Morphology Of Hydroxyapatite Research Articles

Ammonia-sensing ability of differently structured hydroxyapatite blended cellulose nanofibril composite films

Fully bio-based, flexible and lightweight nanocomposite films of different porosity/density were fabricated by integrating variable weight percentages of hydroxyapatite (HAp) nanoparticles within a matrix of cellulose nanofibrils (CNFs) using the one-directional freeze-drying technique, and utilised for study as ammonia sensors. Structural, morphological and thermal-stability characterizations of the samples were assessed by using X-ray diffraction and Fourier transform infrared spectroscopy, scanning electron microscopy, and thermogravimetric analysis. The sensing ability of the films was studied at low operating temperature (25 °C) in the presence of ambient air and 5 ppm of ammonia vapour by two probe electrodes. The results for gas sensing characteristics revealed that the amount and morphology of HAp, its distribution within the micro-porous CNF matrix, and doping on its surface, are the most important parameters which influence the gas sensing performance. It was observed that the film with integrated 5 wt% of HAp exhibited the detection limit of ammonia at a concentration as low as 5 ppm, remarkable high sensitivity (up to 575%) and fast response/recovery (210/30 s) as compared to the HAp (160%, 720/120 s) or CNF (382%, 540/160 s) samples. The designed nanocomposite sensors may be used as gas filters in technological applications using ammonia as indicators for freshness in smart and biodegradable food packaging materials or in high-tech protection clothing.

Microwave treatment and pH influence on hydroxyapatite morphology and structure

This paper reports the influence of microwave treatment duration and pH conditions of initial precursors on the morphological and crystalline dispersity of the hydroxyapatite (HAp) synthesized by hydrothermal method.The obtained HAp samples were studied by scanning electron microscopy, X-Ray diffraction method and low nitrogen adsorption method. We have obtained nanostructured crystalline hydroxyapatite with 95% crystallinity, porous structure and average particles size in interval 17…46 nm consolidated in aggregates with size distribution of 0.5…25 μm. The pH growth from 8 to 13 results in double increase of HAp specific area(from 69 up to 133 m2/g), meanwhile microwave irradiation brings to particles aggregation: HAp treated during 0… 10…30 min have specific surface are 112…67…41 m2/g, respectively. As a result at pH=13 and without microwave irradiation treatment we synthesized HAp with maximum surface compared to the surface of natural HAp that makes obtained HApto be promising material in biotechnological applications.

Synthesis of hydroxyapatite nanoparticles from egg shells by sol-gel method

Hydroxyapatite, [Ca10(PO4)6(OH)2, (HAp)] is widely used in medical fields especially as a bone and teeth substitute. Hydroxyapatite nanoparticles have been succesfully synthesized from egg shells as a source of calcium by using sol-gel method. The egg shells were calcined, hydrated (slaking) and undergone carbonation to form Precipitated Calcium Carbonate (PCC).Then the PCC was added (NH4)2HPO4 to form HAp with variation the mole ratio Ca and P (1.57; 1.67 and 1.77), aging time (24, 48, and 72 hr) and under basic condition pH (9, 10 and 11). The formation of hydroxyapatite biomaterial was characterized using XRD, FTIR, SEM-EDX. The XRD patterns showed that the products were hydroxyapatite crystals. The best result was obtained at 24 hr aging time, pH 9 with hexagonal structure of hydroxyapatite. Particle size of HAp was 35-54 nm and the morphology of hydroxyapatite observed using SEM, it showed that the uniformity crystal of hydroxyapatite.

The significant influence of ionic concentrations and immersion temperatures on deposition behaviors of hydroxyapatite on alkali- and heat-treated titanium in simulated body fluid

Biomimetic deposition of apatite in simulated body fluid (SBF) in vitro has been widely used to evaluate the bioactivity of titanium (Ti) and prepare a functional coating on biomedical metallic substrates. In this study, the deposition behaviors of hydroxyapatite (HA) on Ti samples treated by alkali and heat treatment (AH) in SBFs (1×, 2×, 3× SBF) at 37, 47 and 57°C were researched. The electrochemical results confirmed the characteristic fine and porous network structure on Ti substrate after AH resulted in the decrease of corrosion resistance. SEM images showed that the surface structure and morphology of hydroxyapatite (HA) coatings varied markedly under different soaking conditions. Particularly, high SBF concentrations and immersion temperatures created more homogeneous and dense deposited layers with uniform large spherical HA agglomerates. The results of XRD and FTIR demonstrated that brushite (the precursor of HA) preferentially formed and gradually transformed into HA in SBF with high ion concentration and temperature. Thermodynamic analysis in terms of nucleation and crystal growth mechanism was proposed to fundamentally explain HA deposition process in vitro. This work provides a potential method to rapidly evaluate the bioactivity of Ti-based biomaterials and prepare controlled bioactive coating on the implants.

One-Dimensional Hydroxyapatite Nanostructures with Tunable Length for Efficient Stem Cell Differentiation Regulation.

It is well-accepted that most osteogenic differentiation processes do need growth factors assistance to improve efficiency. As a material cue, hydroxyapatite (HAp) can promote osteogenic differentiation of stem cells only in a way. Up to now, rare work related to the relationship between HAp nanostructures and stem cells in osteogenic differentiation process without the assistance of growth factors has been reported. In this study, one-dimensional (1D) HAp nanostructures with tunable length were synthesized by an oleic acid assisted solvothermal method by adjusting the alcohol/water ratio (η). The morphology of 1D HAp nanostructures can be changed from long nanowires into nanorods with the η value change. Different substrates constructed by 1D HAp nanostructures were prepared to investigate the effect of morphology of nanostructured HAp on stem cell fate without any growth factors or differentiation induce media. Human adipose-derived stem cells (hADSCs), a kind of promising stem cell for autologous stem cell tissue engineering, were used as the stem cell model. The experiments prove that HAp morphology can determine the performance of hADSCs cultured on different substrates. Substrate constructed by HAp nanorods (100 nm) is of little benefit to osteogenic differentiations. Substrate constructed on HAp long nanowires (50 μm) causes growth and spread inhibition of hADSCs, which even causes most cells death after 7 days of culture. However, substrate constructed by HAp short nanowires (5 μm) can destine the hADSCs differentiation to osteoblasts efficiently in normal medium (after 3 weeks) without any growth factors. It is surprise that hADSCs have changed to polyhedral morphology and exhibited the tendency to osteogenic differentiation after only 24 h culture. Hydroxyapatite nanostructures mediated stem cell osteogenic differentiation excluding growth factors provides a powerful cue to design biomaterials with special nanostructures, and helps to elucidate the interaction of stem cell and biomaterials nanostructures. The results from this study are promising for application in bone tissue engineering.

Controlled Synthesis of Hydroxyapatite Using a Novel Natural Rosin-Based Surfactant

Hydroxyapatite (HAP) with multiform morphologies, such as hollow dandelion-like bundles and nanoparticles with a diameter of 50[Formula: see text]nm, was prepared using natural rosin-based surfactant dehydroabietyl phosphate diester (DDPD) as phosphorus source, crystal growth control agent, and template simultaneously by a facile hydrothermal method. Samples were obtained and characterized by X-ray powder diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). Results showed that DDPD and pH value of solution were the key factors for the morphology of HAP. Hollow dandelion-like bundles HAP, containing the Ca-monodehydroabietyl phosphate (PM-Ca) organic metal compounds, were formed at pH[Formula: see text][Formula: see text][Formula: see text]3 without acid-base regulation, and nanoparticles were obtained at pH[Formula: see text][Formula: see text][Formula: see text]12. SEM exhibited that the hollow dandelion-like bundles HAP are of 10[Formula: see text][Formula: see text]m (outer) and 1[Formula: see text][Formula: see text]m (inner) diameter, respectively. Cell viabilities are above 95% when the cells are co-cultured with all HAP samples at concentrations in the range of 250–1000[Formula: see text][Formula: see text]g/ml. It indicated that the prepared HAP with PM-Ca has a good cytocompatibility without apparent toxicity. Finally, the possible formation mechanism of the HAP microstructures was discussed in detail.

The morphological evolution of hydroxyapatite on high-efficiency Pb2 + removal and antibacterial activity

Increasingly more attention has been paid to morphological studies of biomaterials and the physicochemical and biological properties thereof in various applications. Herein, the morphology of hydroxyapatite (HAP) has been evolved into three morphologies (short rod-, flake flower-, and dandelion-like) by using different surfactants under hydrothermal treatments. Moreover, the influences of morphology on selective adsorption of heavy metal ions and antibacterial activity were evaluated in detail. The results showed that selective adsorption of heavy metal ions by HAP was dependent on the morphology, but was independent of the antibacterial activity. Also, morphological evolution mechanism, influencing factors for adsorption, kinetics, isotherms and possible adsorption mechanisms were discussed in this study. The maximum adsorption capacities under the Langmuir model were also shown to depend on the morphology of HAP, with the highest adsorption capacity reaching up to 819.7mgg−1 for dandelion-like structures, which may resulted from such structures having multi-adsorbing sites. In sum, the study provides a material having specific morphologies for high-efficient and selective removal of Pb2+, and offers guidance for modification of antibacterial activity of biomaterials.

Hydroxyapatite Synthesized from Waste Eggshell via Ball Milling

Hydroxyapatite was synthesized using calcium originated from waste eggshell that was reacted with phosphate obtained from diammonium hydrogen orthophosphate by ball milling technique. The samples were mixed at different time from 5 to 150 min. The structure, function group and morphology of hydroxyapatite were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and field emission scanning electron microscopy (FE-SEM). The result showed that the hydroxyapatite phase was appeared after ball milling about 5 min and confirmed with FTIR results. The FE-SEM of hydroxyapatite powder was spherical shape and agglomerate. The crystallinity of hydroxyapatite was increased with increasing ball milling time. This experiment showed that the nano hydroxyapatite could synthesized from waste eggshell by ball milling technique.

Effects of pore distribution of hydroxyapatite particles on their protein adsorption behavior

The relationship between protein adsorption on hydroxyapatite (HAp) particles and their surface structure was investigated. Because the various crystal planes of HAp have been reported to exhibit selective adsorption, numerous studies have focused on developing methods to control HAp morphology for selective adsorption. However, few studies have examined the systematic adsorption of proteins on the HAp particles. We firstly synthesized HAp particles under various aging times and mild reaction conditions intending to obtain HAp particles having various surface structures despite similar morphology, chemical composition, and crystallinity. The aging time affected the pore size distribution of the HAp particles. A peak indicating pores with a diameter of approximately 2.5 nm was observed in the pore size distribution plots of the HAp particles prepared using aging times of 48 h or less. The adsorption of proteins on HAp particles with different surface structures was studied. The bovine serum albumin (BSA) adsorption behavior was influenced by the presence of pores on the HAp surface. The amount of BSA adsorbed on the HAp particles aged 72 h having no pores was nearly 1.5 times that of the other HAp particles having pores. These results indicated that the pore size distribution of HAp particles is one of the most important factors in controlling their protein adsorption behavior.

Recombinant DNA technology and click chemistry: a powerful combination for generating a hybrid elastin-like-statherin hydrogel to control calcium phosphate mineralization.

Understanding the mechanisms responsible for generating different phases and morphologies of calcium phosphate by elastin-like recombinamers is supreme for bioengineering of advanced multifunctional materials. The generation of such multifunctional hybrid materials depends on the properties of their counterparts and the way in which they are assembled. The success of this assembly depends on the different approaches used, such as recombinant DNA technology and click chemistry. In the present work, an elastin-like recombinamer bearing lysine amino acids distributed along the recombinamer chain has been cross-linked via Huisgen [2 + 3] cycloaddition. The recombinamer contains the SNA15 peptide domains inspired by salivary statherin, a peptide epitope known to specifically bind to and nucleate calcium phosphate. The benefit of using click chemistry is that the hybrid elastin-like-statherin recombinamers cross-link without losing their fibrillar structure. Mineralization of the resulting hybrid elastin-like-statherin recombinamer hydrogels with calcium phosphate is described. Thus, two different hydroxyapatite morphologies (cauliflower- and plate-like) have been formed. Overall, this study shows that crosslinking elastin-like recombinamers leads to interesting matrix materials for the generation of calcium phosphate composites with potential applications as biomaterials.

용액의 산도 및 용매의 종류에 따른 수산화인회석의 형태 변화 연구

용액의 산도 및 용매의 종류에 따른 수산화인회석의 형태 변화 연구

Isoexergonic Conformations of Surface-Bound Citrate Regulated Bioinspired Apatite Nanocrystal Growth.

The superior biomechanical properties of bone and dentin are dictated, in part, by the unique plate-like morphology of hydroxyapatite (HAP) nanocrysals within a hierarchically assembled collagen matrix. Understanding the mechanism of crystal growth and thus morphology is important to the rational design of bioinspired apatite nanocrystals for orthopedic and dental applications. Citrate has long been proposed to modulate apatite crystal growth, but major questions exist regarding the HAP-bound citrate conformations and the identities of the interacting functional groups and HAP surface sites. Here, we conducted a comprehensive investigation of the mechanism from the angstrom to submicrometer scale by detailed correlation of the results of high-level metadynamics simulations, employing force-fields benchmarked to experiment and density functional theory calculations with the results of high resolution transmission electron microscopy, nuclear magnetic resonance spectroscopy, solution analysis, and thermogravimetric analysis. Crystal morphology changed from needle- to plate-like with increasing citrate concentration. Citrate adsorbed more strongly on the HAP (100) face than on the (001) face, thus resulting in preferential growth in the [001] direction and the plate-like morphology. Two very different bound conformations were obtained, involving interactions of either one or both terminal carboxyl groups with three or five surface calcium ions, respectively, and a hydrogen bond between the citrate hydroxyl and the HAP surface. Remarkably, despite fewer interaction sites in the single bound carboxyl conformation, the structures were isoexergonic, so both exist at equilibrium. Identification of the former conformation is significant because it allows a greater adsorption density than is traditionally assumed and can help explain concentration-dependence of citrate in modulating crystal morphology. These unique results were enabled first by the application of advanced metadynamics, a technique necessary for the accurate simulation of ionic materials but which is rarely employed in the biomaterials and biomineralization fields and second by the detailed correlation of computational, spectroscopic, and analytical results.

Fast route for synthesis of stoichiometric hydroxyapatite by employing the Taguchi method

The Taguchi experimental design method is an elegant and efficient way of deriving optimum conditions for processes from the minimum number of experiments. We correlated various relevant synthesis parameters in the precipitation synthesis of single-phase pure hydroxyapatite (Ca10(PO4)6(OH)2, HAp) nanoparticles, via a rapid wet precipitation method, without any aging time. Taguchi planning was used for a systematic study of the combined effects of five different parameters: pH, synthesis temperature, synthesis time, drying temperature and calcination temperature. Using T\\aguchi methods, we were able to evaluate the effects of four variations (levels) in each of these five parameters, with just 16 experiments (an L16 (1024) orthogonal array). We assessed the impact of these parameters on four distinct properties, namely crystallite size, surface area, Ca/P atomic ratio and mol% of HAp. Calcination temperature exerted the greatest impact on hydroxyapatite morphology, corresponding to crystallite size and specific surface area, for which the role of other processing parameters was not significant. On the contrary, the Ca:P ratio was affected mainly by pH. These findings were confirmed by microstructural, structural and spectroscopic characterisation. FTIR spectra, revealing the conditions to retain a pure or prevailing hydroxyapatite phase, and also to indicate favourable conditions for A-type substitutions of carbonate for hydroxide groups, or B-type substitution for phosphate groups.

Synthesis of morphologically controlled hydroxyapatite from fish bone by urea-assisted hydrothermal treatment and its Sr2 + sorption capacity

Needle- and sponge-shaped hydroxyapatite (HAp) particles were synthesized from calcined tuna fish bone (Tn1000) and commercially available HAp reagent (ChemHAP) by a urea-assisted hydrothermal treatment using 0.1–1.0M urea solution at 160°C for 3h. The Sr2+ sorption capacity of the synthesized HAp was also investigated using 0–50mM Sr2+ solution at 25°C for 72h to evaluate its performance as a sorbent for environmental remediation. Sponge-shaped HAp was formed under hydrothermal conditions with a urea concentration of 1.0M. With decreasing urea concentration, the morphology of HAp changed from sponge-shaped to needle-shaped crystals, regardless of the starting material. Some calcium carbonate and/or β-tricalcium phosphate impurities were formed from Tn1000 at 0.1–0.5M urea concentration. The Sr2+ sorption mechanism of the synthesized HAp was estimated using Ca ion-exchange reaction and precipitation of SrCO3. The sponge-shaped HAp crystals, which had high specific surface area and CO32− content, exhibited a large ion-exchange capacity with Sr2+. In contrast, the ion-exchange ratio of needle-shaped HAp dramatically decreased with increasing initial Sr concentration. No clear difference in Sr2+ sorption behaviour caused by the choice of HAp synthesis starting material was observed. These results indicate that the Sr sorption mechanism of HAp is influenced by not only its composition but also its crystal morphology.

Novel multiform morphologies of hydroxyapatite: Synthesis and growth mechanism

Morphological evolution of materials becomes a prodigious challenge due to their key role in defining their functional properties and desired applications. Herein, we report the synthesis of hydroxyapatite (HAp) microstructures with multiform morphologies, such as spheres, cubes, hexagonal rods and nested bundles constructed from their respective nanoscale building blocks via a simple cost effective hydro/solvothermal method. A possible formation mechanism of diverse morphologies of HAp has been presented. Structural analysis based on X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy confirms the purity of the HAp microstructures. The multiform morphologies of HAp were corroborated by using Field emission scanning electron microscope (FESEM).

Effect of bio-calcium oxide on the morphology of hydroxyapatite

A study of the Hydroxyapatite (HAp) synthesis through a hydrothermal process was carried out. Bio-Calcium oxide (CaO) obtained by heat treatment of sand dollar was used in the synthesis at different proportions to react with monetite (CaHPO3). Structural and chemical characterization of the samples was carried out using scanning electron microscopy (SEM), X-ray diffraction; Infrared spectroscopy (FTIR), and transmission electron microscopy (TEM). In each sample were observed different morphologies such as agglomerates, hexagonal particles, epitaxial growth, and fibers. O, Ca, P, C and small amounts of Mg and Si were the main chemical components of the sharp morphologies. The hydroxyapatite, whitocklite, portlandite and calcite were the crystalline phases found in each of the samples analyzed. Two different growth shapes of HAp single crystals were found using transmission electron microscopy. The HAp single crystal with six well-defined prismatic faces was reveled to grow along side the <1 0 –1 0> crystallographic direction. The HAp single crystal with fiber morphology grew alongside c-axis. However, both morphologies of HAp single crystals present a ratio Ca/P less compared with the stoichiometric ratio (Ca/P=1.67).

Hydroxyapatite formation from calcium carbonate single crystal under hydrothermal condition: Effects of processing temperature

Hydrothermal processing has been used for synthesis of hydroxyapatite (HAp) crystals with unique morphologies. Our previous studies reported that the morphology of HAp was affected by dissolution behavior of starting materials under a hydrothermal condition. In this study we evaluated the effects of processing temperature on formation and morphology of HAp crystals under a hydrothermal condition. Calcite (CaCO3) single crystal as a starting material was hydrothermally treated in a phosphate solution at various temperatures. After hydrothermal processing for 24h, needle-shaped HAp crystals formed on the surfaces of all the samples. The size of HAp crystals increased with increasing the processing temperature. Plate-shaped HAp was observed on the cross-section of the starting material treated at 200°C. The structure of HAp plates were generated by arrangement of needle-shaped HAp crystals during their crystal growth. The difference in the processing temperature affects the morphology and structure of HAp formed on the starting material under the hydrothermal condition.

Comparison of polyethylene glycol effect on hydroxyapatite morphology produced into different methods: sol–gel and precipitation

Hydroxyapatite (HA) can be used as a bioceramic due to its bioactivity and osteoconductive properties. It is clear that the morphology of HA crystal affects on its specifications such as surface and bioactivity. Because of importance of morphology, in the current research nano-sized HA particles were produced using sol–gel and precipitation methods, and to change the morphology, polyethylene glycol (PEG) was used as an organic modifier. The produced samples were characterized using X-ray powder diffraction (XRD) and scanning electron microscopy and transmission electron microscopy. The results of XRD patterns show that the pure HA can be produced using two methods. Microscopic evaluations prove that the presence of PEG has a significant effect on HA morphology. Indeed, PEG changes the morphology of HA produced by precipitation method to irregular, whereas in sol–gel method its shape leads toward fibrous with high aspect ratio. The exact reason of this variation can be attributed to the difference in mechanism of HA growth in two methods.

Continuous microwave flow synthesis of mesoporous hydroxyapatite.

We have successfully used continuous microwave flow synthesis (CMFS) technique for the template free synthesis of mesoporous hydroxyapatite. The continuous microwave flow reactor consisted of a modified 2.45GHz household microwave, peristaltic pumps and a Teflon coil. This cost effective and efficient system was exploited to produce semi-crystalline phase pure nano-sized hydroxyapatite. Effect of microwave power, retention time and the concentration of reactants on the phase purity, degree of crystallinity and surface area of the final product was studied in detail. X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) were used to study the phase purity and composition of the product, while transmission electron microscopy (TEM) was used to study the effect of process parameters on the morphology of hydroxyapatite. The TEM analysis confirmed the formation of spherical particles at low microwave power; however the morphology of the particles changed to mesoporous needle and rod-like structure upon exposing the reaction mixture to higher microwave power and longer retention time inside the microwave. The in-vitro ion dissolution behavior of the as synthesized hydroxyapatite was studied by determining the amount of Ca(2+) ion released in SBF solution.

Controlled Preparation and Formation Mechanism of Hydroxyapatite Nanoparticles under Different Hydrothermal Conditions

Hydroxyapatite (HAP) nanoparticles with uniform morphologies and controllable size were synthesized successfully by molecular template hydrothermal approach. The organic alcohols including ethanol, glycol, glycerol and butanol were used as templates to regulate the nucleation and crystal growth. The synthesized powders were characterized by X-ray diffraction, Fourier infrared spectrum and transmission electron microscopy. The results showed that the obtained HAP particles were uniform rod-like crystals, and the template molecular structures had significant effect on the morphology and size of HAP particles. The template molecules with longer hydrophobic groups resulted in longer particle length and larger aspect ratio. Compared with the concentration of template molecules, the template molecular structure showed larger influence on controlling the HAP morphology and size. Furthermore, the formation mechanism of these rod-like HAP particles prepared by alkyl alcohol templates was discussed. Moreover, hydrothermal treatment temperature and time could be also used for controlled preparation of HAP nanoparticles.