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A coherent receiver that can demodulate high-speed in-phase and quadrature signals of light is an essential component for optical communication, interconnects, imaging, and computing. Conventional waveguide-based coherent receivers, however, exhibit large footprints, difficulty in coupling a large number of spatial channels efficiently, and limited operating bandwidth imposed by the waveguide-based optical hybrid. Here, we present a surface-normal coherent receiver with nanometallic-grating-based polarizers integrated directly on top of photodetectors without the need for an optical hybrid circuit. Using a fabricated device with the active section occupying a 70-{\mu}m-square footprint, we demonstrate demodulation of high-speed (up to 64 Gbaud) coherent signals in various formats. Moreover, ultra-broadband operation from 1260 nm to 1630 nm is demonstrated, thanks to the wavelength-insensitive nanometallic polarizers. To our knowledge, this is the first demonstration of a surface-normal homodyne optical receiver, which can easily be scaled to a compact two-dimensional arrayed device to receive highly parallelized coherent signals., Comment: 23 pages, 4 figures (main manuscript) + 4 pages, 2 figures (supporting info)

To develop one porous additive material that can be assembled on cigarette filter, and achieve both functions of reducing hazard substances like tar and providing special aroma and moisture, this study innovatively selects the raw materials like baking-carbonized functional flavors with special aroma and konjac glucomannan (KGM) with properties of water absorption, gelling and film-forming, following the steps of casting into membrane shape, thermostatic crosslinking for strength enhancement and freeze-drying for pore creating to prepare 5 porous composite membranes based on baked-carbonized functional flavors and konjac glucomannan (KGM) were prepared. The composite structure, morphologies on the surface and the cross section, porosity structures including mesoporous and macropore of the porous composite membranes were characterized, the tensile performance and aroma constituents through solid phase microextraction and hazardous substances adsorption as packed into the commercial cigarette were also studied. Results showed that all baked-carbonized functional flavors were carbonized into amorphous, and contained the groups of aromatic components like ≡C-H, C=O, C-O-C (aldehydes, esters), cross-linking achieved the entanglement of KGM segments by deacetylation. When compounded, KGM acted as the framework to build the 3D porous network structure, and the functional flavor powders were wrapped into the KGM layer. All porous composite membranes owned some mechanical strength and the internal porosity over 90%, the mesopores and the macropores were ranged with 5–50 nm and 20–255 µm, respectively, which was satisfied for gas flowing and harmful substances adsorption. Aroma and resulting abundance of extracted constituents changed with timing, which equipped the membranes with a comprehensive aroma feeling. Among them, the membrane prepared with the raw material of dark plum showed a better comprehensive performance, especially it could significantly reduce the contents of harmful HCN and phenol in cigarette during smoking.

Fluorapatite exhibits improved bone-bonding and chemical durability under neutral and acidic conditions compared with hydroxyapatite. Typically, an aqueous fluoride solution is used for F− incorporation into the hydroxyapatite. Use of an ionic liquid as F− source provides highly-concentrated ionic environment and can lead to more effective fluorination. In this study, two ionic liquids were added during the synthesis of hydroxyapatite under various conditions, and the differences in the crystalline structure and chemical durability of the resulting fluorapatites were investigated. 1-ethyl-3-methylimidazolium tetrafluoroborate was quite effective for F− incorporation, but not 1-ethyl-3-methylimidazolium hexafluorophosphate. When the temperature was increased to 80 °C, not only the hydroxyapatite or fluorapatite but also CaF2 was generated as a by-product. When the initial pH was decreased to 7, the formed product fully converted to CaF2. The solubility of the product tended to be suppressed in acidic conditions with increase in amount of fluorine substituted in the crystal lattice.

Titania-based materials are attractive for hard tissue repair due to their bone-bonding ability induced by apatite formation in the body environment. Various surface treatments have therefore been developed to produce a hydrated titania layer on Ti and its alloys. Titania takes various valences, such as TiO (Ti2+) and Ti2O3 (Ti3+), as well as typical TiO2 (Ti4+); however, there is no comprehensive study of structural effects on the apatite-forming ability of these titanias. In this study, we investigated apatite formation on titania powders with various valences in simulated body fluid. Anatase- and rutile-type TiO2 formed apatite in simulated body fluid within 7 days, but TiO and Ti2O3 did not. In contrast, when the titania powders were treated with NaOH solution, the surface converted to tetravalent titania and all samples formed apatite. It is proposed that the surface electrical states of TiO and Ti2O3 are strongly affected by their bulk conductivity and that these behaved like pure Ti metal, which has poor apatite-forming ability. Apatite formation was favorable when the titania had a high absolute value and exhibited high fluctuations of zeta potential during initial stages in simulated body fluid, owing to adsorption of large amounts of Ca2+ and HPO42−.

BACKGROUND: Microbeads for bone repair have been widely studied because they can be conveniently used in clinical applications. OBJECTIVE: This study concerns the preparation, physical properties and in vitro characterisation of different types of alginate/calcium phosphate (CaP) ceramic microbeads, which were designed for use as drug delivery systems and bone-regeneration matrices. METHODS: Hybrid microbeads were successfully prepared from sodium alginate and various CaP, namely 𝛼-tricalcium phosphate, 𝛽-tricalcium phosphate and hydroxyapatite using the liquid droplet method. RESULTS: Porosity, swelling properties and in vitro degradation of the microbeads in the aqueous environment were significantly changed by the added CaP. The compressive strength of the blocks fabricated from the beads was around 120 MPa irrespective of the type of CaP. The initial release rate of the model drug methylene blue was suppressed by the addition of CaP. CONCLUSION: The alginate-CaP composite beads hold promising potential as an encapsulation carrier of drugs and component of bone substitutes.

Bioactivity modification helps polymethylmethacrylate (PMMA) bone cement to reinforce its interfacial adhesion to bone tissues through the chemical bonding of apatite. Since Si-OH groups combined w...

Hyperthermia treatment using appropriate magnetic materials in an alternating magnetic field to generate heat has been recently proposed as a low-invasive cancer treatment method. Magnetite (Fe3O4) nanoparticles are expected to be an appropriate type of magnetic thermal seed for this purpose, and the addition of organic substances during the synthesis process has been studied for controlling particle size and improving biological functions. However, the role of the properties of the organic polymer chosen as the modifier in the physical properties of the thermal seed has not yet been comprehensively revealed. Therefore, this study clarifies these points in terms of the molecular weight and the charge of the functional groups of the added polymers. Excepting polyethyleneimine, the Fe3O4 crystallite size decreased with increasing polymer molecular weight. Neutral polymers did not suppress the Fe3O4 formation regardless of the difference in molecular weight, while suppression of the Fe3O4 formation was observed for low molecular weight anionic polymers and high molecular weight cationic polymers. Samples with a small amount of Fe3O4 or with crystallite size less than 10 nm induced low heat generation under an alternating magnetic field.

Octacalcium phosphate (OCP) is a key precursor of biological apatite in hard tissues with excellent osteoconductive and biodegradable properties for bone regeneration. OCP spherical granules are expected to be useful as drug delivery carriers, since OCP has high specific surface area. Although there have been some reports of OCP sphere preparation, methods for preparing pure OCP spheres are limited. The objective of this study is the preparation of spherical granules of pure OCP and assessment of their in vitro biodegradation in physiological conditions. We successfully prepared spherical pure OCP granules with a size of ~500 µm without any organic additives by simple immersion of α‐tricalcium phosphate spherical granules in pH 5.0 acetate buffered solutions at 60°C. The granules had core‐shell structure composed of OCP crystals different particle size. The spherical granules showed 20%‐40% in vitro degradation in physiological conditions; however, the phase transition of OCP was not significantly observed.

Magnetic iron oxides such as magnetite and γ-hematite have attracted considerable attention as thermoseeds for hyperthermia treatment because of their ability to generate heat under an alternating magnetic field. Control of the particle size and their combination with biocompatible polymers are expected to be beneficial for optimization of the nanoparticles. These processes can be accomplished through the synthesis of magnetite in gels, as the network structure of the polymer gel can control the grain growth of the magnetite. However, the effect of the cross-linking density of the gels remains unclear. In this study, we synthesized magnetic iron oxides in situ in chitosan hydrogels with different cross-linking densities and examined the crystalline structure and heat generation under alternating magnetic field. The crystalline phase and amount of magnetite were observed to be dependent on the cross-linking density of the gel, and the heat generation of the nanoparticles was governed by their crystalline structure and particle size rather than solely the amount of formed iron oxide.

Calcium carbonate (CaCO3) can show various properties related to its different crystalline phases and is therefore a useful material for various applications. Wet processes are known to be suitable for preparing metastable CaCO3 polymorphs. Electrolysis has been proposed as a preparation method at ambient conditions. Although several electrolytic approaches have been reported, the effects of the applied current and temperature of the electrolyte on the crystalline phase and morphology of CaCO3 remain unclear. In the present study, we attempted the electrochemical preparation of CaCO3 particles under various electrolysis conditions and discuss the mechanism of CaCO3 particle formation. The crystalline phases and morphologies of the CaCO3 precipitates markedly changed depending on the applied current and method of cooling the electrolyte. We assume that these factors were governed by the degree of change in temperature, supersaturation, and pH of the electrolyte that were induced by differences in the electrolysis current.

Octacalcium phosphate (OCP), an encrusted calcium phosphate complex, has appealed consideration in the field of biomaterial and apothecary, owing to its exceptional biocompatibility. However, not much is known about the effect of Na ion for the formation of OCP, irrespective of pH. Consequently, in this study, we considered the part of the Na ion in OCP growth from dicalcium phosphate dihydrate (DCPD) via hydrolysis by using 0.1 M CH3COONa solutions with adjustment of various pH. Novelty of the study is, expending this way we can synthesize OCP irrespective of pH and most importantly at 37°C, which is an important parameter for acceptable biomaterials. Throughout the study, no foreign phase was observed except OCP. Morphological images are also evident for the attractive OCP flowers.

Artificial hydroxyapatite (HAp) is osteoconductive, but the mechanism is still unclear. It is likely that some serum proteins are adsorbed onto HAp and influence its osteoconductivity. We investigated the adsorption behavior of laminin (LN), which was isolated from murine Engelbreth–Holm–Swarm sarcoma, onto HAp and compared it with nonosteoconductive alpha-type alumina (α-Al2O3). Cell adhesion, spreading, and proliferation on native and LN-adsorbed discs of HAp or α-Al2O3 were examined using murine MC3T3-E1 osteoblastic cells. A larger amount of LN adsorbed onto HAp than α-Al2O3 despite the electrostatic repulsion between LN and HAp, suggesting the specific adsorption of LN onto HAp. The LN adsorbed onto HAp remarkably enhanced initial attachment and spreading of MC3T3-E1 cells, but subsequent proliferation of MC3T3-E1 cells was influenced by the type of material rather than LN adsorption. These fundamental findings imply that LN adsorbed on HAp could trigger osteoconductivity in vivo, aiding in the development of novel biomaterials that specifically adsorb LN and effectively enhance cell attachment and spreading.

Magnetite (Fe3O4) nanoparticles such as thermoseeds for hyperthermia and contrast media in magnetic resonance imaging are attracting increasing attention in biomedicine. The organic modification of nanoparticles is an important technique to improve the biological compatibility and drug delivery functions. Also, the addition of organic molecules and the use of hydrogels as a reaction field in Fe3O4 preparation enable controlling the crystalline phase and particle size. In this chapter, the organic modification of Fe3O4 nanoparticles for biomedical applications is reviewed.

Bioactivity modification helps polymethylmethacrylate (PMMA) bone cement to reinforce its interfacial adhesion to bone tissues through the chemical bonding of apatite. Since Si-OH groups combined with Ca

Ti–Zr alloys are expected to be novel biomaterials with low stress shielding owing to their lower Young’s moduli than pure Ti. The drawback of metallic biomaterials is that their bone-bonding abilities are relatively low. NaOH and heat treatments have been performed to provide Ti–50Zr with apatite-forming ability in the body environment, which is essential for bone bonding. However, the systematic compositional dependence of apatite formation has not been revealed. In the present study, NaOH treatment of Ti–Zr alloys with various compositions and bone-bonding abilities was assessed in vitro by apatite formation in simulated body fluid (SBF). The corrosion current density in NaOH aqueous solution and the amount of Na incorporated into the surface tended to decrease with increasing Zr content. The apatite-forming ability of the treated alloy significantly decreased when the Zr content was ≥60 atom%. This phenomenon is attributed to the (1) low OH content on the surface, (2) low Na incorporation into the treated alloy surface, which enhances apatite formation, and (3) low ability of P adsorption to the Ti–Zr alloy in SBF following Ca adsorption to trigger apatite nucleation. Although the adhesion of the titanate/zirconate layer formed on the surfaces to the substrates increased as Zr content increased, the adhesion between the apatite and the substrate was still low.

Nanocomposites of magnetite (Fe3O4) and reduced graphene oxide (rGO) generate heat under an alternating magnetic field and therefore have potential applications as thermoseeds for cancer hyperthermia treatment. However, the properties of such nanocomposites as biomaterials have not been sufficiently well characterized. In this study, the osteoconductivity of Fe3O4-rGO nanocomposites of various compositions was evaluated in vitro in terms of their apatite-forming ability in simulated body fluid (SBF). Furthermore, the heat generation of the nanocomposites was measured under an alternating magnetic field. The apatite-forming ability in SBF improved as the Fe3O4 content in the nanocomposite was increased. As the Fe3O4 content was increased, the nanocomposite not only rapidly raised the surrounding temperature to approximately 100 °C, but the specific absorption rate also increased. We assumed that the ionic interaction between the Fe3O4 and rGO was enhanced and that Brown relaxation was suppressed as the proportion of rGO in the nanocomposite was increased. Consequently, a high content of Fe3O4 in the nanocomposite was effective for improving both the osteoconductivity and heat generation characteristics for hyperthermia applications.

Organic-inorganic composites are novel bone substitutes that can ameliorate the mismatch of Young's moduli between natural bone and implanted ceramics. Phosphate groups contribute to the formation of apatite in a simulated body fluid (SBF) and the adhesion of osteoblast-like cells. Therefore, modification of a polymer with these functional groups is expected to enhance the ability of the organic-inorganic composite to bond with bone. Two phosphate groups have been used, phosphonic acid (-C-PO

Open in a separate window Chemical modification with specific functional groups has been the conventional method to develop bone-bonding bioactive organic–inorganic hybrids. These materials are attractive as bone substitutes because they are flexible and have a Young’s modulus similar to natural bone. Immobilization of sulfonic acid groups (−SO3H) onto the polymer chain is expected to produce such hybrids because these groups induce apatite formation in a simulated body fluid (SBF) and enhance the activity of osteoblast-like cells. Sulfinic acid groups (−SO2H), which are derivatives of −SO3H, can also induce apatite nucleation. However, the structural effects of such sulfur-containing functional groups on apatite formation have not been elucidated. In the present study, apatite formation on Ca2+-modified copolymers containing −SO2H or −SO3H was investigated in a simulated body environment. The copolymer containing Ca2+ and −SO3H promoted Ca2+ release into the SBF and formed apatite faster (1 day) than the copolymer containing Ca2+ and −SO2H (14 days). In contrast, when they were not modified with Ca2+, the copolymer containing only −SO2H deposited the apatite faster (7 days) than that containing only −SO3H (>7 days) in the solution with Ca2+ concentration 1.5 times that of SBF. The former adsorbed larger amounts of Ca2+ than the latter. The measured stability constant of the complex indicated that the interaction of −SO2–···Ca2+ was more stable than that of −SO3–···Ca2+. It was found that both the release and adsorption of Ca2+ governed by the stability played an important role in induction of the apatite formation and that the apatite-forming ability of sulfur-containing functional groups drastically changed by the coexistence of Ca2+.

Organic–inorganic composites are novel bone substitutes that can ameliorate the mismatch of Young's moduli between natural bone and implanted ceramics. Phosphate groups contribute to the formation of apatite in a simulated body fluid (SBF) and the adhesion of osteoblast-like cells. Therefore, modification of a polymer with these functional groups is expected to enhance the ability of the organic–inorganic composite to bond with bone. Two phosphate groups have been used, phosphonic acid (–C–PO3H2) and phosphoric acid (–O–PO3H2). However, the effects of structural differences between these phosphate groups have not been clarified. In this study, the apatite formation of copolymers modified with Ca2+ and either –C–PO3H2 or –O–PO3H2 was examined. The mechanism of apatite formation is discussed based on analytical and computational approaches. The copolymers containing –O–PO3H2, but not those containing –C–PO3H2, formed apatite in the SBF, although both released similar amounts of Ca2+ into the SBF. Adsorption of HPO42− from –O–PO3H2 in the SBF following Ca2+ adsorption was confirmed by zeta-potential measurement and X-ray photoelectron spectroscopy. The measurement of the complex formation constant revealed that the –O–PO32−⋯Ca2+ complex was thermodynamically unstable enough to convert into CaHPO4, which was not the case with –C–PO32−⋯Ca2+. The formation of CaHPO4-based clusters was found to be a key factor for apatite nucleation. In conclusion, this study revealed that modification with –O–PO3H2 was more effective for enhancing apatite formation compared with –C–PO3H2.

Organic–inorganic composites are novel bone substitutes that can ameliorate the mismatch of Young's moduli between natural bone and implanted ceramics. Phosphate groups contribute to the formation of apatite in a simulated body fluid (SBF) and the adhesion of osteoblast-like cells. Therefore, modification of a polymer with these functional groups is expected to enhance the ability of the organic–inorganic composite to bond with bone. Two phosphate groups have been used, phosphonic acid (–C–PO3H2) and phosphoric acid (–O–PO3H2). However, the effects of structural differences between these phosphate groups have not been clarified. In this study, the apatite formation of copolymers modified with Ca2+ and either –C–PO3H2 or –O–PO3H2 was examined. The mechanism of apatite formation is discussed based on analytical and computational approaches. The copolymers containing –O–PO3H2, but not those containing –C–PO3H2, formed apatite in the SBF, although both released similar amounts of Ca2+ into the SBF. Adsorption of HPO42− from –O–PO3H2 in the SBF following Ca2+ adsorption was confirmed by zeta-potential measurement and X-ray photoelectron spectroscopy. The measurement of the complex formation constant revealed that the –O–PO32−⋯Ca2+ complex was thermodynamically unstable enough to convert into CaHPO4, which was not the case with –C–PO32−⋯Ca2+. The formation of CaHPO4-based clusters was found to be a key factor for apatite nucleation. In conclusion, this study revealed that modification with –O–PO3H2 was more effective for enhancing apatite formation compared with –C–PO3H2.

Hafnium (Hf) has attracted considerable attention as a component of biomedical titanium (Ti) alloys with low Young's moduli and/or shape-memory functionalities, because its cytotoxicity is as low as that of Ti. The drawback of metals is that their bone-bonding ability is generally low. It is known that apatite formation in the body is a prerequisite for bone-bonding. Although several chemical treatments have been proposed for preparing Ti for bone-bonding, there have been no similar investigations for Hf. In the present study, NaOH- and heat-treatments were applied to pure Hf and Ti-Hf alloys and their bone-bonding ability was assessed in vitro with the use of simulated body fluid (SBF). After NaOH- and heat-treatments, anatase formed on alloys with low Hf content (20-40% (atom%) Hf); mixtures of sodium titanate and hafnium titanate formed on alloys with similar Ti and Hf content (60% Hf); and hafnium oxide formed on alloys with high Hf content (80% Hf and pure Hf). Precipitates of apatite were observed on all the metals in SBF, except for the alloy with 60% Hf. We speculated that the hafnium titanate formed on this alloy had a low apatite-forming ability owing to its high negative surface charge, which inhibited P adsorption. The apatite-forming abilities of the Ti-Hf alloys strongly depended on their Hf content. The present results indicate that Hf-based materials have good potential for bone-bonding. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 2519-2523, 2018.

Autograft has been carried out for anterior cruciate ligament (ACL) reconstruction surgery. However, it has negative aspect because patients lose their healthy ligaments from other part. We focus on a chitosan-hydroxyapatite (HAp) composite fiber as a scaffold of ligament regeneration. Chitosan- HAp composite fiber was made by using coagulation method. Chitosan-NaH2PO4 solution was coagulated with coagulation bath including calcium ion to get the mono-fiber and then treated with sodium hydroxide solution to form HAp in fiber matrix. The mechanical property of the fiber was improved by the stretching of the wet one because of the orientation of chitosan molecule and the interaction between chitosan and HAp. Maximum stress was improved with increasing of sodium dihydrogen phosphate until 0.03 M. The swelling ratio of the fiber was inhibited by composited with HAp. Additionally, bone-bonding ability was confirmed by SBF soaking tests.

Microporous spheres in a hybrid system consisting of chitosan and &gamma, glycidoxypropyltrimethoxysilane (GPTMS) have advantages in a range of applications, e.g., as vehicles for cell transplantation and soft tissue defect filling materials, because of their excellent cytocompatibility with various cells. In this study, microporous chitosan-GPTMS spheres were prepared by dropping chitosan-GPTMS precursor sols, with or without a cerium chloride, into liquid nitrogen using a syringe pump. The droplets were then freeze dried to give the pores of size 10 to 50 &mu, m. The cell culture tests showed that L929 fibroblast-like cells migrated into the micropores larger than 50 &mu, m in diameter, whereas MG63 osteoblast-like cells proliferated well and covered the granule surfaces. The spheres with cerium chloride showed antibacterial properties against both gram-negative and gram-positive bacteria.

Polyetheretherketone (PEEK) has attracted much attention as an artificial intervertebral spacer for spinal reconstruction. Furthermore, PEEK plastic reinforced with carbon fiber has twice the bending strength of pure PEEK. However, the PEEK-based materials do not show ability for direct bone bonding, i.e., bioactivity. Although several trials have been conducted for enabling PEEK with bioactivity, few studies have reported on bioactive surface modification of carbon–PEEK composites. In the present study, we attempted the preparation of bioactive carbon-PEEK composites by chemical treatments with H 2 SO 4 and CaCl 2 . Bioactivity was evaluated by in vitro apatite formation in simulated body fluid (SBF). The apatite formation on the carbon–PEEK composite was compared with that of pure PEEK. Both pure PEEK and carbon-PEEK composite formed the apatite in SBF when they were treated with H 2 SO 4 and CaCl 2 ; the latter showed higher apatite-forming ability than the former. It is conjectured that many functional groups able to induce the apatite nucleation, such as sulfo and carboxyl groups, are incorporated into the dispersed carbon phase in the carbon–PEEK composites.

Magnetic microspheres measuring 15-35 µm in diameter are believed to be useful for intra-arterial hyperthermia. In this study, we attempted to prepare titanium dioxide (TiO2 ) microspheres containing magnetic nanoparticles (MNPs). MNP-containing TiO2 microspheres with diameters of approximately 30 µm were successfully obtained by sol-gel reaction of titanium tetraisopropoxide in a water-in-oil emulsion with added cosurfactant of 1-butanol and subsequent heat treatment at 200°C. The microspheres showed ferrimagnetism owing to high content of MNPs in approximately 60 wt % and had a low-crystalline TiO2 matrix. Furthermore, the agar phantom was heated to above 43°C after approximately 1 min under an alternating magnetic field of 100 kHz and 300 Oe and showed in vitro biocompatibility similar to that of MNP-free TiO2 microspheres. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 2308-2314, 2017.

Biofilm formation of periodontal pathogens on teeth surfaces promotes the progression of periodontal disease. Hence, understanding the mechanisms of bacterial attachment to the dental surfaces may inform strategies for the maintenance of oral health. Although hydroxyapatite (HA) is a major calcium phosphate component of teeth, effect of biofilm formation on HA surfaces remains poorly characterized. In this study, biofilm-forming abilities by the periodontal pathogens Aggregatibacter actinomycetemcomitans Y4 and Porphyromonas gingivalis 381 were investigated on dense and porous HAs that represent enamel and dentin surfaces, respectively. These experiments showed greater biofilm formation on porous HA, but differing attachment profiles and effects of the two pathogens. Specifically, while the detachment of A. actinomycetemcomitans Y4 biofilm was observed, P. gingivalis 381 biofilm increased with time. Moreover, observations of HA morphology following formation of A. actinomycetemcomitans Y4 biofilm revealed gaps between particles, whereas no significant changes were observed in the presence of P. gingivalis 381. Finally, comparisons of calcium leakage showed only slight differences between bacterial species and HA types and may be masked by bacterial calcium uptake. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 104A: 2873-2880, 2016.

Natural bone consists of apatite and collagen fiber. Bioactive materials capable to bonding to bone tissue are clinically used as bone-repairing materials. Apatite-organic polymer composites exhibit bone-bonding abilities and mechanical properties similar to those of natural bone, and these materials can be prepared using biomimetic processes in simulated body fluid (SBF). Specific functional groups such as sulfonic and carboxylic acid groups are known to induce the heterogeneous nucleation of apatite in SBF. However, it remains unclear whether structurally related sulfinic acid groups can contribute to apatite formation in the same way, despite sodium sulfonate being used in biomedical applications as a radical polymerization promoter in adhesive dental resin. Herein, we report the preparation of a new hydrogel containing sulfinic acid groups from sodium 4-vinylbenzenesulfinate and 2-hydroxyethyl methacrylate using a radical polymerization reaction and the subsequent incorporation of Ca2+ ions into this material. We also investigated the apatite-forming behavior of these hydrogels in SBF. Hydrogels containing sulfinic acid groups showed higher apatite-forming ability than those without sulfinic acid groups. In addition, the apatite layer formed on the former showed tight adhesion to the hydrogel. This phenomenon was attributed to the heterogeneous nucleation of apatite, induced by the sulfinic acid groups. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 1924-1929, 2017.

Magnetite (Fe 3 O 4 ) nanoparticles and magnetite-based inorganic–organic hybrids are attracting increasing attention in biomedicine, as thermoseeds for hyperthermia and contrast media in magnetic resonance imaging. Controlling the size of Fe 3 O 4 thermoseeds is important, as particle size affects their heat generation under alternative magnetic fields. Fe 3 O 4 is easily synthesized via aqueous processes. We previously demonstrated that adding organic polymers during synthesis affected the size and crystallinity of the resulting Fe 3 O 4 . However, the relationship of the chemical structure of the low-molecular-weight organic additive of its effect on the product has not been elucidated. In this study, organic compounds containing varying functional groups and surface charges were added to the precursor solution of Fe 3 O 4 . Crystalline Fe 3 O 4 formed in the presence of neutral acetone, cationic ethylenediamine, and anionic acetic acid. These nanoparticles had slightly smaller particle sizes than those prepared in the absence of additives. The presence of oxalic acid and tris(hydroxymethyl)aminomethane inhibited Fe 3 O 4 nucleation, instead yielding lepidocrosite- or akaganeite-type FeOOH. These differences were attributed to the ability to form complexes between iron ions and the organic additives. The saturation magnetizations of the products were consistent with Fe 3 O 4 . This indicated that the crystal phase of the iron oxide products differed, even when prepared in the presence of organic additives of the same functional group. It is concluded that state of ion-organic molecule complex in the solutions is a key factor governing nanostructure of the resultant iron oxide.

Polymethyl methacrylate (PMMA)-based bone cement is a popular biomaterial used for fixation of artificial joints. A next-generation bone cement having bone-bonding ability, i.e., bioactivity and antibacterial property is desired. We previously revealed that PMMA cement added with 2-(tert-butylamino)ethyl methacrylate, &gamma, methacryloxypropyltrimethoxysilane and calcium acetate showed in vitro bioactivity and antibacterial activity. This cement contains calcium acetate at 20% of the powder component. Lower content of the calcium acetate is preferable, because the release of a lot of calcium salt may degrade mechanical properties in the body environment. In the present study, we investigate the effects of calcium acetate content on the setting property and mechanical strength of the cement and apatite formation in simulated body fluid (SBF). The setting time increased and the compressive strength decreased with an increase in calcium acetate content. Although the compressive strength decreased after immersion in SBF for 7 d, all the cements still satisfied the requirements of ISO5833. Apatite was formed in SBF within 7 d on the samples where the calcium acetate content was 5% or more. Therefore, it was found that PMMA cement having antibacterial properties and bioactivity can be obtained even if the amount of the calcium acetate is reduced to 5%.

Cobalt-chromium (Co-Cr) alloys are used in clinical practice for the hard tissue reconstruction because of their favorable biocompatibility and mechanical properties. However, their applications have been limited because of their poor bioactivity, making them poor at bone-bonding. In this study, the bioactivity of a Co-Cr alloy was evaluated following the immobilization of cross-linked poly-γ-glutamic acid (γ-PGA) onto its surface via the formation of 11-aminoundecylphosphonic acid self-assembled monolayers (SAMs). Results of X-ray photoelectron spectroscopy revealed the presence of a new P2p peak, which confirms SAMs formation. Furthermore, the surface became highly hydrophobic following the immobilization with γ-PGA. Subsequent treatment with CaCl2 at 0.5 M or more and soaking in a simulated body fluid led to the formation of a low crystalline apatite. The present results show that chemical modification can be used to induce the formation of an apatite layer on the surface of a Co-Cr alloy in simulated body fluid.

Common cancer treatments are invasive and lack specificity, leading to unwanted side effects. Because hyperthermia can kill cancer cells and damage proteins and structures within cells, it has been considered a novel, minimally invasive cancer treatment. However, many hyperthermia treatments cannot heat deep-seated tumors effectively and locally. Heat-generating magnetic microspheres can help address this challenge. However, current research has not produced microspheres that can be sufficiently heated. We prepared magnetic titania (TiO2) microspheres by introducing magnetite nanoparticles (MNPs) into the sol–gel process during water-in-oil emulsion for in situ hyperthermia treatment of cancers. Two types of MNPs were used in this study: One type was synthesized by a chemical coprecipitation method, and the other type was commercially available MNPs. The obtained microspheres contained up to 46.7 wt% MNPs, and their saturation magnetization and coercive force were 34.2 emu/g and 103 Oe, respectively. The particles’ in vitro heating efficiency in an agar phantom was measured in an alternating magnetic field of 300 Oe and 100 kHz. The temperature increase in the agar phantom within 300 s was 4.5 °C for microspheres with MNPs that were synthesized by chemical coprecipitation and 53 °C for microspheres with commercially available MNPs. The excellent heating efficiency of the microspheres may be attributed to the hysteresis losses of the magnetic particles. These microspheres are believed to be promising thermoseeds for hyperthermic treatment of cancer. Magnetic TiO2 microspheres with a diameter of 7–15 μm were obtained by directly introducing preformed magnetic MNPs into a sol–gel process from TTIP in water-in-oil emulsion. The magnetic TiO2 microspheres containing Fe3O4 at a content higher than 46 wt% increased the temperature of the agar phantom to above 43 °C in 3 min. They are expected to be useful for arterial embolization hyperthermic treatment of cancer, but control of their diameter is essential.

Bioactive titania (TiO2) microparticles can be used as drug-releasing cement fillers for the chemotherapeutic treatment of metastatic bone tumors. Porous anatase-type TiO2 microspheres around 15 μm in diameter were obtained through a sol–gel process involving a water-in-oil emulsion with 30:70 SiO2/H2O weight ratio and subsequent NaOH solution treatment. The water phase consisted of methanol, titanium tetraisopropoxide, diethanolamine, SiO2 nanoparticles, and H2O, while the oil phase consisted of kerosene, Span 80, and Span 60. The resulting microspheres had a high specific surface area of 111.7 m2·g− 1. Apatite with a network-like surface structure formed on the surface of the microspheres within 8 days in simulated body fluid. The good apatite-forming ability of the microspheres is attributed to their porous structure and the negative zeta potential of TiO2. The release of rhodamine B, a model for a hydrophilic drug, was rapid for the first 6 h of soaking, but diffusion-controlled thereafter. The burst release in the first 6 h is problematic for clinical applications; nonetheless, the present results highlight the potential of porous TiO2 microspheres as drug-releasing cement fillers able to form apatite.

Bone cement from polymethylmethacrylate powder and methylmethacrylate liquid has been successfully demonstrated as artificial material to anchor joint replacements in bone. However, it lacks the capability to bond directly to bone, so long-term implantation leads to an increased risk of loosening. Bioactive materials show better performance in fixation to bone, and the chemical bonding depends on bone-like apatite formation. This is triggered by surface reactions with body fluid. For these reactions, superficial functional groups like silanol (Si–OH) are ideal sites to induce apatite nucleation and the release of Ca2+ ions accelerates the apatite growth. Therefore, incorporation of materials containing these key components may provide the cement with apatite-forming ability. In this study, phosphoric acid 2-hydroxyethyl methacrylate ester or bis[2-(methacryloyloxy)ethyl] phosphate supplying a phosphate group (PO4H2) was added into methylmethacrylate liquid, while calcium acetate as a source of Ca2+ ions was mixed into polymethylmethacrylate powder. The influences of the combinations on the setting time and compressive strength were also investigated. Apatite was formed on the cements modified with 30 mass% of phosphoric acid 2-hydroxyethyl methacrylate ester or bis[2-(methacryloyloxy)ethyl] phosphate. The induction period was shortened with increased amounts of Ca(CH3COO)2. The setting time could be controlled by the Ca(CH3COO)2/monomer mass ratio. Faster setting was achieved at a ratio close to the mixing ratio of the powder/liquid (2:1), and both increases and decreases in the amount of Ca(CH3COO)2 prolonged the setting time based on this ratio. The highest compressive strength was 88.8 ± 2.6 MPa, higher than the lowest limit of ISO 5833 but was lower than that of the simulated body fluid-soaked reference. The increase of additives caused the decline in compressive strength. In view of balancing apatite formation and clinical standard, bis[2-(methacryloyloxy)ethyl] phosphate is more suitable as an additive, and the optimal modification is a combination of 30 mass% of bis[2-(methacryloyloxy)ethyl] phosphate and 20 mass% of Ca(CH3COO)2.

Although titanium (Ti) is clinically used for hard tissue reconstruction, it has low bone-bonding ability, i.e. bioactivity. Materials able to deposit apatite on their surfaces within the body is considered to exhibit bioactivity. Effects of the metallographic structure and machining process of Ti on its apatite-forming ability remains unclear. In this study, Ti substrates subjected to various preheating and machining processes were then subjected to NaOH and heat treatments. The apatite-forming abilities of resulting Ti were examined in simulated body fluid (SBF). Preheating of the Ti decreased its reactivity with NaOH solution. When quenched or annealed Ti was subjected to NaOH and heat treatments, the induction period for apatite formation in SBF slightly increased. This was attributed to a decrease in sodium titanate and increase in rutile on the Ti surface after the treatments. Substrates subjected to wire-electrical-discharge machining did not form apatite. This was attributed to the inhibition of PO43- adsorption on their surfaces following Ca2+ adsorption, which is an essential process for apatite nucleation. Contamination of Ti surface by components of the brass wire used in the machining contributed to the inhibition. The bioactivity of surface-modified Ti was therefore significantly affected by its thermal treatment and machining process.

Ceramic microspheres composed of β-emitters are useful for in situ radiotherapy of deep-seated cancer by implantation around the tumor. In addition, microspheres 20–30 µm in diameter can combine β-emission with the embolization effect. Yttrium phosphate is an attractive candidate material for such microspheres, because both Y and P play roles as β-emitters. The half-life of 31 P is known to be much larger than that of 90 Y. Therefore, it is expected that yttrium phosphate microspheres with high P content can maintain a longer radiotherapy effect. In the present study, preparation of microspheres with enriched P content has been attempted by water-in-oil emulsions using polyphosphate as a starting material. Yttrium phosphate microspheres with a higher P/Y molar ratio (2.5) than in previously reported YPO 4 microspheres were obtained. It was found that emulsification for sufficient time (more than 10 min) is necessary to obtain microspheres that are 20–30 µm in size. Although the microspheres released Y sparingly, they released larger amounts of P than previously reported YPO 4 microspheres in a simulated body environment. Heat treatment at moderate temperature can suppress P release to some extent. Further improvement in chemical durability through surface modification is essential for long-term clinical use.

In this study, we investigated the surface structure, apatite formation in simulated body fluid (SBF), and visible-light photocatalytic activity of Ti metal subjected to chemical and thermal treatments. Ti metal samples treated with NaOH, a nitrogen-containing solution (0.1 M HNO 3 , 0.1–1.0 M (H 2 N) 2 C O, or 0.1–1.0 M NH 4 Cl), and heat showed apatite formation on their surfaces in SBF, whereas those treated with NaOH, 0.5 or 1.0 M HNO 3 , and heat did not. In the former case, apatite formation may be attributable to the fine network structure of anatase-type TiO 2 doped with a small amount of nitrogen on the surface of the Ti metal. The Ti metal treated with the latter treatment showed higher methylene blue decomposition than the untreated sample and the one treated with the former treatment. This preliminary result suggests that Ti metal treated with NaOH, 0.1 M HNO 3 , and heat can potentially show visible-light-induced antibacterial property as well as bone-bonding ability.

Hyperthermia has been suggested as a novel, minimally invasive cancer treatment method. After implantation of magnetic nano- or microparticles around a tumour through blood vessels, irradiation with alternating magnetic fields facilitates the efficient in situ hyperthermia even for deep-seated tumours. On the basis of this idea, if the microspheres are capable of delivering drugs, they could be promising multifunctional biomaterials effective for chemotherapy as well as hyperthermia. In the present study, magnetite microspheres were prepared by aggregation of the iron oxide colloid in water-in-oil (W/O) emulsion. The release behaviour of alendronate, a typical bisphosphonate, from the microspheres was examined in vitro as a model of the bone tumour prevention and treatment system. The alendronate was successfully incorporated onto the porous magnetite microspheres in vacuum conditions. The drug-loaded microspheres maintained their original spherical shapes even after shaking in ultrapure water for 3 days, suggesting that they have sufficient mechanical integrity for clinical use. It was attributed to high aggregation capability of the magnetite nanoparticles through van der Waals and weak magnetic attractions. The microspheres showed slow release of the alendronate in vitro, resulting from tight covalent or ionic interaction between the magnetite and the alendronate. The release rate was diffusion-controlled type and well controlled by the alendronate concentration in drug incorporation to the microspheres.

Magnetite (Fe3O4) nanoparticles and magnetite-based inorganic–organic hybrids are attracting attention in biomedical fields as thermoseeds for hyperthermia and a contrast medium in magnetic resonance imaging. Size control of Fe3O4 thermoseeds is important as the particle size affects the heat generation properties. Fe3O4 can be easily synthesized via aqueous processes and the presence of organic substances during synthesis can affect the size and crystalline phase of the Fe3O4 formed. In this study, various polymers with different functional groups and surface charges were added to the precursor solution of Fe3O4 to clarify the relationship between the chemical structure of the organic substances and the crystal structure of Fe3O4. At first, coexistence effects of the organic substances in the solutions were clarified. As a result, crystalline Fe3O4 was precipitated even after addition of neutral polyethylene glycol and cationic poly(diallyldimethylammonium chloride). The poly(sodium-4-styrene sulfonate) addition significantly decreased the particle size, while polyacrylic acid addition inhibited Fe3O4 nucleation to afford an amorphous phase. These differences were related to the ease of complex formation from iron ions and coexisting organic polymers. In order to clarify this assumption, a modified experimental procedure was applied for the polyacrylic acid. Namely, the iron oxide precipitation by the NaOH solution was followed by the polyacrylic acid addition. Notably, Fe3O4 nucleation was not inhibited. Hence, the size and crystalline phase of the iron oxide prepared by the aqueous process were drastically affected by organic polymers.