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See detailStimuli-responsive self-assembled macromolecular systems with potential drug delivery applications: structural characterization by Small-Angle Neutron Scattering
Joset, Arnaud ULg

Doctoral thesis (2016)

Colloids are known since the early 19th century but they have mainly sparked interest since the last few decades thanks to their use in biomedical applications or in the design of new materials. The aim ... [more ▼]

Colloids are known since the early 19th century but they have mainly sparked interest since the last few decades thanks to their use in biomedical applications or in the design of new materials. The aim of this thesis is the study of stimuli-responsive colloids by Small-Angle Neutron Scattering (SANS). The stimuli may be the pH, the temperature, the addition of a ligand or of metallic ions or a combination of them. SANS is a useful technique which provides information about the internal structure of nano-objects but also, if appropriate conditions are met, about the organization of the objects in solution. Several samples built from the auto-assembly of block copolymers and liposomes have been prepared. The macroscopic cross sections have been modeled with the aim to infer the main structural parameters of the samples: the global size, the polydispersity, the structure and volume occupied by the hydrophilic and hydrophobic components inside the nano-objects. The SANS measurements have been performed as a function of the intensity of the stimulus, in order to quantify the evolution of the structural parameters. The first experimental part focuses on micellar samples built from sequenced block copolymers. The blocks may be biodegradable (e.g., poly(ε-caprolactone)), biocompatible (e.g., poly(ethylene oxide)), pH-sensitive (e.g., poly(2 vinylpyridine), poly(acrylic acid)) or temperature-sensitive (e.g., poly(N-isopropylacrylamide)). The influence of the concentration and the formation of bridges between micelles have been investigated through the analysis of metallo-supramolecular micellar gels resulting from the self-assembling of polystyrene-block-poly(tert-butylacrylate) PS-b-PtBA-tpy (tpy stands for terpyridine) block copolymers in the presence of transition metal ions. The second part focuses on the analysis of liposomes interacting with an increasing concentration of Randomly Methylated β-cyclodextrins (RAMEB). This part is divided into two chapters. The first one deals with liposomes mainly composed of dimyristoylphosphatidylcholine (DMPC) and the second one investigates the effects of cholesterol doping on the same DMPC liposomes interacting with RAMEB. [less ▲]

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See detailSmall-Angle Neutron Scattering investigation of cholesterol-doped DMPC liposomes interacting with β-cyclodextrin
Joset, Arnaud ULg; Grammenos, Angeliki; Hoebeke, Maryse ULg et al

in Journal of Inclusion Phenomena and Macrocyclic Chemistry (2016), 84(1), 153-161

The Small-Angle Neutron Scattering technique (SANS) has been applied to characterize the influence of a randomly methylated β–cyclodextrin (CD), called RAMEB, on dimyristoylphosphatidylcholine (DMPC ... [more ▼]

The Small-Angle Neutron Scattering technique (SANS) has been applied to characterize the influence of a randomly methylated β–cyclodextrin (CD), called RAMEB, on dimyristoylphosphatidylcholine (DMPC) liposomes doped with cholesterol. From the modelling of the experimental neutron scattering crosssections, the detailed response of the vesicle structure upon addition of increasing amounts of RAMEB up to 30 mM has been assessed. This study has been performed below and above the DMPC bilayer phase transition temperature and shows that cholesterol extraction by RAMEB is linked to a decrease of the average radius and of the aggregation number of the vesicles. This extraction takes place in a dose-dependent way until a more monodisperse population of cholesterol-free liposomes was obtained. In addition, the bilayer thickness evolution was inferred, as well as the liposome coverage by RAMEB. [less ▲]

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See detailInvestigation of the interaction between a β-cyclodextrin and DMPC liposomes: a small angle neutron scattering study
Joset, Arnaud ULg; Grammenos, Angeliki; Hoebeke, Maryse ULg et al

in Journal of Inclusion Phenomena and Macrocyclic Chemistry (2015), 83(3), 227-238

The Small Angle Neutron Scattering technique (SANS) has been applied to investigate the interaction between a cyclodextrin (CD) and liposomes. From the modelling of the experimental neutron scattering ... [more ▼]

The Small Angle Neutron Scattering technique (SANS) has been applied to investigate the interaction between a cyclodextrin (CD) and liposomes. From the modelling of the experimental neutron scattering cross sections, the detailed structure of dimyristoylphosphatidylcholine (DMPC) liposomes is assessed upon addition of increasing amounts of randomly methylated β-CD (RAMEB). This study has been performed at two temperatures bracketing the phase transition of the DMPC bilayers. The fraction of DMPC molecules incorporated into the vesicles is inferred. The dose-dependent phospholipidic extraction by RAMEB is quantified as well as the concomitant evolution of the liposome radius and of the thickness of the hydrophobic and hydrophilic parts of the membrane. The possible formation of CD-DMPC inclusion complexes is also assessed. The data suggest the dose-dependent coverage by RAMEB of the outer liposome interface. Our analysis highlights the important role of temperature on the mechanism of action of RAMEB. These results are discussed in the framework of the Area-Difference-Elasticity model. [less ▲]

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See detailStructure of metallo-supramolecular micellar gels
Mugemana, Clément; Joset, Arnaud ULg; Guillet, Pierre et al

in Macromolecular Chemistry and Physics (2013), 214(15), 1699-1709

A small-angle neutron scattering investigation of metallo-supramolecular micellar gels built from polystyrene-block-poly(tert-butylacrylate) PS-b-PtBA-tpy (-tpy: terpyridine) block copolymers and ... [more ▼]

A small-angle neutron scattering investigation of metallo-supramolecular micellar gels built from polystyrene-block-poly(tert-butylacrylate) PS-b-PtBA-tpy (-tpy: terpyridine) block copolymers and transition metal ions is presented. The influence of the copolymer concentration on the structure and spatial organization of the micelles, as well as the impact of the subsequent addition of metal ions (Fe(II), Ni(II), and Zn(II)) on these characteristics is extensively studied. The experimental scattering cross-sections are fitted with an analytical formula based on the Percus–Yevick hard-sphere model and on the Pedersen–Gerstenberg model for the structure and the form factor, respectively. The resulting structural information is correlated with previously performed light scattering and rheology experiments. [less ▲]

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See detailMetallo-supramolecular micellar gels: a structural study
Mugemana, Clément; Joset, Arnaud ULg; Guillet, Pierre et al

Poster (2013, July 10)

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See detailMetallo-supramolecular micellar gels: a structural study
Mugemana, Clément; Joset, Arnaud ULg; Guillet, Pierre et al

Conference (2013, May 17)

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See detailpH-sensitive micellar systems for controlled drug delivery: synthesis and structural characterization by small-angle neutron scattering
Joset, Arnaud ULg; Jérôme, Christine ULg; Brulet, Annie et al

Poster (2009, May 14)

The aim of the project is the preparation of micellar nanocarriers made of biocompatibles copolymers and their structural analysis by Small Angle Neutron Scattering (SANS). These micelles could be used in ... [more ▼]

The aim of the project is the preparation of micellar nanocarriers made of biocompatibles copolymers and their structural analysis by Small Angle Neutron Scattering (SANS). These micelles could be used in drug delivery applications to fight cancer1. The hydrophobic polycaprolactone (PCL) core is intended to incorporate the drug. The corona of hydrophilic polyethylene oxide (PEO) stabilizes the nanocarriers with respect to the plasma proteins. The pH in the neighborhood of the tumoral cells is lower than in the healthy cells. We incorporated a pH-sensitive sequence of poly(2-vinylpyridine) (P2VP). As a result, these micelles are expected to deliver their drug near the cancerous cells without affecting the healthy cells. When the pH is acidic, the P2VP is protonated and the chains are repulsive. The micellar size is then larger than in basic pH, when the P2VP is precipitated on the PCL core. We prepared PCL65-b-P2VP31 / PCL65-b-PEO114 and PCL32-b-P2VP52 / PCL36-b-PEO114 50:50 mixtures of diblocks copolymers. The resulting mixed micelles are analyzed by SANS. We developed a theoretical model with a spherical water-free PCL core. The PEO corona is described as consisting of gaussian chains with a thickness estimated as twice the chain gyration radius, Rg. We propose two alternatives for handling the P2VP zone. The P2VP molecules are either assumed to be Gaussian chains or they fill a shell of thickness L with possible water penetration.The fitting of the models to the experimental scattering cross sections leads to important structural parameters like the aggregation number, the core radius, the gyration radius and the thickness of the P2VP shell. [less ▲]

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See detailpH-sensitive micellar systems for controlled drug delivery: synthesis and structural characterization by small-angle neutron scattering
Joset, Arnaud ULg; Jérôme, Christine ULg; Brulet, Annie et al

Poster (2009, March)

The aim of the project is the preparation of micellar nanocarriers made of biocompatibles copolymers and their structural analysis by Small Angle Neutron Scattering (SANS). These micelles could be used in ... [more ▼]

The aim of the project is the preparation of micellar nanocarriers made of biocompatibles copolymers and their structural analysis by Small Angle Neutron Scattering (SANS). These micelles could be used in drug delivery applications to fight cancer1. The hydrophobic polycaprolactone (PCL) core is intended to incorporate the drug. The corona of hydrophilic polyethylene oxide (PEO) stabilizes the nanocarriers with respect to the plasma proteins. The pH in the neighborhood of the tumoral cells is lower than in the healthy cells. We incorporated a pH-sensitive sequence of poly(2-vinylpyridine) (P2VP). As a result, these micelles are expected to deliver their drug near the cancerous cells without affecting the healthy cells. When the pH is acidic, the P2VP is protonated and the chains are repulsive. The micellar size is then larger than in basic pH, when the P2VP is precipitated on the PCL core. We prepared PCL65-b-P2VP31 / PCL65-b-PEO114 and PCL32-b-P2VP52 / PCL36-b-PEO114 50:50 mixtures of diblocks copolymers. The resulting mixed micelles are analyzed by SANS. We developed a theoretical model with a spherical water-free PCL core. The PEO corona is described as consisting of gaussian chains with a thickness estimated as twice the chain gyration radius, Rg. We propose two alternatives for handling the P2VP zone. The P2VP molecules are either assumed to be Gaussian chains or they fill a shell of thickness L with possible water penetration.The fitting of the models to the experimental scattering cross sections leads to important structural parameters like the aggregation number, the core radius, the gyration radius and the thickness of the P2VP shell. [less ▲]

Detailed reference viewed: 101 (13 ULg)