Laboratory for Interdisciplinary Physics www-liphy.ujf-grenoble.fr
Unité Mixte de Recherche 5588
CNRS – Université Joseph Fourier Grenoble 1 BP 87 – 38402 ST MARTIN D’HERES Cedex France
Contact : Aurélien GOURRIER
PhD grant application for NANOBONE project
email: [email protected]
The Nanoscience Foundation of Grenoble, France, has recently launched a PhD program for high profile students wishing to perform a Doctoral thesis within one of the laboratories of the excellence network. At the Laboratory for Interdisciplinary Physics, our team, Materials, Optics and Techniques for Life Sciences, currently supports applications on the NanoBone project: Order and disorder at the NANOscale in biological mineral nanoparticles of BONE tissues . The goal of this project is to investigate the impact of disorder and size-scale effects induced by the nanostructure formation of biomineral particles in bone using advanced nanocharacterization techniques in order to: 1) establish the first complete protocol for biomedical characterization of bone at the nanoscale, 2) clearly identify the structural determinants of bone pathologies at this scale and 3) understand how nanoscale physics governs biomineralization processes. At the nanoscale, bone tissues can be viewed as composite assemblies of collagen fibrils of ~ 100 nm in diameter, mechanically reinforced by a calcium phosphate mineral phase which structure has been extensively studied in the past decade. It is now established that, in healthy tissues, it is structured as nanoparticles in the form of thin platelets of no more than 4-6 nm in thickness. Hence, the size, density and organization of the mineral nanoparticles have been identified as potential markers of bone quality and could point to pathological biomineralization defects or, indirectly, to malformation of the collagen matrix, e.g. when subjected to therapeutic treatment. However, the available data only provide a very fragmented and sometimes contradictory view. This stems from two essential aspects. For one, a full characterization, from the organization of the mineral nanoparticles to the atomic nanocrystal structure, requires using very high resolution analytical and imaging techniques, which still constitutes an important technological challenge. Secondly, the stoichiometry of biological apatitic nanocrystals and the presence of numerous ions which substitute to calcium and phosphate ions induce a high degree of disorder, difficult to quantify and rarely taken into account. In addition a large amount of surface ions can easily be altered in bone sample preparations, contributing to the disorder in a way which has to be investigated. Finally, it is remarkable to observe that potential size-scale effects induced by the low dimensionality of the crystals, e.g. lattice distortion gradients towards the nanocrystal surface, are nearly totally ignored in practice. Based on the current knowledge in the field of nanoscience concerning the physics of nanocrystals, we thus propose to conduct the first study taking the effects of order/disorder on the nanocharacterization of biological materials such as bone. To this end, we will combine measurements obtained by a set of advanced techniques: high resolution transmission electron microscopy (HRTEM), small-angle X-ray scattering and diffraction (SAXS/XRD) using synchrotron microbeams as well as Raman and Fourier-transformed infrared (FTIR) microspectroscopies. Several samples will be used: synthetic apatite nanocrystals of well controlled size and composition will be used to evaluate the level of disorder and constraints in the nanocrystals according to their physical-chemical characteristics; human bone samples exhibiting well identified pathological variations will then be analyzed. Ultimately, it is expected that the crossed correlation of our experiments will help identify useful diagnostic parameters and provide an analytical protocol for translational biomedical research. Our results should also be useful for characterization of a broader class of nano(bio)crystals. Students who have demonstrated strong skills in physics, biophysics, materials science are welcome to contact us. An experience with nanoscale characterization, e.g. using AFM, electron microscopy, X-ray scattering or spectroscopy techniques would be an asset. Fluent english is a mandatory condition.