Sintering & Biodegradation of carbonated hydroxyapatite ceramics elaborated by additive manufacturing for the reconstruction of large bone defect – SiBio

SiBio aims to develop and study the biodegradation potential of customized carbonated hydroxyapatite (CHA) based bioceramics with optimized surface curvature porous network for the treatment of critical-sized bone defects. Specific architecture containing gyroïd-like geometries, known to promote the rapid development of mature bone, will be studied. The elaboration of CHA implants requires a sintering atmosphere rich in CO2 to stabilize the phase up to a temperature allowing its densification. Sintering is therefore a crucial step to guarantee the composition, the final mechanical quality of the parts and, consequently, their biological properties. The core of SiBio consists in an in depth study of the reactive sintering of CHA parts under mixed atmosphere to be able to controlled the final microstructure and chemistry. After powder preparation by wet precipitation (WP1), the first objective is to produce non-macrostructured CHA ceramics with controlled carbonate amount and microstructure (WP2). This will be achieved thanks to a sinterability study where multiple parameters, including procedure (e.g., two-step sintering), heating rate, temperature, atmosphere (e.g., PCO2 and PH2O partial pressures) and initial composition will be screened to identify the best sintering protocols with respect to the final composition, microporosity range and mechanical properties. The second objective of SiBio is to thoroughly evaluate the degradation behaviour of macro-structured CHA ceramics. To achieve this, CHA ceramics with controlled composition and gyroïd-like geometries will be manufactured thanks to additive manufacturing technologies (WP3). Then dynamic acellular and cellular in vitro tests will be set up to investigate their biodegradation (WP4). Specific attention will be paid to thoroughly characterized the ceramic at a macro- (e.g., shape, macro-porosity, bulk chemical composition) and micro-scale (e.g., micro-porosity, chemical homogeneity) to study the interplay between ceramic features and its bioactivity. In addition, the questions raised in terms of implant design will be addressed through an outreach action for lay public (WP5) and will make it possible to disseminate the scientific culture of this multidisciplinary research field in a participatory form. The knowledge acquired thanks to SiBio will allow envisaging personalised treatments according to the bone defect to be reconstructed and the characteristics of the patient.