Sodium-doped porous calcium polyphosphate � strength and in vitro degradation characteristics

Event Abstract Back to Event Sodium-doped porous calcium polyphosphate – strength and in vitro degradation characteristics Youxin Hu1, Corey Sermer2, Rita A. Kandel1, 2, Marc D. Grynpas1, 2 and Robert M. Pilliar1, 3 1 University of Toronto, Institute of Biomaterials & Biomedical Engineering,, Canada 2 Mt. Sinai Hospital, Lunenfeld-Tanenbaum Research Institute, Canada 3 University of Toronto, Faculty of Dentistry, Canada Introduction: A previous study[1] reported on the effect of Na doping of calcium polyphosphate (CPP) powders on sintering behaviour to form porous Na-CPP implants as biodegradable bone substitutes or for osteochondral defect repair and regeneration. The present study investigates processing parameters to form such implants with the goal of process optimization to get higher strength, faster degradation and maintain biocompatibility and suitability for in vitro articular cartilage formation. Methods: The formation of 0.01Na2O/CaO mole ratio CPP was achieved by appropriate blending of sodium carbonate into a precursor powder which after calcining, melting and further processing using a 2-Step sinter/anneal[2], resulted in sodium-doped CPP (Na-CPP) porous structures. Samples for mechanical and in vitro degradation studies were made using three different Step-2 crystallization anneals (720, 835 or 950˚C) and characterized by XRD, SS NMR and SEM examination. For mechanical testing (as-made and after in vitro degradation in PBS solution - pH=7.4), 4mm Φ x 6mm cylindrical compressive test and 4mm Φ x 2mm DCT samples (for tensile strength determination) were evaluated as-made and after up to 30 days degradation. Weight loss was estimated from Ca2+ concentrations using ICP-AES. Additional 4mm Φ disc samples of ‘optimized-processed’ samples were prepared for in vitro cartilage formation as reported[3] using primary bovine chondrocytes. After 3 weeks in culture, the resulting biphasic samples were assessed by histology and biochemical analysis. Non-doped CPP ‘controls’ were also included for comparison. Results: SEM examination of prepared Na-CPP and CPP ‘control’ samples indicated larger sinter necks for the Na-CPP samples (sinter neck ratio ≈ 0.6±0.1 cf 0.4±0.1). Fig 1 shows the mechanical test results for the as-made samples prepared using the three different Step-2 annealing temperatures while Fig 2 shows the estimated sample weight loss after 30 days degradation. From these results, the ‘optimized-processed’ samples were selected as the 835˚C Step-2 samples. These displayed strengths and degradation rates approximately double that of pure CPP. Histology and biochemical analysis of in vitro-formed cartilage was the same as for pure CPP ‘control’ samples. Fig 1 Mechanical strengths of Na-CPP under different Step-2 sintering temperatures. Fig 2 Weight losses of Na-CPP using different Step-2 sintering temperatures after 30-days degradation Discussion: With the goal of higher strength and moderately faster degradation rates compared with the ‘control’ porous CPP samples, the results suggest optimum processing of Na-CPP using an 835˚C, Step-2 anneal which resulted in increased strength due to larger sinter necks and possibly strengthening due to second phase precipitates (sodium polyphosphate below XRD detection limit but suggested by NMR results) and faster degradation due to the presence of this second phase. These effects did not appear to affect biocompatibility as indicated by the observed successful in vitro cartilage formation. Conclusions: The results suggest an advantage of porous Na-CPP over pure CPP when formed using appropriate processing. Natural Science & Engineering Research Council (NSERC) of Canada; Canadian Institute for Health Research (CIHR)References:[1] Ue et al, Key Eng Mater (2008) 361-363:281;[2] Pilliar, Hong, Santerre, (2009), U.S. Patent No. 7494614[3] Kandel et al (2006), Biomater 27:4120 Keywords: Bone Regeneration, biomaterial, Calcium phosphate, Bone graft Conference: 10th World Biomaterials Congress, Montréal, Canada, 17 May - 22 May, 2016. Presentation Type: Poster Topic: Biomaterials in musculoskeletal orthopeadics and tissues Citation: Hu Y, Sermer C, Kandel RA, Grynpas MD and Pilliar RM (2016). Sodium-doped porous calcium polyphosphate – strength and in vitro degradation characteristics. Front. Bioeng. Biotechnol. Conference Abstract: 10th World Biomaterials Congress. doi: 10.3389/conf.FBIOE.2016.01.01505 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 27 Mar 2016; Published Online: 30 Mar 2016. Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Youxin Hu Corey Sermer Rita A Kandel Marc D Grynpas Robert M Pilliar Google Youxin Hu Corey Sermer Rita A Kandel Marc D Grynpas Robert M Pilliar Google Scholar Youxin Hu Corey Sermer Rita A Kandel Marc D Grynpas Robert M Pilliar PubMed Youxin Hu Corey Sermer Rita A Kandel Marc D Grynpas Robert M Pilliar Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.