Shifeier Lu

Characterization of nano-structural and nano-mechanical properties of osteoarthritic subchondral bone.

BackgroundAlthough articular cartilage is the primary tissues affected by osteoarthritis (OA), the underlying subchondral bone also undergoes noticeable changes. Despite the growing body of research into the biophysical and mechanical properties of OA bone there are few studies that have analysed the structure of the subchondral sclerosis at the nanoscale. In this study, the composition and nano-structural changes of human osteoarthritis (OA) subchondral bone were investigated to better understand the site-specific changes.MethodsOA bone samples were collected from patients undergoing total knee replacement surgery and graded according to disease severity (grade I: mild OA; grade IV: severe OA). Transmission electron microscopy (TEM), Electron Diffraction, and Elemental Analysis techniques were used to explore the cross-banding pattern, nature of mineral phase and orientation of the crystal lattice. Subchondral bone nano-hydroxyapatite powders were prepared and characterised using high resolution transmission electron microscopy (HR-TEM) and fourier transform infrared spectroscopy (FTIR). Subchondal bone mechanical properties were investigated using a nano-indentation method.ResultsIn grade I subchondral bone samples, a regular periodic fibril banding pattern was observed and the c-axis orientation of the apatite crystals was parallel to the long axis of the fibrils. By contrast, in grade IV OA bone samples, the bulk of fibrils formed a random and undulated arrangement accompanied by a circular oriented pattern of apatite crystals. Fibrils in grade IV bone showed non-hierarchical intra-fibrillar mineralization and higher calcium (Ca) to phosphorous (P) (Ca/P) ratios. Grade IV OA bone showed higher crystallinity of the mineral content, increased modulus and hardness compared with grade I OA bone.ConclusionsThe findings from this study suggest that OA subchondral sclerotic bone has an altered mineralization process which results in nano-structural changes of apatite crystals that is likely to account for the compromised mechanical properties of OA subchondral bones.

Multi-Elemental Profiling of Tibial and Maxillary Trabecular Bone in Ovariectomised Rats

Atomic minerals are the smallest components of bone and the content of Ca, being the most abundant mineral in bone, correlates strongly with the risk of osteoporosis. Postmenopausal women have a far greater risk of suffering from OP due to low Ca concentrations in their bones and this is associated with low bone mass and higher bone fracture rates. However, bone strength is determined not only by Ca level, but also a number of metallic and non-metallic elements in bone. Thus, in this study, the difference of metallic and non-metallic elements in ovariectomy-induced osteoporosis tibial and maxillary trabecular bone was investigated in comparison with sham operated normal bone by laser ablation inductively-coupled plasma mass spectrometry using a rat model. The results demonstrated that the average concentrations of 25Mg, 28Si, 39K, 47Ti, 56Fe, 59Co, 77Se, 88Sr, 137Ba, and 208Pb were generally higher in tibia than those in maxilla. Compared with the sham group, Ovariectomy induced more significant changes of these elements in tibia than maxilla, indicating tibial trabecular bones are more sensitive to changes of circulating estrogen. In addition, the concentrations of 28Si, 77Se, 208Pb, and Ca/P ratios were higher in tibia and maxilla in ovariectomised rats than those in normal bone at all time-points. The present study indicates that ovariectomy could significantly impact the element distribution and concentrations between tibia and maxilla.

Utilisation of Bovine Bone Pellet as a Matrix-Matched Reference Material forCalcified Tissues in LA-ICP-MS Application

One of the most challenging aspects of interpreting quantitative information of biological samples from laser inductively coupled plasma mass spectrometry (LA-ICP-MS) is a lack of appropriate matrix-matched internal standards that is needed for calibrations. There are standards available; however, most certified reference standard materials are suboptimal, due to the high variability and complexity of biological materials, especially for calcified tissues. In the present study, we described an approach in which bovine bone pellets are used as reliable matrixmatched standards for quantitative analysis of bone samples. Bovine tibial bones, sourced from a local butcher shop, were treated with or without autoclave sterilization. The samples were lyophilized over a 24 hour period, after which the elemental distributions in autoclaved, non-autoclaved bone pellets and naive bone fragments were investigated using inductively coupled plasma optical emission spectrometry (ICP-OES) and LA-ICP-MS methods, in addition to homogeneity analysis of non-autoclaved bone pellets. The results demonstrated that non-autoclaved and autoclaved bone pellets shared similar average elemental concentrations after correcting for background signal; natural bone fragments, on the other hand, showed large sample variations. Factors such as low cost and ease of manufacture, “home-made” non-autoclaved bone pellets are the preferred option and these were subjected to further investigations. The homogeneity analysis revealed that non-autoclaved bone pellets had a higher degree of homogeneity, with minimal standard deviations and a uniform particle size of less than 100 μm. These results show that non-autoclaved bovine bone pellets are reliable and easy-to-make alternative to matrix-matched reference material with which to analyse calcified tissues by LA-ICP-MS.