Frontiers of Materials Science (v.4, #4)

Interactions between neural stem cells and biomaterials combined with biomolecules by Ying Wang; Hua Deng; Zhao-Hui Zu; Xing-Can Shen; Hong Liang; Fu-Zhai Cui; Qun-Yuan Xu; In-Seop Lee (325-331).
Neural repair and regeneration have been a tough problem in clinical studies. Tissue engineering using biomaterials along with neural stem cells (NSCs) have shown great potential for treatment, especially along with the biomolecules to regulate the NSCs can get more promising results. The biomolecules in the materials have a favorable impact on cell adhes ion, expansion, and differentiation. Thus, the interactions between biomaterials loading biomolecules and NSCs also receive particular attention. In this review, recent progresses of modified biomaterials by such biomolecules for neural injury and their impact on NSCs behavior will be discussed.
Keywords: biomaterial; neural stem cell (NSC); tissue engineering; biomolecule

Efficient and economical manufacture of heavy steel castings by Hai-Liang Yu; Jin-Wu Kang; Tian-You Huang (332-338).
Heavy steel castings, a symbol of the level of heavy industries, are high-tech products assembling materials, metallurgy, casting, etc. The feasible schemes for economizing manufacturing heavy steel castings were analyzed. The effects of riser design, sand mold, oxidation and deformation of casting during heat treatment, machining allowance, etc., on the economizing manufacture heavy steel castings were reviewed. Realization of efficient and economical manufacture of heavy steel castings will improve the output ratio of metal, shorten manufacturing period, save energy and resource, reduce pollution, and improve the competitiveness of enterprises.
Keywords: heavy steel casting; sand casting; riser; heat treatment; machining allowance

Polymer-directed assembly of water-soluble realgar nanocomposites for antimicrobial applications by Sheng-Ju Ou; Xing-Can Shen; Tao Jin; Jun Xie; Yan-Fang Guo; Hong Liang; Ruo-Bing Hou (339-344).
The poor water-solubility of realgar unfortunately results in poor bioavailability and hampers its medicinal application. In this work, water-soluble realgar nanoparticles (As4S4 NPs) were synthesized in aqueous solution and characterized by X-ray photoelectron spectroscopy. Furthermore, a polymer directed assembly method was used to prepare for the As4S4 nanocomposites with beneficial bioavailability for antimicrobial applications. It is found that the polyvinylpyrrolidone (PVP) has a significant effect on formation and growth of quasispherical As4S4-PVP nanocomposite with a narrow size distribution of (65±5) nm. In the case of using carboxymethylcellulose (CMC), the dendritic As4S4-CMC nanocomposite was obtained with particle size of (120±25) nm in predominant length. The FTIR spectra studies demonstrated the interaction between the polymers and the assembled As4S4. The antimicrobial assays indicated that the stabilized As4S4-polymer nanocomposites showed superior antimicrobial activity against uncoated As4S4 NPs both on gram-positive bacteria Staphylococcus aureus and gram-negative bacteria Escherichia coli. The TEM images of bacterial ultrathin sections showed the damage and disorganization of cell wall, suggesting the membrane-associated antimicrobial activity of As4S4-PVP nanocomposite.
Keywords: realgar; nanocomposite; antimicrobial activity; polymer; water-soluble

In this paper, poly(vinylidene fluoride)-graft-poly(N-isopropylacrylamide) (PVDF-g-PNIPAAm) copolymers were synthesized directly via grafting temperature-sensitive material NIPAAm on PVDF by atom transfer radical polymerization (ATRP). The chemical structure of the graft copolymers was characterized by Fourier transform infrared (FTIR) and 1H-NMR spectroscopy. The temperature-sensitive membranes were prepared from the PVDF-g-PNIPAAm copolymers by the immersion precipitation process of the phase inversion method. The chemical composition and pore structure of the PVDF-g-PNIPAAm membranes were studied by X-ray photoelectron spectroscopy (XPS) and an automatic mercury porosimeter, respectively. The effects of temperature on pure water flux and bovine serum albumen (BSA) rejection ratio of the membranes were also investigated. The results showed that the grafted PNIPAAm chains tended to enrich on the surfaces of the membranes or the membrane pores during the membrane-forming process. Pore diameter and porosity of the copolymer membranes were larger than those of the pristine PVDF membranes. Also, the PVDF-g-PNIPAAm membranes could exhibit temperature-sensitive performance in water flux and BSA rejection measurements.
Keywords: poly(vinylidene fluoride) (PVDF); N-isopropylacrylamide (NIPAAm); atom transfer radical polymerization (ATRP); temperature-sensitive membrane

Drug release behaviors of a pH/temperature sensitive core-shelled bead with alginate and poly(N-acryloyl glycinates) by Kui-Lin Deng; Yu-Bo Gou; Li-Rong Dong; Qian Li; Li-Bin Bai; Ting Gao; Chun-Yuan Huang; Shu-Liang Wang (353-358).
In this study, a pH/temperature sensitive bead with core-shelled structure, as a drug carrier, was prepared by grafting of N-acryloylglycinates on the surface of sodium alginate beads. The pH and temperature sensitivity of the beads originate from sodium alginate (SA) and copoly(N-acryloylglycinates), respectively. Here, indomethacin (IMC) was selected as a drug model molecule and loaded in SA beads. The release of IMC was systematically investigated as a function of temperature, pH, and SA concentration. The amount of IMC released from beads was as high as 61.6%in pH = 7.4 phosphate buffer solution (PBS) over 620 min, whereas only 27.9% IMC diffused into the pH = 2.1 PBS. In addition, the release rates of IMC at 37.5°C were faster than that at 20.0°C and decreased with increasing SA concentration in the beads. The result indicates that the sensitive beads have the potential to be used as an effective pH/temperature-controlled delivery system in the biomedical fields.
Keywords: sodium alginate; pH/temperature sensitive bead; core-shelled structure; drug release

Antibacterial and biological properties of silver-loaded coralline hydroxyapatite by Yu Zhang; Qing-Shui Yin; Hua-Fu Zhao; Jian Li; Yue-Teng Wei; Fu-Zhai Cui; Hua-Yang Huang (359-365).
The antibacterial and biological properties of silver-loated coralline hydroxyapatite (Ag-CHA) as a new antibacterial implant material were investigated in this study. Compared to other antibiotic and chemical bactericidal agents, Ag+ does not bring bacterial resistance to drugs and has less toxicity. The porous CHA was formed by hydrothermal exchange, then Ag+ was loated onto CHA through ion exchange and adsorption. The microstructure and composition of Ag-CHA were characterized by scanning electron microscopy (SEM), Rutherford backscattering spectrometry (RBS), and energy dispersive spectrometry (EDS). Antibacterial activity of Ag-CHA on the clinical strains of Escherichia coli (E. Coli) and Staphylococcus aureus (S. Aureus) was evaluated by the flat plate diffusion method. The antibacterial activity of Ag-CHA was found to be correlated with the concentration of Ag+ in a dose-dependent manner, which indicated that the optimal antibacterial and biocompatible effects of Ag-CHA could be obtained with Ag+ concentrations from 5×10−5 to 1×10−4 mol/L.
Keywords: silver-loated loralline hydroxyapatite (Ag-CHA); antibacterial activity; cytotoxicity

The reversible addition-fragmentation chain transfer (RAFT) polymerization of 2-(2′-iodobenzoyl) ethyl methacrylate (2-IEMA) was performed in benzene solution using 4-cyanopentanoic acid dithiobenzoate (CPADB) as chain transfer agent to yield well-defined iodine-containing methacrylate-based polymers. It is characteristic of a controlled/living polymerization, i.e., linear increase in M n with conversion and narrow molecular distribution. Moreover, the block copolymerization of 2-IEMA with 2-(2′,3′,4′,6′-tetra-O-acetyl-β-Dglucosyloxy) ethyl methacrylate (AcGEMA) and 2-lactobionamidoethyl methacylate (LAMA) was also carried out to give radiopaque glycopolymers by using the same methodology, respectively. The radiopacity of these polymers was evidenced by a routine medical X-ray imaging technique. TEM and DLS analytical results showed that the selected PIEMA-b-PLAMA diblock copolymers can self-assemble in aqueous solution into nearly spherical aggregates of 60–86 nm in diameter.
Keywords: reversible addition-fragmentation chain transfer (RAFT) polymerization; iodine-containing methacrylate-based polymer; radiopacity; glycopolymer

The pathway of HAP nanoparticle uptake into hepatoma carcinoma cells by Mei-Zhen Yin; Xian-Ying Cao; Shi-Pu Li (376-381).
To study the pathway of hydroxyapatite (HAP) nanoparticle uptake into hepatoma carcinoma cells, by selecting bigger particles as contrast, HAP particles with 70.8, 1078.8, and 1906.6 nm mean diameters were prepared. Using TEM, the distribution conditions of the three kinds of HAP particles on the cell membrane surface and within the endochylema, as well as the change in lysosomes was observed after HAP particles were treated onto Bel-7402 cells for 2, 12, 24, and 48 h. The results showed that there were HAP nanoparticles adhering to the depressed part of the plasmalemma, and in the endochylema there were HAP nanoparticles which were enclosed in many vesicles with different sizes. The lysosome had no changes compared to the blank control. The same results were seen for bigger particle groups. Through contrast analysis, it was thought that HAP nanoparticles were internalized into the hepatoma carcinoma cells and then formed vesicles. HAP nanoparticles enclosed in vesicles did not undergo lysosomal digestion. These characteristics are in accord with non-clathrin-mediated endocytosis. Therefore, the pathway of HAP nanoparticle uptake into hepatoma carcinoma cells is possibly caveolae-mediated endocytosis and it has no relation to particle size. This result lays the foundation for further research into the anticancer mechanism of HAP nanoparticles, and plays an important role in the research on nanoparticles as carriers of anticancer drugs.
Keywords: hydroxyapatite (HAP) nanoparticles; hepatoma carcinoma cell; endocytosis; caveolae

The luminescent enhancement of LaPO4:Ce3+,Tb3+ nano phosphors by radial aggregation by Xin Ji; Fei-Jian Zhu; Ha-Lei Zhai; Rui-Kang Tang (382-386).
The rare earth nano phosphors can meet the challenging demand for new functional devices but their luminescence is always poor. Here we report on a simple method to prepare uniform LaPO4:Ce3+,Tb3+ sphere-like nano aggregates from the precipitated nano phosphor crystallites without using any additive. The spontaneous aggregation is induced and controlled only by the suspension pH conditions. It is found that the 100 nm spherical aggregates can significantly improve the green emissions of the LaPO4:Ce3+,Tb3+ nano particles. The intensity of the aggregates can be about 10 times as that of the 80 nm-sized individual ones. This study may provide a useful yet convenient strategy in the improvement and application of nano phosphors.
Keywords: nano phosphor; lanthanide phosphate; aggregation; luminescence; enhancement

We report on the epitaxial growth of SrRuO3 (SRO) thin films on Pt (111)/γ-Al2O3 (111) nSi (111) substrates. The grown thin films are crystalline and epitaxial as suggested by RHEED and XRD experiments. With the use of γ-Al2O3 (001)/nSi (001) and γ-Al2O3 (111)/nSi (111) substrates, crystalline but not epitaxial films have grown successfully. This result implies that lattice mismatch between nSi and SRO prevents the epitaxial growth of SRO film directly on nSi. However, the buffer Pt (111) layer mitigates lattice mismatch that provides to grow epitaxial film on nSi of quality. Morphological study shows a good surface with moderate roughness. Film grown at 700°C is smoother than the film grown at 750°C, but the variation of temperature does not affect significantly on the epitaxial nature of the films.
Keywords: RF-sputtering; molecular beam epitaxy (MBE); X-ray diffraction (XRD); epitaxial Al2O3

Behaviors of different dispersers on morphologies of porous TiO2 films by Ding Ren; Yu Zou; Chang-Yong Zhan; Ning-Kang Huang (394-397).
TiO2 films with nanoparticles dispersed by using three different additives such as acetylacetone, Emulsifier OP-10, and polyethylene glycol, respectively. It is found that for the TiO2 films produced with appropriate amount of Emulsifier OP-10, there are no reaggregation of TiO2 nanoparticles with pores of about 5–20 nm. By adding polyethylene glycol, the pore size of the TiO2 films could be in the range from about 50 to 200 nm. However, by using acetylacetone, aggregations of TiO2 nanoparticles always exist in the TiO2 films. The related mechanism on the aggregation of nanoparticles in the TiO2 slurries is discussed.
Keywords: dye-sensitized solar cell (DSSC); porous TiO2 films; disperser; morphology

Silver nanowires have attracted considerable attention in the past decade, due to their unique physical and chemical properties, which can lead to a wide variety of potential applications. In this work, silver nanowires have been fabricated using an alcohol ionic liquid by a one-step method in the absence of any extra capping agents. The method is based on the reduction of AgNO3 by 1-(3-hydroxylpropyl)-3-methylimidazolium tetrafluoroborate (C3OHmimBF4) in an aqueous solution at 180°C for 18 h. The products were characterized by a scanning electron microscope (SEM), transmission electron microscope (TEM), energy-dispersive X-ray spectrograph (EDS), and powder X-ray diffractometry (XRD). The experimental results indicate that both reaction temperature and special properties of C3OHmimBF4 play important roles in the formation of silver nanowires.
Keywords: silver nanowires; ionic liquid; nanomaterials

A new strategy for synthesizing flame retardant viscose fiber (FR-VF) has been achieved by graft copolymerization of acrylonitrile (AN) onto viscose fiber and the subsequent chemical modification with hydrazine hydrate and zinc acetate. The structure of FR-VF was confirmed by X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectrometry (FTIR). The surface morphology of FR-VF was analyzed using scanning electron microscope (SEM). The results show that the graft copolymerization of AN onto viscose fiber and the reaction of VF-g-PAN with hydrazine hydrate and zinc acetate have been successfully carried out. The thermal properties tested by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) techniques show that the thermal degradation rate of FRVF is slower than that of untreated FR-VF after 300°C. As a result, the char residue increases from 5.2% to 50.4% at 800°C. Furthermore, the burned FR-VF keeps original form as evidenced by SEM analysis, indicating that the obtained FR-VF possesses excellent thermal stability and char forming capability.
Keywords: viscose fiber; flame retardant; graft copolymerization; chemical modification

Single-crystalline silver nanoplates with an average in-plane dimension and thickness of about 700 and 25 nm, respectively, were fabricated on a large scale in aqueous poly(vinyl pyrrolidone)/AgNO3 solution by a simple one-step hydrothermal method. In this process, poly (vinyl pyrrolidone) (PVP) acts as both reducing agent and shape-directing agent. SAED and XRD measurements reveal that the growth of silver nanoplates is mainly dominated by (111) facets.
Keywords: nanomaterials; poly(vinyl pyrrolidone); silver nanoplates

Minor Fe and Yof Fe71.2B24Y4.8 bulk metallic glass (BMG) are replaced by Ni, Nd, and Ge, respectively, and glass-forming ability (GFA) influenced by these similar element substitutions are studied. Except Ge, Ni and Nd can both improve the critical diameter of base BMG from 2 to 3 mm. Therefore, substitutions with chemical similar elements are more effective on GFA enhancement than those with atom size similar elements.
Keywords: metallic glass; minor addition; glass-forming ability (GFA); Fe-based alloys

Analysis of sensitization phenomenon in friction stir welded 304 stainless steel by Nelly Abigail Rodríguez; Efrain Almanza; María de Jesús Pérez; Carlos Rodrigo Muñiz; Scott Packer; Russell Steel (415-419).
This study evaluates the degree of sensitization (DOS) of 304 stainless steel joined by friction stir welding (FSW). Single-loop electrochemical potentiokinetic reactivation tests were performed using a 0.5 mol/L H2SO4 + 0.01 mol/L KSCN solution. Sensitization was promoted by exposition of the stainless steel at temperatures between 400°C and 850°C. The microstructure was characterized using optical microscopy to identify the weld zone and the base metal. The samples treated at 550°C showed the most severe intergranular corrosion. The DOS was lower in the weld zone than in the base metal after heat treatments. This reduction in the DOS for the weld zone indicates that FSW is a beneficial process in joining stainless steel.
Keywords: degree of sensitization (DOS); friction stir welding (FSW); stainless steel