Current Nanoscience - Volume 7, Issue 6, 2011

Primary hepatocytes in conventional mono-layer cultivation have been widely used as in vitro model for various studies. The major limitations of this model, however, are the rapid dedifferentiation and the reduction in liver-specific functions, such as cytochrome P450 (CYP) content, with increasing culture time. The reported studies indicated that the loss of the functional expression could be related to hepatocyte shape changes and the oxidative stress in the well-established hepatocyte isolation procedure with collagenase. Since hepatocytes' responsiveness to their extracellular matrix (ECM) is considered as an important role in the cellular fates of primary hepatocytes culture and Type I collagen is one of the most abundant ECM components in the liver tissue. In this study, two different engineered Type I collagen molecules, nano-sized collagen prepared by using high-voltage electrostatic field system and anti-oxidative collagen prepared by coupling α-lipoic acid, were applied to the hepatocytes cultured in suspension. The results demonstrated that the addition of nano-sized Type I collagen molecules with adequate concentration (5 x 10-4 mg/mL) could facilitate the cell aggregation and the formation of hepatic spheroids to approximately 5 mm in diameter after a 6-day culture in the stirring environment. The hepatocytes in spheroid were able to maintain an in vivo-like morphology and ECM materials secretion capability as seen in SEM observations. We also showed that the addition of anti-oxidative collagen molecules facilitated the maintenance of the gene expression of Cytochrome P450 (CYP3A) of hepatocytes up to 7-day culture. In summary, we have successfully demonstrated that the cell morphology and functional expression of primary cultured hepatocytes could be regulated by engineered collagen molecules as medium supplementation.

Bimetallic nanoparticles have received considerable attention due to their unique optical, magnetic and other properties. Their composition, architecture, shape and size can be adjusted relatively easily in order to change their properties, which provide great potential for their diverse applications. Bimetallic Au-Ag nanoparticles are very attractive because they exhibit remarkable optical properties due to their surface plasmon resonance (SPR) absorption. In this investigation, a simple synthesis process for novel, bimetallic flowerlike Au-Ag composite nanoparticles was developed. Biocompatible folic acid-conjugated chitosan with flexible molecular chains were used as the structure-directing agent in nanoparticle synthesis. The structure and properties of Au-Ag nanoparticles were studied using a variety of analytical techniques including high resolution transmission electron microscopy. These nanoparticles contained an Au core and an Ag shell and the shape and thickness of the Ag shell could be easily controlled by varying the synthesis condition. The formation and growth of flowerlike bimetallic Au-Ag composite nanoparticles was investigated and its mechanism proposed. On the basis of flowerlike Au-Ag nanoparticles which can produce surface enhanced Raman scattering (SERS), a novel SERS tag was formed, which consisted of an Au-Ag flowerlike nanoparticle, embedded Rhodamine B (RhB, a Raman reporter molecule), and a folic acid-conjugated chitosan outer layer. This new SERS tag (RhB@Au-Ag tag) exhibited greatly increased SERS intensity of RhB and hence showed great potential for tumor cell targeting and detection.

The interactions between DNAs and cationic comb-type copolymers like those with quaternary ammonium with N-methylated groups have applications in nanotechnology. N-methylated poly(L-lysine)-graft-dextran copolymers (MPLL-g-Dex) were obtained by methylation of poly(L-lysine)-graft-dextran copolymers (PLL-g-Dex) using dimethyl sulfate under weak basic conditions. The resulting copolymers were characterized using NMR spectroscopy and gel permeation chromatography-multiangle light scattering (GPC-MALS). Both primary and secondary amino groups of the PLL backbones were thoroughly methylated to form quaternary ammonium groups without fragmentation of PLL-g-Dex chains or other detectable side reactions. The interactions of the copolymers with DNAs were assessed by UV melting curves and fluorescence correlation spectroscopic measurements. PLL-g-Dex interacts with double-stranded DNA (dsDNA) in a sequence-independent manner. In contrast the MPLL-g-Dex affinity was lower for dsDNA with higher GC content than for DNA with low GC content. The results suggest that MPLL-g-Dex interacts with DNAs not only through ionic interactions, but also by hydrophobic interactions.

A nanostructured copper electrode (NSCuE) was prepared by copper electroplating in a porous membrane and characterized by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX) and electrochemical impedance spectroscopy (EIS). Various parameters, which can influence the fabrication of copper nanostructures, were examined. After optimizing the fabrication process, electrochemical behaviour of the NSCuE in adenine solutions was investigated by differential pulse voltammetry (DPV) and the results were compared to those obtained using a flat electrode. The research of NSCuE contributes to the development of advanced biosensors which would be an environmentally safe alternative to mercury for the detection of adenine by voltammetric techniques.

Development of biologically inspired experimental processes for the synthesis of nanoparticles is evolving in important branch of nanotechnology. The present study deals with a green, low-cost and reproducible method for the synthesis of Cu2O nanoparticles by reduction of Barfoed's solution, using agriculture wastes of Arachis hypogaea L. (Fabaceae) leaf extracts containing reducing sugars which act as reducing agent at room temperature. The purification process of the Cu2O product does not require expensive methods, since a solid product is obtained from a reaction in liquid phase. The result indicates that aldehyde group present in reducing sugar plays excellent role in the formation of cuprous oxide nanoparticles in the solution. Antibacterial effect of cuprous oxide nanoparticles against gramnegative Escherichia coli was analyzed. The resulting Cu2O nanoparticles were characterized by X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), UV-VIS absorption, and Fourier-transform infrared (FTIR) spectroscopy.

We demonstrate a facile one-step thermal conversion method for the formation of self-assembled three dimensional silver (Ag) microspheres. The total conversion of Ag microspheres from the source materials at an elevated temperature is confirmed via various characterization techniques. The density of self-assembled Ag microspheres can be controlled by adjusting the precursor solution concentration. p-GaN nano-texturing is performed using an inductively coupled plasma (ICP) treatment, with the help of self-assembled Ag microspheres as a mask. The light extraction efficiency of the p-GaN nano-textured light emitting diode (LED) shows a significant improvement of ˜25% over that of conventional LEDs at an injection current of 20 mA.

Egg-white was found to exist in the form of ladder-like structure after a freeze-drying process. Several hierarchically ordered macroporous structures were synthesized by sol-gel method with egg-white template, such as the 3D ladder-like structures of SiO2, TiO2, and C/SiCN nanocables. Thermogravimetric (TG), differential scanning calorimetry (DSC), Scanning electron microscopy (SEM), powder X-ray diffraction (XRD), fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), selected area electron diffraction (SAED) and high-resolution TEM (HRTEM) were employed to characterize the novel macroporous architecture. The results indicate that the hierarchically macroporous architectures were copied completely. The photocatalytic properties of TiO2 replica were also studied. The nearly linear relationship of the MO degradation percentage vs irradiation time suggests that the reaction follows a first-order kinetic mode. Within 2 h, the degradation rate of the methyl orange was reached at 99%, indicating a high efficient photocatalytic property of this ordered TiO2 macroporous architecture.