Apatite Coatings Research Articles

Integrity and zeta potential of fluoridated hydroxyapatite nanothick coatings for biomedical applications

Fluoridated hydroxyapatite (FHA) coatings exhibit great potential for applications on implants which require good bioactivity and high antibacterial activity. This work is a comparative study of chemical stability, adhesive strength and zeta potential of a nanothick (about 200 nm) FHA coating which is densely and uniformly deposited on a titanium substrate electrochemically. The chemical stability of the nanothick coatings was evaluated using a dissolution test in a simulated physiological solution. The dissolution tests indicate that the fluorine-containing calcium phosphate (CaP) coating with an appropriate heat treatment is chemically stable in a physiological environment, even more so than its HA counterpart. The adhesive strength of FHA coatings was evaluated by the critical load obtained from nanoscratching tests. The critical load which caused coating failure in scratching was determined by a method which correlated the scratching morphology with a sudden change in friction coefficient. The adhesive strength of a nanothick FHA coating was 147% larger than that of HA coating with the same thickness level. The fluorine addition does not have a significant effect on the characteristics of the negative zeta potential of apatite coatings. The solid integrity of this nanothick FHA coating makes it an excellent candidate for biomedical applications.

Apatite Coatings Deposited by DC Magnetron Sputtering

not Available.

Development of apatite coatings on Ti–6Al–7Nb dental implants by biomimetic process and EPD: in vivo studies

This paper compares the results of the effects of a biomimetic coating and electrophoretic deposition (EPD) of hydroxyapatite (HA) on the bond strength between the bone, implant and cell compatibility of Ti–6Al–7Nb dental implants. In the biomimetic process, screw shaped implants were chemically etched and NaOH activated to form hydroxycarbonated apatite after they were soaked for six days in a solution that was five times more concentrated than regular simulated body fluid (SBF). Electrophoretic deposition was also used to obtain a uniform coating of HA on other batchs of screws. Elemental, structural and in vivo histological and biomechanical investigations were carried out on the modified surfaces of the screws. The results show that there was a faster reaction of bone towards the coated implants compared to the uncoated one. More mature bones were observed on HA coated implants and increased mechanical strength (torque value) of bone–implant interface. Higher torque was needed to remove elephoretically and biomimetically HA coated screws from its bed compared to that needed for uncoated one (55, 50·16 and 37·45 N cm respectively). Biomimetic and electrophoretic coating with a bioactive HA leads to high integration between bone and implant by increasing the bioactivity of the product and to promoting mechanical properties of the implanted screws and enhanced osseointegration during the healing period. Owing to the higher roughness and porosity of the EPD coated screws (average Ra = 2921±100 nm), the bone growth was much higher than that coated biomimetically (average Ra = 1550±88 nm). Out of the two methods tried to form bioactive surface, EPD yields high bone adhesion when compared to the biomimetic coating.

Comparative study of hydroxyapatite and octacalcium phosphate coatings deposited on metallic implants by PLD method

The aim of the presented study was an analysis of two apatite coatings: hydroxyapatite (HA) and octacalcium phosphate (OCP) as coatings materials for metallic implants. Both layers were deposited by means of the PLD method. As a target material, synthetic, powdered and pressed hydroxyapatite was used. HA was deposited on 316L steel substrate in two temperature ranges for obtaining different coatings: 150±30°C and 430±30°C for OCP and HA, respectively. As an intermediate layer, the nanocrystalline diamond layer (NCD) was deposited. Examined calcium phosphate layers were tested for adhesion of osteoblast cell culture (MG-63). Analytical methods (AFM, FTIR) showed the usefulness of the PLD method for deposition of the apatite layers on metallic implants. Both examined layers showed biocompatibility with human osteoblast cells and presented favorable conditions for their proliferation.

Enhancement of the ALP activity of C3H10T1/2 cells by the combination of an oxysterol and apatite

Biomimetic apatite coating has been used to load osteogenic biomolecules onto the surface of titanium implants. Apatite on the surface of biomaterials is thought to function as a reservoir of biomolecules as well as enhancing osteoconductivity. In this study, 20α-hydroxycholesterol (20α-HC), an osteogenic oxysterol, was used to induce differentiation of a mouse embryo fibroblast cell line (C3H10T1/2) by loading the oxysterol on biomimetically coated apatite of titanium discs. We found that the phosphatase (alkaline phosphatase (ALP)) activity of 20α-HC was significantly higher with ascorbic acid than alone, suggesting a need for ascorbic acid as a co-factor. When 20α-HC was added into the apatite coating solution, the ALP activity of the C3H10T1/2 cells did not increase on the apatite surface, even in the presence of ascorbic acid. However, ALP activity increased dramatically when 20α-HC was loaded by volatilization of EtOH from the apatite coat after dipping discs in 20α-HC-dissolved EtOH. Interestingly, ascorbic acid was not needed for this increase in ALP activity, suggesting a synergistic effect of 20α-HC and apatite. The concentration of calcium ions, a major component of apatite, affected the osteogenic effect of 20α-HC, and the increase in ALP activity was attenuated by L-type calcium channel inhibitors, verapamil and nifedipine. These results demonstrate that calcium ions released from apatite are important in the synergistic effect of 20α-HC and apatite.

Effect of Electrochemical Parameters on the Morphology and Ca/P Ratios of Deposited Apatite Coatings on Metal and Alloy Substrates

not Available.

Plasma spraying of lanthanum silicate electrolytes for intermediate temperature solid oxide fuel cells (ITSOFCs)

A new challenge in the field of solid oxide fuel cells (SOFCs) concerns reducing their operating temperature to 973 K. Apatite ceramics are interesting candidates for SOFC electrolytes due to their high ionic conductivity at this temperature. The present work reports on the fabrication and characterization of La 9SrSi 6O 26.5 coatings obtained by atmospheric plasma spraying with two different plasma spray powers. The microstructure and the composition of the as-sprayed and heat-treated coatings were investigated by several techniques including X-Ray Diffraction, Inductively Coupled Plasma-Atomic Emission Spectroscopy and Scanning Electron Microscopy. The open porosity of the coatings was evaluated by the Archimedean method. It was found that the as-sprayed apatite coatings were composed of an amorphous phase as well as of a crystalline apatite phase, and that they contained chemical heterogeneities resulting from Si volatilization in the high-temperature plasma. Furthermore, a heat treatment rendered it possible to obtain denser, fully crystallized apatite coatings. Ionic conductivity measurements carried out with impedance spectroscopy demonstrated that the conductivity of the apatite coatings – depending on the spraying conditions – increased with sintering.

Biomimetic deposition of apatite coatings on micro-arc oxidation treated biomedical NiTi alloy

The biomedical NiTi alloy was treated by micro-arc oxidation in an electrolytes containing sodium aluminate and sodium hypophosphite at 400 V constant voltages for 30 min. The MAO-treated NiTi has a porous microstructure on its surface and coatings consisting only of the γ-Al2O3 phase. The ceramic coating prepared by micro-arc oxidation is composed of Al, Ti, Ni, O, and P with the atomic concentration of 26.98%, 3.67%, 3.33%, 65.30% and 0.72%, respectively. The MAO-treated NiTi was soaked in a simulated body fluid (1.0SBF) to investigate the biomimetic deposition of apatite on the surface of Al2O3 coated NiTi alloy. It was found that Al2O3 coated NiTi alloy shows an excellent apatite-forming ability after soaking in a simulated body fluid (1.0SBF) for 14 days, while no apatite-forming ability was observed on bared NiTi alloy even though soaking time is up to 28 days.

Biomimetic whisker-shaped apatite coating of titanium powder

Biomimetic apatite coatings on chemically modified titanium powder have been processed and the resulting coating layers evaluated in terms of morphology, composition and structure, using TF-XRD, XPS, SEM, TEM and FTIR analysis. After 7 days immersion in a simulated body fluid (SBF), nanometer-sized fine precipitates with an amorphous whisker-like phase and a Ca/P atomic ratio of 1.94 were obtained on the external surface of the titanium particles. When the immersion time in SBF was extended to 16 days, the coating layer consisted of the whisker-like nanostructured crystals of carbonated hydroxyapatite with a atomic ratio of 3; in such a case, a double coating layer was developed. The double layer could be divided into two regions and could be clearly distinguished: an inner dense region (approximately 200 nm in thickness) which may include hard agglomerated crystals and an outer less dense region (> 500 nm in thickness) in which crystals are loosely distributed.

Changes of Surface Composition and Morphology after Incorporation of Ions into Biomimetic Apatite Coating

Fabrication of trace elements incorporated apatite coating could combine the ions’ pharmaceutical effect into the materials. In this study, strontium, silicon, and fluoride ions have been incorporated into apatite coatings through a biomineralization method, which mimics an in vitro mineralization process. The surface composition is tested with X-ray diffraction and X-ray photoelectron spectroscopy, and the surface morphology is characterized with scanning electron microscopy. Compared with pure hydroxyapatite coating, the strontium, silicon, and fluoride substituted apatite coatings show different morphology as spherical, needle-like, and nano-flake-like, individually. The crystal size of these biomimetic hydroxyapatite coatings decreased after ion substitution. The results of the analysis of surface composition present the ion substitutions are increased with the increasing of ion concentrations in the soaking solution. That means the ion incorporation into the apatite structure based on the biomineralization method could not only vary the ion content in but also change the morphology of the apatite coatings. Herein, the role of ion substitution is considered from the point of view of materials science at the micro structural and surface chemistry levels.

Thin carbonate apatite layer biomimetically-coated on SAM-Ti substrate surfaces

A self-assembled monolayer (SAM) technique was employed to produce carbonate apatite (CA) coatings onto Ti substrates after sulfonation. The Ti substrates thus treated (S-SAM-Ti) were immersed in metastable calcium phosphate solutions containing carbonate to induce precipitation of carbonate apatite on the surface. The uniformity and homogeneity of the CA layer was partly demonstrated by the XPS crater-edge-line analysis. Both calcium and phosphorus were distributed quite evenly within a layer of approximately 1000 nm.

Effect of Bisphosphonate Immobilization of Apatite Coated Titanium Web on Trabecular Bone Response

Effect of Bisphosphonate Immobilization of Apatite Coated Titanium Web on Trabecular Bone Response

Preparation and Characterization of Apatite Coated Rutile TiO2 Composite Powders

Preparation and Characterization of Apatite Coated Rutile TiO2 Composite Powders

Apatite coatings onto titanium surfaces submitted to laser ablation with different energy densities

Abstract Apatite coatings were deposited on titanium surfaces modified by Nd:YVO 4 laser at different energy densities in environment atmosphere. Apatite was synthesized by sol–gel method using calcium nitrate and phosphoric acid as precursors. The titanium modified surfaces were dip-coated into precursor solution and pre-fired at 700 °C in air for 3 h. Analyses by XRD, FTIR and SEM showed the formation of a mixture of phases: hydroxyapatite (HA) and tricalcium phosphate (β-TCP) onto the surfaces submitted to laser ablation. Surface Rietveld analysis showed that a larger amount of non-stoichiometric oxides produced by laser ablation resulted in greater formation of HA on the coating. However, more of the β-TCP phase than HA was observed on surfaces with low amounts of oxides.

Hydrogel Formation of Bisphosphonate Around Apatite Coated Titanium Web

Hydrogel Formation of Bisphosphonate Around Apatite Coated Titanium Web

Biomimetic apatite formation on Ultra-High Molecular Weight Polyethylene (UHMWPE) using modified biomimetic solution

Modifications were performed on a biomimetic solution (SBF), according to previous knowledge on the behavior of ions present in its composition, in order to obtain apatite coatings onto Ultra-High Molecular Weight Polyethylene (UHMWPE) without having to use polymer pre-treatments that could compromise its properties. UHMWPE substrates were immersed into a 30% H(2)O(2) solution for a 24-h period and then submitted to a biomimetic coating method using standard SBF and two other modified SBF solutions. Apatite coatings were only obtained onto UHMWPE when the modified SBF solutions were used. Based on these results, apatite coatings of biological importance (calcium-deficient hydroxyapatite-CDHA, amorphous calcium phosphate-ACP, octacalcium phosphate-OCP, and carbonated HA) can be obtained onto UHMWPE substrates, allowing an adequate conciliation between bonelike mechanical properties and bioactivity.

Depositing an Apatite Coating in/on Massive Chitosan Porous Scaffolds by an Alternate Soaking Method

We hope to improve the biological activity and the osteo-conductivity of a porous polymer scaffold by the deposition of a hydroxyapatite (HA) coating. We used an alternate soaking deposition method to prepare HA coating. A massive chitosan (Cs) porous scaffold was used as a deposition template and immersed alternately in calcium chloride and disodium hydrogen phosphate solutions. Finally, a hydroxyapatite coating was deposited in/on the massive chitosan porous scaffold. The compositions, micromorphology, porosity, inorganic deposition amount and compressive strength were characterized by XRD, FT-IR, SEM, porosity measurements, calcination and a compression experiment. Results indicated that the deposition mineral was a low crystallinity carbonate hydroxyapatite with c axis preferential growth and was similar to hydroxyapatite in natural bone. SEM results showed that the sedimentary hydroxyapatite had a gradient distribution in the scaffold. More deposition was observed on the outer pore wall surface than the inner pore wall surface. The exterior pores of the scaffold were partially blocked but the inner pore structure of the scaffold was still interconnected. The porosity of the deposited scaffold was 94.0% and the deposited hydroxyapatite was 13.5% of the total mass after 6 alternate soaking cycles. The compressive strength of the scaffold increased from 0.055 MPa to 0.109 MPa.

Osteoblastic cell response on magnesium-incorporated apatite coatings

Magnesium is one of the most important bivalent ions associated with biological apatite. A series of magnesium-substituted calcium apatite coatings (Ca 10− x Mg x )(PO 4) 6(OH) 2, where x = 0, 0.50, 1.00, 1.50 and 2.00, are synthesized onto Ti6Al4V substrate by sol–gel dip-coating method to determine how magnesium influences the synthesis and the resulting structural and biological properties. X-ray diffraction (XRD) analysis shows that the incorporation of magnesium helps formation of Mg-containing β-TCP (β-TCMP) phase. X-ray photoelectron spectroscopy (XPS) is used to study the chemical composition and the results show that the apatite structure can only host magnesium less than ∼2.4 wt.% beyond which magnesium aggregates on the surfaces. The incorporation of magnesium slows down the dissolution of Ca 2+ from the coating. The in vitro behavior of the coatings is evaluated with human osteosarcoma MG63 cells for cell morphology and proliferation. Similar cell morphologies are observed on all coatings. The cell proliferation results show that the incorporation of magnesium up to x = 2 has no adverse effect on cell growth.

Proliferation and differentiation of osteoblast‐like MC3T3‐E1 cells on biomimetically and electrolytically deposited calcium phosphate coatings

Biomimetic and electrolytic deposition are versatile methods to prepare calcium phosphate coatings. In this article, we compared the effects of biomimetically deposited octacalcium phosphate and carbonate apatite coatings as well as electrolytically deposited carbonate apatite coating on the proliferation and differentiation of mouse osteoblast-like MC3T3-E1 cells. It was found that MC3T3-E1 cells cultured on the biomimetically deposited carbonate apatite coating demonstrated the greatest proliferation rate and the highest differentiation potential. Cells on the biomimetically deposited octacalcium phosphate coating had lower proliferation rate before day 7, but higher after that, than those on the electrolytically deposited carbonate apatite coating. There was no difference on the expression of early differentiation markers, that is, alkaline phosphatase activity and collagen content, between biomimetically deposited octacalcium phosphate and electrolytically deposited carbonate apatite coatings. However, higher expression of late differentiation markers, that is, osteocalcin and bone sialoprotein mRNA, was found on the biomimetically deposited octacalcium phosphate coating on day 14. These results suggest that the difference in in vitro osteoblast cell performance of calcium phosphate coatings might relate to their physicochemical properties. Biomimetic carbonate apatite coating is the most favorable surface for the proliferation and differentiation of MC3T3-E1 cells.

The effect of temperature and initial pH on biomimetic apatite coating

Bone-like apatite coatings were prepared using a biomimetic method in a simulated body fluid (SBF). The effect of initial pH values and immersing temperatures on biomimetic apatite coating formation was studied. Three different temperatures were used in this study: 24 (room temperature), 40, and 60 degrees C. At each temperature, SBF solutions with three different initial pHs were chosen: low, medium, and high. The total inorganic carbon (TIC) content and pH-time profile of each coating system were recorded during the coating formation. The apatite coatings were characterized using X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), and Fourier transform infra-red (FTIR). It has been found that SBF temperature has a great effect on the bicarbonate decomposition rate. The bicarbonate ions tend to decompose faster as the temperature increases. The decomposition of bicarbonate ions results in a pH increase in the SBF. With different initial SBF pHs, the decomposition of different amounts of bicarbonate ions is required to reach the critical pH range of apatite formation. With different amounts of bicarbonate ions in the SBF, the surface morphology of the biomimetic apatite coating formed is different. Therefore, the initial pH of the SBF solution plays a vital role in controlling the surface morphology of the biomimetic apatite coating. Also, it was found that as the SBF temperature increased, the critical pH range at which biomimetic apatite coating forms decreased. The critical pH range for the SBF prepared at 24, 40, and 60 degrees C was 6.65-6.71, 6.55-6.65, and 6.24-6.42, respectively.