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  • 11
    Electronic Resource
    Electronic Resource
    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
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: 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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00120374
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  • 12
    Electronic Resource
    Electronic Resource
    The growth of chondrocytes using Gelfoam® as a biodegradable scaffold (1995)
    Springer
    Journal of materials science 6 (1995), S. 739-744 
    Details
    ISSN: 1573-4838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Successful articular cartilage resurfacing must overcome several problems: the implant must easily fit the defect, it must be stable within the defect before full incorporation of repair tissue has occurred, and the reparative tissue must closely approximate the structure of normal hyaline cartilage. To this end, several natural and synthetic components have been used, both in vivo and in vitro, to provide a scaffold. These include isolated chondrocyte allografts, intact cartilage allografts, periossteal grafts, reconstructed collagen sponges, hydrogels and carbon fibres. However, promising results have been reported using three dimensional scaffolds in culture with isolated chondrocytes with subsequent implantation. This preliminary in vitro study utilizes Gelfoam® (a purified gelatin sponge) as such a scaffold. The biocompatibility of Gelfoam with both chondrocytes and osteoblast cells was first confirmed. The ability of chondrocytes to replicate and differentiate within Gelfoam scaffolds was assessed biochemically by measurement of the DNA content and glycosaminoglycans (GAG) production over 25 days in culture. The distribution of the cartilagenous matrix produced was observed by light microscopy, and the constituents of this matrix were assessed using specific antibodies and immunolocalization.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00134310
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  • 13
    Electronic Resource
    Electronic Resource
    A comparative study of the use of colorimetric assays in the assessment of biocompatibility (1996)
    Springer
    Journal of materials science 7 (1996), S. 637-643 
    Details
    ISSN: 1573-4838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: A panel of colorimetric assays was assessed for sensitivity, reproducibility, and performance in the investigation of the biocompatibility of a representative range of orthopædic biomaterials, using a commercially available human osteosarcoma-derived cell line. The MTT assay was the most sensitive, with a detection limit of 4×102 cells per well against background, while the NR assay was the least sensitive, with no colour change until the cell density reached 2×104 per well. All of the assays investigated showed a highly significant “edge” effect when within-plate reproducibility was examined; between-plate reproducibility was good for all assays except the MTT assay. When the assays were tested on cells adherent on biomaterials, there was a wide variation in the results obtained; in particular, the MTS assay showed poor reproducibility in the presence of materials. The MTT and BrdU assays both showed sufficient precision to detect cells on two of the materials studied. The study demonstrates that colorimetric assays are potentially useful in biocompatibility assessment but must be fully validated for the application chosen.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00058204
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  • 14
    Electronic Resource
    Electronic Resource
    Heterocyclic methacrylates for clinical applications–further studies of water sorption (1997)
    Springer
    Journal of materials science 8 (1997), S. 667-674 
    Details
    ISSN: 1573-4838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract The room temperature polymerizing system comprising poly(ethyl methacrylate)-tetra hydrofurfuryl methacrylate (PEM/THFMA) has potential in orthopaedic and dental applications, and earlier work has shown it to have unusual water absorption characteristics. This aspect has been studied in further detail, by studying the water absorption behaviour from some biological solutions, and the effect of the addition of an antibiotic (gentamicin). For comparison purposes, a parallel system whereby tetrahydrofuryl methacrylate was replaced by hydroxyethyl methacrylate (PEM/HEMA), was studied. In the case of PEM/THFMA, water uptake was substantially reduced when absorption was carried out from solutions (from about 30% in water to about 1.5% in solutions of higher concentrations), and the corresponding diffusion coefficient increased (by a factor of several hundred). The addition of gentamicin increased uptake, but the extent of increase also decreased in solutions. It was concluded that uptake was related to the osmolarity of the external solution, and also on the presence of osmotic sites within the polymer; hence the uptake process appears to be governed by chemical potential considerations. At the higher uptakes, there was evidence of water clusters. In marked contrast, the uptake by the PEM/HEMA system was independent of the osmolarity of the external solutions, presumably due to the hydrophilic nature of HEMA.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018531722265
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  • 15
    Electronic Resource
    Electronic Resource
    The dependence of osteoblastic response on variations in the chemical composition and physical properties of hydroxyapatite (1997)
    Springer
    Journal of materials science 8 (1997), S. 97-103 
    Details
    ISSN: 1573-4838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract Two synthetic hydroxyapatite powders (A and B), supplied by differentmanufacturers, were physically and chemically characterized before being diepressed and sintered at 1250°C. The powders were characterized using X-raydiffraction (XRD), infrared spectroscopy (IRS), X-ray fluorescence, surface areaanalysis (BET), particle size analysis and scanning electron microscopy (SEM).The materials were then pressed and sintered to produce hydroxyapatite discs ofsimilar densities and grain sizes for in vitro evaluation. The ceramicswere seeded with osteoblastic cells and after 15 days in culture the cellmorphology was assessed using scanning electron microscopy (SEM), theultrastructure of the cells was studied using transmission electron microscopy(TEM) with EDAX, and the rate of cell growth was assessed using biochemicaltechniques. The results clearly showed that the rate of cell proliferation butnot the rate of alkaline phosphatase production, was highl!y dependent on the composition of the hydroxyapatite powders that were used to makethe ceramic discs. The ultrastructural studies confirmed the relativeviabilities of the cells and the nature of the ceramic interface indicatingvisually the marked differences in the performance of the two materials.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018558816871
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  • 16
    Electronic Resource
    Electronic Resource
    Effects of surface-treated cpTi and Ti6Al4V alloy on the initial attachment of human osteoblast cells (1999)
    Springer
    Journal of materials science 10 (1999), S. 869-872 
    Details
    ISSN: 1573-4838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract This study concerns the effect of simple surface treatments on the nature of the oxide layer, of commercially pure titanium (cpTi) and Ti6Al4V alloy substrates and their effect on human osteoblast cells (HOBS). After treatment the surfaces were analyzed by X-ray photoelectron spectroscopy (XPS) in order to identify the surface groups responsible for the cell attachment process. The assessment of cell attachment was monitored by the Alamar blue assay (AB), measuring cell activity, in three types of media: phosphate-buffered saline (PBS), serum containing and serum-free Dulbecco's modified Eagle's cell culture medium (SER+ and SERF respectively). XPS analysis of the treated surfaces revealed consistent peaks representative of TiO2 on all surfaces and Ti0 and Ti2O3 on the non-heat-treated surfaces. The cell activity assays indicated that there were no significant differences in cellular activity caused by surface treatments, but the cellular activity compared between the three types of medium was greatest in the PBS over the initial stages of attachment.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008933318756
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  • 17
    Electronic Resource
    Electronic Resource
    Heterocyclic methacrylate-based drug release polymer system (1994)
    Springer
    Journal of materials science 5 (1994), S. 338-339 
    Details
    ISSN: 1573-4838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: 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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00058958
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  • 18
    Electronic Resource
    Electronic Resource
    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
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: 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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00058973
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  • 19
    Electronic Resource
    Electronic Resource
    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
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: 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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00213141
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  • 20
    Electronic Resource
    Electronic Resource
    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
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: 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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00121696
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