Bone matrix like assemblies of collagen: from liquid crystals to gels and biomimetic materials

Skeletal tissues associate in close interaction, a dense organic matrix and a mineral network. In bone, the major structural protein is type I collagen, associated with inorganic crystals of hydroxyapatite. The three-dimensional arrangement of collagen fibrils in compact bone forms regularly ordered networks and a parallel was evidenced between these structures and molecular assemblies described in liquid crystals. Similar structures are now obtained in vitro. Indeed, when purified type I collagen is highly concentrated in an acid soluble state, the protein spontaneously assembles into ordered liquid crystalline phases. After a sol/gel transition triggered by pH increase, biomimetic materials are formed which resemble the exact compact bone matrix architecture over distances reaching centimetres and more. The properties of these highly ordered materials will be reviewed recalling their supramolecular arrangement and the corresponding patterns when visualised in polarised light microscopy (birefringence) and transmission electron microscopy (TEM). The association of inorganic phases (amorphous silica) to form chiral hybrid materials will also be described so as the behaviour of cells (fibroblast adhesion and migration) when seeded on these dense biomimetic matrices.     

Cylindre transverse isotrope poroélastique chargé cycliquement : application à un ostéonCyclic loading of a transverse isotropic poroelastic cylinder: a model for the osteon

The poroelastic problem associated with a hollow cylinder under cyclic loading is solved. Both fluid and solid phases are supposed compressible. Solid matrix is modeled as an elastic transverse isotropic material. An explicit close-form solution for the steady state is obtained. This cylinder is considered as a model for an osteon, the basic unit of cortical bone. The fluid flow distribution as a function of poroelastic properties and cyclic loading is discussed, as this could influence bone remodeling. To cite this article: A. Rémond, S. Naili, C. R. Mecanique 332 (2004).     

Transverse isotropic poroelastic osteon model under cyclic loading

The poroelastic problem associated with a hollow cylinder under cyclic loading is solved. This cylinder models an osteon, basic unit of cortical bone. Both fluid and solid phases are supposed compressible. Solid matrix is modeled as an elastic transverse isotropic material. An explicit close-form solution for the steady state is obtained. Fluid flow distribution as a function of poroelastic properties and cyclic loading is discussed as it could influence bone remodeling. Strain rate of loading is shown to play a significant role in mass flux in the porous material.     

A novel two‐dimensional preparative chromatography method designed for the separation of traditional animal Tibetan medicine Osteon Myospalacem Baileyi

Animal medicine is an important part in traditional Tibetan medicine. However, information about the chemical composition of animal medicine is very limited, and there is a lack of comprehensive chromatographic purification methods. In the present work, animal medicine Osteon Myospalacem Baileyi was taken as an example and a novel two‐dimensional preparative chromatographic method was established for the preparation of single compounds with high purity from the extract of Osteon Myospalacem Baileyi. The first‐dimension preparation was carried on a DAISO Silica prep column, and ten fractions were obtained from the 112.3 g crude sample within 12 injections. A diol prep column used in nonaqueous mobile phase was selected for the second‐dimension preparation. The purity of the compounds isolated from the crude extract was >98%, which indicated that the method built in this work was efficient to manufacture single compounds of high purity from the extract of Osteon Myospalacem Baileyi. Additionally, this method showed great potential in the purification of weakly polar chemicals and it could act as a good example in the purification of other traditional animal medicines.