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Project
Investigation of supramolecular nanostructures in liquid state using diffusion ordered (DOSY) NMR (FWOAL560)
Nano-particles are extensively used in a broad panel of industrial applications in the fields of catalysis,2en nano-composite materials.3 Among others, their large contact surface with respect to their volume plays a crucial role in various applications. Thorough insight into the surface chemistry of such nanoparticles is accordingly of major importance, in particular also because their chemical properties can be finetuned by functionalizing their surface,4
for instance. Thus, ligands can be grafted in order to prevent aggregation, while also hydrophobic as well as hydrophilic properties can be generated, a protective layer or formation of selective bonds can be promoted. In our HNMR-VUB research group, scientific expertise has been achieved, in collaboration with Dr. F. Ribot, Laboratoire de Chimie de la Matière Condensée de Paris, Université Pierre et Marie Curie, Paris, France, on hybrid nano-particles, inorganic nano-clusters functionalized with organic ligands.
Pure organic nano-particles can also be generated. Thus, surfactants, utilized in cosmetical and pharmaceutical applications, or as detergents, tend, under well defined conditions, to give rise to micelles which can be used to solubilize hydrophobic substances into a hydrophilic medium, with as one of the possible goals, to transport these substances throughout aqueous biological media. Another nano-structure, a liposome, can even be considered as a universal "container" of chemically active substances as drug or diagnostic molecules.
Thus, their specific double layer structure allows hydrophilic substances within the core of the liposome, as well as hydrophobic ones in the double layer, to be transported throughout biological fluids. The circulation time of such liposomes is, however, quite limited since artificial liposomes are immediately recognized by the immune system as antibodies and therefore degraded as fast as possible. A first approach to prevent degradation consists in designing pH-sensitive liposomes by which the liposomes, depending on the acidity degree, undergo some structural changes lengthening their circulation time. A second strategy tends to functionalize the liposomes with a protective polymer layer. The chemical barrier thus formed prevents or at least decreases interactions with the medium (e.g. blood), increasing their circulation time. Within our group, in collaboration with Dr. P. Denkova of the Bulgarian Academy of Sciences, micellar systems, with several types of pure or mixtures of surfactants, were successfully investigated.
Likewise, model liposome systems were explored, with promising results. Functionalized nano-particles, micelles and liposomes can likewise aggregate to supramolecular nanostructures. Such an aggregation can originate from purely physical as well as chemical characteristics. Thus, water soluble, poly-N-isopropylacrylamide (PNIPAM) functionalized gold nano-particles can form thermoresponsive mesoglobules very likely on the basis of physical interactions, but sound evidence to this is still lacking.
Multi-functional ligands enable one, via chemical grafting, either electrostatic or covalent, to aggregate nano-particles toward supramolecular structures of funtionalized nano-particles, for example macrocations "mutually bridged" by bidentate anions. Next to supramolecular structures set up with uniform building stones, different types of building stones can be combined as in the case of the encapsulation of a nano-particle into a micelle or a liposome. This offers prospects to introduce nano-particles into cellular systems. The nanoparticle can thus be isolated or enclosed in the liposome or, provided it is functionalized, the ligands can be mixed up into the double layer. The same principle can also be applied to the encapsulation of functionalizednano-particles into micelles.
for instance. Thus, ligands can be grafted in order to prevent aggregation, while also hydrophobic as well as hydrophilic properties can be generated, a protective layer or formation of selective bonds can be promoted. In our HNMR-VUB research group, scientific expertise has been achieved, in collaboration with Dr. F. Ribot, Laboratoire de Chimie de la Matière Condensée de Paris, Université Pierre et Marie Curie, Paris, France, on hybrid nano-particles, inorganic nano-clusters functionalized with organic ligands.
Pure organic nano-particles can also be generated. Thus, surfactants, utilized in cosmetical and pharmaceutical applications, or as detergents, tend, under well defined conditions, to give rise to micelles which can be used to solubilize hydrophobic substances into a hydrophilic medium, with as one of the possible goals, to transport these substances throughout aqueous biological media. Another nano-structure, a liposome, can even be considered as a universal "container" of chemically active substances as drug or diagnostic molecules.
Thus, their specific double layer structure allows hydrophilic substances within the core of the liposome, as well as hydrophobic ones in the double layer, to be transported throughout biological fluids. The circulation time of such liposomes is, however, quite limited since artificial liposomes are immediately recognized by the immune system as antibodies and therefore degraded as fast as possible. A first approach to prevent degradation consists in designing pH-sensitive liposomes by which the liposomes, depending on the acidity degree, undergo some structural changes lengthening their circulation time. A second strategy tends to functionalize the liposomes with a protective polymer layer. The chemical barrier thus formed prevents or at least decreases interactions with the medium (e.g. blood), increasing their circulation time. Within our group, in collaboration with Dr. P. Denkova of the Bulgarian Academy of Sciences, micellar systems, with several types of pure or mixtures of surfactants, were successfully investigated.
Likewise, model liposome systems were explored, with promising results. Functionalized nano-particles, micelles and liposomes can likewise aggregate to supramolecular nanostructures. Such an aggregation can originate from purely physical as well as chemical characteristics. Thus, water soluble, poly-N-isopropylacrylamide (PNIPAM) functionalized gold nano-particles can form thermoresponsive mesoglobules very likely on the basis of physical interactions, but sound evidence to this is still lacking.
Multi-functional ligands enable one, via chemical grafting, either electrostatic or covalent, to aggregate nano-particles toward supramolecular structures of funtionalized nano-particles, for example macrocations "mutually bridged" by bidentate anions. Next to supramolecular structures set up with uniform building stones, different types of building stones can be combined as in the case of the encapsulation of a nano-particle into a micelle or a liposome. This offers prospects to introduce nano-particles into cellular systems. The nanoparticle can thus be isolated or enclosed in the liposome or, provided it is functionalized, the ligands can be mixed up into the double layer. The same principle can also be applied to the encapsulation of functionalizednano-particles into micelles.
Date:1 Jan 2010 → 31 Dec 2013
Keywords:material science, thermal analysis, chemistry, surface analysis, NMR, polymer science, engineering, electrochemistry
Disciplines:Physical sciences, (Bio)chemical engineering, Other engineering and technology, Chemical sciences, Materials engineering