Spherical Hydroxyapatite Research Articles

Effect of processing conditions on the crystallinity and structure of carbonated calcium hydroxyapatite (CHAp)

Previous synthesis routes created apatites in low crystallinity and high crystallinity states, but a wider range will extend the design capabilities of apatites for hard tissue replacements. While high crystallinity apatites are more conventional, this work investigated lower crystallinity variations from an amorphous state to low crystallinity apatite. Carbonated hydroxyapatite was prepared by precipitating an amorphous phase followed by crystallization at 650 °C at slow (5 °C min−1) and fast heating rates (60 °C min−1). The effect of processing conditions on crystallinity and structural changes was evaluated by thermal analysis, X-ray diffraction, transmission electron microscopy, Fourier transform infrared and Raman spectroscopy. Furthermore, peak deconvolution of IR and Raman spectra resolved the carbonate and phosphate bands and revealed the carbonate and crystalline phase content in CHAp. Similar to precipitation of crystalline apatites, the crystallization at elevated temperature led to carbonate in both the phosphate and hydroxyl positions. Heating at 650 °C provided a nanosized spherical hydroxyapatite containing carbonate controlled by the heating rate. This creates a mechanism for creating a large range in crystallinity with a greater resorption capability for regenerative medicine.

加熱したCa/P モル比1.70 の球状ハイドロキシアパタイトからのCaO の析出

加熱したCa/P モル比1.70 の球状ハイドロキシアパタイトからのCaO の析出

Long-term effects of injectable hydrogel pellet for superior sulcus deformity

Objective To observe the long-term efficacy of injectable hydrogel pellets in treating superior sulcus deformity.Methods Seven cases with superior sulcus deformity received orbital volume augmentation by injectable hydrogel pellets.Preoperative and postoperative photographs and Hertel measurements were examined for the efficacy of volume replacement.Results The overall cosmetic results in superior sulcus deformity and enophthalmos were good in the early stage postoperatively.However,the superior sulcus deformity became obvious with time.Conclusion The final volume of hydrogel pellets in the enophthalmos socket is affected by many factors.The atrophy of orbital fat tissues and inflammation at the operation area are associated with surgery.The further decreased fluid from the surrounding already fluid-deprived region due to the stealing action of the hydroxyapatite sphere in the orbit was another factor. Key words: Anophthalmos, acquired; Volume, expanding; hydrogel pellets, injectable; Deformity, superior sulcus

Effect of hydroxyapatite spheres, whiskers, and nanoparticles on mechanical properties of a model BisGMA/TEGDMA composite initially and after storage

This study investigated the effect of shape, size, and surface modification of hydroxyapatite (HAP) fillers on the degree of conversion (DC) and mechanical properties of a model BisGMA/TEGDMA composite initially and after 4 weeks of storage. Ten percent of conventional glass fillers were replaced by HAP spheres (Sph), silicon-doped spheres (SphSi), whiskers (Wh), silicon-doped whiskers (WhSi), and nanosized HAP particles (Nano). Spheres were specifically structured agglomerates consisting of a central void and radially orientated primary particles, whereas whiskers were compact monocrystals. DC, Vickers hardness (HV), flexural strength (Fs), flexural modulus (Ef), compressive strength (Cs), and compressive modulus (Ec) were tested. There were no significant differences in the DC between all tested groups. HV decreased by 5.4-17% with the addition of HAP, while Fs increased by 13.9-29% except in Nano group (decrease by 13%). After storage, Sph and SphSi groups showed similar HV, Ef, Cs and Ec and higher Fs than the control. The fracture mode of HAP spheres was through the central void whereas whiskers showed longitudinal delamination, transverse, and mixed fractures. HAP spheres with or without silicon- doping have a potential to be part of the filler content of dental composites.

Porous and spherical hydroxyapatite microcomposites for immunoglobulin G adsorption

ABSTRACTA novel porous and spherical hydroxyapatite (HA) microcomposite with an average diameter of 50–100 μm was produced by suspension polymerization for the adsorption of human immunoglobulin G (IgG). The specific surface area of the pure HA and HA microcomposite were found to be 80.25 and 182.53 m2/g, respectively. Characterizations were performed with X‐ray diffraction, Fourier transform infrared spectroscopy, thermogravimetric analysis, and scanning electron microscopy analysis. The swelling ratio of the spherical HA microcomposites was 170%. The maximum adsorption of IgG from aqueous solution was observed at pH 7.0 (5 mM phosphate buffer) and at 45°C in a batch system in which parallel separate experiments were performed independently. An IgG adsorption capacity value of up to 140 mg/g was obtained for the HA microcomposite. The IgG molecules could be repeatedly adsorbed and desorbed through the use of spherical microcomposites without a noticeable loss in the IgG adsorption capacity. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 2764–2771, 2013

Facile template-free synthesis of carbonated hydroxyapatite spheres in aqueous solution

Prickly carbonated hydroxyapatite(CHAp) spheres were obtained via a facile template-free self-assembly method with Na2HPO4 and self-made cubic CaCO3 as reactants. X-ray diffraction results of the product revealed CHAp with high crystallinity could be successfully prepared in a short reaction time. A nucleation mechanism was proposed according to the results of characterizing the resultant powders and analyzing the growth process. It shows that the self-made CaCO3 particles play an important role in the template-free synthesis of prickly spheres.

Separation of lysozyme with magnetically stabilized spherical hydroxyapatite microcomposites in a continuous flow system

ABSTRACTThe aim of this study was to produce a spherical and magnetic hydroxyapatite (HA) microcomposite to use as an adsorbent for the separation of lysozyme in a magnetically stabilized fluidized bed and to separate lysozyme from a protein mixture composed of human immunoglobulin G, human serum albumin, and lysozyme. For this purpose, spherical and magnetic HA microcomposites (50–100 μm) were synthesized by suspension polymerization and characterized by Fourier transform infrared spectroscopy, X‐ray diffraction, scanning electron microscopy, electron spin resonance, vibrating‐sample magnetometry, Brunauer–Emmett–Teller analysis, and a swelling test. The specific surface areas of the pure HA and magnetic HA microcomposite were determined to be 72.25 and 151.53 m2/g, respectively. The swelling ratio of the spherical HA microcomposites was 150%. Adsorption experiments were conducted under conditions that differed in terms of pH, temperature, ionic strength, flow velocity, and magnetic field. According to the findings of the adsorption kinetic studies, the adsorption process was appropriate to pseudo‐first‐order kinetics. The separation of the lysozyme from the protein mixture was achieved by means of a 50 mM pH 7.0 phosphate buffer. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 1602–1610, 2013

Nanocrystalline spherical hydroxyapatite granules for bone repair: in vitro evaluation with osteoblast-like cells and osteoclasts

Conventionally sintered hydroxyapatite-based materials for bone repair show poor resorbability due to the loss of nanocrystallinity. The present study describes a method to establish nanocrystalline hydroxyapatite granules. The material was prepared by ionotropic gelation of an alginate sol containing hydroxyapatite (HA) powder. Subsequent thermal elimination of alginate at 650°C yielded non-sintered, but unexpectedly stable hydroxyapatite granules. By adding stearic acid as an organic filler to the alginate/HA suspension, the granules exhibited macropores after thermal treatment. A third type of material was achieved by additional coating of the granules with silica particles. Microstructure and specific surface area of the different materials were characterized in comparison to the already established granular calcium phosphate material Cerasorb M(®). Cytocompatibility and potential for bone regeneration of the materials was evaluated by in vitro examinations with osteosarcoma cells and osteoclasts. Osteoblast-like SaOS-2 cells proliferated on all examined materials and showed the typical increase of alkaline phosphatase (ALP) activity during cultivation. Expression of bone-related genes coding for ALP, osteonectin, osteopontin, osteocalcin and bone sialoprotein II on the materials was proven by RT-PCR. Human monocytes were seeded onto the different granules and osteoclastogenesis was examined by activity measurement of tartrate-specific acid phosphatase (TRAP). Gene expression analysis after 23days of cultivation revealed an increased expression of osteoclast-related genes TRAP, vitronectin receptor and cathepsin K, which was on the same level for all examined materials. These results indicate, that the nanocrystalline granular materials are of clinical interest, especially for bone regeneration.

Long-term biocompatibility evaluation of 0.5 % zinc containing hydroxyapatite in rabbits

This study investigates the long-term biocompatibility of 0.5% zinc-containing hydroxyapatite compared with hydroxyapatite. Spheres (425<∅<550) of both materials were produced by extrusion of ceramic slurry in calcium chloride and characterized by FTIR, XRD, XRF and SEM. Fifteen White New Zealand rabbits were submitted to general anesthesia, and an perforation (2mm), was made in each tibia, one for zinc-containing hydroxyapatite sphere implantation and one for hydroxyapatite sphere implantation. After 26, 52 and 78weeks, the animals were euthanized, and the fragment containing the biomaterial was harvested. A 30-50μm section was obtained for histological analysis in bright field and polarized light. SEM images revealed similar morphologies between the tested biomaterials. Histological analysis showed that there was no difference between the test groups. The morphometric analysis, however, indicates that there was a greater absorption. The materials are biocompatible, promote osteogenesis and that the zinc-containing hydroxyapatite microspheres were absorbed more quickly.

Dynamic competitive adsorption of bone‐related proteins on calcium phosphate ceramic particles with different phase composition and microstructure

The biocompatibility and bioactivity of biomaterials used for hard tissue repair are closely related to their adsorption capacities for bone-related proteins. In the present study, three types of calcium phosphate (CaP) ceramic particles with different phase composition or microstructure were fabricated, and their protein adsorption abilities were investigated by a self-made device under the simulated dynamic physiological circumstance. The results of X-ray diffraction, field emission scanning electron microscopy, mercury penetration test, and nitrogen sorption test showed that the irregular hydroxyapatite (HA) ceramic particles obtained by conventional drying and sintering (named as HA-C) had fewer micropores and lower specific surface area (SSA) than did the spherical HA or biphasic calcium phosphate (BCP) ceramic particles made by spray drying and sintering (named as HA-S and BCP-S, respectively). The dynamic protein adsorption study proved that both the phase composition and microstructure of CaP ceramic particles affected their adsorption capacities for those bone-related proteins. The spherical HA-S and BCP-S particles with abundant micropores and high SSA showed higher adsorption of serum proteins, including fibronectin and vitronectin, than the irregular HA-C did. On the other hand, in spite of the relatively high concentration of bovine serum albumin (BSA) in the binary bone morphogenetic protein 2 (BMP-2)/BSA solution, BMP-2 adsorption on the three CaP ceramic particles increased with the increase in its initial concentration. Similarly, HA-S and BCP-S particles had a larger amount of the adsorbed BMP-2 per gram solid than HA-C did. Therefore, it could be believed that the difference of various CaP ceramics in the phase composition and microporous structure would affect their binding capacity for those bone-related proteins and thus lead to their difference in osteoinduction.

Preparation and evaluation of spherical Ca-deficient hydroxyapatite granules with controlled surface microstructure as drug carriers

Spherical Ca-deficient hydroxyapatite (HA) granules are expected to be useful drug carriers in bony sites because of their bone regeneration and adsorption ability. In order to control drug loading and release ability of the granules, a controlled surface microstructure was constructed. Spherical Ca-deficient granules composed of micron-sized rod-shaped particles were prepared by hydrothermal treatment of α-tricalcium phosphate (α-TCP) granules, and then, submicron HA particles were precipitated on the obtained granules by immersion in a supersaturated calcium phosphate (CP) solution. When bovine serum albumin was used as a drug model, precipitation of submicron particles causes the loading capability to increase and the release rate to decrease. The spherical Ca-deficient HA granules with the controlled surface microstructure are expected to be useful drug carriers that can act as scaffolds for bone repair.

Research on Preparation and Biological Properties of Dense Hydroxyapatite Spheres

By using carboxy methyl chitosan(CMCS) and gelatin(Gel) as adhesive,the nano–HA slurry which was fabricated via a precipitation process as the raw material,dense HA spheres with a uniform size distribution and good geometry were prepared successfully by means of Sol-Gel method.Dense HA spheres with a porosity of 4.7%±0.6% have a higher compressive strength(8.9±0.4) MPa than that of porous HA spheres(7.9±0.2) MPa with a porosity of 16.4%±0.5%(particles with diameter of 0.5 mm).The results of biomimetic mineralization and cell culture show that dense HA spheres have an excellent biological property.

Fabricating Porous Hydroxyapatite Spheres by a Polymer Sol Route for Biomedical Application

Fabricating Porous Hydroxyapatite Spheres by a Polymer Sol Route for Biomedical Application

Bone forming potential of Sr doped hydroxyapatite hollow spheres in a rat vertebral bone defect model

Bone forming potential of Sr doped hydroxyapatite hollow spheres in a rat vertebral bone defect model

A novel injectable chitosan/polyglutamate polyelectrolyte complex hydrogel with hydroxyapatite for soft-tissue augmentation

This study demonstrated a chitosan (CS)/polyglutamate (PG) polyelectrolyte complex (PEC) hydrogel combined with spherical hydroxyapatite (HAp) particles as an injectable dermal filler for soft-tissue augmentation. The CS/PG PEC hydrogel with oppositely charged ionic cross-linking, a high gel content, and low degradation rate was introduced as a carrier to achieve high shape and volume stability. An MTT assay indicated that the CS/PG PEC had satisfactory cell biocompatibility. This PEC/HAp hydrogel showed good structural integrity in a PBS solution for up to 60 days. Clinical manageability was indexed by an injection force measurement through sterile 27-gauge needles using a texture analyzer. In an animal study, 0.2mL of the PEC and PEC/hydroxyapatite (HAp) were implanted within the dorsal dermis of a swine ear. Injected tissue areas were biopsied 2 weeks, and 2 and 6 months after the injection. According to the histomorphometric results, the PEC and PEC/HAp groups showed percentages of retention of the maximum height of the cross-section of about 44% and 73% at 6 months. New collagen was observed in the central position indicating a possible collagenesis effect. These results suggest that this PEC/HAp system can be used as an alternative for soft-tissue augmentation.

Antimicrobial Performance and Cytotoxicity of Antibiotics Impregnated Hydroxyapatite for Osteomyelitis Treatment

Localized antibiotic beads are often used for treating patients with osteomyelitis or infections of the bone by providing local, sustained and high concentrations of antimicrobial agents to the area of infection, without systemically exposing an individual to antibiotic levels that could result in numerous toxic side effects. In this study, antibiotic impregnated hydroxyapatite spheres were prepared aiming for a functional device of drug carrier and bone graft. Three types of antibiotics were employed including gentamicin, vancomycin and fosfomycin. Antimicrobial susceptibility of antibiotic impregnated beads were tested against two bacterial strains (Pseudomonas aeruginosa ATCC 27853 and Staphylococcus aureus ATCC 25923) by using modified agar diffusion assay. Differences in antimicrobial efficiency were observed and related with respect to differences in molecular weight, mechanism of action and spectrum of activity for each antibiotic. Cytotoxicity by serial extraction technique of all antibiotic impregnated beads were determined by MTT assay. No cytotoxic potential at all extraction periods was observed for vancomycin impregnated on beads. Gentamicin and fosfomycin impregnated beads showed cytotoxic potential only on day 1 extraction, but no cytotoxic potential on longer periods.

A further insight into pores in plasma sprayed hydroxyapatite coating

Pores in hydroxyapatite (HA) coatings affect their mechanical and biological performances, and so far pore characteristic and formation mechanism are not fully understood. In the present study, microstructural observations on plasma sprayed HA coating have been carried out, indicating that globular pores exist commonly on coating surface, cross-sectional facet and fracture surface. Analysis of HA particles plasma sprayed into water shows that hollow HA spheres were formed, and the hollow spheres will transform into globular pores when they impact onto the substrate.

One-Stage Replacement Surgery of Orbital Implants With Noninfectious Complications

Orbital implant-associated complications always affect patients, resulting in multiple operations. One-stage replacement of complicated implants has been attractive for reducing operation times and preventing long-time appearance without artificial eye. We retrospectively analyzed the outcomes of 1-stage replacement surgery of orbital implant. A total of 21 eyes in 21 cases with noninfectious complications, who failed conservative therapies and surgical repairs, were treated with 1-stage orbital implant replacement. After a detailed ophthalmic history was obtained and examinations performed, patients with apparent purulent secretion in conjunctival sac were excluded. The preexisting orbital implant was carefully removed, and a new hydroxyapatite sphere was implanted simultaneously. Wound healing status, prosthesis movement, and cosmetic features were evaluated and recorded after at least 6 months' follow-up. Orbital implant exposure(16 cases) was the main indication of the replacement surgery; other causes included superior orbital area depression (2 cases), conjunctival fistula (1 case), orbital implant malposition (1 case), and the metal material of implant obstructing magnetic resonance imaging scan in 1 case. Eye-socket hollow was redressed in all cases immediately, and 95.23% cases (20/21) could wear an artificial eye and had a good cosmetic appearance, whereas conjunctival sac fistula reoccurred in 1 patient, and the implant was removed ultimately. Conjunctival sac constrictions occurred in 4 cases after operation and were treated by secondary conjunctival sac reconstruction 6 months later. In conclusion, 1-stage replacement of orbital implants offers an effective and efficient strategy for dealing with severe postimplantation noninfectious complications in achieving a symmetrically cosmetic appearance without delay.

Bone‐nanohydroxyapatite spheres interface evaluation by synchrotron radiation X‐ray microfluorescence

Hydroxyapatite (HA) is largely used as bone graft; it seems to be the most promising synthetic implant material, mainly because of its excellent biocompatibility. The crystallinity, particle and pore size of HA are important characteristics and can be modified by decreasing basic structural form below 100 nm and have evoked a great amount of attention for improving prevention, diagnosis, and disease treatment, besides improving bone repair through the biodegradation of the material. The aim of this study was to investigate bone mineral content in bone samples with nanohydroxyapatite and HA spheres, specially its spatial distribution on bone microarchitecture. Circular bone defects were made in both tibiae of 12 White New Zeland adult rabbits (Oryctolagus cuniculus) and were divided randomly into five groups – blood clot (control group), sintered HA, non‐sintered HA, sintered nanoHA and non‐sintered nanoHA – all materials in spherical shape, to smooth handling and accommodation of the surgical bed, and to minimize inflammatory response. The rabbits were euthanatized according to the experimental period of 1 and 4 weeks after surgery. The samples were evaluated by polarized microscopy as well as X‐ray microfluorescence in order to account the bone mineral content bone‐implant interfaces, through synchrotron radiation. Our results revealed greater newly formed bone area in the non‐sintered materials and control groups, and the used technique showed that the amount of calcium of new bone was consistent with both mature bone and HA spheres. In conclusion, the present findings suggest that HA‐based biomaterials are biocompatible, promote osteoconduction and favored bone repair. Copyright © 2011 John Wiley &amp; Sons, Ltd.

Preparation of Submicron-Sized Hydroxyapatite Powders by Spray Pyrolysis

Dense and submicron-sized hydroxyapatite powders were synthesized through spray pyrolysis of calcium phosphate solution with polyethylene glycol (PEG). Irregular shaped and fragile hydroxyapatite aggregates, and spherical and hollow hydroxyapatite particles were obtained after spray pyrolysis at 1100 °C when using calcium phosphate solution with and without PEG, respectively. After dewaxing at 650 °C for 3 hours, the hydroxyapatite aggregates were broken into submicron-sized particles whereas micron-sized spherical hollow particles were almost intact. The relative densities of hydroxyapatite disks made by submicron and micron sized hydroxyapatite particles were about 90% and 81%, respectively, after sintering at 1110 °C for 3 hours. The results were explained in terms of the disintegrating function of carbon which was previously formed among the hydroxyapatite aggregates by the decomposition of PEG during spray pyrolysis.