Abstract Introduction A variation in bone response to fluoride (F− ) exposure has been attributed to genetic factors. Increasing fluoride doses (0 ppm, 25 ppm, 50 ppm, 100 ppm) for three inbred mouse ...strains with different susceptibilities to developing dental enamel fluorosis (A/J, a “susceptible” strain; SWR/J, an “intermediate” strain; 129P3/J, a “resistant” strain) had different effects on their cortical and trabecular bone mechanical properties. In this paper, the structural and material properties of the bone were evaluated to explain the previously observed changes in mechanical properties. Materials and methods This study assessed the effect of increasing fluoride doses on the bone formation, microarchitecture, mineralization and microhardness of the A/J, SWR/J and 129P3/J mouse strains. Bone microarchitecture was quantified with microcomputed tomography and strut analysis. Bone formation was evaluated by static histomorphometry. Bone mineralization was quantified with backscattered electron (BSE) imaging and powder X-ray diffraction. Microhardness measurements were taken from the vertebral bodies (cortical and trabecular bones) and the cortex of the distal femur. Results Fluoride treatment had no significant effect on bone microarchitecture for any of the strains. All three strains demonstrated a significant increase in osteoid formation at the largest fluoride dose. Vertebral body trabecular bone BSE imaging revealed significantly decreased mineralization heterogeneity in the SWR/J strain at 50 ppm and 100 ppm F− . The trabecular and cortical bone mineralization profiles showed a non-significant shift towards higher mineralization with increasing F− dose in the three strains. Powder X-ray diffraction showed significantly smaller crystals for the 129P3/J strain, and increased crystal width with increasing F− dose for all strains. There was no effect of F− on trabecular and cortical bone microhardness. Conclusion Fluoride treatment had no significant effect on bone microarchitecture in these three strains. The increased osteoid formation and decreased mineralization heterogeneity support the theory that F− delays mineralization of new bone. The increasing crystal width with increasing F− dose confirms earlier results and correlates with most of the decreased mechanical properties. An increase in bone F− may affect the mineral–organic interfacial bonding and/or bone matrix proteins, interfering with bone crystal growth inhibition on the crystallite faces as well as bonding between the mineral and organic interface. The smaller bone crystallites of the 129P3/J (resistant) strain may indicate a stronger organic/inorganic interface, reducing crystallite growth rate and increasing interfacial mechanical strength.
Abstract Current clinical tools for evaluating fracture risk focus only on the mineral phase of bone. However, changes in the collagen matrix may affect bone mechanical properties, increasing ...fracture risk while remaining undetected by conventional screening methods such as dual energy x-ray absorptiometry (DXA) and quantitative ultrasound (QUS). The mechanical response tissue analyzer (MRTA) is a non-invasive, radiation-free potential clinical tool for evaluating fracture risk. The objectives of this study were two-fold: to investigate the ability of the MRTA to detect changes in mechanical properties of bone as a result of treatment with 1 M potassium hydroxide (KOH) and to evaluate the differences between male and female bone in an emu model. DXA, QUS, MRTA and three-point bending measurements were performed on ex vivo emu tibiae before and after KOH treatment. Male and female emu tibiae were endocortically treated with 1 M KOH solution for 1–14 days, resulting in negligible collagen loss (0.05%; by hydroxyproline assay) and overall mass loss (0.5%). Three-point bending and MRTA detected significant changes in modulus between days 1 and 14 of KOH treatment (− 18%) while all values measured by DXA and QUS varied by less than 2%. This close correlation between MRTA and three-point bending results support the utility of the MRTA as a clinical tool to predict fracture risk. In addition, the significant reduction in modulus contrasted with the negligible amount of collagen removal from the bone after KOH exposure. As such, the significant changes in bone mechanical properties may be due to partial debonding between the mineral and organic matrix or in situ collagen degradation rather than collagen removal. In terms of sex differences, male emu tibiae had significantly decreased failure stress and increased failure strain and toughness compared to female tibiae with increasing KOH treatment time.
The mechanisms underlying the effect of alterations in type I collagen on bone mechanical properties are not well defined. In a previous study, male and female emu tibiae were endocortically treated ...with 1M potassium hydroxide (KOH) solution for 1-14days. This treatment resulted in negligible mass loss (0.5%), collagen loss (0.05%), no differences in geometrical parameters but significant changes in mechanical properties. The objective of this study was to determine the mechanism of collagen degradation due to KOH treatment in order to explain the previously observed mechanical property changes.
Bone mineral was assessed using x-ray diffraction (XRD), microhardness and backscattered electron imaging (BSE). Bone collagen was assessed using α-chymotrypsin digestion, differential scanning calorimetry (DSC), gel electrophoresis (SDS-PAGE) and polarized light microscopy (PLM).
BSE, microhardness and XRD revealed no changes in bone mineral due to KOH treatment. DSC showed an altered curve shape (lower and broader), indicating a change in collagen organization due to KOH treatment. Decreased α-chain band intensity in 14-day KOH treated groups detected using SDS-PAGE indicated α-chain fragmentation due to KOH treatment. PLM images revealed differences in collagen structure in terms of pattern distribution of preferentially oriented collagen between the periosteal and endocortical regions.
These results suggest that endocortical KOH treatment causes in situ collagen degradation, which explains the previously reported altered mechanical properties.
Compromising the organic component of bone contributes to an increase in bone fragility.
Phosphorus (P) is an essential agricultural nutrient and its production as mineral P fertilizers from phosphate rock is well established. An alternative method involves recovering P from municipal ...wastewater treatment plants (WWTP) for reuse as fertilizer. Life cycle analysis (LCA) studies have been conducted to assess the environmental impacts associated with both processes. However, systematic comparisons of mineral and recovered P fertilizer production processes are scarce in the existing literature. In this review, we examine the goals, functional units, impact categories, and system boundaries of peer-reviewed LCAs for mineral P fertilizer production (n = 5), recovered P fertilizer production (n = 14), or both (n = 5). To enhance the overall impact and usefulness of these studies for policymaking, we propose a standardized approach for comparative P process studies, while emphasizing the need for simultaneously assessing the environmental effects of P fertilizer production and P recovery from WWTPs. We recommend including key impact categories that are relevant to both processes, such as eutrophication, acidification, global warming potential, soil and water pollution, resource use, and toxicity. Furthermore, adopting a functional unit of one kilogram of elemental P would facilitate better comparisons between LCAs. We also recommend standardized system boundaries that encompass the key aspects of each process.
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Abstract The mechanisms of skeletal mineralization have been studied and debated for decades. Recent Raman spectroscopic identification of octacalcium phosphate-like phosphate ions and possibly ...amorphous calcium phosphate ions in nascent bone mineral were claimed to support a transient precursor strategy for bone apatite formation. However, this data does not refute the theory that the newest, detectable bone mineral is very small, poorly crystalline biological apatite, because non-apatitic phosphate species have previously been identified in biological apatite and detected on the surfaces of nano-sized hydroxyapatite crystals.
In recent years there has been ample interest in nanoscale modifications of synthetic biomaterials to understand fundamental aspects of cell-surface interactions towards improved biological outcomes. ...In this study, we aimed at closing in on the effects of nanotubular TiO
surfaces with variable nanotopography on the response on human mesenchymal stem cells (hMSCs). Although the influence of TiO
nanotubes on the cellular response, and in particular on hMSC activity, has already been addressed in the past, previous studies overlooked critical morphological, structural and physical aspects that go beyond the simple nanotube diameter, such as spatial statistics.
To bridge this gap, we implemented an extensive characterization of nanotubular surfaces generated by anodization of titanium with a focus on spatial structural variables including eccentricity, nearest neighbour distance (NND) and Voronoi entropy, and associated them to the hMSC response. In addition, we assessed the biological potential of a two-tiered honeycomb nanoarchitecture, which allowed the detection of combinatory effects that this hierarchical structure has on stem cells with respect to conventional nanotubular designs. We have combined experimental techniques, ranging from Scanning Electron (SEM) and Atomic Force (AFM) microscopy to Raman spectroscopy, with computational simulations to characterize and model nanotubular surfaces. We evaluated the cell response at 6 hrs, 1 and 2 days by fluorescence microscopy, as well as bone mineral deposition by Raman spectroscopy, demonstrating substrate-induced differential biological cueing at both the short- and long-term.
Our work demonstrates that the nanotube diameter is not sufficient to comprehensively characterize nanotubular surfaces and equally important parameters, such as eccentricity and wall thickness, ought to be included since they all contribute to the overall spatial disorder which, in turn, dictates the overall bioactive potential. We have also demonstrated that nanotubular surfaces affect the quality of bone mineral deposited by differentiated stem cells. Lastly, we closed in on the integrated effects exerted by the superimposition of two dissimilar nanotubular arrays in the honeycomb architecture.
This work delineates a novel approach for the characterization of TiO
nanotubes which supports the incorporation of critical spatial structural aspects that have been overlooked in previous research. This is a crucial aspect to interpret cellular behaviour on nanotubular substrates. Consequently, we anticipate that this strategy will contribute to the unification of studies focused on the use of such powerful nanostructured surfaces not only for biomedical applications but also in other technology fields, such as catalysis.
Tissue engineering is a promising approach for articular cartilage repair; however, attempts to develop tissue that mimic native cartilage have been problematic. The synthesis and accumulation of ...extracellular matrix macromolecules may be adversely affected by a change in pH of the media during cell culture. Typically, zwitterion buffers (e.g., HEPES) are used in culture media because they can perform under both slightly acidic and alkaline conditions. However, because chondrocytes tend to rapidly acidify the media, better pH maintenance may be achieved by utilizing additional buffering agents that operate under acidic conditions (e.g., bicarbonate). The purpose of this study was to investigate the combined effect of HEPES and sodium bicarbonate (NaHCO(3)) on extracellular pH and matrix accumulation by cultured articular chondrocytes. Isolated bovine articular chondrocytes were seeded on Millicell filters and cultured in HEPES-buffered media containing 0, 7, or 14 mM NaHCO(3). Throughout the 4-week culture period, the extracellular pH was more neutral with increasing NaHCO(3) concentration. Addition of NaHCO(3) increased synthesis (140 +/- 29%) and accumulation (20 +/- 2%) of proteoglycans whereas collagen was unaffected. There was also an increase in tissue cellularity (41 +/- 13%). Morphologically, increasing numbers of flattened cells, resembling superficial zone chondrocytes, localized to the surface of the in vitro-formed tissue with increasing NaHCO(3) supplementation were observed by light and transmission electron microscopy. Experiments are underway to determine whether these effects are due to pH maintenance or to the increased concentration of bicarbonate ions, which regulate intracellular pH.
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