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  • 1
    Electronic Resource
    Electronic Resource
    Poly(allylammonium acrylate) as a drug-releasing matrix II. Release of drugs entrapped into the polysalt structure (1997)
    Springer
    Polymer bulletin 39 (1997), S. 715-720 
    Details
    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: Abstract. The release of drugs, entrapped into the poly(allylammonium acrylate) (PAAC) polyelectrolyte complex structure, was tested for vitamin B12 (VitB12) and tetracycline (TCY). The PAAC-drug "composites" were obtained by synthesizing PAAC in the presence of either VitB12 or TCY. Weighed samples of the "composites" were sintered as tablets, which were dipped into Dulbecco's PBS (pH 7.3); the release was followed spectrophotometrically. The tests show very low limiting release values, with different kinetic behaviours for TCY and VitB12. The results are discussed and attributed to strong ionic interactions between the polyelectrolyte complex and the dipolar ions VitB12 and TCY.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002890050207
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  • 2
    Electronic Resource
    Electronic Resource
    Effect of chitosan and dextran on the properties of poly(vinyl alcohol) hydrogels (1999)
    Springer
    Journal of materials science 10 (1999), S. 431-435 
    Details
    ISSN: 1573-4838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract Hydrogels are three-dimensional polymeric networks very similar to biological tissues and potentially useful as drug delivery systems. Poly(vinyl alcohol)-based hydrogels containing different amounts of dextran or chitosan were prepared using the freezing–thawing method. Repeated freezing–thawing cycles of a poly(vinyl alcohol) (PVA) aqueous solution lead to the formation of crystallites which act as cross-linking sites, and a hydrogel with a high capacity to swell is obtained. The effects of the two different polysaccharides on the properties of the obtained materials were investigated by differential scanning calorimetry, dynamic mechanical analysis and scanning electron microscopy. In addition the release with time of poly(vinyl alcohol) in aqueous medium, was monitored and evaluated. On the basis of the obtained results it seems that the presence of dextran favors the crystallization process of PVA, allowing the formation of a more ordered and homogeneous structure. Instead, chitosan seems to perturb the formation of PVA crystallites leading to a material with a less regular structure. © 1999 Kluwer Academic Publishers
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008983215833
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  • 3
    Electronic Resource
    Electronic Resource
    Fibers by bioresorbable poly(ester-ether-ester)s as potential suture threads: a preliminary investigation (1999)
    Springer
    Journal of materials science 10 (1999), S. 659-662 
    Details
    ISSN: 1573-4838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract Fibers made by a bioresorbable poly(ε-caprolactone)-block-poly(oxyethylene)-block-poly(ε-caprolactone) copolymer, having a number average molecular mass of about 200 000 Da and an average molar composition of 66% oxycaproyl units and 34% oxyethylene units, were melt-spun, with the aim at using them as suture threads. Their properties were investigated by the stress-strain test and by differential scanning calorimetry (DSC). The results obtained show that the properties of this material depend very strongly on the alignment of its macromolecules. In particular, the only partial alignment, obtainable by a relatively moderate drawing just after the extrusion, leads to values of elongation at break too high for use of the fibers as suture threads. The DSC analysis reveals interesting properties of the material, but also confirms their strong dependence on the extrusion procedure and on the mechanical treatment. In conclusion, the results of this preliminary study show that the spinning technique must be improved, and that further investigations are necessary to ascertain the possibility of using these poly(ester-ether-ester)s for the fabrication of suture threads. © 1999 Kluwer Academic Publishers
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008948010636
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  • 4
    Electronic Resource
    Electronic Resource
    New composites of hydroxyapatite and bioresorbable macromolecular material (1999)
    Springer
    Journal of materials science 10 (1999), S. 283-289 
    Details
    ISSN: 1573-4838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract Composite materials were prepared by mixing in different proportions of hydroxyapatite (HA) and poly(ε-caprolactone-oxyethylene-ε-caprolactone) block copolymer (PCL-POE-PCL) to produce a new resorbable material for biomedical applications. This material has proved to be very interesting for production of periodontal membranes. Mechanical properties are linearly proportional to the amount of HA introduced. Fourier transform infrared (FTIR) investigations have pointed out that HA is able to influence some close ε-caprolactone molecules to start its homopolymerization giving PCL with an end chain ionic bonding. HA grains are therefore surrounded by a film of PCL which grants close connection of HA grains within copolymeric matrix. This interface bond with PCL is, however, an interesting occurrence for preparations of HA/PCL composites. ©1999 Kluwer Academic Publishers
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008905529461
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  • 5
    Electronic Resource
    Electronic Resource
    Hydrogels based on chitosan and dextran as potential drug delivery systems (1999)
    Springer
    Journal of materials science 10 (1999), S. 301-307 
    Details
    ISSN: 1573-4838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract The release of human growth hormone (GH) from bioartificial polymeric materials in the form of hydrogels, was measured in vitro for up to 3 weeks. Poly(vinyl-alcohol) (PVA) was blended, in different ratios, with two biological polymers, dextran and chitosan respectively. These blends were used to prepare hydrogels, using a freeze–thawing method. The hydrogels were loaded with GH, and their potential use as delivery systems was investigated. The release with time of PVA, in aqueous medium, was also monitored and evaluated. Scanning electron microscopy was used to investigate the structure of the hydrogels. The results obtained indicated that GH can be released from both dextran/PVA and chitosan/PVA hydrogels. The initial GH concentration used for sample loading affected the total quantity of GH released but not the pattern of release. The amount of GH released was affected by the content of the biological component. The percentage of PVA released was low but it was, however, related to the content of chitosan and dextran in the blends. ©1999 Kluwer Academic Publishers
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008961614439
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  • 6
    Electronic Resource
    Electronic Resource
    In vitro cytotoxicity testing of chitosan-containing polyelectrolyte complexes (1998)
    Springer
    Journal of materials science 9 (1998), S. 73-76 
    Details
    ISSN: 1573-4838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract Two chitosan-containing polyelectrolyte complexes, chitosan-poly(acrylic acid) and chitosan-poly(styrenesulphonate), were synthesized by polymerizing acrylic acid and sodium styrenesulphonate in the presence of chitosan and chitosan hydrochloride, respectively. The complexes were studied by optical microscopy and tested for cytotoxicity by the Neutral Red uptake, Kenacid Blue R-Binding and 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyl tetrazolium bromide assays. The optical microscopy confirmed the differences in crystallinity and structure already found for the two polycomplexes by other characterization techniques. The cytoxicity tests showed different influences on the cell activity by the extracts of the two polyelectrolyte complexes. Such results were discussed and correlated to the different structures of the two materials. © 1998 Chapman & Hall
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008890829959
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  • 7
    Electronic Resource
    Electronic Resource
    Hydrolysis of poly(ester-ether-ester) block copolymers in the presence of endothelial cells: in vitro modulation of endothelin release (1997)
    Springer
    Polymer bulletin 39 (1997), S. 53-58 
    Details
    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: Abstract. In previous papers, we studied the hydrolytic degradation of six poly(ester-ether-ester) block copolymers, i.e. three poly(ε-caprolactone)-block-poly(oxyethylene)-block-poly(ε-caprolactone) copolymers and three poly(l-lactide)-block-poly(oxyethylene)-block-poly(l-lactide) copolymers. Their degradation products, 6-hydroxyhexanoic acid and l-lactic acid, have now been found to modulate endothelin release by human umbilical vein endothelial cells, with no significant alteration of the vasoconstrictor-vasodilator balance previously determined. The influence of the same degradation products on the cell proliferation has also been determined and discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002890050119
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  • 8
    Electronic Resource
    Electronic Resource
    Poly(allylammonium acrylate) as a drug-releasing matrix I. Release of drugs mixed and sintered with the polyelectrolyte complex (1997)
    Springer
    Polymer bulletin 39 (1997), S. 707-714 
    Details
    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: Abstract. A poly(allylammonium acrylate) complex was tested for drug release in aqueous solution. Sintered tablets of the polyelectrolyte complex, mixed respectively with human serum albumin, vitamin B12, 5-fluorouracil and tetracycline, were made and dipped into Dulbecco's PBS (pH 7.3). The release kinetics, followed spectrophotometrically, is poorly reproducible and very different for the different drugs. An explanation of such behaviours is proposed, based on the chemical structures of the drugs and of the polyelectrolyte complex, as well as on two concurrent processes: the drug extraction and the saturation by the buffer of the poorly uniform drug-complex mechanical mixtures.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002890050206
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