Density Of Hydroxyapatite Research Articles

Plasma electrolytic oxidation deposited HAp-Ta2O5 composite coatings on Ti6Al4V for biomedical applications: The importance of Ta2O5 reinforcing phase

In this research, the focus was placed on enhancing the properties of hydroxyapatite (HAp) coating by the addition of various concentrations of tantalum pentoxide (Ta2O5) nanoparticles, ranging from 0 to 1.5 g/L, to its electrolyte solution. The HAp-Ta2O5 composite coatings were deposited on the Ti6Al4V metallic implant using the plasma electrolytic oxidation technique. The results of the X-ray diffraction test indicated that the increased concentration of Ta2O5 nanoparticles has no significant effect on the phase composition of the coatings. The denser and rougher coatings were fabricated when 1.5 g/L of Ta2O5 nanoparticles were added to the solution. The favorable microstructural properties of the HAp-1.5 g/L Ta2O5 composite coating resulted in a notable improvement in the mechanical properties, i.e., >40% increase in both microhardness and bonding strength compared to HAp. The corrosion resistance of the coated implants was evaluated through electrochemical impedance spectroscopy and potentiodynamic polarization tests. The inclusion of Ta2O5 nanoparticles in HAp coating led to a 72% reduction in the corrosion current density of HAp, indicating the constructive contribution of the nanoparticles to improved corrosion protection. The samples were incubated in simulated body fluid for 7 days to assess their in vitro immersion performance. All of the PEO-derived coatings stimulated the nucleation and growth of apatite grains, showing their superior biomineralization ability. An obvious decrease in the level of harmful ions such as Al3+ and V5+ released from the surface of composite coatings was obtained. These findings suggest that the developed system has potential for dental and orthopedic applications.

Densification of hydroxyapatite through cold sintering process: Role of liquid phase chemistry and physical characteristic of HA powder

Hydroxyapatite is a well-known bioactive material widely employed in bone regeneration applications. Densifying hydroxyapatite at the nanoscale remains challenging with conventional sintering methods. This investigation focuses on the densification of commercially available nano-hydroxyapatite powders through the cold sintering process, utilizing water, acetic acid, and phosphoric acid solutions as transient liquids under 360 MPa pressure at 200 °C. The study systematically examines the influence of physical parameters of hydroxyapatite powder, liquid nature, and ionic concentrations of acid solutions on densification and microstructural characteristics. The relative density of consolidated samples varied with respect to the ionic concentration of the acid solution. Notably, a maximum relative density of 90% has been achieved for hydroxyapatite cold sintered using 2 M phosphoric acid solution without changing the original phase of hydroxyapatite. Overall, this study offers valuable insights into the impact of liquid chemistry on the densification of hydroxyapatite using the cold sintering technique.

Opportunistic screening for osteoporosis using enhanced images based on dual-energy computed tomography material decomposition: a comparison with quantitative computed tomography.

Many patients with malignant tumors require chemotherapy and radiation therapy, which can result in a decline in physical function and potentially influence bone mineral density (BMD). Furthermore, these treatments necessitate enhanced computed tomography (CT) scans for determining disease staging or treatment outcomes, and opportunistic screening with available imaging data is beneficial for patients at high risk for osteoporosis if existing imaging data can be used. The study aimed to investigate the feasibility of opportunistic screening for osteoporosis using enhanced CT based on a dual-energy CT (DECT) material decomposition technique. We prospectively enrolled 346 consecutive patients who underwent abdominal unenhanced and triphasic contrast-enhanced CT (arterial, portal venous, and delayed phases) between June 2021 and June 2022. The BMD, and the density of hydroxyapatite (HAP) on HAP-iodine images and calcium (Ca) on Ca-iodine images were measured on the L1-L3 vertebral bodies. The iodine intake was recorded. Pearson analysis was conducted to assess the correlation between iodine intake and the density values in three phases and the correlation between BMD and the densities of HAP and Ca. Furthermore, linear regression was employed for quantitative evaluation. Bland-Altman analysis was used to evaluate the agreement between calculated BMD derived from DECT (BMD-DECT) and reference BMD derived from quantitative CT (BMD-QCT). Receiver operating characteristic (ROC) analysis was applied to assess the diagnostic efficacy. The HAP and Ca density of the L1-L3 vertebral bodies did not differ significantly among the three phases of contrast-enhanced CT (F=0.001-0.049; P>0.05). Significant positive correlations were found between HAP, Ca densities, and BMD (HAP-BMD: r=0.9472, R2=0.8973; Ca-BMD: r=0.9470, R2=0.8968; all P<0.001). Bland-Altman plots showed high agreement between BMD-DECT and BMD-QCT. The area under the curve (AUC) using HAP and Ca measurements was 0.963 [95% confidence interval (CI): 0.937-0.980] and 0.964 (95% CI: 0.939-0.981), respectively, for diagnosing osteoporosis and was 0.951 (95% CI: 0.917-0.973) and 0.950 (95% CI: 0.916-0.973), respectively, for diagnosing osteopenia. The HAP and Ca density measurements generated through the material decomposition technique in DECT have good diagnostic performances in assessing BMD, which offers a new perspective for opportunistic screening of osteoporosis on contrast-enhanced CT.

The Densification of Hydroxyapatite from Eggshell Waste at Different Sintering Temperature

The Densification of Hydroxyapatite from Eggshell Waste at Different Sintering Temperature

Cold sintering constructed in situ drug-loaded high strength HA-PLA composites: Potential bone substitution material

Hydroxyapatite (HA) is widely used as bone substitute material in repairing bone defects and injuries. However, the high brittleness and low fatigue strength of HA make it difficult to satisfy the long-term service requirements of implants. In general, the mechanical properties of ceramics can be improved by sintering which usually operated above 1000 °C. The high temperature not only brings huge energy consumption and environmental pollution, but also loss the surface-active sites on HA, which greatly limits the biological functions of the material, such as drug loading and degradation. A method that can achieve the densification of HA at a lower temperature is particularly important to improve mechanical and biological properties. In this work, a promising drug-loaded HA-polylactic acid (HA-PLA) composite with high densification and mechanical properties was prepared by cold sintering process at 80 °C, in addition, the relatively low operating temperature enables the material to realize in-situ loading of drugs. The cold-sintered composite with HA/PLA was 7/3 showed the best performance with significant biodegradation (16.8%) and drug release (95%) ability. Therefore, this study provides a simple and universal method for the preparation of biological composite material, which provides a useful platform for efficient in situ drug loading biomaterials.

Biocompatibility of a micro-arc oxidized ZrCuAlAg bulk metallic glass

Abstract Developing materials with high biocompatibility is key to improve the artificial medical implant. Bulk metallic glasses (BMGs) based on Zr have been proposed as promising biomaterials. The present work investigated the biocompatibility of Zr46(Cu4.5/5.5Ag1/5.5)46Al8 BMG in depth by using several biomedical methods. Our results indicate that the BMG material treated by micro-arc oxidation technology (MAO) has good biocompatibility comparable to as-cast Ti–6Al–4V alloy. MAO introduced high density of pores and hydroxyapatite in the surface layer. At a moderate MAO voltage, 350 V, a surface with the highest density of uniform size pores and suitable surface roughness was obtained. The BMG material treated at 350 V thus demonstrated the strongest platelet adhesion, the best blood compatibility, the weakest oral mucous membrane irritation, the weakest inflammation, and fastest recovery of injured cells during the subcutaneous implantation tests, in comparison with the samples treated at other voltages. These results may advance the applications of Zr-based BMGs as biomaterials in future.

Deciphering osteoconductive surface charge effects in sintered hydroxyapatite via piezoresponse force microscopy

Hydroxyapatite (HAp), a main constituent of the cortical bone, retains a large surface charge that plays a critical role in the regeneration of bones, whose source remains an enigma. Here, we used multi-eigenmode piezoresponse force microscopy via Pearson correlation and conducted multiscale material analysis to independently measure the piezoelectric coefficient and the surface charge density of HAp. Quantitative comparison was conducted between the measured surface charge density and the conceptual values computed for all possible candidates of the surface charging such as piezoelectricity, chemically induced surface charging, flexoelectricity, and defect dipole moment. The results presented Ca2+ ions released during local calcium orthophosphate phase transition at the surface as the main source of the surface charging. Further analysis showed that the ion concentration was modulable using a charged conductive tip, implying that the interstitial ions are mobile within the HAp matrix. In this work, we developed a novel method to measure the effective surface charge density of arbitrary material systems, thereby facilitating the investigation of biophysical phenomena related to surface electromechanics. Most importantly, the research promotes a new understanding of the origin of osteoconduction observed in past works conducted on HAp.

Synthesis and densification of hydroxyapatite by mechanochemically-activated reactive cold sintering

We proposed a reactive cold sintering method based on the activation of reactants by ball-milling. Using CaHPO4⋅2H2O and Ca(OH)2 as precursors after mechanical activation for different times, the simultaneous synthesis and densification of hydroxyapatite (HA) products were achieved by cold sintering at temperatures ranging from 50 to 200 °C. The effects of processing parameters including milling time, temperature, uniaxial pressure and holding time on the synthesis and densification behavior of HA were systematically investigated and the underlying mechanisms were addressed. This study provides a simple, feasible and scalable route for the rapid low-temperature synthesis and densification of HA and its composites.

The effect of lanthanum addition on the microstructure and mechanical properties of Mg-modified hydroxyapatite ceramics

In the present paper, the effect of La2O3 (0.25, 0.5 and 1 wt.%) addition on the phase stability, porosity, density, hardness, fracture toughness, compressive strength and brittleness index of hydroxyapatite modified with 1 wt.% of MgO was investigated. Hydroxyapatite (HA) without additives sintered at 1300?C has mixture of dominant hydroxyapatite phase with beta-tricalcium phosphate (?-TCP), alpha-tricalcium phosphate (?-TCP) and calcium oxide (CaO) phases. The microstructure is characterized with transgranular microcracks and oversized grains. Although the density and hardness of the pure HA increased with increasing temperature, a steady decrease in fracture toughness (from 0.96 to 0.71MPa?m1/2) and compressive strength (from 130.2 to 65.6MPa) was observed. For the HA modified with 1 wt.% of MgO the highest compressive strength (183.2MPa) and fracture toughness (1.47MPa?m1/2) were obtained at 1200?C and at this temperature the brittleness index was 3.24 ?m-1/2. Increase in the sintering temperature led to the increase of the brittleness index of the pure HA,MgO modified HA and La2O3-MgO modified HA samples. The addition of 1 wt.%La2O3 to 1 wt.% MgO-HA contributed to the increase in the compressive strength of about 10%(from 183.2 to 202.0MPa), fracture toughness of about 69% (from 1.37 to 2.32MPa?m1/2) and also decrease of the brittleness index from 3.24 to 2.18 ?m-1/2. The best performance after sintering at 1300?C was obtained for the MgO-HA sample with 0.25wt.% La2O3. As a result of this study, a new candidate material for biomedical application with superior mechanical properties and the phases that do not cause adverse reactions in the human body could be 1 wt.% MgO-HA modified with 1 wt.% La2O3 and sintered at 1200?C.

In vivo quantification of bone mineral density of lumbar vertebrae using fast kVp switching dual-energy CT: correlation with quantitative computed tomography.

Osteoporosis is a common, progressive disease related to low bone mineral density (BMD). If it can be diagnosed at an early stage, osteoporosis is treatable. Quantitative computed tomography (QCT) is one of the current reference standards of BMD measurement, but dual-energy computed tomography (DECT) is considered to be a potential alternative. This study aimed to evaluate the feasibility and accuracy of phantomless in vivo DECT-based BMD quantification in comparison with QCT. A total of 128 consecutive participants who underwent DECT lumbar examinations between July 2018 and February 2019 were retrospectively analyzed. The density of calcium (water), hydroxyapatite (water), calcium (fat), and hydroxyapatite (fat) [DCa(Wa), DHAP(Wa), DCa(Fat) and DHAP(Fat), respectively] were measured along with BMD in the trabecular bone of lumbar level 1-2 by DECT and QCT. Linear regression analysis was performed to assess the relationship between DECT- and QCT-derived BMD at both the participant level and the vertebral level. Linear regression models were quantitatively evaluated with adjusted R-square, normalized mean squared error (NMSE) and relative error (RE). Bland-Altman analysis was conducted to assess agreement between measurements. P<0.05 was considered statistically significant. Strong correlations were observed between DECT- and QCT-derived BMD at both the participant level and the vertebral level (adjusted R2 =0.983-0.987; NMSE = 1.6-2.1%; RElinear =0.6-0.9%). Bland-Altman plots indicated high agreement between both measurements. DCa(Fat) and DHAP(Fat) showed relatively similar and optimal predictive capability for QCT-derived BMD (both: adjusted R2 =0.987, NMSE =1.6%, RElinear =0.6%). Fast kVp switching DECT enabled accurate phantomless in vivo BMD quantification of the lumbar spine. DCa(Fat) and DHAP(Fat) had relatively similar and optimal predictive capability.

Influence of flash sintering on phase transformation and conductivity of hydroxyapatite

We report on the influence of current density limits on phase transformation, density, and microstructure of Hydroxyapatite (HAp) subjected to flash sintering experiments. Arrhenius plots of the electrical conductivity during the constant heating rate experiments showed changes in the ionic conductivity mechanisms during the incubation time, contrasting behavior from other materials presented so far. Flash sintering also suppressed the formation of β-tricalcium phosphate, which occurs during conventional sintering. We report herein that low current density limits were able to successfully sinter dense HAp with minimal phase transformations under lower furnace temperature and significantly shorter time processing.

Structural and Morphometric Comparison of Lower Incisors in PACAP-Deficient and Wild-Type Mice.

Pituitary adenylate cyclase activating polypeptide (PACAP) is a neuropeptide with widespread distribution. PACAP plays an important role in the development of the nervous system, it has a trophic and protective effect, and it is also implicated in the regulation of various physiological functions. Teeth are originated from the mesenchyme of the neural crest and the ectoderm of the first branchial arch, suggesting similarities with the development of the nervous system. Earlier PACAP-immunoreactive fibers have been found in the odontoblastic and subodontoblastic layers of the dental pulp. Our previous examinations have shown that PACAP deficiency causes alterations in the morphology and structure of the developing molars of 7-day-old mice. In our present study, morphometric and structural comparison was performed on the incisors of 1-year-old wild-type and PACAP-deficient mice. Hard tissue density measurements and morphometric comparison were carried out on the mandibles and the lower incisors with micro-CT. For structural examination, Raman microscopy was applied on frontal thin sections of the mandible. With micro-CT morphometrical measurements, the size of the incisors and the relative volume of the pulp to dentin were significantly smaller in the PACAP-deficient group compared to the wild-type animals. The density of calcium hydroxyapatite in the dentin was reduced in the PACAP-deficient mice. No structural differences could be observed in the enamel with Raman microscopy. Significant differences were found in the dentin of PACAP-deficient mice with Raman microscopy, where increased carbonate/phosphate ratio indicates higher intracrystalline disordering. The evaluation of amide III bands in the dentin revealed higher structural diversity in wild-type mice. Based upon our present and previous results, it is obvious that PACAP plays an important role in tooth development with the regulation of morphogenesis, dentin, and enamel mineralization. Further studies are required to clarify the molecular background of the effects of PACAP on tooth development.

In vivo evaluation of the role of carbonate ion in hydroxyapatite for bone remodeling

In vivo evaluation of the role of carbonate ion in hydroxyapatite for bone remodeling

Fluoridation of hydroxyapatite with addition of TiF4 and developing the mechanical properties by pressureless sintering

Hydroxyapatite [Ca10(PO4)6(OH)2] powder was sintered with addition of aluminumisoproxide (C9H21AlO3) 4 wt % and various wt % of titanium fluoride TiF4. The prepared pellets were sintered at 1250°C temperature. The various wt % of TiF4 were used for fluoridation and densification of hydroxyapatite. For studying the phase compositions, microstructure and elemental analysis, the sintered specimens were characterized by X-ray diffraction XRD, Scanning electron microscopy SEM, and energy dispersive electron spectroscopy EDAX respectively. After sintering highest relative density was found to be 96.42 % with Vickers hardness and bending strength 1.22–1.62 GPa and 13.39–35.88 MPa respectively. As a result of sintering fluoridated apatite composite material was obtained.

Irisin injected mice display increased tibial cortical mineral density and polar moment of inertia

It has been recently reported that, after physical activity, the skeletal muscle releases Irisin, the newly identified myokine able of driving transition of white adipocytes into brown [1]. This result supported the role of skeletal muscle as endocrine organ, suggesting that it could target other tissues besides adipose tissue. In our previous work, we demonstrated that conditioned media collected from primary myoblasts of exercised mice were able to increase OB differentiation and this effect was Irisinmediated [2]. Here we show that Irisin has positive effect on cortical mineral density and geometry in vivo. Young male mice were injected with r-Irisin and cortical bone adaptation was analyzed by micro-CT at tibial midshaft. Our results show that cortical tissue mineral density is significantly increased in Irisin-injected mice compared to vehicle-injected littermates (+7.15%; p<0.01). Furthermore, this higher density of calcium hydroxyapatite at cortical site is accompanied by increase in periosteal circumference (+7.5%; p<0.03) and polar moment of Inertia (pMOI +19,21%; p<0,01). A greater pMOI indicates stronger resistance of a long bone to torsion and, together with higher bone mineral density, suggests higher protection against fracture. The effect of Irisin is fully comparable to the effect of physical activity that is widely accepted method for increasing bone mineral density and bone size in healthy populations. In view of further proving the involvement of Irisin in bone metabolism, we validate its direct effect on osteoblasts in vitro. Phosphorylation of the MAP kinase ERK and the expression of Atf4 were significantly increased after Irisin treatment, as well as ALP and pro-Collagen I mRNA expression. Our data highlight a novel link in muscle-fat-bone axis demonstrating that Irisin targets bone tissue directly, driving positive effects on cortical mineral density and geometry in vivo. These findings would expand the research of exercise-mimetic drugs that might be widely used to treat osteoporotic patients who are suffering from immobilization and cannot perform physical activity.

Stainless steel 316L–hydroxyapatite composite via powder injection moulding: rheological and mechanical properties characterisation

Powder injection moulding is a manufacturing process capable of producing complex, precise and net-shaped components from metal or ceramic powders at a competitive cost. This study investigated the rheological properties of stainless steel 316L–hydroxyapatite composite by using palm stearin and polyethylene as a binder system, evaluates the physical and mechanical properties, and composition change of the sintered part at different temperatures through powder injection moulding process. Stainless steel 316L powder was mixed with hydroxyapatite by adding a binder system (palm stearin and polyethylene) at 58·0 vol% powder loading prepared via critical powder volume percentage. A green dumbbell-shaped part was produced via plunger-type injection moulding. The green part was sintered at 1000, 1100, 1200 and 1300°C at 3 hours. The value of flow behaviour index n is from 0·1 to 0·39, which is within range of the injectability index. The obtained activation energy is 5·75 kJ mol−1. Morphological results indicate the formation of pores at a sintering temperature of 1000°C, a decrease of pores when the temperature is increased, and the occurrence of densification. At 1300°C it showed the highest mechanical properties of Young's modulus which is 41·18 GPa. The decomposition of hydroxyapatite into β-tricalcium phosphate and tetracalcium phosphate phases started to occur at 1000 and 1100°C, respectively. The highest sintered density is 3·7744 g cm−3 which is close to the density of hydroxyapatite but the mechanical properties is higher than pure hydroxyapatite.

Runx2 activity in committed osteoblasts is not essential for embryonic skeletogenesis

Runx2 transcription factor is essential for the development of mineralized tissue, and is required for osteoblast commitment and chondrocyte maturation. Mice with global deletion of Runx2 exhibit complete failure of bone tissue formation, while chondrocyte-specific Runx2-deficient mice lack endochondral ossification. However, the function of Runx2 after commitment of mesenchymal cells to the osteoblast lineage remains unknown. Here, we elucidate the osteoblast-specific requirements of Runx2 during development of the tissue. Runx2 was deleted in committed osteoblasts using Cre-recombinase driven by the 2.3kbCol1a1 promoter. Surprisingly, Runx2ΔE8/ΔE8 mice were born alive and were essentially indistinguishable from wild-type littermates. At birth, we failed to detect any alterations in skeletal patterning or extent of bone development in homozygous mutants. However, by 4 weeks of age, mutant mice showed obvious growth deficiencies, and weighed 20–25% less than sex-matched wild-type littermates. Micro-CT analysis of the hindlimb revealed a dramatic decrease of 50% in both cortical and trabecular bone volume compared with wild-type mice. Consistent with this observation, trabecular number and thickness were decreased by 51% and 21%, respectively, and trabecular space was increased by 2-fold in limbs of Runx2ΔE8/ΔE8 mice. In addition to poor acquisition of bone mass, the average density of hydroxyapatite was markedly decreased in bone of Runx2ΔE8/ΔE8 mice. Together, these findings demonstrate that loss of Runx2 activity in committed osteoblasts impairs osteoblast function, and that Runx2 is critical for postnatal, but not embryonic endochondral ossification.

Dispersion Stability of Hydroxyapatite-Calcium Phosphate Glass Ceramic-Tertiary Butyl Alcohol System

The sedimentation bulk density and rheology of tertiary-butyl alcohol (TBA)-based hydroxyapatite/calcium phosphate glass ceramic suspension system have been examined in terms of oxide solid loading (10, 15 vol.%), and types of additives (dispersant, dispersant/gelator, dispersant/gelator/surfactant), and calcium phosphate glass ceramic content. Sedimentation density of hydroxyapatite decreased by adding calcium phosphate glass ceramic mainly due to the coarse and hence low surface area of calcium phosphate glass ceramic powder; the decrease effect was nearly offset when the dispersant was added. The suspension viscosity generally behaved in an opposite manner to the sedimentation density. A shear thinning rheology was shown in applied shear rate, regardless of processing variables.

Estimation of Crystallite Size, Lattice Strain and Dislocation Density of Nanocrystalline Carbonate Substituted Hydroxyapatite by X-ray Peak Variance Analysis

X-ray peakprofile analysis by variance method is employed to evaluate the micro structural parameters namely crystallite size, mean squared lattice strain, root mean squared lattice strain and dislocation density of hydroxyapatite (HA) and carbonate substituted [3 wt% (3CHA) and 6 wt% (6CHA)] hydroxyapatite nanoparticles prepared by microwave synthesis technique. The calculated average crystallite sizes of HA, 3CHA and 6CHA by variance method are correlated with the values obtained from Scherer's and transmission electron microscopy (TEM) results. It is found that the results of the average crystallite size measured by variance analysis method are in good agreement with TEM results. The calculated micro structural parameters are also correlated with the in-vitro dissolution study results. It is found that variance method of X-ray peak profile analysis is more appropriate to quantify the micro structural parameters of nanostructured hydroxyapatite based nanoparticles.

An assessment of powder pycnometry as a means of determining granule porosity

A powder pycnometry method, using a commercially available instrument (GeoPyc® with DryFlo® displacement media), was evaluated as a means of measuring the envelope density of hydroxyapatite (HA) granules in the size range of 75–8000 µm. The aims of this study were to (1) investigate the reproducibility of the DryFlo® powder particle size and consolidation properties, (2) determine the number of preparation cycles required before test measurements should be taken, (3) compare the powder pycnometry method to the reference mercury porosimetry method and (4) investigate the effect of granule size on envelope density measurement. DryFlo® was shown to have a reproducible particle size when sampled at multiple locations across three separate containers. A minimum of 1 preparation cycle should be used to ensure consistent packing of the DryFlo® and HA granules. DryFlo® density was found to be insensitive to consolidation forces in the range of 10–100 N. The powder pycnometry method could be linearly calibrated against the reference mercury porosimetry method when considering polydisperse HA granule samples. However, when analyzing narrow particle size fractions limitations in the powder pycnometry method were noted resulting in a reduced particle size range of 1850–4050 µm that could be linearly calibrated against the mercury porosimetry method.