The effect of water, various incorporations and substitutions on physical and chemical properties of bioapatite and mechanical properties of bone tissue

Abstract

Basing on scientific publications and original research the authors specified the effect of incorporation and adsorption of different ions and water molecules on physical, chemical and mechanical properties of bioapatite and determined new directions for investigations of intercrystallite interactions in nanoscale. Inner structure of the apatite crystallites more adaptable to chemical substitutions in comparison with other minerals controls their important characteristics such as a size, solubility, hardness, fragility, formability and thermal stability. The water molecules incorporated in crystallites and adsorbed on their surfaces stabilize them. In case the distances between crystallites become shorter than 10 nm the water molecules adsorbed on their surface play dominant role in bonding between the crystallites. This bond determines the main mechanical properties of bones. We bring forward a suggestion that theoretical model developed on the basis of near edge X-ray spectroscopic studies of bones using the contemporary high brilliant sources of X-ray radiation (synchrotrons and X-ray free electrons lasers) will allow to receive new quantitative data on local electronic and atomic structure (coordination numbers, ionic charges, interatomic distances interatomic and intercrystallite forces) of nanoelements in osseous tissue. The investigation results must bring to construction of new morphologically correct model providing deeper understanding of processes occurring in mineral matrix and mechanical properties of bones.

Thermal changes in young and mature bone nanostructure probed with Ca 2p excitations

“…Both the size distribution of nanocrystallites and their elemental composition in the plates differ in normal and pathological conditions [10,11,17,22,38,39]. The interplay of the 3D atomic structure of OH-Ap with the higher lying levels of the hierarchical organization of bone determines its nanolevel morphology.…”

“…Studying it one can achieve deeper understanding of the hierarchical and self-assembled materials. To date, many efforts have been invested to investigate the role of chemical composition in mechanical and physical properties of bone [10][11][12]. These properties are also tightly related with the skeletal hierarchical organization.…”

Local electronic structure and nanolevel hierarchical organization of bone tissue: theory and NEXAFS study

“…According to the x-ray scattering and microscopic studies the length (L x ), width (L y ) and thickness (L z ) of the crystallites in bone vary in rather wide limits 13<L x <50 nm, 7<L y <25 nm and 1.5<L z <4 nm [1,24,37,38]. To begin with, we neglect the helical shape of the mineralized plate and describe it as a coplanar assembly of the averagesize nanocrystallites as plotted in figure 1, middle panel.…”

“…Both transmission electron microscopic and small angle x-ray scattering methods extensively applied to bones make evident that intra-and inter-fibrilar associations of the crystallites form a series of parallel and spiral wound mineralized plates [5,23,24] as exhibited in figure 1 (upper panel). These plates are usually approximated as coplanar assemblies of the nanocrystallites of HAP [3,23,24]. This assembly is shown in the middle panel of figure 1.…”

“…The morphological picture in figure 1 is a result of the structural and functional relationship between adjacent levels of the hierarchical organization of bone. Size distribution of the crystallites in the mineralized phase is age-related [17,25,26] and depends on atomic incorporations and substitutions [19,24,27,28].…”