Synthetic Calcium Hydroxyapatite Research Articles

Enhanced Release of Calcium Ions from Hydroxyapatite Nanoparticles with an Increase in Their Specific Surface Area.

Synthetic calcium phosphates, e.g., hydroxyapatite (HAP) and tricalcium phosphate (TCP), are the most commonly used bone-graft materials due to their high chemical similarity to the natural hydroxyapatite-the inorganic component of bones. Calcium in the form of a free ion or bound complexes plays a key role in many biological functions, including bone regeneration. This paper explores the possibility of increasing the Ca2+-ion release from HAP nanoparticles (NPs) by reducing their size. Hydroxyapatite nanoparticles were obtained through microwave hydrothermal synthesis. Particles with a specific surface area ranging from 51 m2/g to 240 m2/g and with sizes of 39, 29, 19, 11, 10, and 9 nm were used in the experiment. The structure of the nanomaterial was also studied by means of helium pycnometry, X-ray diffraction (XRD), and transmission-electron microscopy (TEM). The calcium-ion release into phosphate-buffered saline (PBS) was studied. The highest release of Ca2+ ions, i.e., 18 mg/L, was observed in HAP with a specific surface area 240 m2/g and an average nanoparticle size of 9 nm. A significant increase in Ca2+-ion release was also observed with specific surface areas of 183 m2/g and above, and with nanoparticle sizes of 11 nm and below. No substantial size dependence was observed for the larger particle sizes.

Clay/phosphate-based ceramic materials for thermal energy storage – Part I: Effect of synthetic phosphate content on microstructure, thermo-physical and thermo-mechanical properties

Fired clay ceramics are promising materials for TES, thanks to their thermal stability, availability worldwide, low cost and easy shaping and handling. However, their thermo-physical and thermo-mechanical properties have to be improved. For the first time, clay-phosphate ceramics, with synthetic calcium hydroxyapatite (TCP, Ca10(PO4)6(OH)2) as additive, were developed in view of TES application. A parametric study was carried out for different clay/TCP mixtures, wherein the TCP percentage varies from 0 to 16.7 wt%. The best material containing 4.7 wt% TCP allowed increasing up to 20% of the thermal conductivity and 23% of the mechanical strength. Moreover, it was thermally stable up to 1000 °C. These original results demonstrate the suitability of these new materials for heat storage in energy systems such as in a concentrated solar power (CSP) plant, or in a unit of heat recovery from an industrial waste heat source.

The influence of single and binary mixtures of collagen amino acids on the structure of synthetic calcium hydroxyapatite as a nanobiomaterial.

The modifications carried out as part of this study were aimed at examining the effect of the addition of collagen amino acids: glycine, proline and hydroxyproline (used separately and in binary mixtures) on the physicochemical properties of hydroxyapatite obtained in their presence in vitro. The influence of mixtures of amino acids on these properties is an important element of scientific novelty. The obtained samples were tested with the use of instrumental methods: FT-IR, TEM, EDXMA, PXRD and UV spectrophotometry. The results showed the influence of the amino acids used on changes in the relative content of the labile phosphate groups constituting the structure of the hydrated surface layer of crystals. As a consequence, there were differences in some physicochemical properties of the obtained hydroxyapatites (degree of crystallinity, molar Ca/P ratio). It was also determined how the ability of the used amino acids to bind to hydroxyapatite changes.

Synthesis of Rubidium-doped Calcium Hydroxyapatite Nanoparticles for Biomedical Applications

Due to high biocompatibility, bioactivity, and natural occurrence in bones and teeth, synthetic calcium hydroxyapatite (CaHAp) is a widely applied biomaterial in tissue engineering, including orthopedic surgery and dentistry. However, the brittle nature and low strength reduce its durability, which can be improved by doping metal ions. Rubidium (Rb) is an essential trace element that works as an antibacterial agent in the human body; therefore, it can be doped in synthetic Ca-HAp to promote its durability. In this work, Rb-doped calcium hydroxyapatite (Rb-HAp) nanoparticles are synthesized by the coprecipitation method at low temperatures. Phase purity, crystallinity, doping level, and mechanical properties are investigated by X-ray diffraction (XRD), inductively coupled plasma optical emission spectroscopy (ICP-OES), and micro-hardness tester. It is observed that a minute quantity (≈ 0.02%) of Rb remained in the apatite structure when 5% of Rb+ is doped via in situ method. Moreover, small dopant concentration did not affect the crystal structure and the tensile strength of HAp.

Xanthelasma-Like Reaction to Filler Injection.

The purpose of this study is to describe a new complication of a xanthelasma-like reaction which appeared after dermal filler injection in the lower eyelid region. A retrospective case analysis was performed on 7 patients presenting with xanthelasma-like reaction after filler injection to the lower eyelids. Seven female subjects with no history of xanthelasma presented with xanthelasma-like reaction in the lower eyelids post filler injection. Fillers included hyaluronic acid (2 patients), synthetic calcium hydroxyapatite (4 patients), and polycaprolactone microspheres (one patient). Average time interval between filler injection and development of xanthelasma-like reaction was 12 months (range: 6-18 months). Treatment included steroid injections, 5FU injections, ablative or fractionated CO2 laser, and direct excision. Pathology confirmed the lesion was a true xanthelasma in one patient. In treated patients, there was subtotal resolution after laser. Xanthelasma-like reaction resolved completely after direct excision. Three patients elected to have no treatment. Previously there has been one reported case of xanthelasma after filler injection. This case series is the largest to date. Furthermore, this series is notable because xanthelasma-like reactions appeared after injection with 3 different types of fillers. None of the patients had evidence of xanthelasma prefiller injection. The precise mechanism by which filler injection can lead to the formation of xanthelasma-like reaction is unclear. A possible mechanism may be related to binding of low-density lipoprotein and internalization by macrophages. Further investigation is required. Nevertheless, physicians performing filler injections should be aware of this new complication and treatment options.

Study of removal process of manganese using synthetic calcium hydroxyapatite from an aqueous solution

Calcium hydroxyapatite (HAP) was synthesized by a precipitation method, and it was characterized by the XRD technique. The removal of manganese(II) from an aqueous solution on HAP as a function of contact time, pH, ionic strength, temperature, and other monovalent and bivalent ions was studied using a radiotracer, 54Mn, in the batch process. The sorption of manganese on HAP was pH independent ranging from 4 to 6 due to the buffering properties of HAP. The sorption of manganese was rapid, and the percentage of manganese sorption was 99% during the first 20–30 min of the contact time, when the initial concentration of manganese ions was 1 mg/L (ppm) at pH of 5. The sorption kinetics showed that the sorption of manganese on HAP could be simulated by the pseudo-second-order kinetic model very well. The maximum sorption capacity of HAP for manganese calculated based on the Langmuir model was ~58.99 mg/g at pH 5.1 and T = 300 K. The thermodynamic parameters from the temperature-dependent sorption isotherms indicated that the manganese sorption on HAP was an endothermic and spontaneous process. It was observed that in the presence of bivalent ions like Co2+, the manganese sorption by HAP decreases, whereas it remains same in the presence of monovalent ions like Na+.

Influence of the λ780 nm laser light on the repair of surgical bone defects grafted or not with biphasic synthetic micro-granular hydroxylapatite + Beta-Calcium triphosphate

The treatment of bone loss due to different etiologic factors is difficult and many techniques aim to improve repair, including a wide range of biomaterials and, recently, photobioengineering. This work aimed to assess, through histological analysis The aim of this study was to assess, by light microscopy, the repair of bone defects grafted or not with biphasic synthetic micro-granular Calcium hydroxyapatite (HA)+Beta-TCP associated or not with Laser phototherapy – LPT (λ780nm). Forty rats were divided into 4 groups each subdivided into 2 subgroups according to the time of sacrifice (15 and 30days). Surgical bone defects were made on femur of each animal with a trephine drill. On animals of Clot group the defect was filled only by blood clot, on Laser group the defect filled with the clot was further irradiated. On animals of Biomaterial and Laser+Biomaterial groups the defect was filled by biomaterial and the last one was further irradiated (λ780nm, 70mW, spot size∼0.4cm2, 20J/cm2-session, 140J/cm2-treatment) in four points around the defect at 48-h intervals and repeated for 2weeks. At both 15th and 30th days following sacrifice, samples were taken and analyzed by light microscopy. Many similarities were observed histologically between groups on regards bone reabsorption and neoformation, inflammatory infiltrate and collagen deposition. The criterion degree of maturation, marked by the presence of basophilic lines, indicated that the use of LPT associated with HA+Beta TCP graft, resulted in more advanced stage of bone repair at the end of the experiment.

Statistical Studies of the Physicochemical Analytic Results of a Series of Synthetic Calcium Hydroxyapatite Containing Carbonate and Sodium

The objective of this study is to present a simple method of statistical calculation that allowed us to determine the relationship between the different data obtained from the characterization of the synthetic carbonated apatites containing sodium, in order to find the fundamental substitution mechanism(s) for incorporation of Na+ and CO32- and to establish the general formula. For that, a series of hydroxyapatites containing carbonate and sodium (Na-CO3HAps) has been obtained by the precipitation method. All the compounds were characterized by infrared spectra (IR), powder X-ray diffraction (PXRD) and elemental analysis. The statistical treatment of the experiment result allows us to determine the relationship between one variable and the change in the other and to found the fundamental substitution mechanism(s) for incorporation of Na+ and CO32- . Analysis of variance (ANOVA) allows us to test the models proposed.

Studies on removal of cobalt from an alkaline waste using synthetic calcium hydroxyapatite

The removal of cobalt from an alkaline waste solutions containing sodium was carried out using a radiotracer in a batch method using synthetic calcium hydroxyapatite (HAP). The influence of different parameters such as solution pH, contact time, cobalt concentration, and presence of other ions like sodium on cobalt removal was studied. The sorption process followed pseudo-second-order kinetics with necessary time of around 23–25 h to reach equilibrium and the cobalt uptake was quantitatively evaluated using the Freundlich model. The results indicated that the mechanism of cobalt removal by HAP was mainly due to chemisorption on a heterogeneous surface. In the presence of sodium, the sorption of cobalt on HAP was not affected. The sorption of cobalt on HAP was pH independent in the range from 4 to 8, because of its buffering properties. The adsorption of cobalt on HAP was fast and the percentage of cobalt sorption was >97 % during the first 30–40 min of the contact time.

Spectroscopic investigation on formation and growth of mineralized nanohydroxyapatite for bone tissue engineering applications

Synthetic calcium hydroxyapatite (HAP,Ca10(PO4)6(OH)2) is a well-known bioceramic material used in orthopaedic and dental applications because of its excellent biocompatibility and bone-bonding ability. Substitution of trace elements, such as Sr, Mg and Zn ions into the structure of calcium phosphates is the subject of widespread investigation. In this paper, we have reported the synthesis of Sr, Mg and Zn co-substituted nanohydroxyapatite by soft solution freezing method. The effect of pH on the morphology of bioceramic nanomaterial was also discussed. The in vitro bioactivity of the as-synthesized bioceramic nanomaterial was determined by soaking it in SBF for various days. The as-synthesized bioceramic nanomaterial was characterized by Fourier transform infrared spectroscopy, X- ray diffraction analysis, Scanning electron microscopy and Energy dispersive X-ray analysis and Transmission electron microscopic techniques respectively. The results obtained in our study have revealed that pH 10 was identified to induce the formation of mineralized nanohydroxyapatite. It is observed that the synthesis of bioceramic nanomaterial not only support the growth of apatite layer on its surface but also accelerate the growth which is evident from the in vitro studies. Therefore, mineralized nanohydroxyapatite is a potential candidate in bone tissue engineering.

FTIR studies of adsorption and photocatalytic decomposition under UV irradiation of dimethyl sulfide on calcium hydroxyapatite

The adsorption and photocatalytic decomposition under UV irradiation of dimethyl sulfide ((CH 3) 2S: DMS) on synthetic colloidal calcium hydroxyapatite (Ca 10(PO 4) 6(OH) 2: Hap) particles were examined by in vacuo IR measurements. The adsorption isotherms of DMS on Hap exhibited the Langmuir type. The saturated adsorbed amount of DMS was increased with increasing the outgassing temperature of Hap, showing a maximum of 2.4 molecules/nm 2 at 250 °C. Similar tendency could be observed for change in area intensity of surface P-OH bands of Hap estimated from in vacuo IR measurements against outgassing temperature. By adsorption of DMS, the surface P-OH bands of Hap weakened while the CH bands due to DMS appeared. These results revealed that the DMS was adsorbed on surface P-OH groups of Hap. When the UV light was irradiated to the DMS-adsorbed Hap, the surface P-OH bands revived and the CH bands weakened. This fact strongly indicated the photocatalytic decomposition of DMS took place on surface P-OH groups of Hap, which was thought to be due to the formation of surface P-OH radicals by UV irradiation.

A comparative study of platelet-rich plasma, hydroxyapatite, demineralized bone matrix and autologous bone to promote bone regeneration after mandibular impacted third molar extraction.

1) to compare mandibular bone regeneration by applying autologous bone, platelet-rich plasma and two biomaterials (synthetic calcium hydroxyapatite, and demineralized bone matrix), and thus establish the potential benefits of these biomaterials in the regeneration of postextraction alveolar bone, 2) to identify which of them accelerates more bone regeneration and 3) to determine whether there are differences in the postoperative period (pain, swelling, trismus, infection) depending on the material used. It consists in a prospective, controlled (with a split- mouth design) and double blinded study. We use as a model an easily reproducible non-critical bone defect: the defect that remains after extraction of mandibular impacted third molar. The study design is based on the extraction of two mandibular impacted third molars in a patient during the same surgical procedure by the same surgeon. We assessed postoperative clinical data, and short, medium and long term neoformation of alveolar bone after extraction. We compared the two sockets (right and left), which had been grafted in a different way with the various elements mentioned above. In addition, we compared the postoperative inflammatory symptoms between groups. The highest acceleration in bone formation was observed in groups in which we used autologous bone and demineralized bone matrix. There were no statistically significant differences between groups regarding pain, swelling, trismus and infection throughout the postoperative period. According to the results of our study, autologous bone persists as the gold standard material for bone regeneration. Among the assessed biomaterials, demineralized bone matrix has yielded the best results obtained. No significant differences in the postoperative (pain, swelling, trismus and infectious events) were observed, depending on the type of material used as a graft.

Effect of metal-ion-to-fuel ratio on the phase formation of bioceramic phosphates synthesized by self-propagating combustion

Synthetic calcium hydroxyapatite (HAP, Ca10 (PO4)6 (OH)2) is a well-known bioceramic material used in orthopedic and dental applications because of its excellent biocompatibility and bone-bonding ability due to its structural and compositional similarity to human bone. Here we report, for the first time, the synthesis of HAP by combustion employing tartaric acid as a fuel. Calcium nitrate is used as the source of calcium and diammonium hydrogen phosphate serves as the source of phosphate ions. Reaction processing parameters such as the pH, fuel-oxidant ratio and autoignition temperature are controlled and monitored. The products were characterized by powder x-ray diffraction, which revealed the formation of a hexagonal hydroxyapatite phase. Fourier transform infrared spectroscopy (FT-IR) spectra showed that the substitution of a carbonate ion occurs at the phosphate site. The morphology of the particles was imaged by scanning electron microscopy, which also revealed that the particles are of submicron size. Thermal analysis showed that the phase formation takes place at the time of combustion. Surface area and porosity analysis showed that the surface area is high and that the pores are of nanometer size. The mean grain size of the HAP powder, determined by the Debye–Scherrer formula, is in the range 20–30 nm. Chemical analyses to determine the Ca : P atomic ratio in synthesized ceramics were performed, and it was found to be 1 : 1.66.

The batch study of Sr2 + sorption by bone char

Considering the excellent sorption properties of synthetic calcium hydroxyapatite (HAP) towards many divalent cations, the potential application of bone char, the natural source of HAP, for sequestering Sr2 +ions from aqueous solutions has been studied in batch conditions. Contact time, initial solution pH and initial Sr2 + concentrations were varied to examine the effect of these process parameters on the amount of Sr2 + sorbed. The kinetics of Sr2+ sorption was found to be a 2-step process, with contact time of 24 h required for attaining equilibrium. The sorption isotherm was well fitted with Langmuir and DKR theoretical models. Sorption of Sr2 + on bone char was found to be a favorable, thermodynamically feasible and spontaneous process, with the maximum sorption capacity of 0.271 mmol/g and sorption energy of 11.09 kJ/mol. The sorption was pH-independent in the initial pH range 4-10, as a result of excellent buffering properties of bone char (constant final pH), while for pH > 10 sorbed amounts of Sr2 + increased due to attractive electrostatic forces between negatively charged sorbent surface and positively charged metal ions. On the basis of the amount of Ca2 + released and final pH decrease in respect to the point of zero charge of bone char (pHPZC), two possible mechanisms of Sr2 + sorption were identified: ion-exchange and the formation of complex compounds with HAP and carbon active surface sites. The amounts of Sr2 + leached from bone char increased with the increase of Ca2 + content and the decrease of solution pH. In comparison with synthetic HAP, bone char represents a cost-effective alternative for Sr2 + sequestering.

Results of a 2-Year Multicenter Trial of Endoscopic Treatment of Vesicoureteral Reflux With Synthetic Calcium Hydroxyapatite

With no FDA approved material available for endoscopic treatment of vesicoureteral reflux, in 2001 we began a prospective multicenter trial of synthetic calcium hydroxyapatite as a subureteral bulking agent in children with traditional indications for surgical repair. A total of 98 patients (155 ureters) with grades II to IV reflux were enrolled at 10 sites in the United States to obtain 86 patients with completed protocol end points at 3 months. Of the 86 patients 74 underwent renal and bladder ultrasonography, blood count and serum chemistry analysis, and VCUG at 1 year. A total of 46 patients (47%) completed 2-year study end points, including VCUG. At 1 and 2 years 24 of the 74 patients (32%) were cured. Ureteral cure rates were 46% and 40% at 1 and 2 years, respectively. With 35 patients treated and 85% compliance with the required 2-year VCUG the primary center achieved 2-year cure rates of 66% of patients and 72% of ureters. Synthetic calcium hydroxyapatite is a safe, durable and effective material for endoscopic treatment of VUR. Increased experience with the injection of synthetic calcium hydroxyapatite yields improved results.

The Effect of Different Surface Modification Agents on the Dispersion of Nano-Hydroxyapatite (n-HA) Crystallites

The surface of synthetic calcium hydroxyapatite (HA, Ca10(PO4)6(OH)2) was modified through combining freeze-drying, solvent replacement and surface modification methods in an effort to obtain the deaggregative n-HA crystallites. Three surface modification agents: Polyethylene glycol (PEG, Mw: 6000), poly(propyl oxide)-poly (ethyl oxide)-co-poly(propyl oxide)(Pluronic F-127, Mw: 12,000) and poly(d, l-lactide)-co-poly (ethylene glycol) (PELA, Mw: 20,000)were selected. The dispersion of the modified n-HA was characterized by sedimentation time in distilled water, acetone and dimethyl formamide (DMF). The results indicate that the three surface modification agents influence the dispersion of n-HA crystallites in various solvent based on different mechanisms. Transmission electron microscopy (TEM) observation shows that the dried and acetone-replacement powders are composed of needle-like HA crystallites isolated individually. The chosen solvents have a profound effect on the sedimentation time. In distilled water, the dispersion of as-synthesized n-HA crystallites is increased greater by F127 than by PEG. After freeze-drying, the two n-HA particles show homogeneous dispersion in acetone. The colloid stability of freeze-dried HA/PEG, solution-replaced HA/F127 and solution-replaced HA/PELA in DMF were improved significantly. The suspensions remained stable after 30 days with only a blue transparent sol being observed.

Structure of synthetic calcium hydroxyapatite particles modified with pyrophosphoric acid

Synthetic colloidal calcium hydroxyapatite (Ca 10(PO 4) 6(OH) 2: CaHap) was treated with pyrophosphoric acid (H 4P 2O 7: PP) in acetone and the materials were characterized by XRD, TEM, FTIR, and N 2 and H 2O adsorption measurements. XRD patterns and morphology of CaHap particles were essentially not changed by the modification. The additional amount of PO 4 of CaHap was increased with an increase of PP concentration and the Ca/P molar ratio of the particles decreased from 1.62 to 0.81. IR results indicated that the isolated surface P OH band developed with increasing the PP concentration up to 6.0 mmol dm −3 by the reaction of isolated surface P OH groups of CaHap and pyrophosphoric acids. Above 10.2 mmol dm −3 , a hydrogen-bonding surface P OH band appeared at 2913 cm −1 and enlarged with increasing the PP concentration, while the isolated surface P OH band was weakened. The results of N 2 and H 2O adsorption measurements revealed that the modified particles aggregated compared to the unmodified ones, which would be due to the formation of hydrogen-bonding surface P OH groups among the particles.

Retention of fluoride ions from aqueous solution using porous hydroxyapatite: Structure and conduction properties

Synthetic porous calcium hydroxyapatite (noted p-HAp) treated with different fluoride concentrations at room temperature in the presence of carbonate, sodium chloride and phosphate-rich media was investigated. The fluoridation rate of the porous calcium hydroxyapatite was 89% using 1 mol/L [F −] solution compared with 30% for crystalline hydroxyapatite (c-HAp). The high specific surface area of p-HAp (235 m 2 g −1) compared with c-HAp sample (47 m 2 g −1) has an important effect on the removal of fluoride ions from aqueous solution, when p-HAp was treated with high fluoride concentration to produce calcium fluorohydroxyapatite materials. Fluoride adsorption on porous hydroxyapatites (p-HAp) modified their structural and conduction properties.

Adsorption of immunogamma globulin onto various synthetic calcium hydroxyapatite particles

This paper presents data on adsorption of immunogamma globulin (IgG) onto synthetic rodlike calcium hydroxyapatite particles (CaHaps) with various particle lengths and calcium/phosphate (Ca/P) atomic ratios ranging from 1.54 to 1.65 and compares the obtained results to those of acidic (bovine serum albumin, BSA), neutral (myoglobin, MGB), and basic (lysozyme, LSZ) proteins reported before. The effect of electrolyte concentration on IgG adsorption was also examined. The initial rate of IgG adsorption was similar to that of BSA and was slower than that of MGB and LSZ. This fact was interpreted by the difference in the structural stability and molecular weight of these proteins. The isotherms of IgG adsorption onto the CaHap particles were of pseudo-Langmuir type. The saturated amount of adsorbed IgG values ( n s IgG) for the particles with mean particle length less than 70 nm decreased with increasing Ca/P ratio. The adsorption behavior of IgG molecules was very similar to that of basic LSZ, though IgG has zero net charge. The n s IgG value was increased with increased mean particle length of CaHaps; the relationship was less significant than that for BSA but similar to those for MGB and LSZ. The similar adsorption behavior of IgG and LSZ suggested that the F ab parts of IgG molecules preferentially adsorb onto CaHap to provide the reversed Y-shaped conformation of IgG. The change of the adsorption mode of IgG molecules from the reversed Y-shaped conformation to side-on by “spreading” the F c part of IgG molecules onto the particle surface over a longer adsorption time was suggested. The n s IgG value was increased with increasing electrolyte concentration by screening the intra- and intermolecular electrostatic interactions of proteins.

Surface modification of calcium hydroxyapatite with pyrophosphoric acid

The surface of synthetic colloidal calcium hydroxyapatite (Ca 10(PO 4) 6(OH) 2; CaHap) was treated with pyrophosphoric acid (H 4P 2O 7; PP) in acetone and the materials were characterized by XRD, thermal analysis, N 2 adsorption, TEM, and FTIR. No remarkable change in XRD patterns or in particle morphology by the modification was observed. The additional amount of PO 4 of CaHap was increased with an increase in PP concentration. The Ca/P molar ratio of CaHap was decreased from 1.62 to 1.35 by the modification. IR results indicated that the PP reacts with surface POH groups of CaHap to form additional surface POH groups as follows: surface POH+H 4P 2O 7→ surface POPO(OH) 2 + H 3PO 4. When the modified CaHap with Ca/P molar ratio less than 1.50 was treated at 850 °C in air, the materials transformed into β-Ca 3(PO 4) 2.