALAIS, A.BANCAUD, A.ESTEVE, C.ROSSI
Revue Scientifique : ACS Applied Nano Materials, Vol.1, N°9, pp.4716-4725, Septembre 2018 , N° 18279
The association of a metallic fuel (usually aluminum) with an oxidizer (metal oxide or organic compound) creates an exothermic material that can be ignited with an external stimulus such as local heating or spark discharge. These materials with high energetic performances, called nanothermites, have been used to release temperature or pressure waves for civil or military applications (initiators, impact igniters, etc.). However, the energetic performances of these nanothermites are highly dependent on the nanoscale intimacy of the two components. The use of nanoparticles results in an increase of the energy release, but control of their assembly remains particularly challenging. In this work, we demonstrate that the use of DNA to self-organize Al or CuO nanoparticles greatly enhances the energy release of nanothermites by up to 240% compared to classically sonicated nanothermites in hexane, with the heat of reaction prior to Al melting reaching a value of 2.57 kJ·g–1. In particular, we report that the energetic performances can be tuned by controlling the ionic strength during the self-assembly process. These results are supported by ultrafine characterization of the nanocomposite microstructure based on high-resolution transmission electronic microscopy and energy-dispersive X-ray spectroscopy. Besides, we report the surprisingly good energetic performances of randomly mixed nanoparticles dispersed in water, nonetheless 40% lower than DNA-self-assembled nanocomposites. Altogether, our study not only proposes an easy and immediate process for nanocomposites synthesis but also opens the door for opportunities toward large-scale crystalline Al–CuO superlattices with high energetic performances.
C.MAGNANI, C.MONTIS, G.MANGIAPIA, A.F.MINGOTAUD, C.MINGOTAUD, C.ROUX, P.JOSEPH, D.BERTI, B.LONETTI
IMRCP, UNIFI, Forschungszentrum, MILE
Revue Scientifique : Colloids and Surfaces B: Biointerfaces, Vol.168, pp.18-28, Août 2018 , N° 18144
In recent years, there has been a growing interest in the formation of copolymers-lipids hybrid self-assemblies, which allow combining and improving the main features of pure lipids-based and copolymer-based systems known for their potential applications in the biomedical field. In this contribution we investigate the self-assembly behavior of dipalmitoylphosphatidylcholine (DPPC) mixed with poly(butadiene-b-ethyleneoxide) (PBD-PEO), both at the micro- and at the nano-length scale. Epifluorescence microscopy and Laser Scanning Confocal microscopy are employed to characterize the morphology of micron-sized hybrid vesicles. The presence of fluid-like inhomogeneities in their membrane has been evidenced in all the investigated range of compositions. Furthermore, a microfluidic set-up characterizes the mechanical properties of the prepared assemblies by measuring their deformation upon flow: hybrids with low lipid content behave like pure polymer vesicles, whereas objects mainly composed of lipids show more variability from one vesicle to the other. Finally, the structure of the nanosized assemblies is characterized through a combination of Dynamic Light Scattering, Small Angle Neutron Scattering and Transmission Electron Microscopy. A vesicles-to-wormlike transition has been evidenced due to the intimate mixing of DPPC and PBD-PEO at the nanoscale. Combining experimental results at the micron and at the nanoscale improves the fundamental understanding on the phase behavior of copolymer-lipid hybrid assemblies, which is a necessary prerequisite to tailor efficient copolymer-lipid hybrid devices.
O.LIOT, S.AKASH, P.BACCHIN, P.DURU, J.MORRIS, P.JOSEPH
MILE, LGC, IMFT, Levich Institute
Revue Scientifique : Scientific Reports, Vol.8, 12460p., Août 2018 , N° 17438
Blockage of pores by particles is found in numerous industrial and natural processes, including filtration and oil extraction. We present experimental results of filtration through a linear array of ten channels with one dimension which is sub-micron. These silicon-glass nanoslits serve as model pores, through which a dilute dispersion of Brownian polystyrene spheres flows. The clog growth rate at fixed differential pressure is shown to systematically increase with the number of saturated (entirely clogged) pores, indicating that there is an interaction or " cross-talk " between the pores. This observation is interpreted using a model proposed here, based on the concept that the residual permeability allows a clog to act as a filter. A clogged pore is thus the source of a local increase of particle concentration adjacent to the pore, which then diffuses towards other pores. This phenomenon, evidenced and modelled here in one dimension, should be at play in two-dimensional membranes.
B.CHAMI, M.SOCOL, M.MANGHI, A.BANCAUD
MILE, IRSAMC, Toulouse
Revue Scientifique : Soft Matter, Vol.14, N°24, pp.5069-5079, Juin 2018 , N° 18344
DNA separation and analysis have advanced over recent years, benefiting from microfluidic systems that reduce sample volumes and analysis costs, essential for sequencing and disease identification in body fluids. We recently developed the μLAS technology that enables the separation, concentration, and analysis of nucleic acids with high sensitivity. The technology combines a hydrodynamic flow actuation and an opposite electrophoretic force in viscoelastic polymer solutions. Combining hydrodynamics first principles and statistical mechanics, we provide, in this paper, a quantitative model of DNA transport capable of predicting device performance with the exclusive use of one adjustable parameter associated with the amplitude of transverse viscoelastic forces. The model proves to be in remarkable agreement with DNA separation experiments, and allows us to define optimal conditions that result in a maximal resolution length of 7 bp. We finally discuss the usefulness of our model for separation technologies involving viscoelastic liquids.
A.CHALARD, L.VAYSSE, P.JOSEPH, L.MALAQUIN, S.ASSIE-SOULEILLE, B.LONETTI, J.C.SOL, I.LOUBINOUX, J.FITREMANN
MILE, INSERM, ELIA, I2C, IMRCP
Revue Scientifique : ACS applied materials & interfaces, Vol.10, N°20, pp.17004-17017, Mai 2018 , N° 18179
In this work, we demonstrated that the hydrogel obtained from a very simple and single synthetic molecule, N-heptyl-galactonamide was a suitable scaffold for the growth of neuronal cells in 3D. We evidenced by confocal microscopy the presence of the cells into the gel up to a depth of around 200 µm, demonstrating that the latter was permissive to cell growth and enabled a true 3D colonization and organization. It also supported successfully the differentiation of adult human neuronal stem cells (hNSCs) into both glial and neuronal cells and the development of a really dense neurofilament network. So the gel appears to be a good candidate for neural tissue regeneration. In contrast with other molecular gels described for cell culture, the molecule can be obtained at the gram scale by a one-step reaction. The resulting gel is very soft, a quality in accordance with the aim of growing neuronal cells, that requires low modulus substrates similar to the brain. But because of its fragility, specific procedures had to be implemented for its preparation and for cell labeling and confocal microscopy observations. Notably, the implementation of a controlled slow cooling of the gel solution was needed to get a very soft but nevertheless cohesive gel. In these conditions, very wide straight and long micrometric fibers were formed, held together by a second network of flexible narrower nanometric fibers. The two kinds of fibers guided the neurite and glial cell growth in a different way. We also underlined the importance of a tiny difference in the molecular structure on the gel performances: parent molecules, differing by a one-carbon increment in the alkyl chain length, N-hexyl-galactonamide and N-octyl-galactonamide, were not as good as N-heptyl-galactonamide. Their differences were analysed in terms of gel fibers morphology, mechanical properties, solubility, chain parity and cell growth.
M.POBERZNIK, D.COSTA, A.HEMERYCK, A.KOKALJ
Ljubljana, IRCP, M3, Institut Jožef Stefan
Revue Scientifique : Journal of Physical Chemistry C, Vol.122, N°17, pp.9417-9431, Mai 2018 , N° 18147
In the context of elucidating the mechanism by which siloxane-based sol–gel coatings adhere to the surface, the adsorption of a model silanol molecule, CH3Si(OH)3, and its oligomers (up to the trimer) on oxidized and fully hydroxylated aluminum substrates is described using density functional theory (DFT). To link our calculations with the synthesis of siloxane-based sol–gel coatings, the focus is given on the condensation mechanism. We find that the formation of a monodentate bonding mode with the hydroxylated surface via the condensation mechanism is exothermic by ≥0.5 eV in all considered cases. In contrast, the formation of a bidentate bonding mode is exothermic only for the trimer. However, taking entropic contributions into account, we find that the formation of the bidentate bonding mode is exergonic already for the dimer due to favorable entropic effects of a liberated water molecule during the reaction. In contrast, the reaction entropy is unfavorable for the monodentate formation because the effects of the immobilized silanol molecule counteract and surpass those of the liberated water molecule. The monodentate to bidentate transformation is therefore determined by the interplay between entropy and energy, and we find that the longer the oligomer chain, the more likely is the bidentate formation due to increasingly favorable reaction energies. These results further reveal that for the silanol monomer, additional molecule–surface chemical bonds do not form via the condensation mechanism due to the strained configuration it has to adopt in the bidentate bonding mode.
O.LIOT, M.SOCOL, L.GARCIA, J.THIERY, A.FIGAROL, A.F.MINGOTAUD, P.JOSEPH
MILE, IPBS, IMRCP
Revue Scientifique : Journal of Physics: Condensed Matter, Vol.30, N°23, 23400p., Avril 2018 , N° 18148
This paper presents experimental results about transport of dilute suspensions of nano-objects in silicon-glass micrometric and sub-icrometric channels. Two kinds of objects are used: solid, rigid latex beads and spherical capsule-shaped, soft polymersomes. They are tracked using fluorescence microscopy. Three parameters are studied: confinement (ratio between particle diameter and channel depth), Brownian diffusion and particle nature. The aim of this work is to understand how these different parameters affect the transport of suspensions in narrow channels and to understand the different mechanisms at play. Concerning the solid beads we observe the appearance of two regimes, one where the experimental mean velocity is close to the expected one and another where this velocity is lower. This is directly related to a competition between confinement, Brownian diffusion and advection. These two regimes are shown to be linked to the homogeneity of particles distribution in the channel depth, which we experimentally deduce from velocity distributions. This inhomogeneity appears during the entrance process into the sub-micrometric channels, as for hydrodynamic separation or deterministic lateral displacement. Concerning the nature of the particles we observed a shift of transition towards the second regime likely due to the relationships between shear stress and polymersomes mechanical properties which could reduce the inhomogeneity imposed by the geometry of our device.