Introduction: One of the major challenges in the orthopedic field is the repair of critical size osteochondral (OC) defects, above all considering the poor auto-regenerative potential of OC unit. In a previous study, a bi-layered substitute, made of interconnected porous hydroxyapatite (HA) and collagen has been tested[1]. Good results have been obtained in terms of mechanical properties, biocompatibility and tissue regeneration. The goal of this work is to enhance the bony material reasorbibility and to increase the radial compliance of the above-cited scaffold trough HA modification and the design of a new OC scaffold configuration: HONEY.
Materials and Methods: Collagen layer has been obtained according to previous work[2]. Inorganic layer has been fabricated by the foam replication method[3] and it is composed of Mg doped HA (Mg-HA) or Wollastonite (Ws)/HA mixtures or pure HA. Mg-HA has been prepared substituting a 10% molar of calcium ions, keeping the (Ca+Mg)/P=1,67. Ws/HA composites scaffold has been prepared by sintering Ws/HA mixtures powders in a 1/1 ratio. Collagen and inorganic layers have been characterized by SEM, EDX, DRX, compression tests, stability experiments (37°C, pH 7,4) and MTT assays by MG63 cell line. Finally, HONEY has been designed, assembled and characterized by µCT and compression test.
Results and Discussion: The features of collagen layer confirmed the previously obtained results[2]. All inorganic layers exhibited a highly porous and interconnected macro-structure (pore range: 300-800 µm) (Fig 1a); HA and Mg-HA displayed a well-densified microstructure, while HA/Ws showed a plywood like structure (Fig 1b-c). Compression results showed a stress at the failure of about 0,99; 0,63 and 1,35 MPa for HA, Mg-HA and HA/Ws respectively. Ceramic materials exhibited different degradation behaviors: pure HA was almost stable in physiological conditions and significantly lower than Mg-HA and HA/Ws (weight loss: 0,8; 2,9 and 21% after 6 months, respectively). In vitro tests highlighted that the inorganic layers and the collagen layer are cytocompatible, without significant differences in terms of vitality. HONEY was successively obtained (Fig 2).
Conclusion: This paper deals with the improvement of a 3D bi-component scaffold previously described[1]. Ceramic materials reasorbibility has been significantly increased thanks to HA doping and Ws employ. Contemporarily, a new scaffold configuration has been designed allowing decreasing the inorganic, pour reasorbible, component and improving the scaffold radial compliance.
MIUR (PON RINOVATIS No.02_00563_3448479)
References:
[1] Sosio C et al Tissue Eng Part A, 21 N. 3§4, 2015
[2] Gervaso F et al Key Eng Mat, 493-494, 2012
[3] Gervaso F et al J Appl Ceram Technol, 9, 2012