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MISCELE POLIMERICHE DI POLISACCARIDI ANIONICI E CATIONICI E LORO IMPIEGO
No full textNel presente brevetto sono descritte composizioni comprendenti miscele di polisaccaridi polianionici e policationici costituiti da derivati oligosaccaridici del chitosano. Nelle composizioni dell’invenzione tali miscele si sono dimostrate solubili in ambiente acquoso, nonostante che tra i polisaccaridi acidi ed i derivati del chitosano si formino complessi ionici. Inoltre tali composizioni hanno mostrato un significativo comportamento reologico con un incremento inaspettato della viscosità e visco-elasticità, benché i polisaccaridi impiegati abbiano pesi molecolari medi relativamente bassi. Tutto ciò, solubilità e comportamento reologico, rende le composizioni secondo l’invenzione particolarmente vantaggiose dal punto di vista applicativo biomedico, in particolare nella visco-supplementazione in particolare nel campo delle patologie articolari
IDROGELI DI MISCELE DI POLISACCARIDI PER L'INGEGNERIA TISSUTALE E LA VEICOLAZIONE DI COMPOSTI ATTIVI
No full textLa presente invenzione è relativa a idrogeli (matrici 3D) ottenibili da soluzioni di miscele polimeriche binarie di polisaccaridi acidi e di derivati di polisaccaridi basici, quali i derivati oligosaccaridici del chitosano, opportunamente gelificati con agenti gelificanti ed al loro uso nel campo biomedico
Specific Interactions versus Counterion Condensation. 1. Nongelling Ions/Polyuronate Systems
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Biomacromolecules. 2006 Jan;7(1):281-7.
Specific interactions versus counterion condensation. 1. Nongelling ions/polyuronate systems.
Donati I, Cesàro A, Paoletti S.
Source
Department of Biochemistry, Biophysics and Macromolecular Chemistry, University of Trieste, Via Licio Giorgieri 1, I-34127 Trieste, Italy. [email protected]
Abstract
The characteristics of the interaction between nongelling divalent cations (typically Mg(2+)) and polyuronates have been explored by means of isothermal calorimetry. In particular, three polyuronates mimicking separately guluronan (polyguluronate, polyG), mannuronan (polymannuronate, polyM), and polyalternating (polyMG), the three block-components of natural alginate samples, have been treated with divalent ions, and the enthalpy of mixing was determined for different values of the [M(2+)]/[Polym](rep.unit) ratio. Despite the absence of a site-specific chemical bonding between the two, as confirmed by circular dichroism spectroscopy, a substantial deviation of the experimental enthalpy of mixing from the theoretical behavior, as predicted by the classical counterion condensation (CC) theory, was observed. Such deviation has been interpreted in terms of a "generic" nonbonding affinity of the condensed divalent counterion for the polyelectrolytes. The mathematical formalism of the CC theory was extended to include a contribution to the (reduced) free energy and enthalpy arising from the counterion affinity, g(aff,0) and h(aff,0), and allowed the parametrical calculation of the fraction of divalent counterions condensed as function of the reduced thermodynamic quantity g(aff,0). A best fit procedure of the experimental enthalpy of mixing allowed the g(aff,0) and h(aff,0) pair to be estimated for each of the different polyuronates considered, revealing differences in the three samples. In qualitative terms, the results obtained seem to suggest a notable contribution of the desolvation process (i.e., release of structured water as a consequence of the interaction between the divalent counterion and the uronate group) to the enthalpy of affinity for polyM which is counterbalanced and overcome by an ion pairing term (i.e., partial formation of ion-ion and/or ion-dipole bonds) for polyG and polyMG, respectively
HYDROGELE VON POLYSACCHARIDMISCHUNGEN FÜR DAS GEWEBE-ENGINEERING UND ALS WIRKSTOFFTRÄGER. German Patent DE602007004212
No full textThe present invention describes the preparation of hydrogels (or 3D matrices) obtainable from aqueous solutions of mixtures of acid polysaccharides and derivatives of basic polysaccharides, such as oligosaccharide derivatives of chitosan. Said solutions are suitably gelled with either chemical or physical gelling agents with the aim of encapsulating either cells, isolated or in multicellular associations, or pharmacologically active molecules, in solution or suspension, for use in the biomedical and pharmaceutical field
Specific interactions versus counterion condensation, 3: the calcium-induced chain association of pectate
No full textPolyelectrolyte study of the calcium-induced chain association of pectate
No full textThe theoretical model devised in the previous paper (Donati, I.; Benegas, J. C.; Cesàro, A.; Paoletti, S. Biomacromolecules 2006, 7 (5), 1587-1596) for the description of ion-induced chain aggregation is here applied to the case of chain dimerization of poly(galacturonate) in the presence of calcium ions. Particular attention has been directed toward the initial stage of dimer formation [i.e., in the low regime of calcium-to-polymer ratio (Rj)]. Circular dichroism (CD) data allowed evaluation of the fraction, theta, of calcium ions bound within chain dimers according to the "egg-box"-model. The theoretical model was able to reproduce satisfactorily the total molar enthalpy variation experimentally determined; the contributions of affinity (specificity in territorial condensation) and chemical bonding of calcium counterions to the thermodynamic properties of the system (i.e., enthalpy and entropy) were calculated. The intrinsic molar enthalpy of bonding, DeltaH(bond,0), displayed a peculiar sigmoid dependence on Rj. In particular, its decrease toward more negative values was interpreted as stemming from a (cooperative) calcium-induced conformational change that accompanies pectate chain pairing upon junction formation. The calculated pKin of instability of the Ca-(GalA-)4 complex was 10.80, in very good agreement with the corresponding value reported for the Ca-EDTA complex (i.e., 10.96). Significant contributions to the complex stability were the enthalpy of ion pairing (DeltaH(ionpairing,bond) = -5.1 kcal (mol calcium)-1, in good agreement with the value reported for calcium-EDTA: approximately -5.4 kcal (mol calcium)-1), and the entropy of desolvation (DeltaS(desolv,bond) = 43.7 cal mol-1 K-1, well within the range of values reported for calcium-EDTA: 42-57 cal mol-1 K-1)
HYDROGELS OF POLYSACCHARIDE MIXTURES FOR TISSUE ENGINEERING AND AS CARRIERS OF ACTIVE COMPOUNDS. European Patent EP2029629
No full textThe present invention describes the preparation of hydrogels (or 3D matrices) obtainable from aqueous solutions of mixtures of acid polysaccharides and derivatives of basic polysaccharides, such as oligosaccharide derivatives of chitosan. Said solutions are suitably gelled with either chemical or physical gelling agents with the aim of encapsulating either cells, isolated or in multicellular associations, or pharmacologically active molecules, in solution or suspension, for use in the biomedical and pharmaceutical field
POLYMERMISCHUNGEN VON ANIONISCHEN UND KATIONISCHEN POLYSACCHARIDEN UND VERWENDUNG DAVON. German Patent DE602007008879
No full textDescribed in the present application are compositions comprising mixtures of polyanionic polysaccharides and polycationic polysaccharides consisting of oligosaccharide derivatives of chitosan. In the compositions of the invention said mixtures have proven to be soluble in aqueous environments, despite ionic complexes forming between the acid polysaccharides and chitosan derivatives. Said compositions have also demonstrated significant rheological behavior with an unexpected increase in viscosity and viscoelasticity, although the polysaccharides used have relatively low average molecular weights. The said solubility and rheological behavior renders the compositions of the invention particularly advantageous from the biomedical application viewpoint, in particular for viscosupplementation and particularly in the field of articular pathologies and of ophthalmic surgery. polyme
Polymer mixtures of anionic and cationic polysaccharides and use thereof. United States Patent 8951991
No full textDescribed in the present application are compositions comprising mixtures of polyanionic polysaccharides and polycationic polysaccharides consisting of oligosaccharide derivatives of chitosan. In the compositions of the invention said mixtures have proven to be soluble in aqueous environments, despite ionic complexes forming between the acid polysaccharides and chitosan derivatives. Said compositions have also demonstrated significant rheological behavior with an unexpected increase in viscosity and viscoelasticity, although the polysaccharides used have relatively low average molecular weights. The said solubility and rheological behavior renders the compositions of the invention particularly advantageous from the biomedical application viewpoint, in particular for viscosupplementation and particularly in the field of articular pathologies and of ophthalmic surgery
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