PH'D Defense Mme Veronica Müller

Abstract: Orthopedic and dental implants have been widely used for decades and are set to multiply as the population ages and life expectancy increases. However, about 10 % of these implants fail prematurely due to poor osteointegration. Usually, implants are commonly made from titanium alloys, particularly Ti6Al4V, thanks to their good biocompatibility. For better integration with the bone tissue, a modification of their surface morphology with a calcium phosphate coating is often required. Traditionally, these coatings are fabricated by plasma spray, leading to well-crystallized films in the most stable phases (mainly hydroxyapatite, HAP). Even though these plasma-sprayed coatings are commonly used in prostheses, their efficiency is subject to controversy because of several drawbacks related to the high-temperature processing and the excessive thickness of the coatings. This Ph.D. thesis is focused on the low-cost design of innovative biomaterials coatings by a nano-texturing one-step approach using the electrostatic spray deposition (ESD) technique. Due to their bone-bonding ability, HAP, bioactive glasses (BG) belonging to the SiO2-CaO-P2O5 system, and their composites have been selected to coat Ti6Al4V. An original bottom-up mechanism was understood when an organic P5+ precursor was electrosprayed to fabricate single-phase HAP coatings with tuneable microstructure and crystallite size. Various HAP morphologies have been successfully obtained by optimizing ESD parameters, ranging from thin and dense films to thicker and porous 3D coral-type ones. Their biological response in vitro was investigated according to their microstructures and compared to a commercial sample sprayed by plasma. This Ph.D. thesis is also dedicated to the optimization of ESD parameters to achieve S85 (85 SiO2 – 10 CaO – 5 P2O5 mol. %), S75 (75 SiO2 – 20 CaO – 5 P2O5 mol. %), and S58 (58 SiO2 – 37 CaO – 5 P2O5 mol. %). BG coatings characterized by different morphologies ranging from compact cauliflower-type to highly porous coral-like. The bioactivity of these BG coatings was examined in terms of apatiteforming ability by immersion in simulated body fluid (SBF) solution. Finally, S58 BG/HAP composites coatings designed to bring the best of each biomaterial, i.e., high bioactivity index of BG with the long-term stability of HAP, is explored for enhancing the overall osteointegration of Ti6Al4V-based implants.

The PhD defense will be in English in front of the following jury:

Dr. Yoann ROUPIOZ (CNRS, CEA-SyMMES Grenoble, Président)
Prof. Ghislaine BERTRAND (INPT-ENSIACET Toulouse, Rapporteure)
Prof. Eric CHAMPION (IRCER Limoges, Rapporteur)
Dr. Nathalie DOUARD (EMSE St Etienne, Examinatrice)
Prof. Laurent GREMILLARD (CNRS, INSA Lyon, Examinateur)
Prof. Elisabeth DJURADO (Grenoble INP, Directrice)
Dr. Solène TADIER (INSA Lyon, Co-Directrice)