Narrow Results

Six samples of fossilized dinosaur bone and surrounding rock were analyzed by PIXE to investigate general relations between the bone and rock. The powdered samples were brought into an acid solution by a lithium metaborate fusion process. The data were analyzed with chemometric methods to successfully differentiate the bone samples from the complementary rock samples. The Sr/Ca ratio is consistently higher in fossilized bone than the surrounding rock. Ba, Y and U, when found in the rock, appear in significantly higher concentrations in the bone. S and Ti, elements commonly found in rock samples, are not found in the bone samples.

Many kinds of materials are currently used as artificial bone substitutes. Hydroxyapatite (HA), the same as the main inorganic component of bone, is one of commonly used bio-ceramics and has excellent bioactivity and biocompatibility with hard tissues. However, it has problems as the bone filler or bone tissue-engineering scaffold due to low fracture toughness and low degradation rate. Recently, biodegradable materials for bone tissue have been developed to respond the requirement. Collagen, the same as the main organic component of bone, is biocompatible, biodegradable and promotes cell adhesion. A composites associated with HA is expected to have early osteoconduction and bone replacement ability. The present study was to fabricate bone-like composites consist of HA and collagen. Besides the ossiferous ability of the material in vivo is evaluated by using rabbits. Bone-like composites were successfully fabricated in this study, associating the collagen with HA. And the composites presented good osteoconductive and bone replacement potential.

Porous NiTi shape memory alloy (SMA) with 48% porosity and an average pore size of 50–800 μm was synthesized by capsule-free hot isostatic pressing (CF-HIP). To enhance the surface bioactivity, the porous NiTi SMA was subjected to H₂O₂ and subsequent NaOH treatment. Scanning electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy analyses revealed that a porous sodium titanate (Na₂TiO₃) film had formed on the surface of the porous NiTi SMA. An apatite layer was deposited on this film after immersion in simulated body fluid at 37°C, while no apatite could be found on the surface of the untreated porous NiTi SMA. The formation of the apatite layer infers that the bioactivity of the porous NiTi SMA may be enhanced by surface chemical treatment, which is favorable for its application as bone implants.

Calcium phosphate and silicate-modified gold surfaces have potential applications in orthopedic and dental reconstruction, especially when combined with bone cement or dental resins. The aim of this study was to evaluate the formation of a Si–Na–Ca–P glass system nanoshell on functionalized gold nanoparticles. Stable gold nanoparticle suspensions were prepared by controlled reduction of HAuCl₄ using the sodium citrate method to obtain a nanogold-mercaptopropyltrimethyloxysilane (MPTS)–silicate–tetraethylothosilicate (TEOS)-capped particle solution. The nanoshells were formed when directly reacted with a 10^-4 M calcium phosphate ion solution. The median nanoparticle diameter was observed to be 15 nm. The MPTS–silicate–TEOS–functionalized nanoshell more effectively formed a glass shell as compared with a nonsilicate nanoshell. The changes in the surface morphology and composition were observed by a scanning transmission electron microscope equipped with energy-dispersive X-ray spectroscopy. As seen using EDS, the nanoshell was in a glass phase with CaO-poor layers.

Titanium oxide films were prepared using an anodic oxidation method in sulfuric acid solution on the surface of Ti6Al4V alloy at room temperature. The surface energy was obtained by the measurement of contact angles and the calculation with Owens–Wendt–Kaeble's equation. Ti6Al4V with anodic film after chemical treatment with NaOH aqueous solution showed excellent apatite-forming ability and produced a compact apatite layer covering all the surface of titanium after soaking in three times concentration (SBF × 3) for three days. A bioactive titania-CaP film was obtained on Ti6Al4V. Scanning electron microscopy, X-ray diffraction and Fourier Transform Infra-Red were used to analyze composition changes of the bioactive film. It is concluded that the acceleration of the apatite nucleation on the anodized Ti6Al4V with chemical treatment in a modified simulated body fluid was attributed to the novel surface characteristics and the formation of sodium titanate hydrogel layer during chemical pretreatment. The treatment of Ti6Al4V by anodic oxidation and subsequently in NaOH is a suitable method for providing the metal implant with bone-bonding ability.

Properties of materials are determined not only by their composition, but also by their structure. It is, therefore, of great significance to develop the ability of tailoring the structure of materials according to the requirements of intended applications. In this work a novel glutamic acid-assisted hydrothermal process was developed to synthesize apatite crystals with controllable morphologies. Varied morphologies from whisk broom, fibers, mushroom, prickly spheres, to dandelion were produced through modulating both the formation of a transitory phase and its transformation into the final phase.

We have previously reported a blast coating method as a new coating method of titanium (Ti) with apatite (AP) at room temperature. The blast coating method gives much stronger AP coating on Ti surface when compared with those obtained by other coating methods at room temperature. As an initial step to evaluate the usefulness of the blast coating method, we evaluated tissue response and stability of AP coated Ti implant prepared with blast coating method using experimental animals. The AP coating stuck tightly on the Ti surface even after implant procedure. AP coated Ti implant showed excellent tissue response and much better osteoconductivity when compared with pure Ti implant. Therefore we concluded, AP coated Ti implant prepared with the blast coating method has a good potential value as osteoconductive implant material.

Self-assembled-monolayer (SAM) has a special characteristic that it can template the growth of inorganic crystals under the ordinary conditions, which is similar to the action in the living bodies. In the present study, the precipitation of apatite on "OH" terminated SAM surface(silicon) was observed after soaked in SBF (Simulated Body Fluid). On the contrary, little apatite was formed on the SAM surface with "Phenyl" headgroups. PTCS (Phenyltrichlorosilane) was employed to make "Phenyl" terminated hydrophobic SAM . After UV irradiation for 2 hours, "-OH" terminated hydrophilic SAM was obtained. The effects of such factors as pH and Ca/P molar ratio in SBF solution, soaking temperature and time .etc, on the crystallization of apatite were investigated. XRD results revealed the preferentially oriented crystallization of apatite on "OH" terminated SAM.

As a candidate for highly loaded bone substitute, tantalum metal has attractive features such as biocompatibility, high malleability and ductility. The present authors previously showed that NaOH and heat treatments make tantalum metal to form a bonelike apatite layer on its surface in a short period, although even the untreated tantalum metal forms the apatite in a long period. In the present study, bonding strength of the apatite layer, which was formed on the NaOH- and heat-treated tantalum metal, to the substrate was measured under tensile stress and compared with that of the apatite formed on the untreated substrate. The former showed much higher bonding strength than the latter. The higher bonding strength of the former was attributed to a graded structure at the apatite-substrate interface where the apatite gradually changes into the interior metal substrate.

Commercially pure titanium was treated with an H₂O₂/TaC1₅ solution. Thus formed titania gel layer remained amorphous when heated below 200°C and transformed to anatase after heated between 300-600°C. The anatase layers were substantially bioactive to deposit carbonate ion-incorporated apatite after soaked for 1 d in a simulated body fluid (Kokubo’s recipe), while the amorphous layers did not deposit up to 7 d. The apatite particles were preferably nucleated inside the cracks which prevailed in the titania gel layers. After soaking only for 2 d, the specimens were almost completely covered by the apatite. The H₂O₂-treated Ti specimens deposited apatite on both the contact and open surfaces, whereas the NaOH treated Ti specimens only deposited on the contact surfaces. The elimination of peroxide radicals out of titania gel and formation of anatase during heating are considered to be responsible for the improvement of apatite deposition ability.

Hydroxylapatite (HA) coatings on titanium alloy (Ti6A14V) implants are widely used in orthopaedics because the high strength of metals is combined with the osteoconductive properties of calcium phosphate (Ca-P). HA coatings are commonly applied on metal prostheses by plasma spraying. However, this technique presents important drawbacks: inability to cover porous implants and to incorporate biologically active agents, delamination and particles release. Recently, a biomimetic approach has been developed for coating metal implants. This method which mimics biomineralization allows the deposition of a bone-like apatite layer on metal prosthesis. In this study, cleaned and etched Ti6A14V samples were firstly immersed into a Simulated Body Fluid (SBF) solution at 37°C and secondly into SBF solution containing less inhibitors of crystal growth (e.g. Mg²⁺, HCO₃^-). A bone-like apatite layer of ≈15μm precipitated on the titanium alloy surface. Scratch testing showed that Biomimetic Apatite Coating (BAC) is more elastic than the brittle HA-PSC. Furthermore the dissolution rate of BAC is in the same range as HA-PSC. The biomimetic method can produce a stable and well adhered apatite coating on complex shapes at physiological conditions.

It was already revealed that a sol-gel-derived titania forms an apatite on its surface in a simulated body fluid (SBF). It is, however, not clear what structure of titania gel is effective for inducing apatite nucleation on its surface. In the present study, apatite-forming ability of titania gels with different structures, which were formed in different media and heat-treated at different temperatures, were investigated in SBF. The titania gels heat-treated at 300°C took amorphous phases and did not form the apatite on their surfaces even after 14 days irrespective of the media. The titania gels, which were prepared in media containing no additive or acetylacetone and heat-treated at 500 to 800°C to precipitate anatase, formed the apatite on their surfaces within 7 days in SBF. The titania gels, which were prepared in a medium containing diethanolamine and heat-treated at 700 to 800°C to precipitate rutile, formed the apatite within 14 days in SBF. This indicates that a specific structure of titania such as anatase structure is effective for inducing apatite nucleation.

Calcium phosphate clusters approximately 0.8 nm in diameter were detected in a solution containing only CaC1₂, H₃PO₄ and KCl at 25.0°C using an intensity-enhanced dynamic light scattering (DLS) technique. This suggests that tris(hydroxymethyl)aminomethane used as a buffer had no contribution to the formation of the clusters. The clusters were also detected in a simulated body fluid (SBF) with ion concentrations nearly equal to those of human blood plasma and in a solution (1.5SBF) with ion concentrations 1.5 times the SBF at 36.5°C.

Adsorptive properties of hydroxyapatite (HAp) for proteins were studied by Quartz Crystal Microbalance (QCM) method. The time-series reactions of HAp thin films to acidic and basic proteins were analyzed in various pH buffers by the simultaneous resonant frequency and dissipation factor measurements. The amorphous calcium phosphate thin films deposited on the Au-electrode of quartz crystals by rf-magnetron sputtering were transformed into the polycrystalline HAp films by post-annealing treatment in hydrothermal atmosphere. Adsorbate solution was continuously injected by a tube pump at controlled flow rates into the QCM cell equipped with a PC added measurement system. The difference in adsorption for albumin and histone was detected from their resonant frequency shifts. It was suggested that the developed QCM system was effective for studies on protein adsorption behaviors onto HAp.

This study evaluated the possibility of obtaining bioactive coatings on polyethylene/bioactive glass composites exhibiting a very good mechanical performance. High molecular weight polyethylene (HMWPE) was reinforced with 10 to 40% (wt.) of a bioactive glass (BGE1) and a glass-ceramic (BGE1C), in the SiO₂-3CaOP₂O₅-MgO system. The composites were compounded by twin-screw extrusion (TSE) and then injection moulded into dumb-bell tensile samples. The composites presenting adequate mechanical properties were then coated with a bioactive layer by two methodologies: (i) an adapted biomimetic route using a similar glass as a precursor of calcium-phosphate (Ca-P) film deposition, and (ii) the production of a ‘sandwich’ with bioactive glass particles, previously mixed with UHMWPE powders, made to adhere to both faces of tensile samples by compression moulding. The obtained results indicated that it is possible to produce composites presenting a modulus of 11.2 GPa coupled with a tensile strength of around 117 MPa. The developed composites could be coated with a Ca-P layer by an adapted biomimetic route. Furthemore, the ‘sandwich’ route allowed for the production of load-bearing composites, presenting a highly bioactive surface, which strongly adheres to the HMWPE matrix composites.

Since AEROSIL® is one of the reinforcement materials for silicone, we synthesized the organically modified silicate (ORMOSILS) gels reinforced with AEROSIL® starting from poly (dimethylsiloxane) (PDMS), tetraethoxysilane (TEOS) and calcium nitrate (Ca(NO₃)₂•4H₂O) through sol-gel processing. The storage modulus increased with the AEROSIL® content along with the increase in PDMS-AEROSIL® bonds. The gel of a specific composition could deposit apatite within 1 day of soaking in the Kokubo solution, since it included many calcium ions on the surface.