Robin S. Walton

University of Oxford, Oxford, England, United Kingdom

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Publications (4)8.54 Total impact

  • Source
    M Tamaddon · R S Walton · D D Brand · J T Czernuszka
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    ABSTRACT: Collagen type-II is the dominant type of collagen in articular cartilage and chondroitin sulfate is one of the main components of cartilage extracellular matrix. Afibrillar and fibrillar type-II atelocollagen scaffolds with and without chondroitin sulfate were prepared using casting and freeze-drying methods. The scaffolds were characterised to highlight the effects of fibrillogenesis and chondroitin sulfate addition on viscosity, pore structure, porosity and mechanical properties. Microstructure analysis showed that fibrillogenesis increased the circularity of pores significantly in collagen-only scaffolds, whereas with it, no significant change was observed in chondroitin sulfate-containing scaffolds. Addition of chondroitin sulfate to afibrillar scaffolds increased the circularity of the pores and the proportion of pores between 50 and 300 μm suitable for chondrocytes growth. Fourier transform infrared spectroscopy explained the bonding between chondroitin sulfate and afibrillar collagen- confirmed with rheology results- which increased the compressive modulus 10-fold to 0.28 kPa. No bonding was observed in other scaffolds and consequently no significant changes in compressive modulus were detected.
    Full-text · Article · Feb 2013 · Journal of Materials Science Materials in Medicine
  • Robin S. Walton · Jan T. Czernuszka
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    ABSTRACT: Collagens are a major constituent of the extracellular matrices of many biological tissues. Their structural and biological roles in animal tissues have inspired the development of regenerative therapies that incorporate collagen as a base material, thus providing a naturally recognisable surface for cell attachment and proliferation. In this review, recent collagen-related patents / patent applications are divided into three main areas: methods of collagen extraction / purification / synthesis (Area 1), methods of collagen molecular modification / processing (Area 2) and collagen scaffolds / implants (Area 3). Within Area 1, there are disclosures for methods of obtaining collagenous materials, including a method that uses urea to isolate collagen from collagen-containing natural fibres. Methods have also emerged to avoid the risk of cross-species infection including the extraction of collagen from marine sources and the synthesis of modular collagen-like peptides in bacterium models. Within Area 2, there are recently disclosed methods that can increase the resistance of collagen to degradation, including covalent / non-covalent crosslinking and a method of stabilising the collagen triple he-lix through O-methylation. Methods have also been recently disclosed to remove antigenic surface carbohydrate moieties and for processing collagen to induce fibril fusion. Within Area 3, there have been developments in the functional use of collagen in regenerative therapies, including a method to decellularise thick collagen-rich tissue extracts Z scaffold, a method to provide a support mesh for collagen scaffolds such that they hold their external shape on implantation and a method which allows the creation of composite scaffolds and multi-layer scaffolds for trans-tissue implants. In addition, two recent patents disclose the use of collagen injections for the treatment of synovial joints and intervertebral discs. The recent advances in the art represent a culmination of many years of progressive work on collagenous materials from many scientific fields; there now exists a plethora of techniques to obtain collagen, to modify its structure / Vproperties and to implement the material into a functional embodiment for tissue regeneration.
    No preview · Article · Jul 2012
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    ABSTRACT: There is a need in tissue-engineering for 3D scaffolds that mimic the natural extracellular matrix of bone to enhance cell adhesion, proliferation, and differentiation. The scaffold is also required to be degradable. A highly porous scaffold has been developed to incorporate two of the extracellular components found in bone-collagen and hydroxyapatite (HA). The scaffold's collagen component is an afibrillar monomeric type I atelocollagen extracted from foetal calf's skin. This provided a novel environment for the inclusion of HA powder. Five hundred thousand primary human osteoblasts were seeded onto 4 mm cubed scaffolds that varied in ratio of HA to collagen. Weight ratios of 1:99, 25:75, 50:50, and 75:25 hydroxyapatite:collagen (HA:Collagen) were analysed. The scaffolds plus cells were cultured for 21 days. DNA assays and live/dead viability staining demonstrated that all of the scaffolds supported cell proliferation and viability. An alkaline phosphatase assay showed similar osteoblast phenotype maintenance on all of the 3D scaffolds analysed at 21 days. MicroCT analysis demonstrated an increase in total sample volume (correlating to increase in unmineralised matrix production). An even distribution of HA throughout the collagen matrix was observed using this technique. Also at 3 weeks, reductions in the percentage of the mineralised phase of the constructs were seen. These results indicate that each of the ratios of HA/collagen scaffolds have great potential for bone tissue engineering.
    No preview · Article · Sep 2010 · Journal of Biomedical Materials Research Part A
  • Source
    Robin S Walton · David D Brand · Jan T Czernuszka
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    ABSTRACT: Type I collagen is widely used in various different forms for research and commercial applications. Different forms of collagen may be classified according to their source, extraction method, crosslinking and resultant ultrastructure. In this study, afibrillar and reconstituted fibrillar films, derived from acid soluble and pepsin digested Type I collagen, were analysed using Lateral Force Microscopy (LFM), Fourier Transform Infra-Red Spectroscopy (FTIR), Differential Scanning Calorimetry (DSC) and enzymatic stability assays to asses the influence of telopeptides, fibrils and crosslinking. LFM proved to be a useful technique to confirm an afibrillar/fibrillar ultrastructure and to elucidate fibril diameters. FTIR has proved insensitive to ultrastructural differences involving telopeptides and fibrils. DSC results showed a significant increase in T(d) for crosslinked samples (+22-28 degrees C), and demonstrated that the thermal behaviour of hydrated, afibrillar films is more akin to reconstituted fibrillar films than monomeric solutions. The enzymatic stability assay has provided new evidence to show that afibrillar films of Type I collagen can be significantly more resistant to collagenase (by up to 3.5 times), than reconstituted fibrillar films, as a direct consequence of the different spatial arrangement of collagen molecules. A novel mechanism for this phenomenon is proposed and discussed. Additionally, the presence of telopeptide regions in afibrillar tropocollagen samples has been shown to increase resistance to collagenase by greater than 3.5 times compared to counterpart afibrillar atelocollagen samples. One-factor ANOVA analysis, with Fisher's LSD post-hoc test, confirms these key findings to be of statistical significance (P < 0.05). The profound physicochemical effects of collagen ultrastructure demonstrated in this study reiterates the need for comprehensive materials disclosure and classification when using these biomaterials.
    Full-text · Article · Oct 2009 · Journal of Materials Science Materials in Medicine