Investigation of surgical applicability of acryl based tissue expanders
ABSTRACT Hydrogels made of acrylamide (AAm), acrylic acid (AAc) and N-isopropylacrylamide (NIPAAm) display outstanding ability of swelling in vitro and this property can be influenced by the composition of the polymers. Our objective was to study the in vivo behavior of hydrogels made of acrylics and their potential role in surgery.
Cylinder-shaped hydrogels were implanted under the skin of rats in the dorsal region. In group 1 AAm, in group 2 AAc while in group 3 NIPAAm expanders were applied. The observation period lasted 18 days, during this time the length and the diameter of the hydrogels were measured daily. After removal of the polymers the moisture mass and the rheological parameters were determined. Furthermore, biopsies were taken from adjacent tissues.
Expanders achieved the peak of swelling in two weeks. During the observation period their mass significantly increased. NIPAAm polymers demonstrated the highest tendency to retain their preformed shape. Histological analysis revealed that implantation of AAc devices was associated with serious tissue damage while healthy skin was harvested with the other two polymers.
In conclusion, NIPAAm hydrogel seems to be the most promising candidate for surgical utilization.
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ABSTRACT: This review aims at reporting on very recent developments in syntheses, properties and (future) applications of polymer-layered silicate nanocomposites. This new type of materials, based on smectite clays usually rendered hydrophobic through ionic exchange of the sodium interlayer cation with an onium cation, may be prepared via various synthetic routes comprising exfoliation adsorption, in situ intercalative polymerization and melt intercalation. The whole range of polymer matrices is covered, i.e. thermoplastics, thermosets and elastomers. Two types of structure may be obtained, namely intercalated nanocomposites where the polymer chains are sandwiched in between silicate layers and exfoliated nanocomposites where the separated, individual silicate layers are more or less uniformly dispersed in the polymer matrix. This new family of materials exhibits enhanced properties at very low filler level, usually inferior to 5wt.%, such as increased Young’s modulus and storage modulus, increase in thermal stability and gas barrier properties and good flame retardancy.Materials Science and Engineering R Reports 06/2000; 28(1-2-1-2):1-63. DOI:10.1016/S0927-796X(00)00012-7 · 11.79 Impact Factor
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ABSTRACT: The process of mucoadhesion involving a polymeric drug delivery platform is a complex one that includes wetting, adsorption and interpenetration of polymer chains amongst various other processes. The success and degree of mucoadhesion bonding is influenced by various polymer-based properties such as the degree of cross-linking, chain length and the presence of various functional groupings. The attractiveness of mucosal-targeted controlled drug delivery of active pharmaceutical ingredients (APIs), has led formulation scientists to engineer numerous polymeric systems for such tasks. Formulation scientists have at their disposal a range of in vitro and in vivo mucoadhesion testing setups in order to select candidate adhesive drug delivery platforms. As such, mucoadhesive systems have found wide use throughout many mucosal covered organelles for API delivery for local or systemic effect. Evolution of such mucoadhesive formulations has transgressed from first-generation charged hydrophilic polymer networks to more specific second-generation systems based on lectin, thiol and various other adhesive functional groups.European journal of pharmaceutics and biopharmaceutics: official journal of Arbeitsgemeinschaft fur Pharmazeutische Verfahrenstechnik e.V 11/2008; 71(3):505-18. DOI:10.1016/j.ejpb.2008.09.028 · 4.25 Impact Factor
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ABSTRACT: Despite the large number of publications and patents concerning pH/thermoresponsive polymers, few data are available concerning the preparation of thermoresponsive cross-linked microspheres from preformed polymers. Therefore, N-isopropylacrylamide-co-acrylamide-co-(2-hydroxyethyl acrylate) copolymers were obtained as a new thermoresponsive material with a lower critical solution temperature (LCST) around 36 degrees C, in phosphate buffer at pH 7.4, and with a cross-linkable OH group in their structure. The LCST value was determined both by UV spectroscopy and microcalorimetric analysis. These copolymers were solubilised in acidified aqueous solution below their LCST, dispersed in mineral oil, and transformed into stable microspheres by cross-linking with glutaraldehyde. The thermoresponsive microspheres were characterised by optical and scanning electron microscopy, degree of swelling, and water retention. The pore dimensions of the microspheres and the retention volumes of some drugs and typical compounds were evaluated at different temperatures by liquid chromatography. Indomethacin, as a model drug, was included in the microspheres by the solvent evaporation method. Finally, the influence of temperature and of temperature cycling on drug release was investigated.Macromolecular Bioscience 10/2005; 5(10):955-64. DOI:10.1002/mabi.200500099 · 3.65 Impact Factor