Characterisation of Collagen Scaffolds using X-ray Microtomography
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Characterisation of Collagen Scaffolds using X-ray Microtomography Patrick J. Smith, Eleftherios Sachlos1, Samuel McDonald, Nuno Reis, Brian Derby, Paul M. Mummery and Jan T. Czernuszka1 Manchester Materials Science Centre, UMIST and University of Manchester, Grosvenor Street, Manchester, M1 7HS, England. 1 Department of Materials, University of Oxford, Parks Road, Oxford, OX1 3PH, England. ABSTRACT Collagen scaffolds have been produced that incorporate predefined internal channels. The scaffolds were obtained with the aid of sacrificial moulds that have been manufactured using a rapid prototyping technique. A computer aided design file of the mould was created and then realised using an ink-jet printer. A dispersion of collagen was then cast into the mould and frozen. Ethanol was used to dissolve the mould leaving the collagen, which was then freeze dried to produce the final product. The scaffold was then analysed using X-ray microtomography (XMT) to determine whether the desired internal structure was obtained. It was found necessary to add saturated potassium iodide (KI) solution to the scaffold in order to analyse it satisfactorily by XMT. The resultant images indicate that the desired internal structure was obtained. INTRODUCTION The new multidisciplinary field of Tissue Engineering has arisen to satisfy the demand for biological substitutes to repair living tissue [1]. Tissue engineering involves the growth of relevant biological material into the required organ or tissue. However, unaided cells do not grow into the required orientations and therefore the resulting tissues are not of the correct shape. A solution is provided by the use of three-dimensional (3D) scaffolds acting as guides for cellular growth. Tissue engineered scaffolds are porous structures usually made from bioresorbable material containing appropriate factors to induce cell adhesion and growth. This allows the attached cells to migrate and colonise the whole scaffold. During the scaffold degradation, cells proliferate and occupy newly liberated spaces to create a viable tissue replacement [2]. Biodegradable and bioresorbable polymers and ceramics have been used to make 3D scaffolds [3 - 5]. Both synthetic and natural polymers have been used. The material used in this investigation is the natural polymer, collagen. Collagen is an abundant protein present in the connective tissue (and extra-cellular matrix in bone) of mammals. Existing methods for scaffold fabrication are dependant on the generation of pores within the matrix; typical pore generators are salt particles and ice crystals. The distribution of pores however cannot be controlled precisely. As a consequence, current techniques cannot produce complicated internal features, e.g. channels that could act as an artificial vascular system. This internal system is desirable because it allows the flow of a blood-like medium throughout the construct, which supplies oxygen and nutrients to cells migrating deep into the scaffold. Solid Freeform Fabrication (SFF), an outgrowth of Rapi
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