At the microscopic (matrix) scale, oim bone is mostly composed
of woven tissue [20] with unorganized collagen fibers, a high mineral/protein content ratio [21] and [22] and a high porosity [23]. This results in a low bone mineral density (content) measured by DXA on the whole bone level [24]. At the collagen/apatite scale (ultrastructure with nm length scale), oim bone apatite crystals are small and not well aligned [25] and [26] and their crystallinity and chemical composition is altered [21] and [22]. Numerous studies have examined the macroscopic mechanical properties of oim bone [15], [16], [18] and [19], the microscopic matrix mineral content [14], [21], [22] and [24], selleck products or the ultra-structure [25]. Only Grabner et al. investigated both mechanics and mineralization at the microscopic scale [26]. The mechanical measures were however limited to measures of the Vicker’s micro-hardness, which provides no information on the bone matrix elastic properties. No previous study has examined the multi-scale changes in mineral structure, selleck chemicals density, and elastic modulus in oim bone in order to explain how changes at the molecular level are translated into altered mechanical behavior at larger length scales. The objective of this study was to determine the multi-scale material properties in oim
bone, and in particular correlations between local tissue mineralization and elastic modulus at the microscopic (μm) scale. We used 3-point bending to estimate whole bone elastic modulus, quantitative backscattered electron microscopy second (qBSEM) to quantify the amount of bone matrix mineral, nanoindentation to measure the bone matrix elastic and plastic properties, and transmission electron microscopy (TEM) to examine the apatite crystals size and organization. We propose a mechanistic interpretation linking the mechanical and structural properties observed at the matrix scale into a common composite material framework. With an understanding of how structural changes influence mechanical behavior, appropriate pharmaceutical
therapies might be targeted to address particular critical deficiencies in bone. Wild type B6C3Fe-a/a-+/+ mice (WT, 8♀, 7♂) and pathologic B6C3Fe-a/a-Col1a2Oim/Oim mice (oim, 8♀, 12♂) were culled at 8 weeks-old and long bones were collected, cleaned of soft tissues and stored in gauze soaked with a phosphate buffered saline solution at − 18 °C. For each specimen, the right femurs were tested until fracture by 3-point bending using a standard materials testing machine (5866 Instron). The femurs were loaded at the mid-diaphysis in the anterior–posterior direction with a deflection rate of 50 m/s. Force–deflection curves were analyzed with a custom program (Matlab, MathWorks) to measure the bending stiffness (S, N.mm) and ultimate force (Fult, N).