The objective of this study was to develop a biomimetic, highly porous collagen‐hydroxyapatite (HA) composite scaffold for bone tissue engineering (TE), combining the biological performance and the high porosity of a collagen scaffold with the high mechanical stiffness of a HA scaffold. Pure collagen scaffolds were produced using a lyophilization process and immersed in simulated body fluid (SBF) to provide a biomimetic coating. Pure collagen scaffolds served as a control. The mechanical, material, and structural properties of the scaffolds were analyzed and the biological performance of the scaffolds was evaluated by monitoring the cellular metabolic activity and cell number at 1, 2, and 7 days post seeding. The SBF‐treated scaffolds exhibited a significantly increased stiffness compared to the pure collagen group (4‐fold increase), while a highly interconnected structure (95%) was retained. FTIR indicated that the SBF coating exhibited similar characteristics to pure HA. Micro‐CT showed a homogeneous distribution of HA. Scanning electron microscopy also indicated a mineralization of the collagen combined with a precipitation of HA onto the collagen. The excellent biological performance of the collagen scaffolds was maintained in the collagen‐HA scaffolds as demonstrated from cellular metabolic activity and total cell number. This investigation has successfully developed a biomimetic collagen‐HA composite scaffold. An increase in the mechanical properties combined with an excellent biological performance in vitro was observed, indicating the high potential of the scaffold for bone TE. © 2009 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2009

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Osteoblasts respond to mechanical signals which play a key role in the formation of bone however, after extended periods of stimulation they become desensitised. Mechanosensitivity has been shown to be restored by the introduction of resting periods between loadings. The aim of this study was to analyse the effect of rest periods on the response of osteoblast-like cells seeded on collagen-glycosaminoglycan (CG) scaffolds in a flow perfusion bioreactor up to 14 days. Short (10 s) and long (7 h) term rests were incorporated into stimulation patterns. Constructs cultured in the bioreactor had a more homogenous cell distribution albeit with lower cell numbers than the static group. Osteopontin expression was significantly higher on the rest-inserted group than on the steady flow and static control. These results indicate that the insertion of short term rests during flow improves cellular distribution and osteogenic responses on CG constructs cultured in a flow perfusion bioreactor.

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