There is an enduring and unmet need for a bioactive, loadbearing tissue-engineering scaffold, which is biocompatible, biodegradable and capable of facilitating and promoting osteogenesis when implanted in vivo. This study set out to develop a biomimetic scaffold by incorporating osteoinductive hydroxyapatite (HA) particles into a highly porous and extremely biocompatible collagenbased scaffold developed within our laboratory over the last number of years to improve osteogenic performance. Specifically we investigated how the addition of discrete quantities of HA affected scaffold porosity, interconnectivity, mechanical properties, in vitro mineralisation and in vivo bone healing potential. The results show that the addition of HA up to a 200 weight percentage (wt%) relative to collagen content led to significantly increased scaffold stiffness and pore interconnectivity (approximately 10 fold) while achieving a scaffold porosity of 99%. In addition, this biomimetic collagen-HA scaffold exhibited significantly improved bioactivity, in vitro mineralisation after 28 days in culture, and in vivo healing of a critical-sized bone defect. These findings demonstrate the regenerative potential of these biodegradable scaffolds as viable bone graft substitute materials, comprised only of bone's natural constituent materials, and capable of promoting osteogenesis in vitro and in vivo repair of critical-sized bone defects.

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FJ. Scaffold mean pore size influences mesenchymal stem cell chondrogenic differentiation and matrix deposition. Tissue Engineering. Part A. 2015;21(3-4):486-97. -Use Licence - AbstractRecent investigations into micro-architecture of scaffolds has revealed that mean pore sizes are cell type specific and influence cellular shape, differentiation and extracellular matrix secretion.In this context, the overall goal of this study was to investigate whether scaffold mean pore sizes affect mesenchymal stem cell initial attachment, chondrogenic gene expression and cartilage-like matrix deposition. Collagen-hyaluronic acid (CHyA) scaffolds, recently developed in our laboratory for in vitro chondrogenesis, were fabricated with three distinct mean pore sizes (94 μm, 130 μm and 300 μm) by altering the freeze-drying technique used. It was evident that scaffolds with the largest mean pore sizes (300 μm) stimulated significantly higher cell proliferation, chondrogenic gene expression and cartilage-like matrix deposition relative to scaffolds with smaller mean pore sizes (94 μm, 130 μm). Taken together, these findings demonstrate the importance of scaffold micro-architecture in the development of advanced tissue engineering strategies for articular cartilage defect repair.

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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