Calcium Phosphate Films Research Articles

The biocompatibility of nanostructured calcium phosphate coated on micro-arc oxidized titanium

To achieve improved osseointegration, there have been many efforts to modify the surface composition and topography of dental implants. Recently, the anodic oxidation treatment of titanium (Ti) has attracted a great deal of attention. Meanwhile, calcium phosphate is commonly applied to metallic implants as a coating material for fast fixation and firm implant–bone attachment on the account of its demonstrated bioactive and osteoconductive properties. In the present study, anodized surface and calcium phosphate deposition by electron beam evaporation were combined. Nanostructured calcium phosphate film was deposited on the micro-arc oxidized Ti. New apatite layer formed easily on the coated film when incubating in DPBS solution at 37 °C. By adding basic fibroblast growth factor (bFGF) in the DPBS solution, the bFGF could be immobilized in the newly formed apatite layer. The coated film enhanced osseointegration of Ti implants in vivo.

ブラスト処理を施したＴｉ‐６Ａｌ‐４Ｖ合金基板へのリン酸カルシウムコーティングと生体内外評価

Calcium phosphate coating films were fabricated on Ti-6Al-4V alloy plates and implants with a blast-treated surface using radiofrequency (RF) magnetron sputtering and were evaluated in vitro and in vivo. Amorphous calcium phosphate (ACP) and oxyapatite (OAp) films obtained in this study could cover the blast-treated Ti-6Al-4V substrate very efficiently, maintaining the surface roughness. For the in vitro evaluations of the calcium phosphate coating films, bonding strength and alkaline phosphatase (ALP) activity were examined. The bonding strength of the coating films to a blast-treated Ti-6Al-4V plate exceeded 60 MPa, independent of film phases. When compared with an uncoated Ti-6Al-4V plate, the increase in the ALP activity of osteoblastic SaOS-2 cells on a blast-treated Ti-6Al-4V plate coated with the ACP and OAp films was confirmed by a cell culture test. The removal torque of screw type Ti-6Al-4V implants with a blast-treated surface from the femur of a Japanese white rabbit increased with the duration of implantation and it was statistically improved by coating an ACP film two weeks after implantation. The in vitro and vivo studies suggested that the application of the sputtered ACP film as a coating on titanium implants was effective in improving their biocompatibility with the bones.

Parathyroid Hormone Stimulates Osteoblastic Expression of MCP-1 to Recruit and Increase the Fusion of Pre/Osteoclasts

The clinical findings that alendronate blunted the anabolic effect of human parathyroid hormone (PTH) on bone formation suggest that active resorption is involved and enhances the anabolic effect. PTH signals via its receptor on the osteoblast membrane, and osteoclasts are impacted indirectly via the products of osteoblasts. Microarray with RNA from rats injected with human PTH or vehicle showed a strong association between the stimulation of monocyte chemoattractant protein-1 (MCP-1) and the anabolic effects of PTH. PTH rapidly and dramatically stimulated MCP-1 mRNA in the femora of rats receiving daily injections of PTH or in primary osteoblastic and UMR 106-01 cells. The stimulation of MCP-1 mRNA was dose-dependent and a primary response to PTH signaling via the cAMP-dependent protein kinase pathway in vitro. Studies with the mouse monocyte cell line RAW 264.7 and mouse bone marrow proved that osteoblastic MCP-1 can potently recruit osteoclast monocyte precursors and facilitate receptor activator of NF-kappaB ligand-induced osteoclastogenesis and, in particular, enhanced fusion. Our model suggests that PTH-induced osteoblastic expression of MCP-1 is involved in recruitment and differentiation at the stage of multinucleation of osteoclast precursors. This information provides a rationale for increased osteoclast activity in the anabolic effects of PTH in addition to receptor activator of NF-kappaB ligand stimulation to initiate greater bone remodeling.

Hydroxyapatite Formation on Calcium Phosphate Coated Titanium

Calcium phosphate films were prepared by MOCVD using Ca(dpm)2 and (C6H5O)3PO precursors. The phases, composition and morphology of films changed depending on the molar ratio of Ca to P precursors (RCa/P), total pressure (Ptot) and substrate temperature (Tsub). α-tricalcimu phosphate (α-TCP, α-Ca3(PO4)2) films in a single phase were obtained at Tsub = 1073 K, 0.1 < RCa/P < 0.4 and Tsub = 973 K, RCa/P < 0.4. Hydroxyapatite (HAp, Ca10(PO4)6(OH)2) films in a single phase were obtained at Tsub = 1073 K, 0.8 < RCa/P < 1.0 and Tsub = 973 K, 0.5 < RCa/P < 0.6. Ca-P-O films had a dense and smooth surface. HAp formed within 1 day on the α-TCP film and wholly covered the specimens within 2 weeks in a Hanks’ solution. The surface of CVD-HAp film was covered by precipitated HAp within 6 hours.

In Vitro Evaluation of RF Magnetron-Sputtered Calcium Phosphate Films on Titanium

Calcium phosphate coating films were fabricated on mirror-polished or blast-treated titanium substrates using radio-frequency (RF) magnetron sputtering and they were evaluated in vitro. Immersion tests for the films were conducted using phosphate-buffered saline (PBS(-)), and apatite formation and the elution of calcium ions from the films were investigated. The bonding strengths between the calcium phosphate films and titanium substrates before and after the immersion tests were evaluated. After the immersion tests, a decrease in the bonding strength was observed for the coating films on the mirror-polished titanium substrates, while that for the blast-treated titanium substrates was almost the same as that before the immersion tests.

Fabrication of calcium phosphate films for coating on titanium substrates heated up to 773 K by RF magnetron sputtering and their evaluations

Calcium phosphate films were fabricated on titanium substrates heated up to 773 K using radiofrequency (RF) magnetron sputtering. The deposition rate, phase and preferred orientation of the calcium phosphate films were studied. Immersion tests for the films were conducted using Hanks' solution and PBS(−), and the surface reactions on the specimens coated with the calcium phosphate films were investigated. The bonding strength between the coating films and the titanium substrates before and after the immersion tests was evaluated; the bonding strength decreased after the immersion tests. The alkaline phosphatase (ALP) activity of SaOS-2 cells on a titanium plate coated with a calcium phosphate film was examined by conducting a culture test. Calcium phosphate coating increased the ALP activity of SaOS-2 cells cultured for 3 and 7 days. Titanium cylinders were coated with an amorphous calcium phosphate film and implanted into the mandibles of beagle dogs. An increase in the extent of bone-implant contact for the coated titanium cylinders was confirmed 8 to 12 weeks after implantation and compared with the case for uncoated titanium cylinders.

Characterization of a silver-incorporated calcium phosphate film by RBS and its antimicrobial effects

A thin calcium phosphate film was synthesized on both commercially pure Ti and Si wafers by electron beam evaporation of hydroxyapatite as an evaporant with simultaneous Ar ion beam bombardments. Silver was introduced into an ion-beam-assisted deposition of a calcium phosphate thin film for antimicrobial effect. The amount of incorporated silver ions was controlled by immersing calcium-phosphate-coated samples in different AgNO3 concentrations, and Rutherford backscattering spectrometry (RBS) was employed to measure the amounts of substituted silver. The higher concentration of silver in the calcium phosphate film was more effective in reducing the bacteria of Escherichia coli ATCC 8739 and Streptococcus mutans OMZ 65 on contact with respect to controls.

Calcium Phosphate Films Coated on Titanium by RF Magnetron Sputtering for Medical Applications

Calcium phosphate films were coated on commercially pure titanium substrates by radiofrequency magnetron sputtering using β-tricalcium phosphate targets. The films consisted of amorphous calcium phosphate and oxyapatite phases. Immersion tests of the films were carried out in Hanks’ solution and PBS(-), and apatite formation and calcium ion elution from the films were investigated. The titanium cylinders coated with calcium phosphate films were implanted into the mandibles of beagle dogs. These results suggest that coating with calcium phosphate improves the biocompatibility of titanium implants with bone tissue.

Characterization of biomimetic calcium phosphate on phosphorylated chitosan films

This study examined the effect of chitosan degree of deacetylation (DDA), concentration of simulated body fluid (SBF), and mineralization time on the composition, structure, and crystallinity of calcium phosphate (CaP) biomimetically deposited on chitosan and on osteoblast cell growth. Phosphorylated chitosan films of 92.3%, 87.4%, and 80.6% DDA were soaked in SBF (1.0x or 1.5x) for 7, 14, or 21 days. Scanning electron microscopy revealed that CaP precipitated from 1.5x SBF had a porous, granular morphology; while the coatings precipitated in 1.0x SBF were smoother and more uniform. X-ray diffraction showed that films mineralized in 1.0x SBF were amorphous, while films mineralized in 1.5x SBF for 21 days exhibited crystalline peaks similar to hydroxyapatite, with the most crystalline peaks seen on 92.3% DDA chitosan. When mineralized films were placed in cell media for 14 days, more calcium phosphate precipitated onto all films, and the most calcium phosphate was found on 92.3% DDA films mineralized in 1.5x SBF. After seven days of osteoblast culture, there were approximately three times as many cells (based on DNA measurements, p < 0.05) on 92.3% DDA films soaked in 1.0x SBF for seven or 21 days than on 80.6% DDA films soaked in 1.0x SBF for any length of time or any films soaked in 1.5x SBF. The DDA of chitosan, concentration of SBF and mineralization time affect the structure of and biological response to chitosan/biomimetic CaP films, and these factors must be considered when designing new materials to be used in orthopaedic and dental/craniofacial implant applications.

Aerosol-Mediated Fabrication of Porous Thin Films Using Ultrasonic Nebulization

High surface area ceramic films and biopolymer films were fabricated by precipitation at room temperature of a reagent aerosol composed of approximately 1 μm diameter microdroplets laid onto a reactive receiver solution using a completely enclosed system. Calcium phosphate films of up to 340 μm in thickness composed of hollow microspheres were generated by gradual settling and precipitation of the reagent microdroplets on the receiver solution surface. Suitability of the ceramic film as a drug support using alendronate as an example was investigated. Chitosan/alginate biopolymer films were similarly prepared and precipitation with limitation to the air/water interface promoted a wire form copper oxide precursor. Zirconia microspheres were prepared without use of surfactant or template via precursor precipitation in a stirred receiver solution. Additional components could be readily incorporated and the flexibility of the novel approach is consistent with a new general strategy for the preparation of thin films and hollow microspheres of nanostructured materials.

Evaluation of Calcium Phosphate Coating Films on Titanium Fabricated Using RF Magnetron Sputtering

Calcium phosphate coating films fabricated on commercially pure titanium (CP-Ti) substrates using radiofrequency (RF) magnetron sputtering were evaluated in vivo and in vitro for investigating their applications in dental and medical implants. For the in vitro evaluations of the calcium phosphate coating films, the bonding strength and alkaline phosphatase (ALP) activity were examined. The bonding strength of the coating films to a polished titanium plate exceeded 60 MPa. When compared with an uncoated titanium plate, the increase in the ALP activity of SaOS-2 cells (a well-characterized osteosarcoma human cell line exhibiting osteoblast-like properties) on a titanium plate coated with a calcium phosphate film was confirmed by a culture test. Titanium cylinders coated with an amorphous calcium phosphate film were implanted into the mandibles of beagle dogs. The percentage of bone-implant contact in coated titanium was greater than that in uncoated titanium.

Preparation of Hydroxyapatite and Calcium Phosphate Films by MOCVD

Ca-P-O films were prepared by MOCVD using Ca(dpm)2 and (C6H5O)3PO precursors. The crystal phase changed with changing deposition conditions of substrate temperature (Tsub), total pressure (Ptot) and molar ratio of Ca and P precursors (RCa/P). � -tricalcium phosphate (� -Ca3(PO4)2) in a single phase was obtained at Tsub ¼ 973 K, RCa/P < 0:3 and Tsub ¼ 1073 K, RCa/P ¼ 0:1 to 0.5. Hydroxyapatite (Ca10(PO4)6(OH)2) in a single phase was first prepared by MOCVD at Tsub ¼ 973 K, RCa/P ¼ 0:5 and Tsub ¼ 1073 K, RCa/P ¼ 0:8 to 1. The maximum deposition rate of � -TCP and HAp films in a single phase were 6.0 and 4.0 nm s � 1 at Ptot ¼ 0:8 kPa and Tsub ¼ 1073 K, respectively. [doi:10.2320/matertrans.MRA2007145]

Eramosa Lagerstätte—Exceptionally preserved soft-bodied biotas with shallow-marine shelly and bioturbating organisms (Silurian, Ontario, Canada)

The middle Silurian Eramosa Lagerstatte of Ontario, Canada, preserves taxonomically and taphonomically diverse biotas including articulated conodont skeletons and heterostracan fish, annelids and arthropods with soft body parts, and a diverse marine flora. Soft tissues are preserved as calcium phosphate and carbon films, the latter possibly stabilized by early diagenetic sulfurization. It is significant that the biotas also include a decalcified, autochthonous shelly marine fauna, and trace fossils. This association of exceptionally preserved and more typical fossils distinguishes the Eramosa from other Silurian shallow-marine Lagerstatten, such as the Waukesha Lagerstatte, and suggests that the Eramosa is not the product of exceptional preservation in an atypical environment, a bias claimed for many post-Cambrian Lagerstatten. The Eramosa Lagerstatte may provide a more reliable, balanced measure of what has been lost from the Silurian fossil record.

Study of Calcium Phosphate Deposition on Porous Titanium Samples

Surgical implant coatings and grafts for tissue replacement have been made by porous surface materials to improve the implant to bone attachment. In this work, porous titanium samples were produced via powder metallurgy techniques and submitted to the biomimetic process in order to enhance its osteoconductivity. This process allows a nucleation and growth of a calcium phosphate film which makes a chemical bond with titanium. Therefore, it avoids the looseness of this film from substrate. The samples were chemically treated, heat treated at different temperatures and soaked into a modified body fluid solution (mSBF) during periods of 2 and 7 days. Samples with and without pretreatments and not soaked in mSBF were used as controls. SEM and EDX analyses detected a calcium phosphate phase on the sample surfaces treated at 400°C and 600°C and soaked in mSBF for 2 and 7 days. The results demonstrated the potential of the methodology applied for obtaining a bonelike apatite film on porous titanium samples processed by powder metallurgy.

Effect of polyethylene pretreatments on the biomimetic deposition and adhesion of calcium phosphate films

The effect of ultraviolet irradiation and glow discharge (GD) processing of the polyethylene (PE) substrates on deposition of calcium phosphate (CaP) films from supersaturated aqueous calcium phosphate solutions was investigated in this study. CaP coatings deposited on the PE substrates were comprised of elongated clusters of spherical particles and 100% of the free surface area of nearly all of the substrates was covered with a porous CaP film after a 3 day immersion. Nano-scratch tests determined that PE–CaP adhesion was most improved when PE substrates were subjected to 50 W GD treatments. As determined by contact angle measurements, the GD-treated PE samples had the highest electron donor parameter of surface energy, suggesting that enhancing the electron donor parameter of PE leads to improved adhesion with the biomimetic CaP coating.

P.059 In vivo evaluation of calcium phosphate films coated on titanium implant by RF magnetron sputtering

The stability of radiofrequency (RF) magnetron sputtered calcium phosphate was studied under cyclically loaded conditions. The coatings were deposited on titanium bars and tested in either dry or wet conditions. X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray (EDX) analysis and Fourier transform infrared (FTIR) spectroscopy were used to characterize the assputtered and tested coatings. XRD demonstrated that the amorphous structure after annealing at 650 °C changed into a crystalline apatite structure. The residual stresses were determined by the XRD cos2ø method. These residual film stresses were influenced by the coating conditions and the crystalline sputtered coating showed the presence of compressive stresses. SEM demonstrated that, after cyclic loading conditions in air, the crystalline sputter-coated Ti-6AI-4V bars showed a partial coating loss. Furthermore, in wet conditions (simulated body fluid) only the heat-treated sputter-coated bars appeared to be stable. On the other hand, the amorphous coating only showed signs of delamination in the more highly stressed regions, while in the less stressed regions a Ca-P precipitate was formed. On the basis of these results we conclude that calcium phosphate coatings subjected to cyclic loading conditions show an important difference in fatigue behaviour when tested in either dry or wet conditions.

Industrial application of ion beam assisted deposition on medical implants

Hydroxyapatite, one form of calcium phosphate coating, is widely used as a biocompatible material for bone tissue replacement, since it has the ability to bond to osseous tissue due to compositional similarity to the mineral phase of bone. Ion beam assisted deposition (IBAD) has been proved a promising coating method with more advantages, such as higher bonding strength and uniformity film, over other coating methods (plasma spraying technique, sputtering, etc.). The calcium phosphate film formed on dental implant by IBAD is expected to promote the integration of soft tissue and bone with implants in order to prolong their lifetime in body. For this purpose and gaining the application permission from Food and Drug Administration, the characteristics of the coating was evaluated, and the necessary in vitro and in vivo experiment and clinical assessments were made in this paper.

Differential cytokine responses of murine macrophage J774A.1 cells to stainless steel coated with and without hydroxyapatite

Identification of cytokines secreted by macrophages and assessment of macrophage function in response to biomaterials is an important aspect of the host response to biomaterials. In the present study, differential cytokine responses of murine macrophage J774A.1 cells to stainless steel (SS) coated with and without hydroxyapatite (HA) were investigated. HA-coated SS was prepared through the deposition of thin (1 μm thick) calcium phosphate film by electron beam evaporation. SEM micrographs show that the surface of HA-coated SS was smoother than that of SS. Cell growth of J774A.1 macrophages onto HA-coated was about 1.5 times better than that onto intact SS. Reverse transcription-polymerase chain reaction analysis revealed that the mRNA of cytokines, such as tumor necrosis factor-α, transforming growth factor-β and granulocyte macrophage colony stimulating factor, was relatively less expressed in J774A.1 macrophages grown onto HA-coated SS. These results suggest that HA coatings may influence the expression of inflammatory cytokine in macrophages and improve the surface properties of metallic materials.

Composition and crystal structure of resorbable calcium phosphate thin films

Silicon stabilized tricalcium phosphate (Si-TCP) is formed, among other phases, as a result of sintering hydroxyapatite (HA) in the presence of silica (SiO2) at >800°C. Calcium phosphate films sintered at 1000°C on quartz substrates are examined with and without additional SiO2 added to the starting precipitate. Data from transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) separate the undoped film morphology into a surface layer with a monoclinic crystal structure P21/a characteristic of α or Si-tricalcium phosphate and grain size in the range 100–1000 nm and a substrate layer with a crystal structure which is predominantly apatitic P63/m and grain size in the range 30–100 nm. The silicon content is greatest in the substrate layer. The addition of SiO2 to the film material during fabrication induces a more uniform grain size of 10–110 nm and a higher Si content. The structural and phase evolution of these films suggests the nucleation of α-TCP by the local formation of Si-TCP at a SiO2-hydroxyapatite interface. The results are consistent with X-ray diffraction studies and are explained by a model of nucleation and growth developed for bulk powders.

Fabrication of hydroxyapatite thin films for biomedical applications using RF magnetron sputtering

The calcium phosphate thin films for medical applications require similar chemical properties as those of natural bone as well as a uniform surface without any defect, such as cracks and pinholes. In this study, the calcium phosphate thin films were fabricated using RF magnetron sputtering deposition technique at discharge power of 200W, 300W and 400W. The target used for the deposition was sintered HAp. RBS analysis showed that the Ca/P ratio increased with the discharge power becaming close to that of Ca/P=1.67 in ideal HAp. XPS analysis revealed the presence of PO43- and OH− bonds in the calcium phosphate films fabricated. The chemical properties of the calcium phosphate thin films were similar to those of ideal HAp. The AFM results revealed that the thin films prepared had a uniform surface.