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  • 2010-2014  (4)
  • 1990-1994  (11)
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  • 1
    Digitale Medien
    Digitale Medien
    Growth-hormone loaded bioactive ceramics (1991)
    Springer
    Journal of materials science 2 (1991), S. 176-180 
    Details
    ISSN: 1573-4838
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin , Technik allgemein
    Notizen: Abstract A ‘bioactive’ material, capable of active stimulation of osteogenesis, has been produced by adsorbing human growth hormone onto calcium phosphate ceramics. These materials can be used to deliver growth hormone at the bone-ceramic interface. The elution of the hormone occurs in two phases, with an initial rapid release followed by a slow continuous release for up to 25 days. Tricalcium phosphate was found to release growth hormone better than hydroxyapatite, probably due to the higher solubility of the ceramic.In vivo studies using a rabbit model were used to demonstrate osteointegration at the ceramic interface.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00692977
    Standort Signatur Erwartet Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    The regeneration of articular cartilage using a new polymer system (1994)
    Springer
    Journal of materials science 5 (1994), S. 88-95 
    Details
    ISSN: 1573-4838
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin , Technik allgemein
    Notizen: A polymer system based on room temperature polymerising poly (ethylmethacrylate) polymer powder and tetrahydrofurfuryl monomer has been investigated as a biomaterial for encouraging articular cartilage repair. This heterocyclic methacrylate polymer system swells slightly in situ and thus provides a good interface with subchondral bone resulting in mechanical stability with favourable uptake kinetics. Another feature of this polymer system is that it exhibits high water uptake which leads to absorption of the surrounding tissue fluid and matrix proteins, including growth factors; this may encourage the formation of new cartilage. Three weeks after implantation the tissue overgrowth contained cartilage components: chondrocytes, collagen type II, chondroitin 4-sulphate and chondroitin 6-sulphate. In addition numerous chondrocyte clones were observed at the edge of the defect and in the newly repaired tissue. By six weeks a superficial articulating surface was continuous with the normal articular cartilage with underlying tissue which showed some evidence of endochondral ossification. By nine weeks the surface covering of new cartilage had a widened and an irregular zone of calcified cartilage with thickened subchondral bone was present. At eight months the resurfaced cartilage remained intact above a remodelled subchondral bone end plate.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00121696
    Standort Signatur Erwartet Verfügbarkeit
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  • 3
    Digitale Medien
    Digitale Medien
    The release of serum proteins and dye from glass ionomer (polyalkenoate) and acrylic cements: a pilot study (1994)
    Springer
    Journal of materials science 5 (1994), S. 711-714 
    Details
    ISSN: 1573-4838
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin , Technik allgemein
    Notizen: Glass ionomer cements (GICs) are composite materials with the potential for use as improved bone substitutes and cements. The hydrophilic nature of the GIC matrix may confer the ability to release therapeutic agents after surgical implantation which would aid the development of GICs for wider biomedical application. Acrylic and GIC were loaded (5% w/w) with either a model dye or high molecular weight proteins and eluted in vitro over 84 days to study simulated drug release. Serum proteins were also adsorbed on to the surface of acrylic and two different GICs and desorption measured over six days. GIC was a suitable matrix for simple dye and protein release, protein release being greater from the GIC than from the acrylic cement. Selective desorption from the two different GICs studied was noted indicating GICs may be formulated to release specific drugs or proteins.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00120362
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  • 4
    Digitale Medien
    Digitale Medien
    Characterization of the repair tissue in articular cartilage defects using silver-enhanced colloidal gold immunostaining (1994)
    Springer
    Journal of materials science 5 (1994), S. 402-406 
    Details
    ISSN: 1573-4838
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin , Technik allgemein
    Notizen: The newly developed silver-enhanced colloidal gold staining method was used in a rabbit model to characterize the repair tissue in large articular cartilage defects filled with a heterocyclic methacrylate polymer. By 6 weeks the resurfacing tissue consisted of highly organized hyaline-like articular cartilage, fully integrated with the adjacent normal cartilage. Immuno-histochemistry detected collagen type ll, keratan sulphate, chondroitin 4-sulphate and chondroitin 6-sulphate in the matrix of the neocartilage. The level to which the polymer plug was recessed apeared to be critical to the overall quality of the repair tissue. Optimum results were obtained when the top surface of the biomaterial was at the level of the subchondral bone, below the level of the surrounding articular cartilage. Other technical aspects of implantation, that also affect the repair, are also discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00058973
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  • 5
    Digitale Medien
    Digitale Medien
    Collagen and hyaluronic acid based polymeric blends as drug delivery systems for the release of physiological concentrations of growth hormone (1994)
    Springer
    Journal of materials science 5 (1994), S. 770-774 
    Details
    ISSN: 1573-4838
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin , Technik allgemein
    Notizen: Two synthetic polymers, poly(vinyl alcohol) (PVA) and poly(acrylic acid) (PAA) were blended, in different ratios, with two biological polymers, collagen (C) and hyaluronic acid (HA). These blends were used to prepare two different materials, sponges and hydrogels, which were loaded with growth hormone (GH). The GH released, was monitored in vitro using a specific enzyme-linked immunoadsorbent (ELISA) assay. The results show that GH is released in a dose-dependent manner, from HA/PAA sponges and from HA/PVA and C/PVA hydrogels. The amount of GH released was proportional to the percentage of the natural polymer (HA and C). The release of GH from HA/PAA sponges was constant with time, whereas in HA/PVA hydrogels it was linear for the first 3 days followed by a slower release. The GH release pattern in C/PVA hydrogels was different, with a slow release for the first 3 days followed by a more rapid release. The concentrations of GH released from the materials were within a physiological range and sufficient to have a local effect on cellular proliferation. The effects of GH were tested in vitro using primary human osteoblast-like cells (HOBS) and measuring cell proliferation and alkaline phosphatase (ALP), a biochemical marker of HOB cell differentiation.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00120374
    Standort Signatur Erwartet Verfügbarkeit
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  • 6
    Digitale Medien
    Digitale Medien
    A qualitative in vitro evaluation of the degradable materials poly(caprolactone), poly(hydroxybutyrate) and a poly(hydroxybutyrate)-(hydroxyvalerate) copolymer (1994)
    Springer
    Journal of materials science 5 (1994), S. 784-787 
    Details
    ISSN: 1573-4838
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin , Technik allgemein
    Notizen: Abstract A qualitative in vitro evaluation of poly(caprolactone) (PCL), poly(hydroxybutyrate) (PHB) and a poly(hydroxybutyrate)-(hydroxyvalerate) (PHB-PHV) copolymer was carried out using primary human osteoblasts (HOB) and a human osteosarcoma (HOS) cell line. The cells were grown on films of these polymers and cultured for 2 and 4 days with cells grown on Thermanox as a control. The cells on each of the polymers exhibited different cellular morphologies with different rates of cell proliferation. Results from a preliminary degradation study demonstrated that biodegradable materials can be partially degraded using enzymes such as papain and trypsin. Of the solutions tested, papain caused the greatest degradation, with phosphate-buffered saline (PBS) a physiological buffer having very little effect over a six week period. The bone cells were grown on partially degraded polymers and no differences in the performance of HOS and HOB cells on the materials were observed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00213135
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  • 7
    Digitale Medien
    Digitale Medien
    A simple method of cartilage regeneration using a new polymerizing system: ultrastructural characteristics of the repair tissue (1994)
    Springer
    Journal of materials science 5 (1994), S. 793-797 
    Details
    ISSN: 1573-4838
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin , Technik allgemein
    Notizen: Abstract The ultrastructural characteristics of the repair tissue in large articular cartilage defects, filled with a heterocyclic polymerizing system were studied using transmission electron microscopy (TEM) and energy dispersive micro-analysis (EDMA). By six weeks post-implantation, the defects were resurfaced with predominantly hyaline-like articular cartilage. Chondrocytes in both the superficial and deep zones of the repair tissue were highly productive, secreting large amounts of proteoglycans, into a well-organized, rich in collagen fibrils, extracellular matrix. By contrast, in the repair tissue of the defects treated without the biomaterial, proteoglycan synthesis was less and the structure of the matrix was inferior. We conclude that the polymer enhances both chondrocyte metabolism and matrix organization, thus improving the quality of the repair tissue in articular cartilage defects.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00213137
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  • 8
    Digitale Medien
    Digitale Medien
    The use of gelatin as a vehicle for drug and peptide delivery (1994)
    Springer
    Journal of materials science 5 (1994), S. 819-823 
    Details
    ISSN: 1573-4838
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin , Technik allgemein
    Notizen: Abstract Gelatin, a naturally occurring polymer, has been investigated as a vehicle for drug delivery in two different delivery systems: microspheres and as a coating on titanium implants. The gelatin was loaded with recombinant human growth hormone (hGH) which was dispersed within the polymer matrix prior to crosslinking; it was then made into microspheres or coated onto the implants. The release of hGH was monitored in vitro using an “in-house” ELISA system. The effects of pH on the swelling kinetics and the physical properties of the loaded gelatin in the microsphere system were studied. In addition, the effect of ultrasound on the microspheres was investigated as a possible method for controlling the rate of release of hGH, it was demonstrated that exposure to ultrasound significantly increased hGH release. Biocompatibility of the gelatin was determined using both primary human (HOB) and rabbit (ROB) osteoblast-like cells in culture.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00213141
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  • 9
    Digitale Medien
    Digitale Medien
    Evaluation of the responses of human peritoneal macrophages to a range of biomaterials using reflectance light microscopy (1994)
    Springer
    Journal of materials science 5 (1994), S. 752-755 
    Details
    ISSN: 1573-4838
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin , Technik allgemein
    Notizen: The local response to biomaterials consists of a balance between inflammatory and repairtive processes. Macrophages are one of the cell types involved in both these responses. Initially macrophage infiltration is necessary to phagocytose cellular and other debris which result from implantation of a device. Wound healing can then follow. If, however, phagocytosis cannot be completed the macrophages may become highly activated resulting in a chronic inflammatory response. In this paper we examine the activation of human peritoneal macrophages, cultured on a range of materials, by transmitted and reflected light microscopy. The cells were stained for non-specific esterase (NSE), a macrophage marker and indicator of activation. The results showed that cells adhered to all materials tested, except for polyvinyl chloride. Polypropylene caused the greatest degree of macrophage activation, while hydroxyapatite and polytetrafluoroethylene caused the least activation. Macrophages cultured with metal phagocytosed some of the material. We conclude that this technique gives a good indication of the activated state of these cells and can be used in the assessment of the biocompatibility of materials with respect to the immune system.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00120370
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  • 10
    Digitale Medien
    Digitale Medien
    Heterocyclic methacrylate-based drug release polymer system (1994)
    Springer
    Journal of materials science 5 (1994), S. 338-339 
    Details
    ISSN: 1573-4838
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin , Technik allgemein
    Notizen: A heterocyclic methacrylate polymer system, developed originally as a low shrinkage polymer system, has been investigated as a drug release polymer and as a biomaterial for encouraging bone or cartilage regeneration. The system is based on poly (ethyl methacrylate) polymer powder mixed with tetrahydrofurfuryl methacrylate monomer and polymerized at room temperature (PEM/THFM). Promising results have been obtained with this biomaterial, and hence its water uptake properties were investigated in detall, in order to throw some light on the release processes that are involved in vivo and in vitro. Water soluble large molecule analogues were incorporated into the system; these additives increased the water uptake of the system. Isobornyl methacrylate was used as a diluent for the monomer to further reduce the water uptake of the system. In all cases the uptake kinetics did not obey simple diffusion theory, the process being very prolonged and complex.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00058958
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