Thermal behavior of biogenic apatite crystals in bone: An X-ray diffraction study

X-ray diffraction studies of a partially demineralized oriented cortical bone with the controlled depth of analysis

The in vitro demineralization of bone tissue is used for simulating the osteoporosis related bone loss. This way would be helpful in observations of bone apatite dissolution in microstructural level and may give significant input for understanding crystal-chemistry of bone resorption. In the case of cortical bone, demineralization occurs inhomogeneously, with the formation of a superficial demineralized layer and a transition zone with a gradient of concentration and structural characteristics perpendicular to the reaction advance front. Changes in the microstructural parameters of the bone mineral in this interface zone are of great interest for understanding the resorptive processes in the bone associated with osteoporosis. In this work, the SEM-EDX method was used to estimate the sizes of the demineralized and interface layers in the cortical bone during stepwise demineralization in HCl water solution; the general patterns of changes in the concentrations of Ca, P, and Cl in these layers were established. The calculations of the effective penetration depth of X-rays in diffraction mode for the intact and partially demineralized cortical bone were performed. It is shown that the use of CoKα radiation (instead of the usual CuKα) ensures the depth of probing within the interface zone, which allows to adequately assess the microstructural parameters (crystallite sizes and lattice microdeformations) of altered bioapatite in the zone of its interaction with an acid agent. A nonmonotonic change in the average size of crystallites and microdeformations of the apatite lattice was revealed during acid demineralization of the bone. Using asymmetric XRD geometry, the evidence was obtained that the affected mineral of the transition zone does not contain other crystalline phases except for weakly crystallized apatite. For the first time, the depth-controlled XRD analysis was applied to such a complex (surface-gradient) object as partially demineralized cortical bone. Additionally, we propose a rapid, averaging, and non-destructive method for estimating the depth of the reaction front dividing the demineralized and non-demineralized portions of the bone by XRD. The consistency of XRD and SEM-EDX data on the thickness values of the demineralized layer is shown.

Investigating pair distribution function use in analysis of nanocrystalline hydroxyapatite and carbonate-substituted hydroxyapatite

Hydroxyapatite (HA) is a complex material, which is often nanocrystalline when found within a biological setting. This work has directly compared the structural characteristics derived from data collected using a conventional laboratory-based X-ray diffractometer with those collected from a dedicated pair distribution function (PDF) beamline at Diamond Light Source. In particular, the application of PDF analysis methods to carbonated HA is evaluated. 20 synthetic samples were measured using both X-ray diffraction (XRD) and PDFs. Both Rietveld refinement (of laboratory XRD data) and real-space refinement (of PDF data) were used to analyse all samples. The results of Rietveld and real-space refinements were compared to evaluate their application to crystalline and nanocrystalline hydroxyapatite. Significant relationships were observed between real-space refinement parameters and increasing carbonate substitution. Understanding the local order of synthetic hydroxyapatite can benefit several fields, including both biomedical and clinical settings.

The structure of cortical bone as revealed by the application of methods for the calcified matrix study

Calcination and decalcification are basic procedures useful to a morphological approach of a biological, composite material like cortical bone. The study was carried out on a whole human femur conserved in liquid (from an educational collection). Cortical fracturing and SEM observation of vascular canals surface collagen texture was used to study bone deproteination at scalar temperatures (400-1,200°C) and acid bone decalcification at crescent time intervals. Heating burned and vaporized the organic matrix with shrinkage of the bone specimens as documented by the weight loss and transverse surface morphometry. SEM showed a pattern of aligned spherulites at 400°C which maintained the collagen fibrils layout (like a mineral cast), followed by a spherulites fusion progression with the temperature increments. At 1200°C a crystalline-like structure of tightly-packed trapezohendron units. XRD analysis supported the SEM morphology displaying the complete Debey rings of hydroxyapatite and spotted Debey rings of withlockite. Surface Ca and P elution was documented after 12 hr of exposition to the acid solution by dissolution of spherulites and the whole canal surface decalcified in depth after 15 days by SEM-EDAX analysis. The periodic pattern of collagen fibrils was still evident up to 15 days of decalcification together with fine granular deposits of a not-collagenic proteic material, while after 30 days no period was observed in the decalcified fibrils. Collagen mineral cast at 400°C calcination. Complete crystalline transformation at 1200°C. Up to 15 days of decalcification fibrils period maintained.

Icariin prevents bone loss by inhibiting bone resorption and stabilizing bone biological apatite in a hindlimb suspension rodent model

Bone loss induced by microgravity is a substantial barrier to humans in long-term spaceflight. Recent studies have revealed that icariin (ICA) can attenuate osteoporosis in postmenopausal women and ovariectomized rats. However, whether ICA can protect against microgravity-induced bone loss remains unknown. In this study, the effects of ICA on a hindlimb suspension rodent model were investigated. Two-month-old female Wistar rats were hindlimb suspended and treated with ICA (25 mg·kg^-1·d^-1, i.g.) or a vehicle for 4 weeks (n = 6). The bone mass density of the hindlimbs was analyzed using dual-energy X-ray absorptiometry and micro-CT. mRNA expression of osteogenic genes in the tibia and the content of bone metabolism markers in serum were measured using qRT-PCR and ELISA, respectively. The bone mineral phase was analyzed using X-ray diffraction and atomic spectrometry. The results showed that ICA treatment significantly rescued the hindlimb suspension-induced reduction in bone mineral density, trabecular number and thickness, as well as the increases in trabecular separation and the structure model index. In addition, ICA treatment recovered the decreased bone-related gene expression, including alkaline phosphatase (ALP), bone glaprotein (BGP), and osteoprotegerin/receptor activator of the NF-κB ligand ratio (OPG/RANKL), in the tibia and the decreased bone resorption marker TRACP-5b levels in serum caused by simulated microgravity. Notably, ICA treatment restored the instability of bone biological apatite and the metabolic disorder of bone mineral elicited by simulated microgravity. These results demonstrate that ICA treatment plays osteoprotective roles in bone loss induced by simulated microgravity by inhibiting bone resorption and stabilizing bone biological apatite.

Biomineralization improves mechanical and osteogenic properties of multilayer-modified PLGA porous scaffolds

Poly-(lactide-co-glycolide acid) (PLGA) has been widely investigated as scaffold material for bone tissue engineering owing to its biosafety, biodegradability, and biocompatibility. However, the bioinert surface of PLGA may fail in regulating cellular behavior and directing osteointegration between the scaffold and the host tissue. In this article, oxidized chondroitin sulfate (oCS) and type I collagen (Col I) were assembled onto PLGA surface via layer by layer technique (LbL) as an adhesive coating for the attachment of inorganic minerals. The multilayer-modified PLGA scaffold was mineralized in vitro to ensure the deposition of nanohydroxyapatite (nHAP). It was found that nHAP crystals were more uniformly and firmly attached on the multilayer-modified PLGA as compared with the pure PLGA scaffold, which remarkably improved PLGA surface and mechanical properties. Additionally, in vitro biocompatibility of PLGA scaffold, in terms of bone mesenchymal stem cells (BMSCs) attachment, spreading and proliferation was greatly enhanced by nHAP coating and multilayer deposition. Furthermore, the fabricated composite scaffold also shows the ability to promote the osteogenic differentiation of BMSCs through the up-regulation of osteogenic marker genes. Thus, this novel biomimetic composite scaffold might achieve a desirable therapeutic result for bone tissue regeneration. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A: 2714-2725, 2018.

Hydrophilicity, Viscoelastic, and Physicochemical Properties Variations in Dental Bone Grafting Substitutes

The indication-oriented Dental Bone Graft Substitutes (DBGS) selection, the correct bone defects classification, and appropriate treatment planning are very crucial for obtaining successful clinical results. However, hydrophilic, viscoelastic, and physicochemical properties’ influence on the DBGS regenerative potential has poorly been studied. For that reason, we investigated the dimensional changes and molecular mobility by Dynamic Mechanical Analysis (DMA) of xenograft (cerabone^®), synthetic (maxresorb^®), and allograft (maxgraft^®, Puros^®) blocks in a wet and dry state. While no significant differences could be seen in dry state, cerabone^® and maxresorb^® blocks showed a slight height decrease in wet state, whereas both maxgraft^® and Puros^® had an almost identical height increase. In addition, cerabone^® and maxresorb^® blocks remained highly rigid and their damping behaviour was not influenced by the water. On the other hand, both maxgraft^® and Puros^® had a strong increase in their molecular mobility with different damping behaviour profiles during the wet state. A high-speed microscopical imaging system was used to analyze the hydrophilicity in several naturally derived (cerabone^®, Bio-Oss^®, NuOss^®, SIC^® nature graft) and synthetic DBGS granules (maxresorb^®, BoneCeramic^®, NanoBone^®, Ceros^®). The highest level of hydrophilicity was detected in cerabone^® and maxresorb^®, while Bio-Oss^® and BoneCeramic^® had the lowest level of hydrophilicity among both naturally derived and synthetic DBGS groups. Deviations among the DBGS were also addressed via physicochemical differences recorded by Micro Computed Tomography, Scanning Electron Microscopy, Fourier Transform Infrared Spectroscopy, X-ray powder Diffractometry, and Thermogravimetric Analysis. Such DBGS variations could influence the volume stability at the grafting site, handling as well as the speed of vascularization and bone regeneration. Therefore, this study initiates a new insight into the DBGS differences and their importance for successful clinical results.

Calcium Phosphate Bioceramics: A Review of Their History, Structure, Properties, Coating Technologies and Biomedical Applications

Calcium phosphate (CaP) bioceramics are widely used in the field of bone regeneration, both in orthopedics and in dentistry, due to their good biocompatibility, osseointegration and osteoconduction. The aim of this article is to review the history, structure, properties and clinical applications of these materials, whether they are in the form of bone cements, paste, scaffolds, or coatings. Major analytical techniques for characterization of CaPs, in vitro and in vivo tests, and the requirements of the US Food and Drug Administration (FDA) and international standards from CaP coatings on orthopedic and dental endosseous implants, are also summarized, along with the possible effect of sterilization on these materials. CaP coating technologies are summarized, with a focus on electrochemical processes. Theories on the formation of transient precursor phases in biomineralization, the dissolution and reprecipitation as bone of CaPs are discussed. A wide variety of CaPs are presented, from the individual phases to nano-CaP, biphasic and triphasic CaP formulations, composite CaP coatings and cements, functionally graded materials (FGMs), and antibacterial CaPs. We conclude by foreseeing the future of CaPs.

Insight into bone-derived biological apatite: ultrastructure and effect of thermal treatment

Objectives. This study aims at examining the ultrastructure of bone-derived biological apatite (BAp) from a series of small vertebrates and the effect of thermal treatment on its physiochemical properties. Materials and Methods. Femurs/fin rays and vertebral bodies of 5 kinds of small vertebrates were firstly analyzed with X-ray microtomography. Subsequently, BAp was obtained with thermal treatment and low power plasma ashing, respectively. The properties of BAp, including morphology, functional groups, and crystal characteristics were then analyzed. Results. The bones of grouper and hairtail were mainly composed of condensed bone. Spongy bone showed different distribution in the bones from frog, rat, and pigeon. No significant difference was found in bone mineral density of condensed bone and trabecular thickness of spongy bone. Only platelet-like crystals were observed for BAp obtained by plasma ashing, while rod-like and irregular crystals were both harvested from the bones treated by sintering. A much higher degree of crystallinity and larger crystal size but a lower content of carbonate were detected in the latter. Conclusion. Platelet-like BAp is the common inorganic component of vertebrate bones. BAp distributing in condensed and spongy bone may exhibit differing thermal reactivity. Thermal treatment may alter BAp's in vivo structure and composition.

Insight into biological apatite: physiochemical properties and preparation approaches

Biological apatite is an inorganic calcium phosphate salt in apatite form and nano size with a biological derivation. It is also the main inorganic component of biological hard tissues such as bones and teeth of vertebrates. Consequently, biological apatite has a wide application in dentistry and orthopedics by using as dental fillers and bone substitutes for bone reconstruction and regeneration. Given this, it is of great significance to obtain a comprehensive understanding of its physiochemical and biological properties. However, upon the previous studies, inconsistent and inadequate data of such basic properties as the morphology, crystal size, chemical compositions, and solubility of biological apatite were reported. This may be ascribed to the differences in the source of raw materials that biological apatite are made from, as well as the effect of the preparation approaches. Hence, this paper is to provide some insights rather than a thorough review of the physiochemical properties as well as the advantages and drawbacks of various preparation methods of biological apatite.

Effect of hydrazine based deproteination protocol on bone mineral crystal structure

In several bone deproteination protocols the chemical agent used for protein cleavage is hydrazine. The effect of hydrazine deproteination method on the crystal size and crystallinity of the bone mineral was studied. Bovine bones were subjected to this protocol and the crystal size and crystallinity of the remaining bone mineral were determined by X-ray Diffraction (XRD), by measuring the width at the half of the maximum intensity of the (002) reflection. It was found that hydrazine deproteination induces noteworthy increase of crystal size and crystallinity. The effect was enhanced by increasing hydrazine temperature from 25 to 55°C. Furthermore, infrared spectroscopy revealed that hydrazine facilitates the removal of carbonate and acid phosphate ions from bone mineral. It is proposed that the mechanism of modification of crystal size and crystallinity lies on the removal of these ions thus, resulting in crystal re-organization.

Comparative study on inorganic composition and crystallographic properties of cortical and cancellous bone

OBJECTIVE

To comparatively investigate the inorganic composition and crystallographic properties of cortical and cancellous bone via thermal treatment under 700 °C.

METHODS

Thermogravimetric measurement, infrared spectrometer, X-ray diffraction, chemical analysis and X-ray photo-electron spectrometer were used to test the physical and chemical properties of cortical and cancellous bone at room temperature 250 °C, 450 °C, and 650 °C, respectively.

RESULTS

The process of heat treatment induced an extension in the a-lattice parameter and changes of the c-lattice parameter, and an increase in the crystallinity reflecting lattice rearrangement after release of lattice carbonate and possible lattice water. The mineral content in cortical and cancellous bone was 73.2wt% and 71.5wt%, respectively. For cortical bone, the weight loss was 6.7% at the temperature from 60 °C to 250 °C, 17.4% from 250 °C to 450 °C, and 2.7% from 450 °C to 700 °C. While the weight loss for the cancellous bone was 5.8%, 19.9%, and 2.8 % at each temperature range, the Ca/P ratio of cortical bone was 1.69 which is higher than the 1.67 of stoichiometric HA due to the B-type CO₃²⁻ substitution in apatite lattice. The Ca/P ratio of cancellous bone was lower than 1.67, suggesting the presence of more calcium deficient apatite.

CONCLUSION

The collagen fibers of cortical bone were arrayed more orderly than those of cancellous bone, while their mineralized fibers ollkded similar. The minerals in both cortical and cancellous bone are composed of poorly crystallized nano-size apatite crystals with lattice carbonate and possible lattice water. The process of heat treatment induces a change of the lattice parameter, resulting in lattice rearrangement after the release of lattice carbonate and lattice water and causing an increase in crystal size and crystallinity. This finding is helpful for future biomaterial design, preparation and application.

The drug release study of ceftriaxone from porous hydroxyapatite scaffolds

Hydroxyapatite (HAP) is an important biomedical material that is used for grafting osseous defects. It has an excellent bioactivity and biocompatibility properties. To isolate hydroxyapatite, pieces of cleaned cattle's bone were heated at different temperature range from 400 degrees C up to 1,200 degrees C. A reasonable yield of 60.32% w/w HAP was obtained at temperature range from 1,000 degrees C to 1,200 degrees C. Fourier transform infrared spectra and the thermogravimetric measurement showed a clear removal of organic at 600 degrees C as well as an excellent isolation of HAP from the bones which was achieved at 1,000-1,200 degrees C. This was also confirmed from X-ray diffraction of bone sample heated at 1,200 degrees C. The concentration ions were found to be sodium, potassium, lithium, zinc, copper, iron, calcium, magnesium, and phosphate present in bones within the acceptable limits for its role in the bioactivity property of HAP. Glucose powder was used as a porosifier. Glucose was novel and excellent as porogen where it was completely removed by heating, giving an efficient porosity in the used scaffolds. The results exhibited that the ceftriaxone drug release was increased with increasing the porosity. It was found that a faster, higher, and more regular drug release was obtained from the scaffold with a porosity of 10%.

Quantitative monitoring of extracellular matrix production in bone implants by 13C and 31P solid-state nuclear magnetic resonance spectroscopy

We used (31)P and (13)C solid-state nuclear magnetic resonance (NMR) spectroscopy to detect and analyze the major organic and inorganic components (collagen type I and bioapatite) in natural rabbit bone and beta-tricalcium phosphate implants loaded with osteogenically differentiated mesenchymal stem cells. High-resolution solid-state NMR spectra were obtained using the magic-angle spinning (MAS) technique. The (31)P NMR spectra of bone specimens showed a single line characteristic of bone calcium phosphate. (13)C cross-polarization (CP) MAS NMR spectra of bone exhibited the characteristic signatures of collagen type I with good resolution for all major amino acids in collagen. Quantitative measurements of (13)C-(1)H dipolar couplings indicated that the collagen segments are very rigid, undergoing only small amplitude fluctuations with correlation times in the nanosecond range. In contrast, directly polarized (13)C MAS NMR spectra of rabbit bone were dominated by signals of highly mobile triglycerides. These quantitative investigations of natural bone may provide the basis for a quality control of various osteoinductive bone substitutes. We studied the formation of extracellular bone matrix in artificial mesenchymal stem cell-loaded beta-tricalcium phosphate matrices that were implanted into the femoral condyle of rabbits. The NMR spectra of these bone grafts were acquired 3 months after implantation. In the (31)P NMR spectra, beta-tricalcium phosphate and bone calcium phosphate could be distinguished quantitatively, allowing recording of the formation of the natural bone matrix. Further, (13)C CPMAS allowed detection of collagen type I that had been produced in the implants. Comparison with the spectroscopic data from natural bone allowed assessment of the quality of the bone substitute material.