On the solid state of bone (original) (raw)
Related papers
Electric properties of non-irradiated and gamma-irradiated bone
Journal of Non-Crystalline Solids, 2002
Dielectric spectroscopy has been applied to study the effect of water and c-irradiation on bone. Measurements were performed in the electric field frequency range of 10 1-10 5 Hz and at temperatures from 22 to 240°C. The bone samples contained about 3% water by mass at room temperature. The doses of c-irradiation were 5, 50, 100, 300 and 1000 kGy. The influence of water and c-irradiation on the permittivity and conductivity of bone is significant at temperatures above 100°C. Results of this paper would suggest that c-irradiation initiates two important processes: cross-linking for doses 5 and 50 kGy and main-chain degradation for higher doses. Analysis of polarisation and conduction mechanisms for bone was interpreted on the basis of proton transport.
International Journal of Biological Macromolecules, 1999
The effect of g-irradiation with doses from 10 to 500 kGy on the electrical conductivity (g) of dry bone was studied. Temperature measurement of electrical conductivity were made from 393 to 533 K. The dependence obtained indicates the increase in g with temperature. An increase in irradiation dose resulted in a decreased g value for each dose up to temperature 462 K. Temperature 462 K was interpreted as the temperature of collagen melting point in dry bone. Above 462 K, g values were dose independent. A dose of 500 kGy shifted the melting point to lower temperature. In addition, the activation energy for the charge conduction process was calculated. Obtained values for electrical conductivity and activation energy were typical for dielectrics and indicated degradation of the organic component of bone.
Changes in thermal and electrical properties of bone as a result of 1 MGy-dose γ-irradiation
International Journal of Biological Macromolecules, 2003
Determination of temperature dependencies of electric conductivity and thermal properties by differential scanning calorimetry (DSC) allow to analyse the processes of charge and heat transport in the bone being a complex collagen-hydroxyapatite (HAP)-water system. Modification of the bone structure by high doses of ␥-radiation changes the electrical and thermal properties of the bone. Electrical conductivity (σ) of the bone decreases with consecutive heating runs. The decrease in σ observed for irradiated samples was explained by the scission of the main chain of collagen macromolecule. Irradiation decreased the hydration level in the bone, its denaturation temperature and increased both enthalpy and entropy of the denaturation process.
Effect of ultraviolet light on the dielectric behavior of bone at microwave frequencies
Annals of Biomedical Engineering, 1982
The dielectric constant of bone and its two components (collagen and apatite) were determined at 9.2 GHz in a room temperature environment by the cavity perturbation technique. After samples were exposed to ultraviolet light, repeat measurements under identical conditions showed decreases in both the real and the imaginary parts of the dielectric constant in all cases. The present work describes the technique and a possible mechanism of ultraviolet interaction with bone.
Electric behaviour of natural and demineralized bones. Dielectric properties up to 1 GHz
Journal of Biological Physics, 1992
In this paper we have measured the dielectric spectrum of water-saturated bones in native and demineralized states up to 1 GHz in the time domain. A novel method of analysis of the time domain spectroscopy data has been used. The results show a dielectric dispersion centered around 400 MHz for native samples and around 200 MHz for demineralized ones. The proposed mechanism for this dispersion is the movement of polar side chains, which is in agreement with what happens in hydrated collagen fibres.
Electric fields modulate bone cell function in a density-dependent manner
Journal of Bone and Mineral Research, 2009
The influence of an extremely low frequency (ELF) electric field stimulus (30 Hz at 6 pV/cm rms), known to promote bone formation in vivo, was evaluated for its ability to affect bone cell function in vitro. To accomplish this, we developed an apparatus for the exposure of monolayer cell systems to electric fields in a manner that provides relatively uniform electric field exposure of multiple cell samples as well as a rigorous sham exposure. We show that field exposure significantly limits the normal increase in osteoblastic cell number and enhances alkaline phosphatase activity compared to sham-exposed samples. Moreover, these alterations are shown to occur in a cell density-dependent manner. Samples plated at 6 x lo3 cells/cm' show no effect of field exposure, In samples plated at 30 x lo' cells/cm', 72 h of field exposure resulted in 25% fewer cells in the exposed samples, and a doubling of alkaline phosphatase activity in those cells compared to sham exposure. Experiments using a 12 h exposure to preclude significant changes in cell number during the exposure show this density-dependent response to be biphasic. Sparse cultures ( < 50 x lo3 cells/cm') were not found to be affected by the field exposure, but increases in alkaline phosphatase activity occurred in cultures at densities of 50-200 x lo3 and 200-350 x lo3 cells/cm' and no effect on alkaline phosphatase activity was seen in confluent cell cultures of greater than 350 x lo3 cells/cm'. This work suggests that the demonstrated osteogenic effect of this specific electric field stimulus on bone tissue may be initiated by an alteration of the differentiated status of the osteoblasts in the tissue rather than by stimulating cell proliferation, as has been previously suggested. As importantly, a more thorough characterization of this density-dependent interaction with electric fields may help to identify the mechanism of transduction by which ELF electric fields interact with cells.
Nature Communications
X-rays are invaluable for imaging and sterilization of bones, yet the resulting ionization and primary radiation damage mechanisms are poorly understood. Here we monitor in-situ collagen backbone degradation in dry bones using second-harmonic-generation and X-ray diffraction. Collagen breaks down by cascades of photon-electron excitations, enhanced by the presence of mineral nanoparticles. We observe protein disintegration with increasing exposure, detected as residual strain relaxation in pre-stressed apatite nanocrystals. Damage rapidly grows from the onset of irradiation, suggesting that there is no minimal ‘safe’ dose that bone collagen can sustain. Ionization of calcium and phosphorous in the nanocrystals yields fluorescence and high energy electrons giving rise to structural damage that spreads beyond regions directly illuminated by the incident radiation. Our findings highlight photoelectrons as major agents of damage to bone collagen with implications to all situations where...
A review of the dielectric properties of the bone for low frequency medical technologies
Biomedical Physics & Engineering Express, 2018
The dielectric properties are key parameters that quantify the interaction between electromagnetic waves and human biological tissues. In particular, the development of electromagnetic-based medical technologies rely on knowledge of the dielectric properties of bone, specifically for applications such as electrical stimulation and bone health monitoring. Electrical stimulation is used in clinics to promote the healing of bone fractures, treating non-unions, congenital pseudarthrosis, bone regeneration and during bone implant procedures. The response of the bone to any external electrical stimulation is governed by the dielectric properties of the bone, which vary with the applied frequency of the stimuli. Bone mineral density is considered a key indicator of osteoporosis diagnosis, and is assumed to be related to the dielectric properties of the bone. Therefore, dielectric properties of bones may potentially be used to diagnose osteoporosis. The bone dielectric properties can be assessed non-invasively for bone health monitoring. Several research studies have reported dielectric properties of cortical and trabecular bones in recent literature. Since dielectric properties of bone determine the response of the tissue to therapies, it is important to compile and analyze the reported dielectric data in order to have a thorough understanding of these properties. It is established from the literature that the low frequency (10 Hz-1 GHz) dielectric properties of bone are particularly important in diagnostic applications, as the correlation between the dielectric properties and bone mineral density is more significant than at higher frequencies. In this paper, the low frequency dielectric properties of the bone reported in the literature are compiled and quantitatively analysed. The results suggest that there is a significant inter-and intra-species variation in the reported dielectric data from human, bovine, porcine, and rat bone tissues. Moreover, the relationship between the dielectric properties and bone mineral density is inconsistent across the various studies, indicating that further research in this area is needed.
Electric Phenomenon in Bones as a Result of Piezoelectricity of Hydroxyapatite
Conducted biomineralogical studies indicate piezoelectric properties of apatite, which is one of the major components of bone. This publication presents hypothetical correlations between piezoelectric properties of bone apatite and the accompanying electromagnetic phenomena in bones and their environment. It notes the correlations between electrical properties of bones and changes in the electromagnetic field around bones, as well as connections between external pressure changes etc. and electrical phenomena in the bones.
Dielectric properties of natural and demineralized collagen bone matrix
IEEE Transactions on Dielectrics and Electrical Insulation, 2011
In this paper, measurements of dielectric properties of fluid-saturated cortical and trabecular bovine bones are presented. Results are reported for native and demineralized states from 80 MHz to 1 GHz. A non invasive technique using open-ended coaxial lines is proposed, and compared to invasive configurations. Measurements are performed in time domain and data are processed using system identification techniques in continuous and discrete domains. These are very interesting tools for signal processing when working with time domain spectroscopy data. As a validation test for the system identification technique, data are also obtained in the frequency domain. A clear evidence of relaxation processes around 0.2 to 0.4 GHz is shown, which may be due to the movement of polar side chains of the collagen fibers. A strong difference between the dielectric properties of native and demineralized bones was found. The experiments here reported aim to contribute to a more in-depth knowledge of the relaxation processes due to the fully hydrated collagen matrix and its relation to the mineralized phase.