Pressure- and heat-induced insertion of CO2 into an auxetic small-pore zeolite

When the small-pore zeolite natrolite is compressed at ca. 1.5 GPa and heated to ca. 110 °C in the presence of CO₂, the unit cell volume of natrolite expands by 6.8% and ca. 12 wt % of CO₂ is contained in the expanded elliptical channels. This CO₂ insertion into natrolite is found to be reversible upon pressure release.

Synthesis and structural properties of Anhydrous Rare Earth Cinnamates, [RE(cinn)3]

Anhydrous rare earth tris(cinnamates) [RE(cinn)3] (RE = La–Lu, Y and Sc and cinnH = trans-cinnamic acid) were prepared by metathesis in water and by direct reaction of the metal with cinnamic acid in a 1,2,4,5-tetramethylbenzene flux at ca. 200 °C. X-ray crystal structure determinations and X-ray powder data show that, in the solid state, the larger lanthanoids (La–Dy) form an isomorphous polymeric series consisting of homoleptic nine-coordinate metal centres bonded to three chelating and bridging tridentate cinnamates. The late REIII cinnamate (RE = Dy, Ho–Lu, Y) complexes also form linear one-dimensional polymeric chains with all RE metal atoms being seven-coordinate. The cinnamates are either bound tridentate bridging in a μ-η2:η1 fashion, or μ-η1:η1syn-syn bidentate bridging. A structural break occurs at dysprosium which has been characterised in both crystallographic forms, and gives solely the late RE form when precipitated at 80 °C. ScIII cinnamate was also isolated as an analytically pure precipitate which was, again, found to be anhydrous in nature. A structural change was identified by powder XRD between the late REIII cinnamates and ScIII cinnamate.

Biodegradable Mg-Zr-Ca alloys for bone implant materials

Mg–Zr–Ca alloys were developed for new biodegradable bone implant materials. The microstructure and mechanical property of the Mg–xZr–yCa [x=0·5, 1·0% and y=1·0, 2·0% (wt-% hereafter)] alloys were characterised by optical microscopy, compressive and hardness tests. The in vitro cytotoxicity of the alloys was assessed using osteoblast-like SaOS₂ cells. The corrosion behaviour of these alloys was evaluated by soaking the alloys in simulated body fluid (SBF) and modified minimum essential medium (MMEM). Results indicated that the mechanical properties of the Mg–Zr–Ca are in the range of the mechanical properties of natural bone. The corrosion rate and biocompatibility decreases with the increase in the Ca content in the Mg–Zr–Ca alloys. The solutions of SBF and MMEM with the immersion of the Mg–Zr–Ca alloys show strong alkalisation. The Zr addition to the Mg–Zr–Ca alloys leads to an increase in the corrosion resistance, compressive strength and the ductility of the alloys, and a decrease in the elastic modulus of the Mg–Zr–Ca alloys.

Collagen type-I leads to in vivo matrix mineralization and secondary stabilization of Mg-Zr-Ca alloy implants

Biodegradable magnesium-zirconia-calcium (Mg-Zr-Ca) alloy implants were coated with Collagen type-I (Coll-I) and assessed for their rate and efficacy of bone mineralization and implant stabilization. The phases, microstructure and mechanical properties of these alloys were analyzed using X-ray diffraction (XRD), optical microscopy and compression test, respectively, and the corrosion behavior was established by their hydrogen production rate in simulated body fluid (SBF). Coll-I extracted from rat tail, and characterized using fourier transform infrared (FT-IR) spectroscopy, was used for dip-coating the Mg-based alloys. The coated alloys were implanted into the femur bones of male New Zealand white rabbits. In vivo bone formation around the implants was quantified by measuring the bone mineral content/density (BMC/BMD) using dual-energy X-ray absorptiometry (DXA). Osseointegration of the implant and new bone mineralization was visualized by histological and immunohistochemical analysis. Upon surface coating with Coll-I, these alloys demonstrated high surface energy showing enhanced performance as an implant material that is suitable for rapid and efficient new bone tissue induction with optimal mineral content and cellular properties. The results demonstrate that Coll-I coated Mg-Zr-Ca alloys have a tendency to form superior trabecular bone structure with better osteoinduction around the implants and higher implant secondary stabilization, through the phenomenon of contact osteogenesis, compared to the control and uncoated ones in shorter periods of implantation. Hence, Coll-I surface coating of Mg-Zr-Ca alloys is a promising method for expediting new bone formation in vivo and enhancing osseointegration in load bearing implant applications.

Exposure to As(III) and As(V) changes the Ca��⁺-activation properties of the two major fibre types from the chelae of the freshwater crustacean Cherax destructor

Arsenic is a known carcinogen found in the soil in gold mining regions at concentrations thousands of times greater than gold. Mining releases arsenic into the environment and surrounding water bodies. The main chemical forms of arsenic found in the environment are inorganic arsenite (As(III)) and arsenate (As(V)). Yabbies (Cherax destructor) accumulate arsenic at levels comparable to those in the sediment of their environment but the effect on their physiological function is not known. The effects of arsenic exposure (10 ppm sodium arsenite, AsNaO2 - 5.7 ppm As(III)) and 10 ppm arsenic acid, Na2HAsO4·7H2O - 2.6 ppm As(V)) for 40 days on the contractile function of the two major fibre types from the chelae were determined. After exposure, individual fibres were isolated from the chela, "skinned" (membrane removed) and attached to the force recording apparatus. Contraction was induced in solutions containing increasing [Ca(2+)] until a maximum Ca(2+)-activation was obtained. Submaximal force responses were plotted as a percentage of the maximum Ca(2+)-activated force. As(V) exposure resulted in lower levels of calcium required for activation than As(III) indicating an increased sensitivity to Ca(2+) after long term exposure to arsenate compared to arsenite. Myosin heavy chain and tropomyosin content in individual fibres was also decreased as a result of arsenic exposure. Single fibres exposed to As(V) produced significantly more force than muscle fibres from control animals. Long-term exposure of yabbies to arsenic alters the contractile function of the two major fibre types in the chelae.