Frontiers of Materials Science (v.8, #2)

Graphene has emerged as a new carbon nanoform with great potential in many applications due to its exceptional physical and chemical properties. Especially, graphene and its derivatives are also gaining a lot of interest in the biomedical field as new components for biosensors, tissue engineering, and drug delivery. This review presents unique properties of graphene, the bio-effects of graphene and its derivatives, especially their interactions with cells and the development of graphene-based biosensors and nanomedicines for cancer diagnosis and treatment.
Keywords: graphene; graphene oxide (GO); cell; sensor; cancer

This article reports the environmentally benign synthesis of gold nanoparticles (GNPs) using methanol extract of Azolla microphylla as the stabilizing and reducing agent. The GNPs were characterized by UV-vis spectrophotometry and FTIR, and the morphological characteristics were analyzed by XRD, FESEM-EDX and HRTEM. The GNPs could be formed in very short time, even in less than 30 min. The nanoparticles measured by UV-spectrophotometer demonstrated a peak at 540 nm corresponding to surface plasmon resonance spectra, and the peaks showed by FTIR suggested the presence of organic biomolecules on the surface of the GNPs. XRD results confirmed the crystalline nature of the GNPs, and FESEM-EDX and HRTEM analyses had been performed in the size ranges of 17–40 nm and 1.25–17.5 nm respectively. The synthesized GNPs showed excellent antioxidant activity. This study shows the feasibility of using plant sources for the biosynthesis of GNPs.
Keywords: Azolla microphylla ; gold nanoparticle (GNP); antioxidant activity; surface plasmon resonance; green chemistry

Liver normal cells and cancer cells co-cultured on surfaces modified by different chemical functional groups, including mercapto (-SH), hydroxyl (-OH) and methyl (-CH3) groups. The results showed that different cells exhibited changes in response to different surfaces. Normal cells on -SH surface exhibited the smallest contact area with mostly rounded morphology, which led to the death of cancer cells, while cancer cells could not grow on -CH3 groups, which also died. In the co-culture system, the -CH3 group exhibited its unique effect that could trigger the death of cancer cells and had no effects on normal cells. Our findings provide useful information on strategies for the design of efficient and safe regenerative medicine materials.
Keywords: tumor suppressor; chemical functional group; co-culture system; regenerative medicine material

A thermosensitive chitosan-based hydrogel for controlled release of insulin by Ting-Ting Gao; Ming Kong; Xiao-Jie Cheng; Gui-Xue Xia; Yuan-Yuan Gao; Xi-Guang Chen; Dong Su Cha; Hyun Jin Park (142-149).
Present study aims at synthesizing a thermosensitive hydrogel for controlled release of insulin. According to a modified method, hydroxybutyl chitosan (HBC) hydrogel possessed thermal sensitivity is prepared which can form hydrogel at over 25°C. The HBC hydrogel is non-cytotoxic to mice fibroblasts cells (L929). Insulin is 100% entrapped in the hydrogel, 38% of which is released in vitro from the concentration of 5% hydrogel after 48 h, whereas by enzymolysis with lysozyme, 80% of the total insulin is released after 48 h. This study suggests that HBC hydrogel could be utilized for controlled release of insulin in a non-invasive manner.
Keywords: hydroxybutyl chitosan; hydrogel; thermosensitive; insulin; controlled release

A protocol aiming at making use of the huge amount of naturally existing wastes such as defoliation, pericarp and egg shell for nanostructured composite materials was proposed. In this study, a green synthetic route using naturally existing membrane as support was developed for the synthesis of nanostructured and porous metal- or metal oxide-carbon composite films. Different metallic ions (Co2+, Ni2+, Fe3+, Mn2+ or Cu2+) can be easily adsorbed onto egg membranes and the followed calcination process results in the formation of Co/C, Ni/C, Fe3O4/C, MnO/C or Cu/Cu2O/CuO/C composite films. The electrochemical studies demonstrate that such composite films would have potential applications in energy fields. This method would provide a general green concept for chemical synthesis and be beneficial to the global sustainable future.
Keywords: green synthesis; metal; metal oxide; composite; electrochemistry

Surface modification of apatite-wollastonite glass ceramic by synthetic coupling agent by Qin Long; Da-Li Zhou; Xiang Zhang; Jia-Bei Zhou (157-164).
In this study, lysine was introduced into the surface of apatite—wollastonite glass ceramic (AW-GC) to improve its cytocompatibility by two steps reaction procedure. Firstly, lysine connected to N-β-(aminoethyl)-γ-aminopropyl trimethoxy silane (A-1120) by covalent binding of amide group. Secondly, the lysine-functionalized A-1120 was deposited on the surface of AW-GC through a silanization reaction involving a covalent attachment. FTIR spectra indicated that lysine had been immobilized onto the surface of AW-GC successfully. Bioactivity of the surface modified AW-GC was investigated by simulated body fluid (SBF), and the in vitro cytocompatibility was evaluated by coculturing with human osteosarcoma cell MG63. The results showed that the process of hydroxyapatite layer formed on the modified material was similar to AW-GC while the mode of hydroxyapatite deposition was changed. The growth of MG63 cells showed that modifying the AW-GC surface with lysine enhances the cell adhesion and proliferation.
Keywords: surface modification; apatite—wollastonite glass ceramic (AW-GC); lysine; silane coupling agent; cytocompatibility

Origin of high mechanical quality factor in CuO-doped (K, Na)NbO3-based ceramics by Wen-Feng Liang; Ding-Quan Xiao; Jia-Gang Wu; Wen-Juan Wu; Jian-Guo Zhu (165-175).
The origin of a high mechanical quality in CuO-doped (K, Na)NbO3-based ceramics is addressed by considering the correlations between the lattice positions of Cu ions and the hardening effect in K0.48Na0.52 + xNbO3-0.01CuO ceramics. The Cu ions simultaneously occupy K/Na and Nb sites of these ceramics with x = 0 and 0.02, only occupy the K/Na site of the ceramics with x = −0.02, and mostly form a secondary phase of the ceramics with x = −0.05. The Cu ions lead to the hardening of ceramics with an increase of E C and Q m by only occupying the K/Na site, together with the formation of double hysteresis loops in un-poled compositions. A defect model is proposed to illuminate the origin of a high Q m value, that is, the domain stabilization is dominated by the content of relatively mobile O2− ions in the ceramics, which has a weak bonding with CuK/Na defects.
Keywords: lead-free piezoelectric ceramic; (K, Na)NbO3 (KNN); mechanism of hardening effect; mechanical quality factor Q m ; domain stabilization

Phase field crystal simulation of grain boundary movement and dislocation reaction by Ying-Jun Gao; Qian-Qian Deng; Si-Long Quan; Wen-Quan Zhou; Chuang-Gao Huang (176-184).
The phase field crystal (PFC) model is used to simulate the premelting dislocation movement of the symmetric tilt grain boundary (STGB) under strain action when the system temperature is at far from the melting point and close to the melting point, respectively. The results show a local premelting occurs surrounding the dislocations as the premelting temperature is approached to from below temperature. The premelting dislocations of the STGB can glide under strain action, and the premelting region is a companion for dislocation gliding. The process of STGB decay is very similar at the two high temperature conditions. As premelting presents, it diminishes the gliding resistance for the dislocations and leads to a faster movement of dislocations, and also brings about more energy reduction of the system during the decay process of STGB. In spite of applying strain to these premelting samples in whole decay processes of STGB, the premelting dislocation region does not obviously develop and extend. This indicates that the external strain action does not promote the premelting at the high temperature, and cannot induce more premelting dislocation, which can be owed to the premelting phase around the dislocation exhibit fluid-like properties and to the premelting dislocation easily gliding and relaxing the strain energy; this is in agreement with the results of experiments and molecular dynamics.
Keywords: phase field crystal (PFC) model; grain boundary (GB); premelting dislocation; strain

Simulation of epitaxial growth on convex substrate using phase field crystal method by Ying-Jun Gao; Li-Lin Huang; Qian-Qian Deng; Kui Lin; Chuang-Gao Huang (185-192).
Phase field crystal (PFC) model is employed to simulate the process of growth of epitaxial layer on plane-convex substrate with a lattice mismatch and a small inclination angle. The variation of the systematic free energy, the total atomic number of the epitaxial layer, and the effect of the curvature and the angle of the substrate are analyzed. The results show that when the surface of the substrate is plane, the free energy increases with the increase of the substrate inclination angle, and also the total atomic number of the epitaxial layer increases; while the surface of the substrate is convex, the free energy decreases with the increase of substrate angle and so also the total atomic number of the epitaxial layer decrease. This is the reason that the frontier of surface of epitaxial layer changes from the step bunching to the hill-and-valley facet structure with the increasing of the inclination angle of convex substrate. These results are in good agreement with the other method results.
Keywords: heteroepitaxy; phase field crystal (PFC); convex substrate; atomic number

Facile synthesis of magnetic iron oxide nanoparticles and their characterization by Sushilkumar A. Jadhav; Suresh V. Patil (193-198).
Magnetic iron oxide nanoparticles are synthesized by suitable modification of the standard synthetic procedure without use of inert atmosphere and at room temperature. The facile synthesis procedure can be easily scaled up and is of important from industrial point of view for the commercial large scale production of magnetic iron oxide nanoparticles. The synthesized nanoparticles were characterized by thermal, dynamic light scattering, scanning electron microscopy and transmission electron microscopy analyses.
Keywords: iron oxide; iron oxide nanoparticle; co-precipitation