title: Multi-scale mechanical response of freeze-dried collagen scaffolds for tissue engineering applications.
abstract: Tissue engineering has grown in the past two decades as a promising solution to unresolved clinical problems such as osteoarthritis. The mechanical response of tissue engineering scaffolds is one of the factors determining their use in applications such as cartilage and bone repair. The relationship between the structural and intrinsic mechanical properties of the scaffolds was the object of this study, with the ultimate aim of understanding the stiffness of the substrate that adhered cells experience, and its link to the bulk mechanical properties. Freeze-dried type I collagen porous scaffolds made with varying slurry concentrations and pore sizes were tested in a viscoelastic framework by macroindentation. Membranes made up of stacks of pore walls were indented using colloidal probe atomic force microscopy. It was found that the bulk scaffold mechanical response varied with collagen concentration in the slurry consistent with previous studies on these materials. Hydration of the scaffolds resulted in a more compliant response, yet lesser viscoelastic relaxation. Indentation of the membranes suggested that the material making up the pore walls remains unchanged between conditions, so that the stiffness of the scaffolds at the scale of seeded cells is unchanged; rather, it is suggested that thicker pore walls or more of these result in the increased moduli for the greater slurry concentration conditions.
authors.affiliation: Engineering Department, University of Cambridge, Trumpington Street, Cambridge CB2 1PZ, UK; Cambridge Centre for Medical Materials, Department of Materials Science and Metallurgy, University of Cambridge, 27 Charles Babbage Road, Cambridge CB3 0FS, UK.
authors.forename: Giovanni S
authors.initials: GS
authors.lastname: Offeddu
authors.affiliation: Cambridge Centre for Medical Materials, Department of Materials Science and Metallurgy, University of Cambridge, 27 Charles Babbage Road, Cambridge CB3 0FS, UK.
authors.forename: Jennifer C
authors.initials: JC
authors.lastname: Ashworth
authors.affiliation: Cambridge Centre for Medical Materials, Department of Materials Science and Metallurgy, University of Cambridge, 27 Charles Babbage Road, Cambridge CB3 0FS, UK.
authors.forename: Ruth E
authors.initials: RE
authors.lastname: Cameron
authors.affiliation: Engineering Department, University of Cambridge, Trumpington Street, Cambridge CB2 1PZ, UK. Electronic address: mlo29@cam.ac.uk.
authors.forename: Michelle L
authors.initials: ML
authors.lastname: Oyen
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D002417:Cattle; D024042:Collagen Type I; D004548:Elasticity; D005612:Freeze Drying; D008422:Materials Testing; D055595:Mechanical Phenomena; D008567:Membranes, Artificial; D023822:Tissue Engineering; D054457:Tissue Scaffolds; D014783:Viscosity
chemical_list: D024042:Collagen Type I; D008567:Membranes, Artificial
keywords: Colloidal probe AFM; Indentation; Scaffolds mechanics; Type I collagen; Viscoelastic