The bioactivity of titanium-cuttlefish bone-derived hydroxyapatite composites sintered at low temperature

ABSTRACT

The most limiting features of titanium as a bone substituent are lack of bioactivity and high Young’s modulus. We have prepared titanium-hydroxyapatite (Ti-HAp) composites using titanium hydride as sintering agent to provide titanium sintering at lower temperature and preserve the stability of apatite phase. After low temperature sintering, no hydroxyapatite decomposition was detected. Pure titanium samples sintered in the presence of hydride showed smooth surface indicating good densification at 800°C. Higher HAp content resulted in decreased density and higher porosity due to the formation of micro- and macro-pores caused by the integration of HAp particles into titanium matrix and titanium hydride decomposition. However, Vickers microhardness test showed increased hardness for Ti-HAp composite with 10% of HAp regarding pure Ti. The bioactivity of Ti-HAp composites evaluated in simulated body fluid significantly improved with HAp content. The presence of HAp has lowered the cytotoxic effect of Ti-based composites on Hek293 cells.     

Valorisation of phenolic composition,antioxidant and cell growth activities of tomato waste

Tomato waste, a by-product in juice processing, obtained from different tomato genotypes, was subjected to evaluation as potential source of phenolic antioxidants and anticancer agents. Some individual phenolic compounds, including phenolic acids and flavonoids, were identified and quantified by HPLC. The antioxidant activity of tomato waste extracts was tested by measuring their ability to scavenge hydroxyl and superoxide anion radicals by ESR spectroscopy. The highest hydroxyl radical scavenging activity (IC₅₀ = 0.03 mg/ml) was obtained in the case of Novosadski niski waste extract. The Rutgers waste extract showed the best performance in scavenging superoxide anion radicals (IC₅₀ = 0.45 mg/ml). Cell growth effects were determined in HeLa, MCF7 and MRC-5 cell lines by SRB test. In all cell lines antiproliferative effects were observed at higher investigated concentrations (?6.3 mg/ml). The strongest activity against cancer cells was observed by Saint Pierre extract in HeLa cell line (IC₅₀ = 13.7 mg/ml).     

Solar spectrum management for effective hydrogen production by hybrid thermo-photovoltaic water electrolysis

Solar Hydrogen is one of the potential key technologies to fuel human's progress. Optimizing the utilization of sunlight to produce Hydrogen using a hybrid thermo-electrolysis system is useful to promote such technology to broad deployment. Theoretically, it was found that a proper sunlight utilization management by an optimized spectral splitting of the solar spectrum between heating water to produce steam on the one hand and producing electricity via photovoltaic cell to energize the steam electrolysis on the other hand leads to an efficient sunlight to Hydrogen conversion. We report in this theoretical work that 82% sunlight to Hydrogen conversion efficiency can be accomplished from the proposed optimized hybrid thermo-photovoltaic system that employs a 90% efficient solar-thermal convertor. Additionally, it was found that for the proposed optimized hybrid system a quadratic enhancement for both the photovoltaic conversion efficiency and the net solar to hydrogen conversion efficiency can be obtained from employing more efficient solar to thermal convertor. Unlike the previous works, which have handled the optimal photon management in the hybrid thermo-photovoltaic system, our proposed optimization method accounts thoroughly the major losses in the photovoltaic conversion like the thermalization process and the limiting fill factor of the PV cell. Therefore, the methodology and the results of this work are more realistic and could be a useful recipe for an optimal sunlight spectrum management for an effective solar-hydrogen production, which could thrive as a reliable carbon-free-source of energy.     

Structural and Magnetic Properties of Single Domain PEG-Coated Fe<Subscript>x</Subscript>Ni<Subscript>80−x</Subscript>Co<Subscript>20</Subscript> (x = 20, 40) Ternary Alloys Synthesized by Chemical Method

In the present study, we have synthesized nanocrystalline Fe _x Ni_80?xCo₂₀ (x = 20 and 40) alloys via modified sodium borohydride reduction route in aqueous medium. The phase purity and microstructural analysis of the materials were done using powder X-ray diffraction (XRD) and transmission electron microscopy (TEM). Fe–Ni–Co alloys crystallize in face centered cubic (fcc) structure having the values of lattice parameters, a = 3.5460 and 3.5634 Å, for Fe₂₀Ni₆₀Co₂₀ and Fe₄₀Ni₄₀Co₂₀, respectively. The average crystallite sizes were found to be 30 and 26 nm for Fe₂₀Ni₆₀Co₂₀ and Fe₄₀Ni₄₀Co₂₀, respectively. Fe₂₀Ni₆₀Co₂₀ and Fe₄₀Ni₄₀Co₂₀ alloys crystallize in nearly spherical shape morphologies having TEM particle sizes of 24 and 36 nm, respectively. Selected area electron diffraction (SAED) patterns confirm face centered cubic crystal structure and polycrystalline nature of the materials. Low temperature studies indicate that Fe–Ni–Co alloys show ferromagnetism at least up to 300 K. The effective magnetic anisotropy constant (K) for Fe₂₀Ni₆₀Co₂₀ and Fe₄₀Ni₄₀Co₂₀ alloys are found to be 14 and 4.2 kJm^?3, respectively. These results have been explained on the basis of size, shape and surface effects in the nano-materials. The contribution corresponding to spin relaxation and dipolar interactions between nano-particles on magnetic characteristics of Fe₂₀Ni₆₀Co₂₀ and Fe₄₀Ni₄₀Co₂₀ alloys have been explained qualitatively during the magnetic analysis.     

Bio-dissolution of copper from Khetri lagoon material by adapted strain of Acidithiobacillus ferrooxidans

Bioleaching involves the use of iron and sulfur oxidizing microorganisms to catalyze the dissolution of valuable metals. In this investigation, lagoon material contains 0.39% Cu, in which the major copper bearing mineral is chalcopyrite associated with other minerals present as minor phase. Leaching experiments were carried out using an adapted strain of Acidithiobacillus ferrooxidans with various parameters such as presence/absence of iron, pH, pulp density and temperature. Base of the medium was 9 K (without ferrous) Bio-dissolution of copper was found to be maximum, i.e., 80.9% with 9 K⁺ (with ferrous) at pH-2.0, 10% pulp-density and 35 °C within an incubation period of 30 days.     

A peptide nucleic acid (PNA) is more rapidly internalized in cultured neurons when coupled to a retro-inverso delivery peptide. The antisense activity depresses the target mRNA and protein in magnocellular oxytocin neurons

A peptide nucleic acid (PNA) antisense for the AUG translation initiation region of prepro-oxytocin mRNA was synthesized and coupled to a r etro-inverso peptide that is rapidly taken up by cells. This bioconjugate was internalized by cultured cerebral cortex neurons within minutes, according to the specific property of the vector peptide. The PNA alone also entered the cells, but more slowly. Cell viability was unaffected when the PNA concentrations were lower than 10 microM and incubation times less than for 24 h. Magnocellular neurons from the hypothalamic supraoptic nucleus, which produce oxytocin and vasopressin, were cultured in chemically defined medium. Both PNA and vector peptide-PNA depressed the amounts of the mRNA coding for prepro-oxytocin in these neurons. A scrambled PNA had no effect and the very cognate prepro-vasopressin mRNA was not affected. The antisense PNA also depressed the immunocytochemical signal for prepro-oxytocin in this culture in a dose- and time-dependent manner. These results show that PNAs driven by the retro-inverso vector peptide are powerful antisense reagents for use on cells in culture.     

Alcohol-induced conditioned taste aversions in chemically labyrinthectomized rats

Male rats were chemically labyrinthectomized (n = 22) by intratympanic injections of sodium arsanilate, and control rats (n = 15) received intratympanic injections of isotonic saline. All rats were tested for labyrinthine integrity and then adjusted to a 23 h.d-1 water deprivation schedule. Both labyrinthectomized and control rats were exposed to a conditioned taste aversion (CTA) procedure or a control procedure. The CTA technique involved pairing a novel saccharin taste with subsequent intraperitoneal injection of ethanol (1.5 g.kg-1; 15% solution). The control CTA procedure paired a novel saccharin taste with injections of isotonic saline. Following two conditioning trials and 3 d of water only, saccharin preference ratios were obtained in two-bottle choice tests (saccharin vs. water) over 4 consecutive days. Control rats conditioned with ethanol exhibited a strong CTA (p < 0.01) relative to control rats injected with saline. Labyrinthectomized rats drinking saccharin followed by ethanol injections showed a strong CTA (p < 0.01) if conditioning occurred 29-30 d post-labyrinthectomy. However, CTA's were not apparent in labyrinthectomized rats conditioned with ethanol 19 d post-labyrinthectomy. Thus, ethanol-induced CTA formation varied across the post-labyrinthectomy time period.     

Triple-phase boundary and power density enhancement in thin solid oxide fuel cells by controlled etching of the nickel anode

Fabrication of microporous structures for the anode of a thin film solid oxide fuel cell (SOFC(s)) using controlled etching process has led us to increased power density and increased cell robustness. Micropores were etched in the nickel anode by both wet and electrochemical etching processes. The samples etched electrochemically showed incomplete etching of the nickel leaving linked nickel islands inside the pores. Samples which were wet- etched showed clean pores with no nickel island residues. Moreover, the sample with linked nickel islands in the anode pores showed higher output power density as compared to the sample with clean pores. This enhancement is related to the enlargement of the surface of contact between the fuel-anode-electrolyte (the triple-phase boundary).     

Interplay of Depletion Forces and Biomolecular Recognition in the Hierarchical Assembly of Supramolecular Tubes

Crowding effects have a profound impact on the hierarchical organization of cellular architectures. In the fields of systems chemistry and soft matter, this effect has not received much attention so far. Here, it is explored how poly(ethylene glycol) (PEG) as a crowding agent invokes depletion forces that act on synthetic supramolecular tubes. Hence, supramolecular tubes are pushed from their random orientation into hierarchically assembled bundles due to the PEG-induced crowded environment. The resulting morphology of formed bundled architectures can be tuned by the concentrations of both the supramolecular tubes and the PEG. The introduction of biotin groups at the surface of the tubes allows the engineering of biotin–streptavidin crosslinks between them. The order of introducing PEG and streptavidin in the system further affects the formed hierarchical assemblies, as well as their resistance toward dilution. The strategy described here provides a new route to establish hierarchically organized supramolecular architectures, combining crowding and specific biomolecular interactions, which shows the potential for controlling the structure of supramolecular materials and other soft matter systems.