Hydroxyapatite Calcium Phosphate Research Articles

In vitro corrosion investigations of plasma-sprayed hydroxyapatite and hydroxyapatite-calcium phosphate coatings on 316L SS

The present paper discusses various issues associated with biological corrosion of uncoated and plasma-sprayed hydroxyapatite (HA)-coated 316L SS and studies the effect of contents of calcium phosphate (CaP) on corrosion behaviour of hydroxyapatite (HA) coatings in simulated body fluid (Ringer’s solution). Three types of coatings, i.e. HA + 20 wt% CaP (type 1), HA + 10 wt% CaP (type 2), HA (type 3), were laid on 316L SS using plasma-spraying technique. Structural characterization techniques including X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX) were used to investigate the crystallinity, microstructure and morphology of the coatings. Electrochemical potentiodynamic tests were performed to determine the corrosion resistance of uncoated and all the three coatings. After the electrochemical corrosion testing, the samples were examined by XRD, SEM and EDX. The electrochemical study showed a significant improvement in the corrosion resistance after HA coating and corrosion resistance of type 3 coating was found maximum.

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.

Tumoral Calcinosis in the Nose in a Patient With Scleroderma

Tumoral calcinosis is a rare calcifying disorder with deposition of calcium phosphate and calcium hydroxyapatite within the soft tissue at periarticular sites. There have been series of sporadic cases of tumoral calcinosis in the trunk and the extremities due to renal failure. However, we describe a 35-year-old woman without renal problems or trauma history who had tumoral calcinosis in the nose. This is the first report on facial occurrence.

Properties of Gelatin/Carbonate Apatite Composite Compared to Bovine Bone

Bone is a composite of approximately 65% inorganic phase (carbonate apatite, CHA) and a 35% organic phase (mostly collagen). To date, several commercial composites consisting of natural or synthetic polymers and calcium phosphates ( hydroxyapatite, tricalcium phosphate, biphasic calcium phosphates) are recommended for use in bone repair. Objective: The aim of this study was to compare the physico-chemical properties of gelatin/carbonate apatite composites with that of bovine bone. Native (Gel) or cross-linked (Gel*) was used. Methods: The CHA was prepared by hydrolysis method. The gelatin (denatured collagen) was cross-linked using Genipin. The gelatin/CHA composite were prepared by mixing of 35% gelatin and 65% CHA and freeze-drying. The composites were characterized using x-ray diffraction (XRD), FT-IR spectroscopy, scanning electron microscopy (SEM) and thermogravimetry (TGA). Dissolution properties were determined in acidic buffer (0.1M KAc, pH 6, 37°C). Mechanical strength was determined using 3-point bend test. Bovine bone was similarly characterized for comparison. Results: The composition and crystallite size of the CHA were similar to that of the bone mineral. The Gel/CHA and Gel*/CHA composites showed several physico-chemical properties (crystallinity, composition, thermal stability, mechanical strength, dissolution rate) similar to that of bone. Gel*/CHA compared to Gel/CHA composites showed lower elastic modulus, flexural strength, dissolution rate, swelling and higher porosity. Conclusion: The Gel*/CHA composites presented several properties similar to those of bovine bone and may have potential as bone substitute materials.

Arsenic Removal by Precipitation with Calcium Phosphate Hydroxyapatite

The removal of arsenic from synthetic arsenic contaminated water sample by precipitating arsenic (in the form of arsenate oxyanion) with calcium phosphate hydroxyapatite, HAp, was studied under conditions that induce arsenate incorporated calcium phosphate hydroxyapatite, Ca (P/As)HAp, to form. Arsenate is able to substitute for a fraction of the phosphate in HAp host material as it forms. Consequently, arsenic is successfully removed from the contaminated water achieving up to 99% arsenic removal from 25 ppm initial arsenic concentration. The Ca:(P+As) and P:As mole ratios were found to play an important role in arsenic removal efficiency. Higher Ca:(P+As) and P:As mole ratios give higher arsenic removal efficiency. Surprisingly, the pH of the initial anion solution, a key parameter in arsenic speciation, was found to not have a significant effect on arsenic removal by this process. The advantage of this process is that the precipitation can occur rapidly at relatively low levels of arsenic contamination, implying an easy and inexpensive process for arsenic removal can be developed based on this approach.

Application of hydroxyapatite-calcium phosphate in nasal augmentation

Objective To investigate the practicability and maneuverability of applying partical hydroxylaptite artificial bone to rehabilitate saddle nose as well as removing materials from the malposition of nasal implant.Methods We used the incision beside nasal columella and detached atunnel in deep of nasal aponeurosis.Then we put hydroxyapatite into the detached tunnel,at the same time press position of operation from skin to obtain a nice form.At last we sewed up the incision.Results In 15000 cases of nasal implant operations with follow-up within last 18 years,the successful cases were 94 ％,while the failing ones were 6 ％.Conclusions Applying partical hydroxylaptite artificial bone to saddle nose and nasal implant can obtain a satisfactory,long-tcrm and stable result.It can he an optional surgical method in nasal augmentation. Key words: Hydroxyapatite-calcium phosphate; Nasal augmentation; Saddle nose

Mechanical characteristics of composites of polylactide and nanosized calcium phosphates formed in supercritical carbon dioxide

Composite materials for biomedical applications based on polylactide, a bioresorbable polymer, and nanosized calcium phosphate (hydroxyapatite) were produced using supercritical (SC) carbon dioxide. For composites with different polymer-to-mineral ratios, the bending stress-strain diagrams were investigated. The elasticity moduli of composites obtained in SC-CO2 from powdered bioresorbable polymer and bioactive nanoceramics ranged elastic modulus of natural bone. Experiments on adhesion of human embryonic fibroblasts demonstrated the suitability of generated samples for use in bone tissue scaffold engineering and regenerative medicine.

Biomimetic chitosan–calcium phosphate composites with potential applications as bone substitutes: Preparation and characterization

A novel biomimetic technique for obtaining chitosan-calcium phosphates (Cs-CP) scaffolds are presented: calcium phosphates are precipitated from its precursors, CaCl(2) and NaH(2) PO(4) on the Cs matrix, under physiological conditions (human body temperature and body fluid pH; 37°C and pH = 7.2, respectively). Materials composition and structure have been confirmed by various techniques: elemental analysis, Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDX), and scanning electron microscopy (SEM). FTIR and SEM data have shown the arrangement of the calcium phosphates-hydroxyapatite (CP-Hap) onto Cs matrix. In this case the polymer is acting as glue, bonding the calcium phosphates crystals. Behavior in biological simulated fluids (phosphate buffer solution-PBS and PBS-albumin) revealed an important contribution of the chelation between -NH3(+) and Ca(2+) on the scaffold interaction with aqueous mediums; increased quantities of chitosan in composites permit the interaction with human albumin and improve the retention of fluid. The composites are slightly degraded by the lysozyme which facilitates an in vivo degradation control of bone substitutes. Modulus of elasticity is strongly dependent of the ratio chitosan/calcium phosphates and recommends the obtained biomimetic composites as promising materials for a prospective bone application.

Catalytic Conversions of Biomass Derivatives Over Apatite Compounds

Calcium phosphate hydroxyapatite, Ca10(PO4)6(OH)2, is a typical apatite compound which has a high thermal stability and an affinity for organic compounds of biomass derivatives. It has a capacity for substitutions of Ca2+ ions and PO43- ions by other cations and anions. Here in, we will report the selective conversions of biomass derivatives, such as ethanol and lactic acid, into useful chemicals over the apatite compounds, such as Ca10(PO4)6(OH)2, Sr10(PO4)6(OH)2, Pb10(PO4)6(OH)2, and Ca10(VO4)6(OH)2. The apatite compounds were powders prepared by the hydrothermal method. In the ethanol conversion, the Sr-P apatite catalyst exhibited high 1-butanol selectivity (sel. > 80 C-%), which was significantly higher than that over the Ca-P apatite catalyst. In contrast, the Pb-P apatite catalyst selectively gave acetaldehyde, and the Ca-V apatite catalyst accelerated the dehydration into ethylene.

Phase composition of ceramic based on calcium hydroxyapatite powders containing byproducts of the synthesis reaction

Ceramic materials based on calcium phosphates are widely used to manufacture bone implants. Such materials can be single-phase or a multiphase composite. Some properties of the materials based on calcium phosphates, for example, solubility, largely depend on the phase composition. The Ca : P ratio (molar) for different calcium phosphates ranges from 0.5 for monocalcium phosphate Ca(H 2 PO 4 ) 2 to 2 for tetracalcium phosphate Ca 4 (PO 4 ) 2 O. Calcium hydroxyapatite (HAP) Ca 10 (PO 4 ) 6 (OH) 2 with C a:P= 1.67 exhibits the lowest solubility. As a rule, in monophase materials based on calcium phosphates HAP is a bioresistive phase, i.e., a phase that resists dissolution during implantation. In ceramic composite materials the bioresorbable phases can be represented by calcium-deficient HAP (Ca-DHAP), tricalcium phosphate (TCP) Ca 3 (PO 4 ) 2 , calcium pyrophosphate (CPP) Ca 2 P 2 O 7 , renanite NaCaPO 4 , double potassium calcium phosphate KCaPO 4 , calcium carbonate CaCO 3 , double potassium calcium or sodium potassium carbonates, and glasses in the systems CaO – P 2 O 5 ,C aO –P 2 O 5 –N a 2 O, CaO – P 2 O 5 –K 2 O, CaO – P 2 O 5 – SiO 2 –N a 2 O, and CaO – P 2 O 5 – SiO 2 –K 2 O. The choice of system for obtaining biocompatible materials based on calcium phosphates is determined by the elements contained in the structure of natural bone. Powders with high sintering activity must be used to ob

Correction of facial linear scleroderma ‘coup de sabre’ with BoneSource ®

Linear scleroderma is a subtype of localised scleroderma. When linear scleroderma occurs on the anterior portion of the scalp and forehead, it may assume an ivory-like, depressed configuration similar to the stroke of a sabre and called 'coup de sabre'. Atrophic changes affect subcutaneous tissue and skin, with later involvement of the muscles and osteocartilaginous framework. Various operative interventions, such as skin flap, fat graft, dermofat graft and bone graft could be used for correction of this deformity, but there is no definite satisfactory treatment modality. We report the case of a 19-year-old female with a band-like indurated skin lesion with depression in the frontoparietal region of the scalp. Through bicoronal incision and subperiosteal dissection the defect was fully exposed. The depressive lesion was slightly hyperaugmented using BoneSource (calcium phosphate hydroxyapatite cement; Stryker Leibinger Corp., Kalamazoo, MI, USA), considering skin and soft tissue atrophy. Surgical outcome was excellent in cosmetic and functional aspects without any complication. The patient was followed for 36 months after the operation; the defect was satisfactorily corrected and no postoperative problems have been found.

Growth of hydroxyapatite in a biocompatible mesoporous ordered silica

A novel biomaterial (HA-SBA-15) has been developed based on the growth of calcium phosphate hydroxyapatite (HA) nanoparticles within an organized silica structure (SBA-15). Characterization of the material was carried out using a combination of X-ray diffraction, X-ray fluorescence, transmission electron microscopy, N 2 adsorption–desorption isotherms and nuclear magnetic resonance. Transmission electron microscopy observations and N 2 porosimetry revealed the crystallization of hydroxyapatite nanoparticles inside the mesopore cavities of the silica structure. Specific surface areas of 760 m 2 g −1 and 260 m 2 g −1 were measured for the SBA-15 and the HA-SBA-15 material, respectively. The hydroxyl groups present in the silica nanostructure surface have brought about cationic defects in the silicium sites, mainly with those of tetrahedral symmetry, and promoted the formation of siloxanes. 29Si MAS-NMR analysis shows a significant reduction of the silanol groups concentration with HA growing within the base (SBA-15) material. Studies and brain tissue biocompatibility tests were carried out. Histopathological studies on the SBA-15 implant material showed no changes to the tissue nearby. The results confirmed the synthesis of a silica-based composite containing HA nanoparticles with the potential for biomedical applications.

Interface science in formation of biominerals and biomolecules

The prototype for the minerals in bone and teeth is usually considered to be the basic calcium phosphate hydroxyapatite (HA), containing impurities, such as carbonate and structural defects. It has been proposed that the biological apatite is formed via precursor phases, such as octacalcium phosphate (OCP). The initial precursors maturate with aging and may alter its surface property depending on the proceeding of the hydrolysis into HA regarding adsorption affinity for various biomolecules existing around the forming biominerals. The maturation of the biominerals could be modulating the process of additional mineralization after the initial mineral deposition happened within the hard tissues.

Biocompatibility of calcium phosphate-coated and of geometrically structured nickel–titanium (NiTi) by in vitro testing methods

Abstract Nickel–titanium shape memory alloys (NiTi-SMA) have outstanding mechanical properties (superelasticity, shape memory effect) that make them very interesting for clinical applications. Due to the high nickel content of the material, there are concerns about possible immunological reactions of the surrounding tissue. The proliferation of osteoblast-like cells (MG-63) and the cytokine release (interleukin (IL)-6, IL-8, tumor necrosis factor (TNF)-α) from polymorphonuclear neutrophil (PMN) leukocytes as well as peripheral blood mononuclear cells (PBMC) in response to different NiTi specimen was studied: (a) NiTi coated with calcium phosphate (octacalcium phosphate + hydroxyapatite; OCP/HAP) from an supersaturated aqueous solution, consisting of a dense layer of sharp-edged platelets; (b) NiTi coated with calcium phosphate (hydroxyapatite) by high-temperature plasma-spraying, consisting of a rough dense layer of globular particles; (c) NiTi after geometrical structuring (microdrilling). In the first two cases, the aim was to improve the biocompatibility while retaining the mechanical properties. In the third case, the effect of mechanical treatment (damage of the passivating TiO 2 surface layer) was investigated. In comparison to non-coated samples the OCP/HAP-coated SMA led to an increase in the release of cytokines, in contrast, the HAP-coated samples led to a decrease in cytokine release from PBMC. The attachment, viability, and the proliferation of MG-63-cells in the near vicinity of microdrilled structures was not different from non-strained surface areas. These results show that cell-biological in vitro techniques are suitable for the prediction of tissue reactions towards implant coatings or mechanically altered NiTi-surfaces. The surface morphology (platelets versus globular particles) appear to play a significant role that supersedes that of the chemical composition of the surface.

Process-phase-properties relationship in radio frequency (RF) plasma synthesized hydroxyapatite (HA)

Radio frequency suspension plasma spraying (RFSPS) was used to synthesize ultra-fine (20 nm–2 μm) hydroxyapatite (HA)–Ca 10(PO 4) 6(OH) 2 and ZrO 2–HA–Calcium Phosphate (CaP) nano-composite powders. The ultra-fine powders were consolidated using the spark plasma sintering (SPS) process and in-vitro investigation of the sintered compacts revealed bioactive behavior inherent in the original powder. The influence of various plasma processing parameters and HA suspension concentrations on the characteristics of the as-sprayed powders were studied. The powders were characterized using particle size measurements, X-ray diffraction (XRD), scanning electron microscopy (SEM), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM) and differential scanning calorimetry (DSC). It was revealed from XRD and TEM analysis that a significant amount of amorphous material contributed to the overall phase composition of plasma processed HA. Consequently, quantitative XRD analysis was performed with the Rietveld technique, employing alumina (Al 2O 3) as the internal standard. As-sprayed powders produced with miscellaneous plate power levels and suspension concentrations, were analyzed. Rietveld analysis also determined structural changes to the HA lattice after the spray process. The compacts consolidated through SPS from ultra-fine HA powders exhibited Young's modulus and microhardness of approximately 103 GPa and 550 Hv, respectively, and fracture toughness ∼1.2 MPa m 1/2. In-vitro results indicated that the compacts were bioactive revealing a precipitated layer of apatite one week following immersion.

Quantification in situ of crystalline cholesterol and calcium phosphate hydroxyapatite in human atherosclerotic plaques by solid-state magic angle spinning NMR.

Because of renewed interest in the progression, stabilization, and regression of atherosclerotic plaques, it has become important to develop methods for characterizing structural features of plaques in situ and noninvasively. We present a nondestructive method for ex vivo quantification of 2 solid-phase components of plaques: crystalline cholesterol and calcium phosphate salts. Magic angle spinning (MAS) nuclear magnetic resonance (NMR) spectra of human carotid endarterectomy plaques revealed (13)C resonances of crystalline cholesterol monohydrate and a (31)P resonance of calcium phosphate hydroxyapatite (CPH). The spectra were obtained under conditions in which there was little or no interference from other chemical components and were suitable for quantification in situ of the crystalline cholesterol and CPH. Carotid atherosclerotic plaques showed a wide variation in their crystalline cholesterol content. The calculated molar ratio of liquid-crystalline cholesterol to phospholipid ranged from 1.1 to 1.7, demonstrating different capabilities of the phospholipids to reduce crystallization of cholesterol. The spectral properties of the phosphate groups in CPH in carotid plaques were identical to those of CPH in bone. (31)P MAS NMR is a simple, rapid method for quantification of calcium phosphate salts in tissue without extraction and time-consuming chemical analysis. Crystalline phases in intact atherosclerotic plaques (ex vivo) can be quantified accurately by solid-state (13)C and (31)P MAS NMR spectroscopy.

Calcium and disease: molecular determinants of calcium crystal deposition diseases.

Deposition of basic calcium phosphate (hydroxyapatite, octacalcium phosphate and tricalcium phosphate) (BCP) and crystalline calcium pyrophosphate dihydrate (CPPD) is associated with a variety of aging-related pathologies, including osteoarthritis, cartilage degeneration and pseudogout. These diseases of calcium deposition serve as some of the best-studied examples of how calcium-regulated changes in gene expression can directly lead to pathogenic consequences. Tissue damage can result when crystals stimulate cells to release matrix-degrading molecules or secrete cytokines that stimulate the release of matrix-degrading molecules. Exposure of cultured cells to crystals induces expression of cellular proto-oncogenes such as c-fos, c-myc and c-jun, by a calcium-dependent mechanism, and this response can be blocked by a potential therapeutic compound, phosphocitrate. Activation of the c-fos and c-jun genes is directly involved in expression of metalloproteinases such as collagenase and stromelysin, suggesting that crystal-mediated activation of these genes is directly involved in pathogenesis. In this review recent advances in the molecular mechanisms responsible for crystal-mediated cell activation are discussed.

Transformation of amorphous calcium phosphate hydroxyapatite in the presence of some ions.

Transformation of amorphous calcium phosphate hydroxyapatite in the presence of some ions.

Determination of cholecalciferol and related substances by calcium phosphate hydroxyapatite and calcium phosphate fluoroapatite high-performance liquid chromatography

Abstract A qualitative and comparative study by HPLC using two new stationary phases, hydroxy- and fluoroapatites, showed the separation under optimized conditions of vitamin D 3 and its related compounds, produced by irradiation and heating of provitamin D 3 .

MRI of orbital hydroxyapatite implants.

Our aim was to use MRI for the postsurgical assessment of a new form of integrated orbital implant composed of a porous calcium phosphate hydroxyapatite substrate. We studied ten patients 24-74 years of age who underwent enucleation and implantation of a hydroxyapatite ball; 5-13 months after surgery, each patient was examined by spinecho MRI, with fat suppression and gadolinium enhancement. Fibrovascular ingrowth was demonstrated in all ten patients as areas of enhancement at the periphery of the hydroxyapatite sphere that extended to the center to a variable degree. The radiologist should aware of the MRI appearances of the coralline hydroxyapatite orbital implant since it is now widely used following enucleation. MRI is a useful means to determine successful incorporation of the substrate into the orbital tissues. The normal pattern of contrast enhancement should not be mistaken for recurrent tumor or infection.