Browsing
     by title


0-9 A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

or enter first few letters:   
OK
Full Text
See detailLa chitine dans le règne animal
Jeuniaux, Charles ULg

in Bulletin de la Société Zoologique de France (1982), 107(3), 363-386

Chitin, a high linear polymer composed of N-acetylglucosamine residues attached by B-1,4 glycosidic linkages, is often used in the animal kingdom as an organic support of cuticular and exoskeletal ... [more ▼]

Chitin, a high linear polymer composed of N-acetylglucosamine residues attached by B-1,4 glycosidic linkages, is often used in the animal kingdom as an organic support of cuticular and exoskeletal structures. A specific enzymatic method allows the detection and quantitative measurement of chitin, and may be suitable for pointing out the existence of some linkage to other constituents ("free" and "bound" chitin). Chitin is mainly organised, at the ultrastructural level, in microfibrils (glycoprotein complex). Chitin is a constituent of diverse structures, built up by Protozoa, mainly Ciliates (kystic membranes, sheaths). In Diblastic Metazoa, chitin is secreted by the ectoderm of most Hydrozoa and of some Octocorallia and Scyphozoa, but is completely lacking in Porifera and Ctenophora. Among Triblastic Metazoa, chitin is frequently secreted by the ectoderm of Spiralia, as well Pseudocoelomates (mainly in egg envelopes) as Protostomian Coelomates (in cuticles, shells, setae, operculae, scales, spicules, etc.), with the exception of Sipunculida. Chitin does not seem to be secreted at all by Acoelomates. Peritrophic membranes of Arthropoda and Annelida seem to be of endodermic origin, as well as different types of cuticular formations in the stomach of many Molluscs. Chitin is a frequent constituent of ectodermic productions in Lophophorates (tubes, ectocyst, shells), in Pogonophora (tubes) and in Chaetognatha. The secretion of this polysaccharide is entirely lacking in Echinoderms, Stomochordates and Chordates, with the remarkable exception of the peritrophic membrane in Tunicates. Chitin biosynthesis thus appears as a biochemical characteristic, which must be used with care when discussing the systematic position and phylogenetic relationships. [less ▲]

Detailed reference viewed: 22 (0 ULg)
Full Text
See detailChitinous Cuticle and Systematic Position of Tardigrada
Bussers, Jean-Claude ULg; Jeuniaux, Charles ULg

in Biochemical systematics (1973), 1

The chitinous nature of the cuticle, jaws and stomodaeum of three species of Tardigrada has been definitely proven using a specific micromethod involving a preparation of purified chitinase. These ... [more ▼]

The chitinous nature of the cuticle, jaws and stomodaeum of three species of Tardigrada has been definitely proven using a specific micromethod involving a preparation of purified chitinase. These chemical characteristics are in favour of the phylogenetic closeness between Tardigrada and the Arthropoda. [less ▲]

Detailed reference viewed: 12 (1 ULg)
Full Text
Peer Reviewed
See detailChitinous microfibres in the inner epicuticle of crab and myriapod sclerites
Compère, Philippe ULg; Schilito, Bruce; Gaill, Françoise et al

in Domard, Alain; Jeuniaux, Charles; Muzzarelli, Ricardo (Eds.) et al Advances in chitin sciences, volume I (1996)

Detailed reference viewed: 14 (0 ULg)
Full Text
Peer Reviewed
See detailThe Chitobiose-Binding Protein, DasA, Acts as a Link between Chitin Utilization and Morphogenesis in Streptomyces Coelicolor
Colson, Séverine ULg; van Wezel, G. P.; Craig, Matthias ULg et al

in Microbiology (2008), 154(Pt 2), 373-82

Streptomycetes are mycelial soil bacteria that undergo a developmental programme that leads to sporulating aerial hyphae. As soil-dwelling bacteria, streptomycetes rely primarily on natural polymers such ... [more ▼]

Streptomycetes are mycelial soil bacteria that undergo a developmental programme that leads to sporulating aerial hyphae. As soil-dwelling bacteria, streptomycetes rely primarily on natural polymers such as cellulose, xylan and chitin for the colonization of their environmental niche and therefore these polysaccharides may play a critical role in monitoring the global nutritional status of the environment. In this work we analysed the role of DasA, the sugar-binding component of the chitobiose ATP-binding cassette transport system, in informing the cell of environmental conditions, and its role in the onset of development and in ensuring correct sporulation. The chromosomal interruption of dasA resulted in a carbon-source-dependent vegetative arrest phenotype, and we identified a second DasR-dependent sugar transporter, in addition to the N-acetylglucosamine phosphotransferase system (PTS(GlcNAc)), that relates primary metabolism to development. Under conditions that allowed sporulation, highly aberrant spores with many prematurely produced germ tubes were observed. While GlcNAc locks streptomycetes in the vegetative state, a high extracellular concentration of the GlcNAc polymer chitin has no effect on development. The striking distinction is due to a difference in the transporters responsible for the import of GlcNAc, which enters via the PTS, and of chitin, which enters as the hydrolytic product chitobiose (GlcNAc(2)) through the DasABC transporter. A model explaining the role of these two essentially different transport systems in the control of development is provided. [less ▲]

Detailed reference viewed: 90 (12 ULg)
Full Text
See detailChitosan and chitosan derivatives in drug delivery and tissue engineering
Riva, Raphaël ULg; Raguelle, Héloïse; des Rieux, Anne et al

in Jayakumar, Rangasamy; Prabaharan, M.; Muzzarelli, Ricardo A. A. (Eds.) Chitosan for Biomaterials II (2011)

Chitosan is a nontoxic, biodegradable, and biocompatible polysaccharide of β(1-4)-linked d-glucosamine and N-acetyl-d-glucosamine. This derivative of natural chitin presents remarkable properties that ... [more ▼]

Chitosan is a nontoxic, biodegradable, and biocompatible polysaccharide of β(1-4)-linked d-glucosamine and N-acetyl-d-glucosamine. This derivative of natural chitin presents remarkable properties that have paved the way for the introduction of chitosan in the biomedical and pharmaceutical fields. Nevertheless, the properties of chitosan, such as its poor solubility in water or in organic solvents, can limit its utilization for a specific application. An elegant way to improve or to impart new properties to chitosan is the chemical modification of the chain, generally by grafting of functional groups, without modification of the initial skeleton in order to conserve the original properties. The functionalization is carried out on the primary amine group, generally by quaternization, or on the hydroxyl group. This review aims to provide an overview of chitosan and chitosan derivatives used for drug delivery, with a special emphasis on chemical modifications of chitosan to achieve specific biomedical purpose. The synthesis of the main chitosan derivatives will be reviewed. The applications of chitosan and these chitosan derivatives will be illustrated. [less ▲]

Detailed reference viewed: 214 (11 ULg)
Full Text
Peer Reviewed
See detailChitosan as a Tool for the Purification of Waters
Jeuniaux, Charles ULg

in Muzzarelli, Riccardo; Jeuniaux, Charles; Gooday, Graham W. (Eds.) Chitin in Nature and Technology (1986)

It is well known that surface waters are polluted not only by inorganic chemicals such as heavy metals, but also by organic compounds. Owing to the high sorption capacities of chitosan this polymer can be ... [more ▼]

It is well known that surface waters are polluted not only by inorganic chemicals such as heavy metals, but also by organic compounds. Owing to the high sorption capacities of chitosan this polymer can be utilized as a tool for the epuration of wastewaters on polluted stream waters. Some typical examples of the application of chitosan to this kind of environmental problems are given here. They include the prevention of water pollution by highly toxic chlorinated aromatic compounds, metal ions, and dyes which are amply used in the textile industry. The recovery of proteins from wastewaters is an example of pollution control utilized in other industries, including shrimp processing, as well. [less ▲]

Detailed reference viewed: 1 (0 ULg)
See detailChitosan based nanofiber-membranes for tissue engineering
Jérôme, Christine ULg

Conference (2010, November 29)

Detailed reference viewed: 22 (5 ULg)
Full Text
Peer Reviewed
See detailChitosan enriched three-dimensional matrix reduces inflammatory and catabolic mediators production by human chondrocytes
Oprenyeszk, Frédéric ULg; Sanchez, Christelle ULg; Dubuc, Jean-Emile et al

in PLoS ONE (2015), 10(5),

This in vitro study investigated the metabolism of human osteoarthritic (OA) chondrocytes encapsulated in a spherical matrix enriched of chitosan. Human OA chondrocytes were encapsulated and cultured for ... [more ▼]

This in vitro study investigated the metabolism of human osteoarthritic (OA) chondrocytes encapsulated in a spherical matrix enriched of chitosan. Human OA chondrocytes were encapsulated and cultured for 28 days either in chitosan-alginate beads or in alginate beads. The beads were formed by slowly passed dropwise either the chitosan 0.6%- alginate 1.2% or the alginate 1.2% solution through a syringe into a 102 mM CaCl2 solution. Beads were analyzed histologically after 28 days. Interleukin (IL)-6 and -8, prostaglandin (PG) E2, matrix metalloproteinases (MMPs), hyaluronan and aggrecan were quantified directly in the culture supernatant by specific ELISA and nitric oxide (NO) by using a colorimetric method based on the Griess reaction. Hematoxylin and eosin staining showed that chitosan was homogeneously distributed through the matrix and was in direct contact with chondrocytes. The production of IL-6, IL-8 and MMP-3 by chondrocytes significantly decreased in chitosan-alginate beads compared to alginate beads. PGE2 and NO decreased also significantly but only during the first three days of culture. Hyaluronan and aggrecan production tended to increase in chitosan-alginate beads after 28 days of culture. Chitosan-alginate beads reduced the production of inflammatory and catabolic mediators by OA chondrocytes and tended to stimulate the synthesis of cartilage matrix components. These particular effects indicate that chitosan-alginate beads are an interesting scaffold for chondrocytes encapsulation before transplantation to repair cartilage defects. [less ▲]

Detailed reference viewed: 110 (30 ULg)
See detailChitosan nanofiber membranes for tissue engineering - synthesis, characterization and properties
Toncheva, Natalia ULg; Aqil, Abdelhafid ULg; Croisier, Florence ULg et al

Poster (2010, November 29)

This poster was presented by Natalia Toncheva

Detailed reference viewed: 54 (4 ULg)
Full Text
Peer Reviewed
See detailChitosan nanoparticles for siRNA delivery: Optimizing formulation to increase stability and efficiency
Ragelle, Héloïse; Riva, Raphaël ULg; Vandermeulen, G. et al

in Journal of Controlled Release (2014), 176

This study aims at developing chitosan-based nanoparticles suitable for an intravenous administration of small interfering RNA (siRNA) able to achieve (i) high gene silencing without cytotoxicity and (ii ... [more ▼]

This study aims at developing chitosan-based nanoparticles suitable for an intravenous administration of small interfering RNA (siRNA) able to achieve (i) high gene silencing without cytotoxicity and (ii) stability in biological media including blood. Therefore, the influence of chitosan/tripolyphosphate ratio, chitosan physicochemical properties, PEGylation of chitosan as well as the addition of an endosomal disrupting agent and a negatively charged polymer was assessed. The gene silencing activity and cytotoxicity were evaluated on B16 melanoma cells expressing luciferase. We monitored the integrity and the size behavior of siRNA nanoparticles in human plasma using fluorescence fluctuation spectroscopy and single particle tracking respectively. The presence of PEGylated chitosan and poly(ethylene imine) was essential for high levels of gene silencing in vitro. Chitosan nanoparticles immediately released siRNA in plasma while the inclusion of hyaluronic acid and high amount of poly(ethylene glycol) in the formulation improved the stability of the particles. The developed formulations of PEGylated chitosan-based nanoparticles that achieve high gene silencing in vitro, low cytotoxicity and high stability in plasma could be promising for intravenous delivery of siRNA. [less ▲]

Detailed reference viewed: 45 (9 ULg)
Full Text
Peer Reviewed
See detailChitosan-based biomaterials for tissue engineering
Croisier, Florence ULg; Jérôme, Christine ULg

in European Polymer Journal (2013), 49(4), 780-792

Derived from chitin, chitosan is a unique biopolymer that exhibits outstanding properties, beside biocompatibility and biodegradability. Most of these peculiar properties arise from the presence of ... [more ▼]

Derived from chitin, chitosan is a unique biopolymer that exhibits outstanding properties, beside biocompatibility and biodegradability. Most of these peculiar properties arise from the presence of primary amines along the chitosan backbone. As a consequence, this polysaccharide is a relevant candidate in the field of biomaterials, especially for tissue engineering. The current article highlights the preparation and properties of innovative chitosan-based biomaterials, with respect to their future applications. The use of chitosan in 3D-scaffolds – as gels and sponges – and in 2D-scaffolds – as films and fibers – is discussed, with a special focus on wound healing application. [less ▲]

Detailed reference viewed: 128 (27 ULg)
Full Text
See detailChitosan-based biomimetic scaffolds and methods for preparing the same
Filée, Patrice; Freichels, Astrid ULg; Jérôme, Christine ULg et al

Patent (2011)

The invention concerns chitosan biomimetic scaffolds and methods for modulating their intrinsic properties such as rigidity, elasticity, resistance to mechanical stress, porosity, biodegradation and ... [more ▼]

The invention concerns chitosan biomimetic scaffolds and methods for modulating their intrinsic properties such as rigidity, elasticity, resistance to mechanical stress, porosity, biodegradation and absorbance of exudates. Therefore, the present invention relates to a layered chitosan scaffold wherein said layered scaffold comprises at least two fused layers, wherein at least one of the fused layers comprises a chitosan nanofiber membrane and the other fused layer comprises a porous chitosan support layer. Moreover, the present invention provides a layered chitosan scaffold characterized by (i) a good adhesion between the porous and nanofiber layers, (ii) a tuneable porosity of the nanofiber layer by tuning the distance between the nanofibers, (iii) a stable nanofibers and porous morphology even when immersed in water or other solvents and a process for the preparation of such layered chitosan scaffold. Finally, the present invention provides the use of the layered electrospun chitosan scaffold of the invention or the layered electrospun chitosan scaffold produced by the process of the invention as a wound dressing, in tissue engineering or for biomedical applications. [less ▲]

Detailed reference viewed: 67 (4 ULg)
Full Text
See detailChitosan-based biomimetic scaffolds and methods for preparing the same
Filée, Patrick; Freichels, Astrid ULg; Jérôme, Christine ULg et al

Patent (2011)

The invention concerns chitosan-based biomimetic scaffolds and methods for modulating their intrinsic properties such as rigidity, elasticity, resistance to mechanical stress, porosity, biodegradation and ... [more ▼]

The invention concerns chitosan-based biomimetic scaffolds and methods for modulating their intrinsic properties such as rigidity, elasticity, resistance to mechanical stress, porosity, biodegradation and absorbance of exudates. Therefore, the present invention relates to a layered chitosan-based scaffold wherein said layered scaffold comprises at least two fused layers, wherein at least one layer consists of a chitosan nanofiber scaffold membrane and at least one of the other layers of a porous chitosan scaffold support layer. Moreover, the present invention provides a layered chitosan-based scaffold characterized by (i) a good adhesion between the porous and nanofiber layers, (ii) a tuneable porosity of the nanofiber layer by tuning the distance between the nanofibers, (iii) a stable nanofibers and porous morphology even when immersed in water or other solvents and a process for the preparation of such layered chitosan-based scaffold.Finally, the present invention provides the use of the layered electrospun chitosan-based scaffold of the invention or the layered electrospun chitosan-based scaffold produced by the process of the invention as a wound dressing, in tissue engineering or for biomedical applications. [less ▲]

Detailed reference viewed: 63 (12 ULg)
Full Text
See detailChitosan-based nanofibers for wound dressing
Aqil, Abdelhafid ULg; Tchemtchoua Tateu, Victor ULg; Colige, Alain ULg et al

Poster (2011, May 12)

Detailed reference viewed: 79 (10 ULg)
See detailChitosan-based nanofibers mats for tissue engineering
Aqil, Abdelhafid ULg; Croisier, Florence ULg; Colige, Alain ULg et al

Conference (2016, May)

Polymer hydrogels resemble the natural living tissue due to their high water content and soft consistency. They find many applications in the design and production of contact and intraocular lenses ... [more ▼]

Polymer hydrogels resemble the natural living tissue due to their high water content and soft consistency. They find many applications in the design and production of contact and intraocular lenses, biosensors membranes, matrices for repairing and regenerating a wide diversity of tissues and organs. Polysaccharides such as chitosan and hyaluronic acid based hydrogels have shown a great potential for biomedical and pharmaceutical applications, on account of their remarkable compatibility with physiological medium. Besides, it is degraded in a physiological environment into non-toxic products, which make them outstanding candidates for short- to medium-term applications, especially for tissue engineering. In this respect, the preparation of nanometric fibers mats based on this polysaccharide are highly interesting as such structure mimics the one of skin extracellular matrix. Such nanofibrous materials can be prepared by electrospinning (Figure 1). This technique uses a high voltage to create an electrically charged jet of polymer solution to obtain polymer fibers ranging from nanometers to a few microns in diameter. We thus have investigated strategies allowing to generate chitosan based nanofiber mats exhibiting a mechanical resistance strong enough to be easily handled while keeping the peculiar features of chitosan hydrogels favoring the interaction with cells and soft tissues to provide efficient tissue reconstruction. In a first strategy, polysaccharide-based nanofibers with a multilayered structure were prepared by combining electrospinning (ESP) and layer-by-layer (LBL) deposition techniques. Elastic nanofibers bearing charges at their surface were firstly prepared by electrospinning poly(ε-caprolactone) (PCL) with a polyelectrolyte precursor. After activation by adjusting the pH, the layer-by-layer deposition of chitosan and hyaluronic acid, can be used to coat the electrospun fibers. A multilayered structure is then achieved by alternating the deposition of the positively charged chitosan with the deposition of a negatively charged polyelectrolyte. These novel polysaccharide-coated PCL fiber mats remarkably combine the mechanical resistance typical of the core material (PCL) – particularly in the hydrated state –, with the surface properties of chitosan. Besides, crosslinked nanofibrous mats of chitosan and polyethylene oxide blends, were successfully prepared via electrospinning technique followed by heat mediated chemical crosslinking. This chemical cross-linking allows adjusting the mechanical resistance of the mats while preserving their biocompatibility. In both cases, the control of the nanofiber structure offered by the electrospinning technology, makes the developed processes very promising to precisely design biomaterials for tissue engineering. Preliminary cell culture tests corroborate the potential use of such systems in wound healing applications. [less ▲]

Detailed reference viewed: 129 (11 ULg)
See detailChitosan-based nanofibers with multilayered structure for wound healing application
Croisier, Florence ULg; Detrembleur, Christophe ULg; Jérôme, Christine ULg

Poster (2011, November 21)

Chitosan is a natural polymer that intrinsically presents haemostatic, mucoadhesive, antimicrobial and immunostimulant properties. This polysaccharide has shown a great potential for biomedical ... [more ▼]

Chitosan is a natural polymer that intrinsically presents haemostatic, mucoadhesive, antimicrobial and immunostimulant properties. This polysaccharide has shown a great potential for biomedical applications, on account of its remarkable compatibility with physiological medium and its biodegradability. In this respect, nanometric fibers are highly interesting as their assembly mimics the skin extracellular matrix structure. Such nanofibrous materials can be prepared by electrospinning (ESP) and can be used as scaffolds, a.o. to form a temporary, artificial extracellular matrix. In the present study, electrospinning technique was combined with layer-by-layer deposition method (LBL) – a well-known method for surface coating, based on electrostatic interactions – in order to prepare multilayered chitosan-based nanofibers for wound healing application. [less ▲]

Detailed reference viewed: 118 (10 ULg)
See detailChitosan-based wound dressings produced by electrospinning
Croisier, Florence ULg; Sorlier, Pierre; Jérôme, Christine ULg

Poster (2011, April 29)

Detailed reference viewed: 35 (2 ULg)
Full Text
See detailChitosan-based wound dressings produced by electrospinning
Croisier, Florence ULg; Sorlier, Pierre; Jérôme, Christine ULg

Poster (2010, September 07)

Detailed reference viewed: 31 (4 ULg)
Full Text
Peer Reviewed
See detailChitosan-coated electrospun nanofibers with antibacterial activity
Croisier, Florence ULg; Sibret, Pierre ULg; Dupont-Gillain, Christine C. et al

in Journal of Materials Chemistry B (2015), 3(17), 3508-2517

Charged nanofibers were prepared by electrospinning (ESP) poly(ε-caprolactone) with a copolymer bearing carboxylic acid functions. The presence of these functions allowed exposing some negative charges on ... [more ▼]

Charged nanofibers were prepared by electrospinning (ESP) poly(ε-caprolactone) with a copolymer bearing carboxylic acid functions. The presence of these functions allowed exposing some negative charges on the fiber surface, by dipping the fibers in a phosphate buffer. A layer of chitosan, a polycation in acidic medium, was then deposited on the nanofiber surface, thanks to electrostatic attraction. Fibers were characterized at each step of the process and the influence of the copolymer architecture on chitosan deposition was discussed. The antibacterial activity of the resulting fibers was finally assessed. [less ▲]

Detailed reference viewed: 58 (15 ULg)
Full Text
See detailChitosan-coated nanofibers for wound dressing
Croisier, Florence ULg; Colige, Alain ULg; Jérôme, Christine ULg

Conference (2015, March 23)

Detailed reference viewed: 25 (1 ULg)