TY - JOUR A1 - Raju, Rajarshi Roy A1 - Liebig, Ferenc A1 - Klemke, Bastian A1 - Koetz, Joachim T1 - pH-responsive magnetic Pickering Janus emulsions JF - Colloid and polymer science : official journal of the Kolloid-Gesellschaft N2 - We report ultrasonically generated pH-responsive Pickering Janus emulsions of olive oil and silicone oil with controllable droplet size and engulfment. Chitosan was used as a pH-responsive emulsifier. The increase of pH from 2 to 6 leads to a transition from completely engulfed double emulsion droplets to dumbbell-shaped Janus droplets accompanied by a significant decrease of droplet diameter and a more homogeneous size distribution. The results can be elucidated by the conformational change of chitosan from a more extended form at pH 2 to a more flexible form at pH 4-5. Magnetic responsiveness to the emulsion was attributed by dispersing superparamagnetic nanoparticles (Fe3O4 with diameter of 13 +/- 2 nm) in the olive oil phase before preparing the Janus emulsion. Incorporation of magnetic nanoparticles leads to superior emulsion stability, drastically reduced droplet diameters, and opened the way to control movement and orientation of the Janus droplets according to an external magnetic field. KW - Janus emulsion KW - Chitosan KW - pH-responsive KW - Magnetic-responsive KW - Cryo-SEM KW - TEM Y1 - 2018 U6 - https://doi.org/10.1007/s00396-018-4321-z SN - 0303-402X SN - 1435-1536 VL - 296 IS - 6 SP - 1039 EP - 1046 PB - Springer CY - New York ER - TY - JOUR A1 - Vijayakrishnan, Balakumar A1 - Issaree, Arisara A1 - Corilo, Yuri E. A1 - Ferreira, Christina Ramires A1 - Eberlin, Marcos N. A1 - Peter, Martin G. T1 - MSn of the six isomers of (GlcN)(2)(GlcNAc)(2) aminoglucan tetrasaccharides (diacetylchitotetraoses) rules of fragmentation for the sodiated molecules and application to sequence analysis of hetero-chitooligosaccharides JF - Carbohydrate polymers : an international journal devoted to scientific and technological aspects of industrially important polysaccharides N2 - The six possible isomers of di-N-acetylchitotetraoses [AADD, ADDA, ADAD, DADA, DAAD, and DDAA, where D stands for 2-amino-2-deoxy-3-D-glucose (GlcN) and A for 2-acetamido-2-deoxy-beta-D-glucose (GlcNAc)] were analyzed by ESI(+)-MSn. Collision induced dissociation via MSn experiments were performed for the sodiated molecules of m/z 769 [M+Na](+) for each isomer, and fragments were generated mainly by glycosidic bond and cross-ring cleavages. Rules of fragmentation were then established. A reducing end D residue yields the (O.2)A(4) cross-ring [M-59+Na](+) fragment of m/z 710 as the most abundant, whereas isomers containing a reducing end A prefer to lose water to form the [M-18+Na](+) ion of m/z 751, as well as abundant (O.2)A(4) cross-ring [M-101+Na](+) fragments of m/z 668 and B-3 [M-221+Na](+) ions of m/z 548. MS3 of C- and Y-type ions shows analogous fragmentation behaviour that allows identification of the reducing end next-neighbour residue. Due to gas-phase anchimeric assistance, B-type cleavage between the glycosidic oxygen and the anomeric carbon atom is favoured when the glycon is an A residue. Relative ion abundances are generally in the order B >> C > Y, but may vary depending on the next neighbour towards the non-reducing end. These fragmentation rules were used for partial sequence analysis of hetero-chitooligosaccharides of the composition D(2)A(3), D(3)A(3), D(2)A(4), D(4)A(3), and D(3)A(4). KW - Chitosan KW - Fragmentation KW - Oligosaccharides KW - Sequence analysis KW - Tandem mass spectrometry Y1 - 2011 U6 - https://doi.org/10.1016/j.carbpol.2010.04.041 SN - 0144-8617 VL - 84 IS - 2 SP - 713 EP - 726 PB - Elsevier CY - Oxford ER - TY - THES A1 - Rusu, Viorel Marin T1 - Composite materials made of chitosan and nanosized apatite : preparation and physicochemical characterization T1 - - N2 - Taking inspiration from nature, where composite materials made of a polymer matrix and inorganic fillers are often found, e.g. bone, shell of crustaceans, shell of eggs, etc., the feasibility on making composite materials containing chitosan and nanosized hydroxyapatite were investigated. A new preparation approach based on a co-precipitation method has been developed. In its earlier stage of formation, the composite occurs as hydrogel as suspended in aqueous alkaline solution. In order to get solid composites various drying procedures including freeze-drying technique, air-drying at room temperature and at moderate temperatures, between 50oC and 100oC were used. Physicochemical studies showed that the composites exhibit different properties with respect to their structure and composition. IR and Raman spectroscopy probed the presence of both chitosan and hydroxyapatite in the composites. Hydroxyapatite as dispersed in the chitosan matrix was found to be in the nanosize range (15-50 nm) and occurs in a bimodal distribution with respect to its crystallite length. Two types of distribution domains of hydroxyapatite crystallites in the composite matrix such as cluster-like (200-400 nm) and scattered-like domains were identified by the transmission electron microscopy (TEM), X-ray diffraction (XRD) and by confocal scanning laser microscopy (CSLM) measurements. Relaxation NMR experiments on composite hydrogels showed the presence of two types of water sites in their gel networks, such as free and bound water. Mechanical tests showed that the mechanical properties of composites are one order of magnitude less than those of compact bone but comparable to those of porous bone. The enzymatic degradation rates of composites showed slow degradation processes. The yields of degradation were estimated to be less than 10% by loss of mass, after incubation with lysozyme, for a period of 50 days. Since the composite materials were found biocompatible by the in vivo tests, the simple mode of their fabrication and their properties recommend them as potential candidates for the non-load bearing bone substitute materials. N2 - Inspiriert von Natur, bei der Kompositmaterialien aus Polymermatrices und anorganischen Füllstoffen z.B. in Knochen, Krustentieren und Eierschalen vorzufinden sind, wurde die Herstellungsmöglichkeit von Kompositmaterial aus Chitosan und Hydroxyapatitdispersionen untersucht. Basierend auf einem Kopräzipitationsverfahren wurde eine neue Herstellungsmethode entwickelt, die als flexibler Zugang zu einem Spektrum von Komposittypen führt. In den frühen Phasen der Kompositbildung entsteht ein in der wässrigen alkalischen Lösung suspendiertes Hydrogel, das durch Filtration und Zentrifugation isoliert werden kann. IR und Ramanspektroskopie klären das Vorhandensein von Chitosan und Hydroxyapatit im Kompositmaterial. Hydroxyapatit ist als Nanopartikel der Größe von 15-50 nm in bimodaler Verteilung in der Chitosanmatrix dispersiert, und in durch Transmissionselektronenmikroskopie (TEM), X-Ray Diffraction (XRD) und Konfokaler Laserscanmikroskopie (CSLM) nachweisbaren 200-400 nm großen Clustern assembliert. NMR-Relaxationsmessungen an Hydrogelkompositmaterial decken die Existenz zweier Klassen vorkommenden Wassers im Netzwerk auf, gebundenes und freies Wasser. Mechanische Tests zeigen, dass die mechanische Festigkeit etwa eine Größenordnung unter der von massivem Knochen liegt, der Festigkeit von porösem Knochen aber gleichkommt. Enzymatische Abbauraten des Kompostimaterials sind als langsam einzuschätzen. Eine 50-tägige Einwirkzeit von Lysozym führte zu einem Abbau von 10 % der Kompositmasse. Die sich durch in vivo Tests herausstellende Biokompatibilität, die einfachen Herstellungsmöglichkeiten und die physikochemischen Eigenschaften empfehlen dieses Material als vielversprechenden Kandidaten für Knochenersatzmaterial in mäßig belasteten Bereichen. KW - Chitosan KW - Hydroxyapatit KW - Nanopartikel KW - Kompositmaterial KW - Chitosan KW - hydroxyapatite KW - nanoparticles KW - composites Y1 - 2004 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-2316 ER -