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  • 1
    Unknown
    Basel, Beijing, Wuhan : MDPI
    Keywords: chitosan ; alginate ; agar ; carrageenans ; exopolysaccharides ; chemical modification ; drug delivery ; gene delivery
    Description / Table of Contents: Biopolymers, as natural polysaccharides, are considered benign polymers for what concerns the environment. This is not a new invention, but at best a renaissance: the first type of polymers used by human kind were animal hides, cellulose, silk, wool. Among benefits of natural occurring biopolymers there are potential biocompatibility, renewable resources, low processing costs, tailoring of structure by genetic manipulation, and, as said, environmentally compatibility. Limits are, sometimes, premature degradation and high production costs due to the very high purity required for medical uses. Polysaccharides are not drugs by themselves, but their use in pharmaceutical field, for example as drug carriers or antimicrobial, anti-inflammatory or anticoagulant agents, is increasingly promising. Marine polysaccharides include chitin, chitosan, alginate, agar and carrageenans. Chitosan is a cationic carbohydrate biopolymer derived from chitin, the second most abundant polysaccharides present in nature after cellulose. The main sources of chitin are the shell wastes of shrimps, lobsters and crabs. For its characteristics, chitosan founds particular application as non viral vector in gene delivery. Films from chitosan are very tough and long lasting. Alginates derive from seaweed extraction (pheophyceae), and are mainly used in drug delivery and as hydrogels for immobilizing cells and enzymes, due to the mild conditions of cross-linking through bivalent cations (Ca2+). Agar (or agar-agar) and carrageenans are linear polysaccharides from red seaweeds. They are highly reactive chemically and are peculiar for thermoreversible gel formation. Exopolysaccharides (EPS), substantial components of the extracellular matrix of many cells of marine origin, also have to be mentioned for their potential interest in pharmaceuticals, and new EPS producing bacteria, particularly from extreme marine environments, are being isolated. The possibility of chemical modification, blending and addition of biodegradable additives allows to tailor the final properties of polysaccharides and opens the doors to wider applications, particularly in pharmaceutical area. This issue is intended to explore any new potentiality of marine polysaccharides, as those above mentioned, deriving from chemical or chemical-physical modifications, and the scaling-up of their pharmaceutical applications.
    Pages: Online-Ressource (VIII, 224 Seiten)
    Edition: Printed Edition of the Special Issue Published in Marine Drugs
    ISBN: 9783038428985
    Language: English
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  • 2
    Unknown
    Basel, Beijing, Wuhan : MDPI
    Keywords: chitosan ; alginate ; agar ; carrageenans ; exopolysaccharides ; chemical modification ; drug delivery ; gene delivery
    Description / Table of Contents: Biopolymers, as natural polysaccharides, are considered benign polymers for what concerns the environment. This is not a new invention, but at best a renaissance: the first type of polymers used by human kind were animal hides, cellulose, silk, wool. Among benefits of natural occurring biopolymers there are potential biocompatibility, renewable resources, low processing costs, tailoring of structure by genetic manipulation, and, as said, environmentally compatibility. Limits are, sometimes, premature degradation and high production costs due to the very high purity required for medical uses. Polysaccharides are not drugs by themselves, but their use in pharmaceutical field, for example as drug carriers or antimicrobial, anti-inflammatory or anticoagulant agents, is increasingly promising. Marine polysaccharides include chitin, chitosan, alginate, agar and carrageenans. Chitosan is a cationic carbohydrate biopolymer derived from chitin, the second most abundant polysaccharides present in nature after cellulose. The main sources of chitin are the shell wastes of shrimps, lobsters and crabs. For its characteristics, chitosan founds particular application as non viral vector in gene delivery. Films from chitosan are very tough and long lasting. Alginates derive from seaweed extraction (pheophyceae), and are mainly used in drug delivery and as hydrogels for immobilizing cells and enzymes, due to the mild conditions of cross-linking through bivalent cations (Ca2 ). Agar (or agar-agar) and carrageenans are linear polysaccharides from red seaweeds. They are highly reactive chemically and are peculiar for thermoreversible gel formation. Exopolysaccharides (EPS), substantial components of the extracellular matrix of many cells of marine origin, also have to be mentioned for their potential interest in pharmaceuticals, and new EPS producing bacteria, particularly from extreme marine environments, are being isolated.The possibility of chemical modification, blending and addition of biodegradable additives allows to tailor the final properties of polysaccharides and opens the doors to wider applications, particularly in pharmaceutical area. This issue is intended to explore any new potentiality of marine polysaccharides, as those above mentioned, deriving from chemical or chemical-physical modifications, and the scaling-up of their pharmaceutical applications.
    Pages: Online-Ressource (X, 290 Seiten)
    Edition: Printed Edition of the Special Issue Published in Marine Drugs
    ISBN: 9783038429005
    Language: English
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  • 3
    Unknown
    Basel, Beijing, Wuhan : MDPI
    Keywords: chitosan ; alginate ; agar ; carrageenans ; exopolysaccharides ; chemical modification ; drug delivery ; gene delivery
    Description / Table of Contents: Biopolymers, as natural polysaccharides, are considered benign polymers for what concerns the environment. This is not a new invention, but at best a renaissance: the first type of polymers used by human kind were animal hides, cellulose, silk, wool. Among benefits of natural occurring biopolymers there are potential biocompatibility, renewable resources, low processing costs, tailoring of structure by genetic manipulation, and, as said, environmentally compatibility. Limits are, sometimes, premature degradation and high production costs due to the very high purity required for medical uses. Polysaccharides are not drugs by themselves, but their use in pharmaceutical field, for example as drug carriers or antimicrobial, anti-inflammatory or anticoagulant agents, is increasingly promising. Marine polysaccharides include chitin, chitosan, alginate, agar and carrageenans. Chitosan is a cationic carbohydrate biopolymer derived from chitin, the second most abundant polysaccharides present in nature after cellulose. The main sources of chitin are the shell wastes of shrimps, lobsters and crabs. For its characteristics, chitosan founds particular application as non viral vector in gene delivery. Films from chitosan are very tough and long lasting. Alginates derive from seaweed extraction (pheophyceae), and are mainly used in drug delivery and as hydrogels for immobilizing cells and enzymes, due to the mild conditions of cross-linking through bivalent cations (Ca2 ). Agar (or agar-agar) and carrageenans are linear polysaccharides from red seaweeds. They are highly reactive chemically and are peculiar for thermoreversible gel formation. Exopolysaccharides (EPS), substantial components of the extracellular matrix of many cells of marine origin, also have to be mentioned for their potential interest in pharmaceuticals, and new EPS producing bacteria, particularly from extreme marine environments, are being isolated.The possibility of chemical modification, blending and addition of biodegradable additives allows to tailor the final properties of polysaccharides and opens the doors to wider applications, particularly in pharmaceutical area. This issue is intended to explore any new potentiality of marine polysaccharides, as those above mentioned, deriving from chemical or chemical-physical modifications, and the scaling-up of their pharmaceutical applications.
    Pages: Online-Ressource (X, 564 Seiten)
    Edition: Printed Edition of the Special Issue Published in Marine Drugs
    ISBN: 9783038429029
    Language: English
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  • 4
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary A study on the solution grafting of monoethylmaleate onto a saturated ethylene-propylene rubber was conducted. The grafting degree was followed by titration methods as function of the time of reaction and amount of initiator. The insertion of unsaturated molecules always led to some degradation of the polymeric backbone. The subsequent cyclization reaction of grafted monoethylmaleate to maleic anhydride was also studied by Fourier Transform Infrared Spectroscopy either in bulk or in solution. A different behaviour was found in the two cases; furthermore, a different mechanism of reaction led to different amounts of inter- and intra-chain anhydride formation.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Thermal and mechanical properties of various functionalized ethylene-propylene rubbers (EPR) were evaluated. The samples studied varied both in the type of functional groups and in the grafting degree. Grafted molecules included succinic anhydride, 2-(dimethylamino)ethylsuccinimide and 2-(dimethylamino)ethyl methacrylate. The insertion of these groups was found to influence deeply the elastic response of rubbers, leading to the formation of network whose properties were dependent upon the density of polar crosslinks introduced. On the other hand, the thermal properties were less influenced, i.e. the glass transition temperature Tg increased only slightly with increasing content of functional groups.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Influences of type and content of functional groups on the mechanical response of various functionalized (grafted) ethylene-propene rubbers (EPRs) are reported. Grafted molecules include succinic anhydride (SA), monomethyl succinate (MMS) and 2-(dimethylamino)ethylsuccinimide (DAESI). A semiquantitative correlation between the decrease of the mechanical properties at high grafting degree and degradation of the polyolefinic backbone is given. Also a study of the dynamic-mechanical properties of the functionalized rubbers is reported. A rubbery plateau is found, the strength and temperature dependence of which is a function of the type and content of the grafted molecules.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Base functionalization of saturated ethylene-propylene rubbers (EPR) was performed either by means of the radical grafting of 2-(dimethylamino)ethyl methacrylate onto EPR or by the reaction of a succinic anhydride grafted EPR with N,N-dimethylethylenediamine. Differences in the structure of the grafted molecules and in their thermal stability are also reported. An investigation is made on the reactivity of EPR having tertiary amino pendant groups toward acid functionalized EPR leading to gelation.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Ethylene-propylene random copolymers bearing grafted succinic anhydride functions have been reacted with an α,ω-hydroxyl telechelic polybutadiene to obtain elastomeric interpolymer complexes. A kinetic study has been carried out by infrared techniques to study the influence of the addition of catalyst, stoichiometry, and temperature on the degree of monoesterification reaction.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 0887-6266
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A new series of polyimides was synthesized by addition polymerization of 4,4′-(bismaleimido)-diphenylmethane, 1,4-piperazine and an amino-terminated polydimethylsiloxane. The synthesis was carried out in m-cresol solution following a two-step procedure. Copolymers containing 15 and 20 wt.-% of the polydimethylsiloxane elastomer were prepared, together with the unmodified base copolymer. Infrared spectroscopy, 13C and 1H NMR, thermal and thermogravimetric analyses were used to characterize the copolymers. The DSC curves of all the samples showed an exotherm in the temperature range 230-280°C, attributable to curing and addition reactions involving the chain-end groups. Different glass transition temperatures (Tg) were observed, depending on the elastomer content. Thermogravimetric analysis indicated that no significant changes occur in the thermal stability of rubber-modified copolymers.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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