Thin HA Research Articles

Ceramic Powder Bed Laser Sintering (CPBLS) on copper-doped hydroxyapatite: Creation of thin (5–50 μm thick) consolidated ceramic patterns

Implants made of ceramics, and more particularly of calcium phosphates (hydroxyapatite: HA, mainly), promoting intimate contact with natural bone are nowadays merging. Addition of copper ions in bio-ceramics is expected to increase the biological compatibilities of bone graft substitutes. Previous works have shown that copper-doped hydroxyapatite (Cu-doped HA) ceramics can be prepared by solid-state sintering between HA and CuO powder mixtures at about 1100 °C; but, copper-substituted HA was found to be metastable leading to apatitic grains and Cu-rich grain boundaries during the sintering process. Ultra-rapid sintering is so needed. Selective laser sintering (SLS) is an additive manufacturing process that possesses the advantage to be based on ultra-fast sintering process under laser irradiation. SLS being used in literature for the application of laser on polymer-ceramic or poymer-metal composites the proper term all along the paper is Ceramic Powder Bed Laser Sintering (CPBLS). To achieve densification of Cu-doped HA ceramics from CPBLS process, one should control the composition/morphology/structure of the powder bed as well as three other important CPBLS parameters: (i) the applied energy from the laser beam, (ii) the laser power and the laser scanning speed, (iii) the distance between two successive lased lines. In this paper, the impact of all the main CPBLS parameters controlling the sintering of dip-coated Cu-doped HA layers on glass substrates is carefully investigated. Possibility of the creation of thin consolidated Cu-doped HA ceramic patterns, using the ultra-fast CPBLS process, is finally shown.

スパッタ薄膜HA インプラントの樹脂ブロックへの埋入トルクによるHA 膜密着強さ

スパッタ薄膜HA インプラントの樹脂ブロックへの埋入トルクによるHA 膜密着強さ

Smart nanoparticles assembled by endogenous molecules for siRNA delivery and cancer therapy via CD44 and EGFR dual-targeting

We developed an anticancer siRNA delivery system (named HLPR) through modular assembly of endogenous molecules. The structure of HLPR was a tightly condensed siRNA-peptide inner core in turn surrounded by the disordered lipid layer and thin HA coating from which the EGFR-targeted amino acid sequences of YHWYGYTPQNVI partially protrude outside of cell surfaces. Both HA and YHWYGYTPQNVI anchored on HLPR were responsible for targeting CD44 and EGFR overexpressed on the tumor cell surfaces, respectively. HLPR was relatively stable in the blood circulation and reached the tumor tissue in vivo through passive and active targeting. Then HLPR entered tumor cells mainly through EGFR-mediated pathway followed by the separation of HA from the remaining parts of nanocomplexes. The HA-uncoated complexes escaped the endosome through the membrane fusion function of DOPE and released cargoes (siRNA and peptide/siRNA) in the cytoplasm. HLPR significantly inhibited the growth of implanted subcutaneous liver tumors without toxicity.

Effect of silicate doping on the structure and mechanical properties of thin nanostructured RF magnetron sputter-deposited hydroxyapatite films

Silicon-doped hydroxyapatite-based (Si-HA) coatings were deposited via radio frequency (RF) magnetron sputtering on the surface of titanium that was treated with a pulsed electron beam. This study aimed to evaluate the effect of Si doping on the structure and mechanical properties of thin HA films. The content of the silicon was 1.2 and 4.6at.% for the coatings prepared using the Si-HA precursor powders with a chemical formula Ca10(PO4)6−x(SiO4)x(OH)2−x where, x=0.5 and 1.72. Pure HA (Ca10(PO4)6(OH)2) coatings were deposited for comparison. The as-deposited films were analysed with respect to their composition, state of chemical binding and microstructure using XPS, FTIR, XRD, and SEM. We hypothesized that the addition of Si would affect the mechanical features of the coatings due to microstructure changes. The effect of the introduction of Si on the nanohardness and the Young's modulus as well as the adhesion strength and scratch resistance of the HA coating was investigated using nanohardness testing and a scratch test, respectively. Examination of the coating microstructure using SEM and AFM revealed that Si doping influenced the surface morphology and led to a smaller grain size. The tendency to form an amorphous structure also increased with an increase in the Si content. A monotonous decrease in both the nanohardness and the elastic modulus was observed with an increase in the Si content. A maximum nanohardness of ~7GPa was obtained for the Si-free HA coating, whereas the hardness decreased to ~4.3GPa for the films with a Si content of 1.2at.%. The addition of 4.6at.% Si to the HA coating resulted in a reduction in the elastic modulus, whereas the nanohardness was very similar to that of the uncoated substrate. The adhesion behaviour of the coatings demonstrated different responses. In the case of pure HA coatings, failure occurred due to the low cohesion of the coating, whereas the crystalline Si-HA coatings with a Si content of 1.2at.% deformed plastically without crack formation and without detaching from the titanium substrate, which resulted in a greater coating stability.

薄膜HA インプラントの生物学的安全性と有効性： 埋植試験および使用模擬試験

薄膜HA インプラントの生物学的安全性と有効性： 埋植試験および使用模擬試験

Evaluation of biological safety of a thin HA sputta-coated implant

Evaluation of biological safety of a thin HA sputta-coated implant

Antibacterial Properties of Silver‐Loaded Plasma Polymer Coatings

In a previous paper, we proposed new silver nanoparticles (SNPs) based antibacterial coatings able to protect eukaryotic cells from SNPs related toxic effects, while preserving antibacterial efficiency. A SNPs containing n‐heptylamine (HA) polymer matrix was deposited by plasma polymerization and coated by a second HA layer. In this paper, we elucidate the antibacterial action of these new coatings. We demonstrated that SNPs‐loaded material can be covered by thin HA polymer layer without losing the antibacterial activity to planktonic bacteria living in the near surroundings of the material. SNPs‐containing materials also revealed antibacterial effect on adhered bacteria. Adhered bacteria number was significantly reduced compared to pure HA plasma polymer and the physiology of the bacteria was affected. The number of adhered bacteria directly decreased with thickness of the second HA layer. Surprisingly, the quantity of cultivable bacteria harvested by transfer to nutritive agar decreased not only with the presence of SNPs, but also in relation to the covering HA layer thickness, that is, oppositely to the increase in adhered bacteria number. Two hypotheses are proposed for this surprising result (stronger attachment or weaker vitality), which raises the question of the diverse potential ways of action of SNPs entrapped in a polymer matrix.

56th Annual Meeting of the American Academy of Implant Dentistry and the World Congress of Oral Implantology 7 Abstracts, 2007

56th Annual Meeting of the American Academy of Implant Dentistry and the World Congress of Oral Implantology 7 Abstracts, 2007

Fabrication and Characterization of Bioactive Cancellous-Like Surface on Titanium

Bioactive porous surface on metal implants are benefit for forming the continuous interface with “mechanical interlocking” and “chemical bonding” between implants and bones. In the present study, the main attention was concentrated on fabricating a porous bioactive surface on Ti substrate. Porous surface was first fabricated by two-step etched. Then thin HA coating was deposited on the pre-treated porous Ti surface by sol-gel method and immediately sintered at 500°C for 1 hour. The structure and morphology of HA coating formed on the porous surface were characterized by thin-film X-ray diffrac- tion and scanning electronic microscopy, respectively. Rietveld method and Warren-Averbach Fourier Transfer Analysis were employed to determine the lattice parameters, crystallite size and micro-strain of HA coating. The SEM results indicated that an interconnecting porous surface with cancellous structure and mean diameter about 1/m was etched on the Ti substrate, and the surface was covered by a thin particle coating. The TF-XRD results testified that the thin coating was poor crystalline HA.

Effects of Thin Hydroxyapatite Coating on Initial Response of Osteoblast-Like Cells

To combine the bioinert titanium with the biological active coating of hydroxyapatite [HA, Ca10(PO4)6(OH)2] a new pulsed laser deposition(PLD) method was applied. The initial osteoblast-like MC3T3-E1 cell response to this thin HA coated(<1μm) surface was compared with non-coated surfaces. Cell responses on four different pure titanium surfaces, such as smooth titanium, HA coated smooth titanium, rough titanium and HA coated rough titanium, were compared. Cell morphology and attachment were examined by scanning electron microscopy after 6, 24 and 72 hrs of culture, cell proliferation by MTS assay after 3, 7 and 14 days. The differentiation of the cells was analyzed by real time PCR up to 21 days. The cells were well spread and attached on all surfaces and showed more irregular shapes on the HA coated specimens. They proliferated continuously on all specimens up to 14 days. Smooth surface specimens showed better cell proliferation than rough ones after 7 days, and the HA coated specimens demonstrated slightly greater MTS activity than the non-coated groups after 14 days. The surface topography affected cell proliferation initially however; there was no significant difference afterwards. Thin HA coating influenced the expression of some genes related with cell differentiation.

Development of thin electrophoretically deposited hydroxyapatite layers on TiAl6V4 hip prosthesis

Hydroxyapatite ceramics for biomedical applications are often used in form of coatings to increase the biocompatibility of metallic implants, e.g. the femoral shaft of a hip prosthesis. A new method to produce such layers is electrophoretic deposition (EPD). The aim of this study was to investigate the influence of different powders and process parameters on the quality of the electrophoretically deposited thin HA layers. In order to attain layers with a thickness less than 50 μm, it is essential to use fine powders with particle sizes in the sub-micron range, and to stabilize these powders in suspension. We show that commercially available hydroxyapatite powders, which usually have a strong tendency to agglomerate, can be milled to particle sizes smaller than 500 nm by adding an organic dispersant. When such milled powders are used together with optimized process parameters, thin and homogenous layers can be produced by EPD. Using either aqueous or non-aqueous suspensions, hydroxyapatite layers can be deposited directly onto a metallic hip shaft, or onto a polymeric membrane, producing thin free-standing ceramics used for special biomedical applications.

Sterilization and Deodorization of Titanium Oxide and Hydroxyapatite Coating by Sputtering Technique

TiO2 and HA thin film double coating has been proposed. The TiO2/HA thin film was coated on the glass by a Radio Frequency magnetron sputtering, and the characteristic of the thin film has been studied. The absorption of Formaldehyde (HCHO) gas in the TiO2/HA thin film was detected by gas chromatography, and the sterilization of Escherichia coli (E. coli) was evaluated in the antibacterial test. In the deodorization test, HCHO gas remained 0[%], 11[%] and 85[%] for TiO2/HA thin film, TIO2 thin film and thin film respectively. The sterilization result shows that E. coli for TiO2/HA thin film and HA thin film decreased 89[%] and 75[%] respectively.

Development of Hydroxyapatite Thin Film on Titanium Substrate by Electrophoretic Deposition

Electrophoretic deposition was used for HA coating on dental implants with different coating thickness. The HA coating thickness was examined in terms of applied voltage and time, and powder concentration in suspension. Nano-size HA and SiO2-CaO-P2O5-B2O3 bioglass powders were synthesized by sol-gel method. Polyvinyl alcohol (3 wt%) as a binder was resolved in ethyl alcohol, then, nano HA powder was dispersed ultrasonically in the mixture for 15 min and pH was adjusted with HNO3 for positive charging on particle. Titanium substrate was held on cathode and counter electrode was platinum. HA with 0.5 % and 0.03 % of powder concentration was deposited electrophoretically at 10~20 V for 1~20 minutes. The thickness of as-deposited HA layer decreased from nearly 80 µm (0.5 %, 20 V, 10 min) to 4~5 µm (0.03%, 10V, 1 min) as powder concentration, applied voltage and time decreased, respectively. The surface of HA coating layer deposited in lower powder concentration showed much more homogeneous and relatively dense morphology, in contrast, the surface in thick suspension became rough or porous and was easily spalled. In a co-deposition of HA and bioglass, co-deposited glass played an important role in increasing bonding strength between coating layer and substrate. It is believed that electrophoretic deposition method can be one of alternatives for relatively thin and easy HA coating.

Ion beam and laser processing for hydroxyapatite formation

We present a study of simultaneous exposure of ion-implanted metal substrates to laser irradiation and solution. The proposed method for a growth of hydroxyapatite (HA, bone- and teeth-like material) employs a deposition system and a process, which allows interaction between a scanning laser beam and a liquid precursor solution (simulated body fluid, SBF), and also lasers illumination of the substrates during the laser–liquid interaction. We examine the grown layers by XRD, FTIR and Raman spectroscopy, SEM, EDX, and light microscopy. It is suggested that the HA nucleation begins with the absorption of photon energy by the substrate and the effect of the laser irradiation is to promote and enhance the HA nucleation process. Subsequent two-stage immersion of the irradiated samples in SBF yields the growth of a very thin HA layer, which overgrows to a thicker and porous layer.

Plasma sprayed graded titanium hydroxyapatite coatings

A series of graded titanium-hydroxyapatite (HA) coatings have been produced by single gun plasma spray technology, and their performance was compared with that of pure HA coating. The results show that deformed HA and titanium particles exhibit an alternate distribution in respective networks formed within the coatings. In comparison with a pure HA coating, less cracks appeared on the surface of the graded coatings and the shear bond strength was increased by 50-80%. The graded coating with two interlayers and a thin outer HA layer contained crystalline HA, an amorphous phase, α-tricalcium phosphate (TCP), β-TCP, tetracalcium phosphate (TTCP), TiO2 and TiN; while no Ti-HA compounds were formed. As compared with pure HA coating, the graded coating contained more decomposed phases TCP and TTCP, resulting from titanium catalysing HA decomposition.

The effect of hydroxyapatite thickness on metal ion release from stainless steel substrates

The corrosion behaviour of 350 stainless steel coated with hydroxyapatite, HA, by plasma spraying was studied in Hank's Balanced Salt Solution, HBSS, and compared with that of polished passivated surfaces. Two different nominal thicknesses, 50 μm and 200 μm, corresponding to what one might consider a thin and a thick coating, respectively, were used. Only HA coatings with a thickness of 200 μm were capable of reducing the electrical charge consumed at constant potential to values lower than those measured for polished surfaces. However, no HA detachment occurred for both thicknesses, as opposed to what has been found in a previous work [1] with Ti6Al4V alloy coated with 50 μm HA. No iron, chromium or nickel were detected in solution by Atomic Absorption Spectroscopy with electrothermal atomization (ET-AAS). These elements were also absent from the bulk of the HA coating, both after a 6 month immersion period and electrochemical accelerated tests. The data indicate that in spite of the relatively low corrosion resistance of stainless steel as compared to that of titanium alloys, a thin (50 μm) HA coating prevents the release of metal ions, while remaining adherent to the substrate.