Frontiers of Materials Science (v.2, #2)

Special issue featuring articles from the 3rd Asian Symposium on Biomineralization by H. Kamiya; Q. Q. Zhang; In-Seop Lee; F. Z. Cui (119-119).

The biodegradation of hydrocarbons by microorganisms is one of the primary ways by which an oil spill is eliminated from contaminated sites. One such spill was that of the Russian tanker the Nakhodka that spilled heavy oil into the Sea of Japan on January 2, 1997. This paper describes the three main processes of the Nakhodka oil spill, including: (1) the weathering of hydrocarbon-degrading bacteria (genus Pseudomonas) and crystallized organic compounds from the Nakhodka oil spill-polluted seashores after nine years; (2) the laboratory-scale biodegradation of the Nakhodka oil spill over a 429-day period; and (3) the bioavailability of kaolinite clay minerals and the role they play in seawater polluted with the Nakhodka oil spill.Upon the slow evaporation of the Nakhodka oil spill during the 9-year weathering, the dendritic crystal growth of paraffin (a mixture of alkanes) occurred in the oil crust under natural conditions. Heavy metals were obtained in the original heavy oil samples of three seashores in the Sea of Japan. Si, S, Ti, Cr, Ni, Cu, and Zn were found in the original Nakhodka oil spill samples whereas these heavy metals and S were no longer present after 9 years. The anaerobic reverse side of the oil crust contained numerous coccus-type bacteria associated with halite. The hydrocarbon-degrading bacteria and paraffin wax in the oil crust may have a significant effect on the weathering processes of the Nakhodka oil spill during the 9-year bioremediation.A biodegradation process of heavy oil from the Nakhodka oil spill by indigenous microbial consortia was monitored over 429 days in the laboratory. The indigenous microbial consortia consisted of bacteria and fungi as well as the bacterium Pseudomonas aeruginosa isolated from Atake seashore, Ishikawa Prefecture, Japan. Both bacteria and fungi had a significant role in the observed biodegradation of heavy oil during the 429-day bioremediation with respect to the pH of the solution. Hydrocarbon-degrading bacteria had a tendency to play the greatest role under neutral to alkaline condition (pH; 7–7.8). On the contrary, when pH shifted to acidic (pH; 2–4) levels, the fungi took over to degrade heavy oil. During the period, the aliphatic hydrocarbons were reduced significantly but the aromatic hydrocarbons remained relatively constant even after 429 days of bioremediation.Experimental study was undertaken to investigate the bioavailability of kaolinite clay minerals and the role they play in seawater polluted with the Nakhodka oil spill. TEM/EDS imaging suggested that the clays present in oil-polluted seawater were capable of stimulating oil-degrading bacteria probably because Si from clays facilitates bacterial usage of oil and C-O-Na-Si complexes on the surfaces of bacterial cell walls are a stimulator for oil-degrading bacterial growth in seawater contaminated with the Nakhodka oil spill.
Keywords: hydrocarbon-degrading bacteria; Pseudomonas ; Nakhodka oil spill; bioremediation; heavy oil; paraffin wax; aliphatic hydrocarbons; aromatic hydrocarbons; kaolinite; clay minerals

Fine structure and development of the collar enamel in gars, Lepisosteus oculatus, Actinopterygii by Ichiro Sasagawa; Mikio Ishiyama; Hiroyuki Yokosuka; Masato Mikami (134-142).
The fine structure of collar enamel and the cells constituting the enamel organ during amelogenesis in Lepisosteus oculatus was observed by light, scanning electron and transmission electron microscopy. In the enamel, slender crystals were arranged perpendicular to the surface and the stripes that were parallel to the surface were observed, suggesting that the enamel in Lepisosteus shares common morphological features with that in sarcopterygian fish and amphibians. Ameloblasts containing developed Golgi apparatus, rough endoplasmic reticulum (rER) and secretory granules were found in the secretory stage. In the maturation stage, a ruffled border was not seen at the distal end of the ameloblasts, while many mitochondria and lysosome-like granules were obvious in the distal cytoplasm. The enamel organ consisted of the outer dental epithelial cells, stratum reticulum cells and ameloblasts, but there was no stratum intermedium. It is likely that the ameloblasts have less absorptive function in comparison with the inner dental epithelial cells facing cap enameloid.
Keywords: amelogenins; enamel; bony fish; Lepisosteus

Calcium phosphate coating on magnesium alloy for modification of degradation behavior by Fu-zhai Cui; Jing-xin Yang; Yan-peng Jiao; Qing-shui Yin; Yu Zhang; In-Seop Lee (143-148).
Magnesium alloy has similar mechanical properties with natural bone, but its high susceptibility to corrosion has limited its application in orthopedics. In this study, a calcium phosphate coating is formed on magnesium alloy (AZ31) to control its degradation rate and enhance its bioactivity and bone inductivity. Samples of AZ31 plate were placed in the supersaturated calcification solution prepared with Ca(NO3)2, NaH2PO4 and NaHCO3, then the calcium phosphate coating formed. Through adjusting the immersion time, the thickness of uniform coatings can be changed from 10 to 20 μm. The composition, phase structure and morphology of the coatings were investigated. Bonding strength of the coatings and substrate was 2–4 MPa in this study. The coatings significantly decrease degradation rate of the original Mg alloy, indicating that the Mg alloy with calcium phosphate coating is a promising degradable bone material.
Keywords: metal (alloys); calcium phosphate(s); coating(s); degradation; dental/endosteal implant

Magnesium alloy has similar mechanical properties with natural bone and can degrade via corrosion in the electrolytic environment of the human body. Calcium phosphate has been proven to possess bioactivity and bone inductivity. In order to integrate both advantages, calcium phosphate coating was fabricated on magnesium alloy by a biomimetic method. Supersaturated calcification solutions (SCSs) with different Ca/P ratio and Cl concentration were used as mimetic solutions. The morphology, composition and formation process of the coating were studied with scanning electron microscopy (SEM), energy dispersive spectrometer (EDS), Fourier transformed infrared spectroscopy (FTIR) and X-ray diffraction (XRD). The results show that a uniform calcium phosphate coating was observed on magnesium alloy, the properties of which could be adjusted by the SCSs with different Ca/P ratio. The formation process of the coating was explored by immersing magnesium alloy in SCSs with different Cl concentration which could adjust the hydrogen production. According to SEM results, the hydrogen bubbles were associated with the formation of grass-like and flower-like coating morphologies. In conclusion, the biomimetic method was effective to form calcium phosphate coating on magnesium alloy and the morphology and composition of the coating could be accommodated by the Ca/P ratio and Cl concentration in SCSs.
Keywords: magnesium alloy; calcium phosphate coating; degradation behaviour; formation process

Characterization of organic matrix components of pearl oyster, Pinctada fucata and their implications in shell formation by Chihiro Nogawa; Mami Obara; Megumi Ozawa; Aya Sato; Akiko Watanabe; Ryo Yamazaki; Daishi Yamada; Kana Akiniwa; Tetsuro Samata (156-161).
Mollusks make their shells by biomineralization using Ca2+ and CO3 2− from natural environment. In molluscan shells, two types of CaCO3 crystal which are aragonite and calcite form the species-dependent microstructures. It is believed that shell organic matrices act for control of the crystal types and microstructures. Shell of Pinctada fucata is divided into aragonitic nacreous layer and calcitic prismtic layer. In the recent years, several novel matrix components have been identified in pearl oyster shells by subsequent solubilization of the insoluble matrix, even in the nacreous layer which abounds in the data. In them, we focused our attention on a component, of which the N-terminal amino acid sequence was determined, and attempted cloning genes encoding it. As a result, several clones with typical sequence for the ORF (open reading frame) region were identified and the amino acid sequences were deduced. Further analysis of northern hybridization clarified the tissue specific expressions of the transcripts of the identified genes.
Keywords: pearl oyster; shell microstructure; CaCO3 crystal polymorphism; organic matrix; repeat sequences

Daily oscillation of gene expression associated with nacreous layer formation by Yoko Miyazaki; Tomomi Usui; Aya Kajikawa; Hajime Hishiyama; Norifumi Matsuzawa; Takuma Nishida; Akira Machii; Tetsuro Samata (162-166).
Three major organic matrix components, nacrein, MSI60 and N16 have been reported from the nacreous layer of Japanese pearl oyster, Pinctada fucata. Though several in vitro experiments have been carried out to elucidate the functions of these molecules details have not yet been clarified. In this report, we tempt to clarify the gene expression levels encoding the above three proteins between samples of 1) summer and winter seasons and 2) ocean and aquarium environments by using real-time polymerase chain reaction (PCR).It was confirmed that the biomineralization process of P. fucata is mainly influenced by the circatidal rhythm of the ocean environment. The gene expressions coding for N16 and MSI60 increased at the time of high tide, while that of nacrein increased at the time of low tide. The similar tendency observed in N16 and MSI60 showed the possibility that both components are secreted simultaneously, supporting a hypothesis that N16 forms cross-linkage with MSI60 to form the membrane. The expressions of MSI60, N16 and glyceraldehyde-3-phosphate dehydrogenase (GAPDH) genes were remarkable in winter season, while no variation was found in the expression level of the nacrein gene in summer and winter season.The study is the first attempt regarding the seasonal and circadian rhythms observed on gene expressions incorporated into molluscan shell formation. The results will give a new insight into the relationship between molluscan physiology and the mechanism of shell formation.
Keywords: Pinctada fucata ; nacreous layer; organic matrix; real-time polymerase chain reaction (PCR); circadian rhythm; circatidal rhythm

N-linked oligosaccharide in MSP-1 and its implication for scallop calcification by Michiko Norizuki; Daisuke Takakura; Tetsuro Samata (167-171).
We speculated the structure of the N-linked oligosaccharides enzymatically released from the organic matrix (OM) component in the foliated layer of Patinopecten yessoensis. The 80 kDa component of the soluble OM was detected by lectin blotting and was identified as MSP-1 using liquid chromatography/mass spectrometry (LC/MS/MS). LC/MS/MS analysis of the N-glycan liberated from MSP-1 detected a hybrid-type N-glycan, which contained sulfite and sialic acid at its terminus based on the characteristic Y ions. The data strongly imply that MSP-1, a sulfated OM glycoprotein, participates in molluscan biomineralization by creating a favorable environment for calcium ion uptake through sulfite acid and sialic acid. Further analyses of oligosaccharides linked to the OM components in wide variety of species and shell microstructures may definitely contribute in elucidation of molluscan biomineralization at the molecular level.
Keywords: biomineralization; Glycosylation; N-glycosylation; LC/MS/MS analysis

Microsphere integrated gelatin-siloxane hybrid scaffolds were successfully synthesized by using a combined sol-gel processing, post-gelation soaking and freeze-drying process. A bone-like apatite layer was able to form in the Ca2+-containing porous hybrids upon soaking in a simulated body fluid (SBF) up to 1 day. The rate of gentamicin sulfate (GS) release from the GS-loaded gelatin-siloxane hybrid microsphere became constant after a 4 h burst. The antibacterial activity was assessed by the agar diffusion test (ADT) and the bactericidal effect test. It is evident that the as-synthesized porous scaffolds have excellent bioactivity and antibacterial activity, and may be favorable in bone tissue engineering.
Keywords: gelatine; silxoane; tissue engineering; bioactivity; antibacterial activity

Apatite crystal in hard tissue of conodont fossils by Hiroyuki Mishima; Mituo Kakei; Toshio Yasui; Saori Miyamoto; Yasuo Miake; Takaaki Yanagisawa (179-181).
The present study was aimed at examining the nature of apatite crystal in the tooth apparatus of a conodont fossil using transmission electron microscopy (TEM), scanning electron microscopy (SEM), laser Raman microprobe spectrometry and electron-probe microanalysis (EPMA). The hard tissue of the condont consisted of 2 layers and the organization varied with the size of the crystal. Higher magnification showed that the crystals were observed in the lattice of (100) and the central dark lines were not present. Ca, P, and F were detected in the crystal using EPMA. Our results indicate that the apatite crystal in conodont fossils is not hydroxyapatite but fluorapatite.
Keywords: conodont; apatite crystal; lattice images; laser Raman microprobe spectrometry; trace elements; electron-probe microanalyzer (EPMA)

The intermetallic compound NiAl has excellent potential for high temperature structural applications but suffers from low temperature brittleness and insufficient high temperature strength. One way to remove these deficiencies is the reinforcement by high strength ceramic fibers. Such intermetallic matrix composites can be conveniently fabricated by the hot pressing of matrix coated fibers. Al2O3 single crystal fibers show excellent chemical stability with the NiAl matrix, but the residual thermal compressive stresses during cool down dramatically degrades the fiber strength and thus, renders the composite useless for structural applications. We report on an experimental and computational study to mitigate this problem and to fabricate Al2O3/NiAl composites with sufficient high temperature strength. Analytical TEM, mechanical testing and push-out tests were employed to characterize chemistry, microstructure and mechanical properties of the composites. It will be shown that a processing window exists that allows producing intermetallic matrix composites with promising mechanical properties.
Keywords: NiAl composite; interface structure; mechanical property; Al2O3 fiber

A photoinitiator HTD bearing in-chain benzophenone (BP) and coinitiator tertiary amine, based on 4-hydroxybenzophenone (HBP), toluene-2,4-diisocyanate (TDI) and N,N-dimethylethanolamine (DMEA), was synthesized and characterized by 1H-NMR and UV-vis absorption spectroscopy. HTD had longer absorption wavelength in the UV-vis absorption spectra than the low molecular counterpart BP. The kinetics of photopolymerization was studied by real-time Fourier transformation infrared (FTIR) spectroscopy. It showed that HTD was a more effective photoinitiator than BP. When this photointiator was used to initiate polymerization of acrylates, both rate of polymerization and final conversion increased with increase of initiator concentration and light intensity. UV-vis extract analysis showed that the extractability of HTD was much lower than BP/DMEA on the same environment condition.
Keywords: kinetics; photoinitiator; photopolymerization; benzophenone (BP)/amine

Investigation of kinetics and morphology development for polyurethane-urea extended by DMTDA by Zai-feng Li; Jin-yan Li; Jian Sun; Bao-qun Sun; Jin-jing Wang; Qiang Shen (200-204).
The relationship between the reactions kinetics and morphology development during the polyurethaneurea (PUU) curing process has been investigated simultaneously by in situ Fourier transform infrared spectroscopy (FTIR). The data of the FTIR spectra showed that with the increase of conversion, the absorbance of NH bands increases and its band sites shifts to lower wavenumbers; the absorbance of free urethane carbonyl kept nearly constant at low conversion, and then decreased much because of the interaction of the formed urea links, and then changed little at high conversion owing to the diffuse control. The band sites of hydrogen bonded urea carbonyl similarly shifted to lower wavenumbers and the absorbance of the hydrogen bonded urea carbonyl, associated with the phase separation of hard segments, became stronger with buildup of hydrogen bond between urea links. The carbonyl bands available during curing process were further assigned. Both interactions, such as hydrogenised effect and phase separation, played a major role in the matrix formation of the PUU polymer.
Keywords: polyurethane-urea (PUU); kinetics; morphology; Fourier transform infrared spectroscopy (FTIR)

Chitosan rod reinforced by self-crosslinking through thermal treatment by Zheng-ke Wang; Qiao-ling Hu; Ruo-chong Fei; Jia-han Ke; Jia-cong Shen (205-208).
Chitosan (CS) rods were reinforced at high temperatures to form network structure by self-crosslinking of amino groups. Properties of treated CS rods were studied by FTIR spectroscopy, intrinsic viscosity measurement, mechanical properties testing and water absorption measurement. The FTIR spectra indicated that the CS configuration was transformed from β-CS for untreated CS rods to α-CS for thermally treated CS rods. Meanwhile, the crosslinking also occurred between amino groups of CS. Due to the increase in the crosslinking degree, the intrinsic viscosity increased with the rising of temperature. It was found that the network structure enhanced the bending strength of CS rods, which reached 154.8 MPa when CS rods were treated at 140°C for 2 h. Thermal treatment also reduced the water absorption of CS rods. Due to the improved mechanical properties, thermally treated CS rods could be used as a novel device for internal fixation of bone fracture.
Keywords: chitosan (CS); thermal treatment; reinforcement

Hydrogel nanoparticles could be prepared by using linoleic acid (LA) modified carboxymethyl chitosan (CMCS) after sonication. Bromelain could be loaded onto nanoparticles of LA-CMCS. Factors affecting the activity of the immobilized enzyme, including temperature, storage etc., were investigated in this study. The results showed that the stability of bromelain for heat and storage was improved after immobilization on nanoparticles. The Michaelis constant (K m) of the immobilized enzyme was smaller than that of free enzyme, indicating that the immobilization could promote the stability of the enzyme and strengthen the affinity of the enzyme for the substrate.
Keywords: bromelain; immobilization; nanoparticles

Preparation and antibacterial activity of chitosan microshperes in a solid dispersing system by Ming Kong; Xi-guang Chen; Yu-ping Xue; Cheng-sheng Liu; Le-jun Yu; Qiu-xia Ji; Dong Su Cha; Hyun Jin Park (214-220).
In this study, we investigated the interface contacting inhibition behaviors of chitosan against bacterial in the dispersing state. For that purpose, chitosan microspheres (CMs) in the dispersing state was prepared by the emulsification cross-linking method. The CMs had smooth surface and spherical shape with the diameter of about 124 µm. They were stable after sterilization at 121°C and 150 kPa for 20 min. The CMs had similar antibacterial activity to that of chitosan in the solution form. Their antibacterial activities increased with the increase of the CM concentration, while decreased with the increase of pH of the system. It was found that the CMs with the degree of deacetylation (DD) of 63.6% exhibited the highest antibacterial activity, while the CMs with the DD of 83.7% exerted the lowest antibacterial activity among the three tested samples.
Keywords: chitosan; dispersing system; antibacterial activity; microsphere

Improvements of anticoagulant activities of silk fibroin films with fucoidan by Zhen Gao; Song Wang; He-sun Zhu; Dong-xu Zhao; Jia-chao Xu (221-227).
Fucoidan (FC), an effective anticoagulant constituent extracted from brown algae, was introduced into silk fibroin (SF) for improving its blood compatibility. The SF and SF/FC blend films were characterized by attenuated total reflectance Fourier-transform infrared (ATR-FTIR), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and dynamic contact angle determinator (CA). The in vitro anticoagulant activities of the films were evaluated by activated partial thromboplastin time (APTT), thrombin time (TT) and prothrombin time (PT) measurements. The endothelial cell attachment and proliferation viability on the film were assessed by micropipette aspiration technique and MTT assay, respectively. The testing results indicated that the introduction of FC increased the roughness, hydrophilicity and sulfate component of the film surface without impeding the formation of β-sheet conformation in SF. More important, FC brought excellent anticoagulant activity and better endothelial cell affinity to SF. The SF/FC blend film was hopeful to be used as blood-contacting biomaterials.
Keywords: silk fibroin (SF); fucoidan (FC); anticoagulant activity; endothelial cell affinity

Effect of single-walled carbon nanotubes on primary immune cells in vitro by Jin-chao Zhang; Xiao-yu Ji; Cui-lian Liu; Shi-gang Shen; Shu-xiang Wang; Jing Sun (228-232).
Carbon nanotubes (CNTs) are emerging as innovative tools in nanobiotechnology. However, their toxic effects on environment and health have become an issue of great concern. The effect of single-walled carbon nanotubes (SWCNTs) on primary immune cells in vitro was studied in this paper. The results indicated that SWCNTs (25 and 50 μg/mL) could promote the proliferation of spleen cells. However, they had no significant effect on the proliferation of spleen cells at concentrations of 1 and 10 μg/mL. They also had no effect on T-lymphocyte proliferation stimulated by concanavalinA (ConA) at lower concentrations. Moreover, they turned to inhibit T-lymphocyte proliferation at higher concentrations. It was found that SWCNTs inhibited the B-lymphocyte proliferation stimulated by lipopolysaccharides (LPS) at concentrations of 1, 10, 25 and 50 μg/mL. What is more, they significantly decreased the Natural Killer (NK) cell activity compared with the control group at all tested concentrations. The results suggest that SWCNTs have possibly negative effects on immune cells in vitro.
Keywords: carbon nanotubes (CNTs); Natural Killer (NK) cell activity; T-lymphocyte; B-lymphocyte; immune cells