Samuel Guillot - Academia.edu (original) (raw)

Papers by Samuel Guillot

Research paper thumbnail of Determination of Water Content in Internally Self-Assembled Monoglyceride-Based Dispersions from the Bulk Phase

Langmuir, 2007

We determined the water intake of internally structured oil-loaded monoglyceride-based dispersion... more We determined the water intake of internally structured oil-loaded monoglyceride-based dispersions. This was possible through small-angle X-ray scattering (SAXS) experiments on the corresponding bulk mesophases because the structural parameters in full hydration conditions are identical to those of the dispersed particles. From low water contents to full hydration, the bulk phases depend strongly on the amount of oil. At room temperature in excess water and with increasing oil concentration, successive bicontinuous cubic, reverse hexagonal, micellar cubic, and inverse micellar-type isotropic fluid phases are found. The solubilized water is determined as a function of the oil content for each phase, and it is found to range from 5-33 wt %.

Research paper thumbnail of Influence of the Stabilizer Concentration on the Internal Liquid Crystalline Order and the Size of Oil-Loaded Monolinolein-Based Dispersions

Langmuir, 2010

The internal phase of monolinolein-based dispersions loaded with tetradecane or (R)-(þ)-limonene ... more The internal phase of monolinolein-based dispersions loaded with tetradecane or (R)-(þ)-limonene was investigated as a function of the stabilizer content by small-angle X-ray scattering. Phase transitions at the colloidal scale were found in some of nanostructured aqueous dispersions by increasing the stabilizer content. For particles containing a bicontinuous cubic phase, a large increase of the stabilizer concentration promoted a liquid crystalline phase transition from the Pn3m to the Im3m cubic symmetry. The coexistence of both phases is observed in an intermediate stabilizer concentration range. For particles with an internal micellar cubic Fd3m symmetry, the internal structure changes in the isotropic fluid L 2 phase. In case of particles with an internal hexagonal phase (H 2 symmetry), the increasing amount of stabilizer did not alter the lattice parameter but decreased the size of the nanostructured domain. Moreover, we showed for hexagonal and emulsified micellar phase particles that the increase of the stabilizer content induced a strong decrease of the mean hydrodynamic size of the particles, allowing producing nanostructured lipid-based liquid crystalline particles down to a radius of 70 nm at the same energy input.

Research paper thumbnail of Surfactant-Induced Collapse of Polymer Chains and Monodisperse Growth of Aggregates near the Precipitation Boundary in Carboxymethylcellulose−DTAB Aqueous Solutions

Langmuir, 2003

... Samuel Guillot, † Michel Delsanti, ‡ Sylvain Désert, ‡ and Dominique Langevin* †. Laboratoire... more ... Samuel Guillot, † Michel Delsanti, ‡ Sylvain Désert, ‡ and Dominique Langevin* †. Laboratoire de Physique des Solides, Bâtiment 510, Université Paris-Sud, 91405 Orsay Cedex, France, and Service de Chimie Moléculaire, CEA Saclay, 91191 Gif-sur-Yvette Cedex, France. ...

Research paper thumbnail of Confinement of DNA in Water-in-Oil Microemulsions

Langmuir, 2008

The study of systems that allow DNA condensation in confined environments is an important task in... more The study of systems that allow DNA condensation in confined environments is an important task in producing cell-mimicking microreactors capable of biochemical activities. The water droplets formed in water-in-oil emulsions are potentially good candidates for such microcompartments. The anionic surfactant AOT was used here to stabilize the droplets. We have studied in detail the DNA distribution and the structural modifications of these microemulsion drops by varying the concentration and molecular weight of DNA and using various techniques such as light, X-ray, and neutron scattering, electrical conductivity, and surface tension. DNA induces the formation of large drops into which it is internalized. The size of these drops depends on the amount of DNA dissolved in water as well as on its molecular weight. The local DNA concentration is very high (>100 mg/mL). The large drops coexist with small empty drops (not containing DNA), similar to those found in the DNA-free microemulsion.

Research paper thumbnail of Internally self-assembled particles entrapped in thermoreversible hydrogels

Journal of Colloid and Interface Science, 2009

The present study describes the development of thermogelling emulsions by the entrapment of inter... more The present study describes the development of thermogelling emulsions by the entrapment of internally self-assembled emulsion droplets (ISAsomes) within a thermoreversible hydrogel made of κ-carrageenan.

Research paper thumbnail of Internal organisation in polyelectrolytes/oppositely charged surfactants colloidal complexes anticipating precipitated nanostructures

The European Physical Journal E, 2011

In this paper, we relate the periodic nanostructures found in the colloidal complexes and the con... more In this paper, we relate the periodic nanostructures found in the colloidal complexes and the concentrated phases obtained with polyelectrolyte/surfactant aqueous solutions. We present small-angle X-ray scattering studies of the self-organisation of the anionic polymer carboxymethylcellulose with three cationic quaternary ammonium surfactants with different head and tail groups: hexadecyl trimethyl, hexadecyl ethyl dimethyl and didodecyl dimethyl ammonium bromides. We investigated the mesophases obtained above a precipitation threshold. The mixed solutions with the double-chained surfactant led to lamellar phases, in which the repeat distance only depends on the surfactant/carboxyl charge molar ratio. We show that an internal lamellar organisation already takes place in the dilute phase containing colloidal complexes found below the precipitation threshold.

Research paper thumbnail of Direct and indirect thermal transitions from hexosomes to emulsified micro-emulsions in oil-loaded monoglyceride-based particles

Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2006

We identified the possible internally self-assembled phases that occur in oil-loaded monoglycerid... more We identified the possible internally self-assembled phases that occur in oil-loaded monoglyceride-based nanoparticles that are dispersed in water. Temperature versus composition of the dispersed phase "T-δ" phase diagrams were constructed at a constant dispersed phase content upon varying the oil/monoglyceride weight ratio at a wide range of temperatures (1-90 • C). We mainly focused on the determination of these phase diagrams by changing the oil type or the monoglyceride purity. They were built when investigating the internal structure of the particles by means of small angle X-ray scattering (SAXS). We show that some internally self-assembled emulsified particles may contain a discontinuous cubic phase (Fd3m symmetry), depending on the oil content. However, the extension of this phase in the diagram strongly depends on the oil. This emulsified liquid crystalline phase is inserted between the inverse hexagonal H 2 phase and the inverse micellar solution L 2 phase, as was previously found in bulk. Moreover, we managed to find the existence of an indirect thermal transformation from hexosomes to emulsified micro-emulsions through micellar cubosomes (emulsified reversed discontinuous micellar cubic phase) within a narrow range of an oil/monoglycerides ratio. This transition via temperature has not been published to our knowledge in these dispersed systems.

Research paper thumbnail of X-ray Diffraction Study of the Structure of Carboxymethylcellulose–Cationic Surfactant Complexes

Research paper thumbnail of Carbon Nanotubes as Structural Nanofibers for Hyaluronic Acid Hydrogel Scaffolds

Biomacromolecules, 2008

We have successfully dispersed functionalized single-walled carbon nanotubes (SWNTs) within hyalu... more We have successfully dispersed functionalized single-walled carbon nanotubes (SWNTs) within hyaluronic acid-water solutions. Hybrid hyaluronic acid (HA) hydrogels with SWNTs were then formed by cross-linking with divinyl sulfone. We have found a considerable change in the morphology of the lyophilized hybrid hydrogels compared to HA hydrogels. The high water uptake capacity, an important property of HA hydrogels, remained almost unchanged after 2 wt % SWNT (vs HA) incorporation, despite a dramatic enhancement in the dynamic mechanical properties of the hybrid hydrogels compared to native ones. We have found a 300% enhancement in the storage modulus of hybrid hydrogel with only 2 wt % of SWNTs vs HA (0.06 wt % vs total weight including water content). This apparent contradiction can be explained by a networking effect between SWNTs, mediated by HA chains. As in biological tissue, HA plays a dual role of matrix and linker for the rigid reinforcing nanofibers.

Research paper thumbnail of Loading and release of internally self-assembled emulsions embedded in a magnetic hydrogel

Applied Physics Letters, 2014

We have investigated drug loading and release from thermosensitive gel emulsions with external tr... more We have investigated drug loading and release from thermosensitive gel emulsions with external triggering by an alternating magnetic field (AMF) for on-demand drug delivery. Superparamagnetic iron oxide nanoparticles dispersed in gel emulsions were used to study the loading and release capabilities, with the stable nitroxide radical 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO) serving as the model drug. AMF activation gave similar results to temperature activation in a water bath at 37 C, showing that the principal effect of the AMF is a temperature increase without burst release. These results suggest that the system could play an important role in the development of advanced drug delivery. V C 2014 AIP Publishing LLC. [http://dx.doi.org/10.1063/1.4862811] Confinement and controlled release of drugs through constrained geometries continue to be an active topic in nanotechnology with a special focus on biopharmaceutical applications. 1,2 One attractive challenge is to design devices for long-term therapies, with a zero premature release rate, i.e., "on-demand" release patterns. During the ON mode, delivery could be activated with a controlled release rate while during the OFF mode, delivery through continuous leakage should be negligible since too rapid release or "burst release" might lead to more side effects and thus needs to be controlled. Among the potential candidates, a combination of drug carrying nanoporous lipid particles, having intrinsically high surface areas, with stimulus-responsive hydrogels appears particularly promising.

Research paper thumbnail of Internally structured pickering emulsions stabilized by clay mineral particles

Journal of Colloid and Interface Science, 2009

The present study aims to describe emulsion particles containing a dispersed phase composed of na... more The present study aims to describe emulsion particles containing a dispersed phase composed of nanostructured lipid mesophases and stabilized by montmorillonite and/or Laponite clay platelets. The size distributions of these emulsion particles were found independent of the clay mineral content and of the initial internal composition that determines the internal structure. The stabilization of the droplets by a shell of smectite layers was found possible even by montmorillonite which has a length of the same order or more than the droplets to stabilize. The clay platelets give a local flatness to the droplets that may influence the internal structure. In this paper, we describe the conditions to obtain such soft particles of about 220 nm, and we show by direct visualization the internal mesophase complexity and the shape of the particles. In particular, TEM analysis showed elongated particles with bent-back channels at their center but a different morphology at the periphery due to flat border conditions imposed by the presence of the clay minerals.

Research paper thumbnail of Determination of Water Content in Internally Self-Assembled Monoglyceride-Based Dispersions from the Bulk Phase

Langmuir, 2007

We determined the water intake of internally structured oil-loaded monoglyceride-based dispersion... more We determined the water intake of internally structured oil-loaded monoglyceride-based dispersions. This was possible through small-angle X-ray scattering (SAXS) experiments on the corresponding bulk mesophases because the structural parameters in full hydration conditions are identical to those of the dispersed particles. From low water contents to full hydration, the bulk phases depend strongly on the amount of oil. At room temperature in excess water and with increasing oil concentration, successive bicontinuous cubic, reverse hexagonal, micellar cubic, and inverse micellar-type isotropic fluid phases are found. The solubilized water is determined as a function of the oil content for each phase, and it is found to range from 5-33 wt %.

Research paper thumbnail of Influence of the Stabilizer Concentration on the Internal Liquid Crystalline Order and the Size of Oil-Loaded Monolinolein-Based Dispersions

Langmuir, 2010

The internal phase of monolinolein-based dispersions loaded with tetradecane or (R)-(þ)-limonene ... more The internal phase of monolinolein-based dispersions loaded with tetradecane or (R)-(þ)-limonene was investigated as a function of the stabilizer content by small-angle X-ray scattering. Phase transitions at the colloidal scale were found in some of nanostructured aqueous dispersions by increasing the stabilizer content. For particles containing a bicontinuous cubic phase, a large increase of the stabilizer concentration promoted a liquid crystalline phase transition from the Pn3m to the Im3m cubic symmetry. The coexistence of both phases is observed in an intermediate stabilizer concentration range. For particles with an internal micellar cubic Fd3m symmetry, the internal structure changes in the isotropic fluid L 2 phase. In case of particles with an internal hexagonal phase (H 2 symmetry), the increasing amount of stabilizer did not alter the lattice parameter but decreased the size of the nanostructured domain. Moreover, we showed for hexagonal and emulsified micellar phase particles that the increase of the stabilizer content induced a strong decrease of the mean hydrodynamic size of the particles, allowing producing nanostructured lipid-based liquid crystalline particles down to a radius of 70 nm at the same energy input.

Research paper thumbnail of Surfactant-Induced Collapse of Polymer Chains and Monodisperse Growth of Aggregates near the Precipitation Boundary in Carboxymethylcellulose−DTAB Aqueous Solutions

Langmuir, 2003

... Samuel Guillot, † Michel Delsanti, ‡ Sylvain Désert, ‡ and Dominique Langevin* †. Laboratoire... more ... Samuel Guillot, † Michel Delsanti, ‡ Sylvain Désert, ‡ and Dominique Langevin* †. Laboratoire de Physique des Solides, Bâtiment 510, Université Paris-Sud, 91405 Orsay Cedex, France, and Service de Chimie Moléculaire, CEA Saclay, 91191 Gif-sur-Yvette Cedex, France. ...

Research paper thumbnail of Confinement of DNA in Water-in-Oil Microemulsions

Langmuir, 2008

The study of systems that allow DNA condensation in confined environments is an important task in... more The study of systems that allow DNA condensation in confined environments is an important task in producing cell-mimicking microreactors capable of biochemical activities. The water droplets formed in water-in-oil emulsions are potentially good candidates for such microcompartments. The anionic surfactant AOT was used here to stabilize the droplets. We have studied in detail the DNA distribution and the structural modifications of these microemulsion drops by varying the concentration and molecular weight of DNA and using various techniques such as light, X-ray, and neutron scattering, electrical conductivity, and surface tension. DNA induces the formation of large drops into which it is internalized. The size of these drops depends on the amount of DNA dissolved in water as well as on its molecular weight. The local DNA concentration is very high (>100 mg/mL). The large drops coexist with small empty drops (not containing DNA), similar to those found in the DNA-free microemulsion.

Research paper thumbnail of Internally self-assembled particles entrapped in thermoreversible hydrogels

Journal of Colloid and Interface Science, 2009

The present study describes the development of thermogelling emulsions by the entrapment of inter... more The present study describes the development of thermogelling emulsions by the entrapment of internally self-assembled emulsion droplets (ISAsomes) within a thermoreversible hydrogel made of κ-carrageenan.

Research paper thumbnail of Internal organisation in polyelectrolytes/oppositely charged surfactants colloidal complexes anticipating precipitated nanostructures

The European Physical Journal E, 2011

In this paper, we relate the periodic nanostructures found in the colloidal complexes and the con... more In this paper, we relate the periodic nanostructures found in the colloidal complexes and the concentrated phases obtained with polyelectrolyte/surfactant aqueous solutions. We present small-angle X-ray scattering studies of the self-organisation of the anionic polymer carboxymethylcellulose with three cationic quaternary ammonium surfactants with different head and tail groups: hexadecyl trimethyl, hexadecyl ethyl dimethyl and didodecyl dimethyl ammonium bromides. We investigated the mesophases obtained above a precipitation threshold. The mixed solutions with the double-chained surfactant led to lamellar phases, in which the repeat distance only depends on the surfactant/carboxyl charge molar ratio. We show that an internal lamellar organisation already takes place in the dilute phase containing colloidal complexes found below the precipitation threshold.

Research paper thumbnail of Direct and indirect thermal transitions from hexosomes to emulsified micro-emulsions in oil-loaded monoglyceride-based particles

Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2006

We identified the possible internally self-assembled phases that occur in oil-loaded monoglycerid... more We identified the possible internally self-assembled phases that occur in oil-loaded monoglyceride-based nanoparticles that are dispersed in water. Temperature versus composition of the dispersed phase "T-δ" phase diagrams were constructed at a constant dispersed phase content upon varying the oil/monoglyceride weight ratio at a wide range of temperatures (1-90 • C). We mainly focused on the determination of these phase diagrams by changing the oil type or the monoglyceride purity. They were built when investigating the internal structure of the particles by means of small angle X-ray scattering (SAXS). We show that some internally self-assembled emulsified particles may contain a discontinuous cubic phase (Fd3m symmetry), depending on the oil content. However, the extension of this phase in the diagram strongly depends on the oil. This emulsified liquid crystalline phase is inserted between the inverse hexagonal H 2 phase and the inverse micellar solution L 2 phase, as was previously found in bulk. Moreover, we managed to find the existence of an indirect thermal transformation from hexosomes to emulsified micro-emulsions through micellar cubosomes (emulsified reversed discontinuous micellar cubic phase) within a narrow range of an oil/monoglycerides ratio. This transition via temperature has not been published to our knowledge in these dispersed systems.

Research paper thumbnail of X-ray Diffraction Study of the Structure of Carboxymethylcellulose–Cationic Surfactant Complexes

Research paper thumbnail of Carbon Nanotubes as Structural Nanofibers for Hyaluronic Acid Hydrogel Scaffolds

Biomacromolecules, 2008

We have successfully dispersed functionalized single-walled carbon nanotubes (SWNTs) within hyalu... more We have successfully dispersed functionalized single-walled carbon nanotubes (SWNTs) within hyaluronic acid-water solutions. Hybrid hyaluronic acid (HA) hydrogels with SWNTs were then formed by cross-linking with divinyl sulfone. We have found a considerable change in the morphology of the lyophilized hybrid hydrogels compared to HA hydrogels. The high water uptake capacity, an important property of HA hydrogels, remained almost unchanged after 2 wt % SWNT (vs HA) incorporation, despite a dramatic enhancement in the dynamic mechanical properties of the hybrid hydrogels compared to native ones. We have found a 300% enhancement in the storage modulus of hybrid hydrogel with only 2 wt % of SWNTs vs HA (0.06 wt % vs total weight including water content). This apparent contradiction can be explained by a networking effect between SWNTs, mediated by HA chains. As in biological tissue, HA plays a dual role of matrix and linker for the rigid reinforcing nanofibers.

Research paper thumbnail of Loading and release of internally self-assembled emulsions embedded in a magnetic hydrogel

Applied Physics Letters, 2014

We have investigated drug loading and release from thermosensitive gel emulsions with external tr... more We have investigated drug loading and release from thermosensitive gel emulsions with external triggering by an alternating magnetic field (AMF) for on-demand drug delivery. Superparamagnetic iron oxide nanoparticles dispersed in gel emulsions were used to study the loading and release capabilities, with the stable nitroxide radical 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO) serving as the model drug. AMF activation gave similar results to temperature activation in a water bath at 37 C, showing that the principal effect of the AMF is a temperature increase without burst release. These results suggest that the system could play an important role in the development of advanced drug delivery. V C 2014 AIP Publishing LLC. [http://dx.doi.org/10.1063/1.4862811] Confinement and controlled release of drugs through constrained geometries continue to be an active topic in nanotechnology with a special focus on biopharmaceutical applications. 1,2 One attractive challenge is to design devices for long-term therapies, with a zero premature release rate, i.e., "on-demand" release patterns. During the ON mode, delivery could be activated with a controlled release rate while during the OFF mode, delivery through continuous leakage should be negligible since too rapid release or "burst release" might lead to more side effects and thus needs to be controlled. Among the potential candidates, a combination of drug carrying nanoporous lipid particles, having intrinsically high surface areas, with stimulus-responsive hydrogels appears particularly promising.

Research paper thumbnail of Internally structured pickering emulsions stabilized by clay mineral particles

Journal of Colloid and Interface Science, 2009

The present study aims to describe emulsion particles containing a dispersed phase composed of na... more The present study aims to describe emulsion particles containing a dispersed phase composed of nanostructured lipid mesophases and stabilized by montmorillonite and/or Laponite clay platelets. The size distributions of these emulsion particles were found independent of the clay mineral content and of the initial internal composition that determines the internal structure. The stabilization of the droplets by a shell of smectite layers was found possible even by montmorillonite which has a length of the same order or more than the droplets to stabilize. The clay platelets give a local flatness to the droplets that may influence the internal structure. In this paper, we describe the conditions to obtain such soft particles of about 220 nm, and we show by direct visualization the internal mesophase complexity and the shape of the particles. In particular, TEM analysis showed elongated particles with bent-back channels at their center but a different morphology at the periphery due to flat border conditions imposed by the presence of the clay minerals.