Formation Of Calcium Phosphate Phases Research Articles

Impact of ZrO2 Content on the Formation of Sr-Enriched Phosphates in Al2O3/ZrO2 Nanocomposites for Bone Tissue Engineering.

This study investigates the profound impact of the ZrO2 inclusion volume on the characteristics of Al2O3/ZrO2 nanocomposites, particularly influencing the formation of calcium phosphates on the surface. This research, aimed at advancing tissue engineering, prepared nanocomposites with 5, 10, and 15 vol% ZrO2, subjecting them to chemical surface treatment for enhanced calcium phosphate deposition sites. Biomimetic coating with Sr-enriched simulated body fluid (SBF) further enhanced the bioactivity of nanocomposites. While the ZrO2 concentration heightened the oxygen availability on nanocomposite surfaces, the quantity of Sr-containing phosphate was comparatively less influenced than the formation of calcium phosphate phases. Notably, the coated nanocomposites exhibited a high cell viability and no toxicity, signifying their potential in bone tissue engineering. Overall, these findings contribute to the development of regenerative biomaterials, holding promise for enhancing bone regeneration therapies.

ZrO2-phosphates porous ceramic obtained via SPS-RS “in situ” technique: Bacteria test assessment

Abstract The work presents an original way to obtain porous and mechanically strong (to 560 MPa) ZrO2 ceramics containing calcium phosphates, HAP (Ca10(PO4)6(OH)2) and TCP (Ca3(PO4)2), using SPS-RS technique. “In situ” formation of calcium phosphate phases (15 and 50 wt%) has been observed in the bulk of ZrO2 arising from solid-phase interaction of CaO and CaHPO4 mixture at SPS conditions (900–1300 °C). Temperature regime for “in situ” interaction was optimized in accordance with HAP and TCP stability investigations under conditions of oxidative annealing and SPS heating without ZrO2. Addition of a poreforming agent (carbon template) has been demonstrated to enhance the porosity of the ZrO2-phosphate ceramics. Effect of the poreformer amount (2, 5, 10 and 15 wt%) on the structural and mechanical properties of ceramics has been studied by the means of mercury porosimetry, low-temperature nitrogen sorption, microscopy, and other analytical techniques. Microbiological tests were performed to assess the efficiency of bacterial film formation on the samples of composite ceramics depending on the calcium phosphate content. Morphology of the biofilms and the relative surface they occupied on the ceramics were investigated using electron microscopy and image processing method based on local binary pattern (LBP) classifier. Suggested SPS-RS method provides porous and mechanically strong ZrO2-phosphate composite ceramics containing biocompatible components HAP and TCP, which can be prospective for bone-ceramic implants for bone tissue recovery.

Development and relative comparison of polypyrrole-calcium phosphate composite coatings with differential concentration of chlorophyll functionalized polymer particle achieved through pulsed electro deposition

Polypyrrole-calcium orthophosphate-hydroxyapatite functional composite coating is synthesized over the metallic implant surfaces through pulsed electrochemical deposition. Polypyrrole particles are photo-functionalized with the help of chlorophyll during polymerization for their dispersion in the aqueous electrolyte bath. In-situ formation of calcium phosphate phases along with co-deposition of chlorophyll functionalized-polypyrrole particles lead to formation of a ceramic-polymer composite coating. Concentration of chlorophyll molecule in the solution greatly affects the polymerization reaction and subsequent incorporation of functionalized polymer in final coating. Thus, various types of composites structures are developed based on differential amount of polypyrrole presence through varying concentration of chlorophyll, for a detailed comparative study. The polymer chain length and formation bond energy significantly influence the in-situ formation mechanism along with crystal growth direction and rate of formation of various calcium phosphate phases. At low concentration, polymer reinforced hydroxyapatite flakes are formed. High concentration of chlorophyll lead to formation of both the individual polymer phase along with polymer reinforced calcium phosphate phase. While at very high concentration, a polymer layer is formed reinforced with nanocrystalline hydroxyapatite particles. Reinforced coating exhibits three fold higher electrochemical corrosion resistances as compared to bare hydroxyapatite coating. All the coating surfaces display superior osteoconduction capabilities through the formation of stoichiometric hydroxyapatite spherical particles within 7 to 14 days of contact. During osteoconduction, a unique nano porous honeycomb structure over the formed apatite surface enriched with sodium and magnesium ions are formed which would help to ensure higher protein absorption along with a better bonding of cells over the coating surface. Thus, this ceramic-polymer composite developed for the first time through chlorophyll functionalization, can act as one of the potential materials for improvement of both bio-functionalities and corrosion resistance of metallic implant surfaces.

Microstructural investigation of porous titanium coatings, produced by thermal spraying techniques, using plasma atomization and hydride-dehydride powders, for orthopedic implants

The present study focuses on porous titanium (commercially pure Ti) coatings for future use on medical implants, manufactured by specific thermal spray method. Its objective is to investigate the possibility of Ti porosity to offer room for medication storage in addition to bone growth promotion. Three specimens for each different type of coating were produced by different sets of thermal spray process/feedstock powder, namely, (1) Flame Spray (FS) with spherical Plasma Atomization (PA) powder, (2) Atmospheric Plasma Spray (APS) with spherical PA powder and (3) APS with angular Hydride – Dehydride (HDH) powder. The specific types of specimens along with the two powders produced by the PA and HDH processes were characterized using various techniques, namely (a) Roughness measurements of the coated surfaces and thickness measurements of the coatings, which disclosed the highest values for the FS-PA coating, Ra = 11.19 ± 0.21 μm and average thickness of 281 μm, (b) Optical microscopy and SEM-EDS to study the surface morphology and microstructure of the coatings and discover any possible oxidation or other phases. The porosity percentage was measured and the pore size distribution was also estimated. The porosity percentages of the coatings ranged from 12% on the APS-PA coating to 34% on the FS-PA coating, (c) XRD analyses which showed varying titanium oxide formations for each type of specimen. These oxides may prove to be beneficial for the development of osseous tissue, (d) assessment of biological response of the coatings in vitro that resulted in satisfactory primary response in a physiological environment and the formation of calcium phosphate phases with Ca/P ratio of 1.61 and (e) Vickers microhardness measurements, which resulted in values that fluctuated from 786.6 for the FS-PA coating to 967.6 for the APS-HDH coating. Overall, the produced FS-PA coating is characterized by high porosity content and satisfactory bioactivity, in order to fulfill the objective of the project for biomolecule incorporation and drug storage.

In vitro apatite-forming ability of calcium aluminate blends

Abstract Calcium aluminate cement (CAC) blends show great potential as biomaterial when compared to commercial products used in odontology and orthopedics. Mixtures of CAC +4 wt% of different additives (alumina, zirconia, zinc oxide, tricalcium phosphate or hydroxyapatite) containing compositions, resulted in samples with low porosity levels and smaller pore sizes after their contact with simulated body fluid (SBF) solution, which was associated with apatite precipitation on the materials’ surface. In order to certify these aspects, the in vitro apatite-formation ability (bioactivity) of CAC blends was evaluated by pH and calcium concentration measurements in SBF for samples previously treated (or not) with sodium silicate (SS) solution. The surface of the samples after immersion in SBF or SBF/SS was analyzed by scanning electron microscopy (SEM), energy dispersive X-ray (EDX) analysis and confocal Raman spectroscopy. In addition, the in vitro apatite deposition and the osteoblastic cell viability were also evaluated. SEM results showed that the precipitation of phases was detected on the CAC blend samples’ surfaces. The presence of calcium and mainly phosphorus by EDX indicated the formation of calcium phosphate phases. Moreover, the presence of a more homogeneous apatite-like layer on the samples’ surface was observed after treatment with sodium silicate solution. The detection of the Raman signature at 960 cm −1 , confirmed the presence of an apatite-like layer on the surface of the compositions after immersion in SBF or SBF/SS. Regarding the osteoblastic cell viability results, blends with collagen, zinc oxide and zirconia presented better results when compared to commercial products.

Influence of different chemical treatments on the surface of Al2O3/ZrO2 nanocomposites during biomimetic coating

The objective of this study is to evaluate the influence of different chemical surface treatments (H3PO4, HNO3, and NaOH) in the formation of calcium phosphate phases on the surface of Al2O3/ZrO2 (5vol%) nanocomposite. For this purpose, Al2O3/ZrO2 samples were shaped, calcined at 400°C, sintered at 1500°C, subjected to different chemical treatments, and biomimetically coated from 14 to 21 days. Surface characterization was performed by scanning electron microscopy, atomic force microscopy, confocal microscopy, X-ray diffraction, and infrared spectroscopy. It was observed that the preliminary chemical treatment favored the formation of particular calcium phosphate phases of interest, such as α-TCP (alpha-tricalcium phosphate), β-TCP (beta-tricalcium phosphate), and HA (hydroxyapatite). The differences among the percentages of the phases formed affected the homogeneity of calcium phosphate distribution within the nanocomposites as well as the roughness of the formed layer, effectively contributing to adhesion, proliferation, and desired cell biofixation on bone implant.

Fabrication of 3D calcium phosphates based scaffolds using bacterial cellulose as template

Bacterial cellulose – calcium phosphates composite materials were synthesized by successive immersing of bacterial cellulose membranes prepared in our laboratory in precursor solutions under ultrasonic irradiation, which provides the necessary cations for the formation of calcium phosphate phases at the surface of bacterial cellulose fibers. The subsequent thermal treatment at 700 or 1000°C of the hybrid materials previously described allowed the obtaining of 3D porous scaffolds with different morphologies, as a function of the number of immersing cycles and calcining temperature. All samples exhibit similar phase composition, mainly based on hydroxyapatite and buchwaldite (sodium calcium phosphate). In the case of the composites thermally treated at lower temperature, the microstructure is fluffy and composed of large grains and monocrystalline nanorods, while the masses calcined at higher temperatures have a trabecular appearance, looking like a natural bone. The biological properties of the resulting architectures were also investigated.

Synthesis of Nano Calcium Phosphate via Biomimetic Method for Bone Tissue Engineering Scaffolds and Investigation of its Phase Transformation in Simulated Body Fluid

In this study the formation of calcium phosphate phase via double diffusion method into a hydrogel matrix was investigated and its phase transformation in simulated body fluid was studied. White precipitate was formed within the hydrogel, due to the diffusion of calcium and phosphate ions through the hydrogel matrix in similar pH to human body. Phase composition, microstructure and structural groups in the composite samples were also characterized by X-Ray Diffraction (XRD), scanning electron microscopy (SEM) and Fourier transform infra-red (FTIR) analyses. Microstructure of precipitates formed within middle hydrogel, showed that detected materials are composed of carbonated hydroxyapatite and dicalcium phosphate dihydrate (DCPD, brushite). The particle size was about 10 nm .Analysis results showed that after incubation in simulated body fluid, dicalcium phosphate dehydrate phase transformed into crystalline hydroxy apatite.

<i>In Silico</i> Experiments of Carbon Dioxide Atmosphere and Buffer Type Effects on the Biomimetic Coating with Simulated Body Fluids

The formation of calcium phosphate phases is extremely important in a biomedical engineering context. These phosphates are used in many applications, such as grafts, drug-delivery processes and evaluation of the bioactivity of metallic surfaces. Considering this scenario, it is useful to evaluate the thermodynamic conditions for the precipitation of phosphates of biomedical interest, mainly hydroxyapatite. In this work, we investigate the effects of two important factors using a thermodynamic framework: 1) carbon dioxide partial pressure; and 2) buffer type (2-Amino-2-hydroxymethyl-propane-1,3-diol, known as TRIS and 2-[4-(2-hydroxyethyl)piperazin-1-yl] ethanesulfonic acid, also called HEPES), on the driving force behind the precipitation of calcium phosphates in simulated body fluids. The in silico results show that the pH value is governed by carbon dioxide content, as expected to occur in vivo. Moreover, the buffers can deplete the free calcium available in solution and, consequently, can cause difficulties in the calcium phosphate precipitation.

In-situ mineralization of chitosan/calcium phosphate composite and the effect of solvent on the structure

Solvent played an important role in the formation of calcium phosphate phase of the chitosan/calcium phosphate composites. In this investigation, ethanolacetic acid mixtures were employed as solvents, and various calcium phosphate phases, such as brushite, amorphous calcium phosphate, and hydroxyapatite, were introduced into the chitosan/calcium phosphate composites by using in-situ preparation process. The results showed that the structures of composite were influenced remarkably by the morphology and the distribution of calcium phosphate phase. In addition, the bioactivity of composites was governed mainly by the characters of calcium phosphate phases in composites, since calcium phosphate phases could induce the growth of hydroxyapatite coating on the surfaces of composites. On the surface of chitosan/brushite composite, the formed hydroxyapatite coating consisted of oriented plate crystallites, which selfassembled into spherical-like crystals. When other calcium phosphate phase was introduced into composites, the polymorphs of hydroxyapatite layer would change greatly. The oriented plate crystallites became bigger, and meanwhile, the self-assembled aggregates became less and smaller. In addition, with the shift of the prior nucleating point, the growth orientation of plate crystallites was transformed.

The use of hydroxyapatite as a new inorganic consolidant for damaged carbonate stones

The feasibility and the effectiveness of using hydroxyapatite (HAP) formed by reacting limestone with a solution of diammonium hydrogen phosphate (DAP) in mild conditions, as a consolidant for carbonate stones were investigated. Firstly, a novel method for predamaging limestone was developed. Then, the effects of DAP solution concentration and reaction duration were evaluated to define the best treatment conditions, and the strengthening effect was evaluated on artificially damaged Indiana Limestone samples. Treated samples exhibit a significant increase in the dynamic elastic modulus and tensile strength, which is attributed to microcrack reduction and pore filling consequent to formation of calcium phosphate phases at grain boundaries, as assessed by SEM/EDS and ESEM/EBSD. Consequent to a slight reduction of coarser pores, as revealed by MIP, the sorptivity of treated samples is only slightly reduced, so that water and water vapor exchanges with the environment are not significantly blocked.

Preliminary Results of the Use of Hydroxyapatite as a Consolidant for Carbonate Stones

ABSTRACTThe effectiveness of using hydroxyapatite (HAP) as a consolidant for carbonate stones was evaluated. HAP was chosen as a consolidating agent since it is notably less soluble than calcite and has a similar crystal structure and a close lattice match to it. Among possible methods for forming HAP, the reaction between the calcite of the stone and a solution of diammonium hydrogen phosphate (DAP) in mild conditions was chosen. Indiana Limestone samples, artificially damaged by heating to 300°C for 1 hour, were treated with a 1 molar DAP solution by partial immersion and capillary absorption for 48 hours or by brushing until apparent refusal and wrapping with a plastic film for 48 hours. After washing in deionized water for 3 days and drying under a fan at room temperature until constant weight, the improvements in dynamic elastic modulus and tensile strength were evaluated. The formation of calcium phosphate phases was observed by scanning electron microscopy (SEM) and the phase characterization performed by energy dispersive X-ray spectroscopy (EDS) and electron back-scattered diffraction (EBSD). The water absorption modification after the consolidating treatment was then assessed. Results show that treated samples experienced significant increases in dynamic elastic modulus and tensile strength, as a consequence of crack reduction and pore filling consequent to HAP deposition at grain boundaries. The sorptivity of the treated samples is reduced by 26-44% (based on treatment technique), so that water and water vapor exchanges with the environment are not blocked.

Mineralization behaviour of collagen type I immobilized on different substrates

Collagen type I as a robust fibre protein and main component of the extracellular matrix of most tissues is increasingly utilized for surface engineering of biomaterials using different immobilization methods. In the present work we studied the mineralization behaviour of fibrillar collagen type I in simulated body fluid as a measure for conformational changes caused by adsorptive immobilization or immobilization by partial incorporation into the anodic oxide layer on c.p.-titanium using microscopic and vibration spectroscopic methods. Adsorptive immobilization on highly oriented pyrolytic graphite (HOPG) and c.p.-titanium without collagen were used as references. In the initial phase (1–24 h) the kinetics of formation and the morphology of calcium phosphate phases (CPP) are strongly influenced both by the substrate and the immobilization method. Compared to HOPG both types of immobilization on titanium increasingly inhibit the formation of CPP. For longer times (30 d) these initial differences disappear-mineralization product on titanium, irrespective of the presence of collagen, is a mixture of amorphous calcium phosphate and octacalcium phosphate. Contrary to this the mineralization of HOPG substrates results in hydroxy apatite. This is discussed with respect to the conditions during the immobilization as well as the resulting interactions between substrate and immobilized collagen. It is shown that the mineralization process exhibits a high sensitivity with respect to conformational changes caused by these interactions. Possible cell biological relevance of these conformational changes is discussed.

Hydroxyapatite coating on Ti6Al4V alloy using a sol–gel derived precursor

A simple rapid-heating method was successfully developed for calcium phosphate coatings on Ti6Al4V substrates deposited by using a sol–gel derived precursor. After five repetitions of coating procedures and heat treatment at 600 °C, the formation of hydroxyapatite (HA) has been confirmed by X-ray diffractometry (XRD) analyses and the substrate material was found to be slightly oxidized. The residual organics, as revealed by X-ray photoelectron spectroscopy (XPS) spectra of a coating calcined at 400 °C, might retard the formation of calcium phosphate phase, thus only small amount of calcium phosphate phase is present. After calcining at 600 °C, calcium phosphate phase is the only one identifiable by XPS spectra. The adhesive strength of the five-coating layer on the substrate is around 60 MPa. The surface morphology of the thick HA film, calcined at 400 °C and then consolidated at 600 °C, displays porous structure arisen from rapid-heating of the bulk precursor.

A ph study of calcium phosphate seeded precipitation

The formation of calcium phosphate phases over a range of pH has been investigated at 37°C using a constant composition method. At a controlled ionic strength of 0.10 mole/liter, and Ca/P = 1.333 the precipitation of octacalcium phosphate appears to be limited to a pH range of 6 to 7. At pH 5, dicalcium phosphate dihydrate is formed at all supersaturations whereas at pH 5.5, it occurs only at high supersaturation; octacalcium phosphate precipitating at low supersaturation. At higher pH (7.4 and 8.0), the results point to the formation of a hydroxyapatite-like material.