Examination of the Dynamic Mechanical Properties of Tissue Engineering Scaffolds
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Examination of the Dynamic Mechanical Properties of Tissue Engineering Scaffolds Heather Kauth1 and Catherine Klapperich1,2 Laboratory for Biomedical Materials Research, Boston University, Dept. of Manufacturing Engineering,1 and Dept. of Biomedical Engineering,2 44 Cummington St., Boston, Massachusetts 02215
ABSTRACT Scaffolds of both natural and synthetic materials have been widely utilized to provide a three dimensional environment for cell growth. The characteristics of these scaffolds play a vital, but sometimes ambiguous, role in tissue engineering constructs. Collagen-glycosaminoglycan matrices have been used clinically as artificial skin implants. Previous research in our laboratory on this model has shown that gene expression is regulated by mechanical stress applied to the matrix. In this work we begin the process of quantifying the effects of mechanical stress and preparation technique on a matrix comprised of type I collagen and chondroitin-6-sulfate. Compressive loads were applied to the matrices using a dynamic mechanical analyzer at 37 degrees Celsius and retrofitted with 5% carbon dioxide gas flow. All samples were tested hydrated in either simulated body fluid or PBS. Storage and loss modulus data are presented. Mechanical tests were performed on collagen-GAG meshes both seeded with human dermal fibroblasts and not seeded with cells. Continuing work includes gene expression analysis of the cells on the seeded matrices in order to identify differential gene expression induced by mechanical loading.
INTRODUCTION and BACKGROUND Over the last 25 years tissue engineering scaffolds of different composition have been proposed. Among these, matrices composed of collagen and glycosaminoglycans have been the topic of extensive study. These materials form an open pore structure suitable for the migration of cells into the scaffold. Cell-seeded meshes have been shown efficacious at regenerating dermis and have also shown some success with peripheral nerve regeneration [1]. Similar scaffolds have been suggested for the regeneration of more complex structures [2]. Collagen-GAG matrices have been approved for use in the treatment of severe burns and in diabetic and venous ulcers. A variety of parameters affect the success of these scaffolds in tissue regeneration, such as degree of crosslinking and average pore size [3,4]. The mechanical environment of the mesh also has a significant effect on the characteristics of the cell/mesh interface. Previous studies have examined the effects of mesh stiffness on fibroblast contraction of collagen-GAG matrices [5]. Other workers have measured the mechanical properties of these meshes using unconfined compression tests [6] . Our goal was to look at the mechanical properties of these meshes both before and after hydration and before and after cell seeding.
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EXPERIMENTAL DETAILS Mesh Fabrication and Seeding Bovine tendon collagen (Cat # C9879, Sigma, St. Louis, MO) and chondroitin-6sulfate (Cat # C4384, Sigma, St. Louis, MO) three dimensional meshes were fab
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