Synthesis of polypyrrole nanorods via sacrificial removal of aluminum oxide nanopore template: A study on cell viability, electrical stimulation and neuronal differentiation of PC12 cells.

Synthesis of nanomaterials having uniform shape and size is a challenging task. Properties exhibited by such substrates would be compatible and homogeneous compared to the average properties displayed by those substrates with heterogeneous size. Herein, we report the synthesis of polypyrrole nanorods (PPy-NRs) of almost uniform size via oxidative chemical polymerization of pyrrole within anodized aluminum oxide nanopores followed by sacrificial removal of the template. Field emission scanning electron microscopy (FE-SEM), fourier transformed infra-red (FT-IR) spectra, X-ray diffraction (XRD), and ultra-violet-visible-near infra-red (UV-Vis-NIR) spectra of the substrate were used to analyze the physicochemical properties of as-synthesized PPy-NRs. PPy-NRs treated MC3T3-E1 and PC12 cells exhibited good biocompatibility in CCK-8 and live/dead assays. The assay showed more cell viability on PC12 cell lines. Electrical stimulation through PPy-NRs treated PC12 cells accelerated neuronal differentiation compared to those without electrical stimulation during in vitro cell culture.

Towards a molecular understanding of the water purification properties of Moringa seed proteins.

Seed extracts from Moringa oleifera are of wide interest for use in water purification where they can play an important role in flocculation; they also have potential as anti-microbial agents. Previous work has focused on the crude protein extract. Here we describe the detailed biophysical characterization of individual proteins from these seeds. The results provide new insights relating to the active compounds involved. One fraction, designated Mo-CBP3, has been characterized at a molecular level using a range of biochemical and biophysical techniques including liquid chromatography, X-ray diffraction, mass spectrometry, and neutron reflection. The interfacial behavior is of particular interest in considering water purification applications and interactions with both charged (e.g. silica) and uncharged (alumina) surfaces were studied. The reflection studies show that, in marked contrast to the crude extract, only a single layer of the purified Mo-CBP3 binds to a silica interface and that there is no binding to an alumina interface. These observations are consistent with the crystallographic structure of Mo-CBP3-4, which is one of the main isoforms of the Mo-CBP3 fraction. The results are put in context of previous studies of the properties of the crude extract. This work shows possible routes to development of separation processes that would be based on the specific properties of individual proteins.

The removal of Al2O3 particles from grit-blasted titanium implant surfaces: effects on biocompatibility, osseointegration and interface strength in vivo.

For the improvement of surface roughness and mechanical interlocking with bone, titanium prostheses are grit-blasted with Al(2)O(3) particles during manufacturing. Dislocated Al(2)O(3) particles are a leading cause of third-body abrasive wear in the articulation of endoprosthetic implants, resulting in inflammation, pain and ultimately aseptic loosening and implant failure. In the present study, a new treatment for the removal of residual Al(2)O(3) particles from grit-blasted, cementless titanium endoprosthetic devices was investigated in a rabbit model. The cleansing process reduces residual Al(2)O(3) particles on titanium surfaces by up to 96%. The biocompatibility of the implants secondary to treatment was examined histologically, the bone-implant contact area was quantified histomorphometrically, and interface strength was evaluated with a biomechanical push-out test. Conventional grit-blasted implants served as control. In histological and SEM analysis, the Al(2)O(3)-free implant surfaces demonstrated uncompromised biocompatibility. Histomorphometrically, Al(2)O(3)-free implants exhibited a significantly increased bone-implant contact area (p=0.016) over conventional implants between both evaluation points. In push-out testing, treated Al(2)O(3)-free implants yielded less shear resistance than conventional implants at both evaluation points (p=0.018). In conclusion, the new surface treatment effectively removes Al(2)O(3) from implant surfaces. The treated implants demonstrated uncompromised biocompatibility and bone apposition in vivo. Clinically, Al(2)O(3)-free titanium prostheses could lead to less mechanical wear of the articulating surfaces and ultimately result in less aseptic loosening and longer implant life.

Extraction of alumina and sodium oxide from red mud by a mild hydro-chemical process.

A mild hydro-chemical process to extract Al(2)O(3) in red mud to produce sodium aluminate hydrate was investigated, and the optimum conditions of Al(2)O(3) extraction were verified by experiments as leaching in 45% NaOH solution with CaO-to-red mud mass ratio of 0.25 and liquid-to-solid ratio of 0.9, under 0.8 MPa at 200 degrees C for 3.5h. Subsequent process of extracting Na(2)O from the residue of Al(2)O(3) extraction was carried out in 7% NaOH solution with liquid-to-solid ratio of 3.8 under 0.9 MPa at 170 degrees C for 2h. Overall, 87.8% of Al(2)O(3) and 96.4% of Na(2)O were extracted from red mud. The final residues with less than 1% Na(2)O could be utilized as feedstock in construction materials. The chemical reactions taking place in both Al(2)O(3) and Na(2)O extractions from red mud are proposed.

Collection of SiO2, Al2O3 and Fe2O3 particles using a gas-solid fluidized bed filter.

The filtration of SiO(2), Al(2)O(3) and Fe(2)O(3) particles with average sizes of 4 and 40 microm using a fluidized bed filter at 40 and 300 degrees C was studied. The collection mechanisms, interparticle forces and bounce-off effect between filtered particles and collectors were analyzed to determine their effect on particle filtration. Experimental results showed that the collection efficiency of 4 microm SiO(2) and Al(2)O(3) particles exceeded that of 40 microm particles. Contrarily, the 40 microm Fe(2)O(3) particles were collected more efficiently than the 4 microm particles, because of the differences between the microstructures of SiO(2), Al(2)O(3,) and Fe(2)O(3) particles. The interaction between the particles affected the removal of mixed SiO(2), Al(2)O(3) and Fe(2)O(3). The particle size distribution (PSD) of the particles in the exit was governed by the operating temperature, the original size of the filtered particles, the interparticle force and the hardness of the particles and the collectors. The smallest particles were not those most easily elutriated from the fluidized bed filter because they agglomerated with each other or with large particles. The van der Waal's force dominated the forces between 4 and 40 microm particles. The main collection mechanism for 4 and 40 microm particles was direct interception. The effect of impaction increased with particle size above 40 microm. The strong impaction and bounce-off effect reduced the collection efficiency of 40 microm SiO(2) and Al(2)O(3) particles. However, the strong interparticle force between Fe(2)O(3) particles and collectors contributed to the high collection efficiency of the Fe(2)O(3) particles.

Filtration of nano-particles by a gas-solid fluidized bed.

The filtration of 80 nm SiO2 and Al(2)O(3) particles in a gas stream using fluidized beds was studied. Silica sand and activated carbon (A.C.) were adopted as bed materials to filtrate 80 nm SiO2 and Al(2)O(3) particles. The collected particles were elutriated from the fluidized bed, so the filtration was a dynamic process and the variations of the removal efficiency with time were studied. Experimental results showed that the filtrations of 80 nm SiO2 and Al(2)O(3) particles with a bed material of silica sand were not dynamic processes but the filtration by A.C. was. The removal efficiencies for SiO2 and Al(2)O(3) particles using silica sand as bed material were held steady and found to be equal, between 86 and 93%. A.C. is considered to be more efficient than silica sand because it has a high specific surface area. However, the experimental data yield conflicting results. The removal efficiency of Al(2)O(3) particles fell from 92% initially to 80% at the end of test-a little lower than that obtained by filtration using silica sand. A higher voidage of A.C. than silica sand weakens the removal of nanoparticles since the diffusion mechanism dominates. The removal efficiency of SiO2 by A.C. decayed from 83 to 40% with time passed. The huge differences between the filtration efficiency of SiO2 and that of Al(2)O(3) particles by A.C. was associated with the extensive segregation of SiO2 and A.C. particles, which caused more SiO2 particles to move to the top of the bed, where they were elutriated. The weak inter-particle force for SiO2 decreased the removal efficiency also.

Preparation and thermoluminescence properties of aluminium oxide doped with europium.

There is little information concerning the use of rare earths as dopants of Al2O3. This paper presents the preparation method and the results of studying the thermoluminescence characteristics of Al2O3:Eu exposed to ultraviolet light. Phosphor powder was obtained by the evaporation method. Optimum dopant concentration was 10% at an evaporation temperature of 700 degrees C. The powder obtained was submitted to thermal treatments at high temperatures in order to stabilise the traps. Diffraction patterns showed amorphous powder up to 500 degrees C; as the temperature was raised crystalline phases of Al2O3 appeared. The photoluminescence spectrum induced by 250 nm UV light exhibited four well defined peaks characteristic of the Eu3+ ion. The glow curve exhibited two peaks at 180 and 350 degrees C. The sensitivity of Al2O3:Eu was 10 times lower than Al2O3:C. The thermoluminescence response was linear from 2.4 to 3000 microJ.cm(-2) of spectral irradiance, and the fading 2% in a month. From these results it can be concluded that Al2O3:Eu has potential as an UV dosemeter.