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Bioresponsive ceramics, a new concept in ceramic biomaterials, respond to biological molecules or environments, as exemplified by salts composed of calcium ions and phosphate esters (SCPEs). SCPEs have been shown to form apatite in simulated body fluid (SBF) containing alkaline phosphatase (ALP). Thus, surface modification with SCPEs is expected to improve the apatite-forming ability of a material. In this study, we modified the surface of α-tricalcium phosphate (α-TCP) using methyl, butyl, or dodecyl phosphate to form SCPEs and investigated their apatite formation in SBF and SBF containing ALP. Although apatite did not form on the surface of the unmodified α-TCP in SBF, apatite formation was observed following surface modification with methyl or butyl phosphate. When ALP was present in SBF, apatite formation was especially remarkable on α-TCP modified with butyl phosphate. These SCPEs accelerated apatite formation by releasing calcium ions through dissolution and supplying inorganic phosphate ions, with the latter process only occurring in SBF containing ALP. Notably, no apatite formation occurred on α-TCP modified with dodecyl phosphate, likely because of the low solubility of the resulting calcium dodecyl phosphate/calcium phosphate composites. This new method of using SCPEs is anticipated to contribute to the development of novel ceramic biomaterials. [ABSTRACT FROM AUTHOR]

Graphical abstract Abstract Surface modification by sodium hydroxide (NaOH) and subsequent heat treatment can provide titanium and its alloys an apatite-forming ability in simulated body fluid (SBF), and is used clinically to treat titanium alloy hip joints in Japan. However, there is no systematic study on the relationship between the amount and chemical state of metals incorporated into titanium and the apatite-forming ability in SBF. We have studied this relationship herein by treating NaOH–modified titanium with aqueous solutions containing different types (aluminum, calcium, chromium, copper, zinc, and silver) and concentrations (0.01, 0.1, and 1 M) of metal ions. As a result, we found that formation of anatase and the chemical states of the metals incorporated into titanium control the apatite-forming ability. Further, the chemical states of the metals can be interpreted in terms of the ionization tendency. These findings would aid future design of metal-doped bioactive titanium for orthopedic or dental implants. [ABSTRACT FROM AUTHOR]

Titanium (Ti) treated with NaOH and hot water, and heated in an ammmonia (NH 3 ) gas atmosphere for 1 or 3 h exhibited in vitro apatite formation within 7 days when soaked in simulated body fluid (SBF). Moreover, the treated Ti decomposed methylene blue and showed excellent bactericidal activity against Escherichia coli under visible light irradiation. The surface treatment resulted in the formation of a fine network of N-doped anatase-type titania (TiO 2-x N x ) on the Ti surface, which was responsible for both the apatite formation in SBF and the visible light-induced antibacterial activity. These preliminary results highlight the efficacy of our simple method for producing novel bioactive Ti with visible light-induced antibacterial activity, which could be applied to orthopaedic and dental implants without the risk of infection. [ABSTRACT FROM AUTHOR]

Iron-based compounds, especially magnetite (Fe3O4), can be a candidate of thermoseeds for hyperthermia therapy. When iron-based compounds are applied for bone tumor treatment, they should have a heat-generating property and a bone-bonding property. However, the bone-bonding property of iron-based compounds is still unclear. The bone-bonding property of materials is estimated by their bone-like apatite formation property in simulated body fluid (SBF). The method to estimate apatite forming ability of materials by utilizing SBF was introduced by Kokubo et al. We thus report fundamental research into the behavior of iron oxides and an iron oxyhydroxide namely: FeO, Fe3O4, α-Fe2O3, γ-Fe2O3, and α-FeOOH, in SBF. Calcium phosphate precipitation was found in Fe3O4 and α-Fe2O3 within 7 and 28 days after soaking in SBF, respectively, while FeO, γ-Fe2O3, and α-FeOOH did not. Our results indicate that Fe3O4 and α-Fe2O3 have a better potential bone-bonding property than FeO, γ-Fe2O3, and α-FeOOH. The induction of apatite precipitation in SBF can be attributed to the specific structure of Fe-OH groups on the surface of Fe3O4 and α-Fe2O3. [ABSTRACT FROM AUTHOR]

Highlights: [•] Ti metal treated with NaOH, NH4OH, and heat formed apatite in simulated body fluid. [•] Nitrogen-doped TiO2 might be formed on the surface of the treated Ti metal. [•] The treated Ti metal decomposed methylene blue under visible light. [ABSTRACT FROM AUTHOR]

Abstract: The zeta potential of alumina (Al2O3) powder with different crystalline phases, prepared by heat treatment of boehmite, was measured in simulated body fluids in order to discuss the mechanism on in vivo formation of a calcium and phosphorus (CaP)-rich layer on bone cement containing δ-Al2O3-based bead powder. γ, δ, and θ-Al2O3 powders were obtained by heat treatment of boehmite powder at 600°C, 900°C, and 1025°C, respectively. It was found that δ-Al2O3 gave a negative zeta potential in an acidic simulated body fluid, whereas γ-Al2O3 and θ-Al2O3 gave a positive potentials. During the bone fracture healing process, acidic conditions are maintained at the site of fracture for several days. Consequently, it is speculated that the negative surface potential of δ-Al2O3 in an acidic body fluid, similar to the fracture site, might be responsible for the in vivo formation of the CaP-rich layer on the overlying bone cement, given that the negatively charged surface of δ-Al2O3 would attract calcium ions from the surrounding body fluid, thereby facilitating the formation of the CaP-rich layer. [Copyright &y& Elsevier]

Abstract: Indwelling catheters made of silicone elastomers sometimes cause serious infections owing to their poor biocompatibility. It is believed that these infections can be prevented by coating the silicone surface with apatite, which has excellent biocompatibility. If the surface of the silicone elastomer is in advance modified to have an apatite-forming ability, apatite can be coated on the modified silicone surface by soaking it in an aqueous solution such as a simulated body fluid (SBF) supersaturated with respect to apatite. In this study, silicone substrates were irradiated by four types of ion beams (Ar cluster, Ar cluster and monomer (Ar CM), O2 cluster, and O2 cluster and monomer (O2 CM) ion beams) at an acceleration voltage of 7kV and a dose of 1×1015 ions/cm2, and subsequently soaked in CaCl2 solution. The apatite-forming abilities of the substrates were examined using a metastable calcium phosphate solution whose ion concentration was 1.5 times that of SBF (1.5 SBF). Silicon oxide (SiO x ) clusters were formed on the silicone surface and the hydrophilicity of the substrates was improved by the irradiation, irrespective of the ion species used. The irradiation with O2 CM ion beams resulted in the highest apatite-forming ability among the analyzed ion beams. [Copyright &y& Elsevier]

Poly(tetramethylene oxide) (PTMO)–CaO–Ta2O5 hybrids were prepared by hydrolysis and polycondensation of triethoxysilane-functionalized PTMO (Si–PTMO), tantalum ethoxide (Ta(OEt)5) and CaCl2. In the system CaO-free PTMO–Ta2O5, Si–PTMO/Ta(OEt)5 weight ratios were 30/70, 40/60 and 50/50 (hybrids PT30Ca0, PT40Ca0 and PT50Ca0, respectively). In the system PTMO–CaO–Ta2O5, the Si–PTMO/Ta(OEt)5 weight ratio was 40/60 and CaCl2/Ta(OEt)5 mole ratios were 0.05, 0.10 and 0.15 (hybrids PT40Ca5, PT40Ca10 and PT40Ca15, respectively). Crack-free transparent monolithic hybrids were obtained for all the examined compositions except for PT30Ca0. Even CaO-free hybrids PT40Ca0 and PT50Ca0 formed apatite on their surfaces in a simulated body fluid (SBF) within 14 days. Hybrid PT40Ca0 showed higher mechanical strength, which was increased by soaking in SBF, and larger strain to failure than human cancellous bone. The CaO-containing hybrids showed higher apatite-forming ability than the CaO-free hybrids, and its apatite-forming ability increased with increasing CaO content. Hybrids PT40Ca10 and PT40Ca15 formed apatite within 3 days. The mechanical strength of PT40Ca15 was, however, lower than PT40Ca0 and was decreased by soaking in SBF. Thus obtained flexible bioactive CaO-free PTMO–Ta2O5 hybrids are expected to be useful as bone substitutes. [ABSTRACT FROM AUTHOR]

Abstract Nanocomposites of magnetite (Fe 3 O 4) 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 Fe 3 O 4 -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 Fe 3 O 4 content in the nanocomposite was increased. As the Fe 3 O 4 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 Fe 3 O 4 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 Fe 3 O 4 in the nanocomposite was effective for improving both the osteoconductivity and heat generation characteristics for hyperthermia applications. Graphical abstract Unlabelled Image [ABSTRACT FROM AUTHOR]

Chitin fibres constituting a non-woven fabric were carboxymethylated in monochloro acetic acid and treated with saturated Ca(OH)2 aqueous solution. Within 3 days in a simulated body fluid with pH value and ion concentrations nearly equal to those of human blood plasma, a bonelike apatite layer formed on the surface of fibres of the treated fabric. The apatite–chitin fibre composite thus prepared is expected to be useful as a flexible bioactive bone-repairing material. [Copyright &y& Elsevier]