Current Nanoscience - Volume 6, Issue 5, 2010

Curcumin is a natural anti-cancer compound utilized on a wide variety of human cancer cell lines and animal carcinogenesis models. However, its clinical application has been limited for its minimal systemic bioavailability. Nanoparticle-based drug delivery approaches have the potential for rendering hydrophobic molecules such as curcumin dispersible in aqueous media, thus overtaking the limits of its poor solubility. In this paper, we reported the preparation and chemical-physical characterization of Nanostructured Lipid Carriers (NLC) containing curcumin, based on Imwitor, Compritol or Precirol as lipid matrix. By in vitro experiments, we have demonstrated that these nano-systems are able to carry curcumin into LAN5 neuroblastoma cells and their effect on cell mortality is higher than free curcumin. However, the best results were obtained when the NLC-c system was utilized. Moreover, we have demonstrated that curcumin activates Hsp70 protein and that this effect is enhanced when the same dose of curcumin is administered as drug-loaded NLC. The obtained results clearly suggest that these nanoparticles are a potential curcumin delivery systems and encourage, in future, for planning in vivo studies towards cancer and other diseases that might benefit from the curcumin effects.

Ag2Se/Se core/shell heterostructure nanoparticles (NPs) have been successfully synthesized by using silver nitrate (AgNO3) along with sodium selenosulfate (Na2SeSO3) as Se source in the presence of bovine serum albumen (BSA) as a foaming and stabilizing agent. The entire process was carried out at ambient pressure in aqueous phase at room temperature (RT). A possible mechanism to interpret the formation of the core/shell nanostructure accompanied by selenium shells transforming from amorphous Se (a-Se) into crystalline trigonal Se (t-Se) was proposed based on flourier transformation infrared (FT-IR) and ultraviolet-visible (UV-vis) analysis. The morphology and chemical composition of these BSA-conjugated NPs have been characterized with high-resolution transmission electron microscopy (HR-TEM), energy dispersive spectroscopy (EDS) and X-ray powder diffraction (XRD). In addition, the novel heterostructure was unambiguously confirmed by elemental mapping of an individual particle. The environmentally benign method would be useful for preparing bio-modified heterostructure nanomaterials at RT through the soft template effect of biomacromolecules.

The field of nanotechnology spans the synthesis of nanoscale matters, understanding/utilizing their exotic physicochemical and optoelectronic properties, and organization of nanoscale structures into predefined superstructures. Over the past decade, researchers in various fields of chemistry have been studying novel methods through which the morphology and the dimensions of inorganic materials can be controlled at the micro- or even the nano-scopic level. As far as the synthesis of nanoparticles is concerned, there is an evergrowing need to develop clean, non-toxic, and environmentally friendly (“green chemistry”) synthetic procedures in the pursuit of nanotechnology, especially for nanoproducts targeted at bioapplications. Thus, during the last few years, “green” has become a common term to designate those nanomaterials with the aim of replacing nondegradable and toxic regents, thereby reducing the environmental pollution. Biological processes have recently been considered as possible methods for the synthesis of nanoparticles, especially the development of “reen” synthetic approaches. The advantageous features of the biomolecules' applications in nanomaterials green synthesis are that they possess the ability to guide the oriented growth of organic or inorganic substances, and are thermally and chemically stable, easy to obtain, cheap, and, most importantly, environmentally friendly. Combined with traditional chemical techniques, the biomolecules- assisted synthesis method has proven promising in the generation of a large variety of inorganic structures that are currently unattainable through any other methods. Herein, we review the biomolecules-assisted green synthesis of nanomaterials in this context, which covers our recent interesting results and mainly includes (1) nanomaterials obtained by biomolecules-assisted green method, (2) growth mechanism, and (3) their properties.

Drug eluting stents (DESs) have considerably reduced the occurrence of restenosis followed by balloon angioplasty. But the recent concerns of late stent thrombosis have rekindled an interest in developing an improved stent. A multidisciplinary approach of nanotechnology and biotechnology is the next frontier for this. This presents a comprehensive overview of the evolving nanobiotechnological approaches for biomedical implants and articulates the potential of these technologies to design the next generation stent. A diverse range of nano-delivery systems are being used to transport drugs, genes and oligonucleotides from the stent surface to remodel the damaged local vascular biology. In addition, the review encompasses the upcoming technologies which include modulation of the stent surface nano-topography by regulating the nanocoatings, use of nanotubes to increase the biocompatibility and promote endothelial cell proliferation, inhibit smooth muscle cell growth, and deliver drugs.

In this study, we first report the selective synthesis of TiO2 nanorods of pure rutile, anatase and brookite TiO2 by the hydrothermal treatment of precursor titanate nanosheets. The synthesized TiO2 nanorods exhibit highly crystalline structure with different phases and morphologies. The experimental results indicate that morphologies of products depended significantly on the pH values of the reaction process. Following this, a possible model, dissolving-recrystallizing-growing, was proposed for the formation of TiO2 nanorods with different phases.

Thermo, pH and magnetic field responsive core-shell particles of poly(acrylonitrile-co-N-isopropylacrylamide (p(AN-c- NIPAM)) were synthesized by microemulsion polymerization. Fe3O4 nanomagnetic particles were encapsulated inside core-shell polymeric particles during the polymerization and simultaneous crosslinking reaction of AN and NIPAM using ethylene glycol dimethacrylate (EGDMA) as a crosslinker and ammonium persulfate (APS) as initiator. To increase the hydrophilicity of the particles, the hydrophobic core, which contains nitrile groups were converted to the amidoxime group by amidoximation reaction and the conversion, was confirmed by FT-IR and swelling experiments. To demonstrate the usage of the synthesized particles as potential guided drug delivery vehicles, a calcium channel blocker, Verapamil, was used for in vitro drug release studies from p(AN-c-NIPAM), amidoximated p(AN-c- NIPAM) and composite p(AN-c-NIPAM) particle systems in phosphate buffer solution (PBS) at two different temperatures, at room (~25°C) and 40°C (> LCST: Lower Critical Solution Temperature of p(NIPAM)), respectively.

The carrier statistics in carbon nanotubes (CNTs) with nonparabolic energy spectrum is studied in order to predict the ultimate (intrinsic) drift velocity as a function of temperature, concentration, and chirality. The extremely high mobilities in CNTs do not necessarily lead to higher saturation velocity that is limited to the intrinsic velocity calculated using Arora's formalism [V. K. Arora, Current Nanoscience 5, 227(2009)]. The ballistic nature of the mobility when CNT length is smaller than the scattering-limited mean free path is delineated. The results are of enormous importance in extracting carrier transport properties from a variety of experiments performed on CNTs.

This study presents a simple yet effective hydrothermal route for selective generation of (Gd1-xEux)2O3 (x=0.03-0.13) redphosphor nanorods and nanotubes. Detailed characterizations of the products were achieved by combined means of XRD, FT-IR, TGA/DSC, BET, FE-SEM, HR-TEM, PL/PLE, fluorescence decay analysis, and transient techniques. The precursors are of hexagonal (Gd1-xEux)(OH)3, whose morphology (nanotube or nanorod) is largely affected by the final pH of the hydrothermal reaction. A minimum annealing at 600 °C is needed to crystallize solid-solution oxides of desirable photoluminescence, while at 1000 °C the polycrystalline precursors mostly transform into single-crystalline oxides. The two types of phosphors exhibit nearly identical positions of the PLE/PL bands and similar asymmetry factors of luminescence [I(5D0→7F2)/I(5D0→7F1)], but the nanotubes show a significantly stronger red emission at ~613 nm (~2.3 times that of the nanorods) upon UV excitation into the charge transfer band at ~250 nm. The quenching concentration of Eu3+ was found to be ~8 at% and the quenching mechanism is dominantly exchange interaction. Luminescent properties of the nanorod and nanotube phosphors, in terms of PL/PLE intensity, fluorescence lifetime and asymmetry factor of luminescence, have been successfully correlated to the phase evolution process, annealing temperature, Eu3+ content, and particle morphology

In this paper, we explore the electromechanical, optical, and luminescent properties of aluminum doped zinc oxide (ZnO) nanorods. The design of aqueous solution growth ZnO nanorods with an aluminum doped zinc oxide nanostructure is discussed, and electrical, optoelectronic, and mechanical properties of the obtained nanorods are described. The results show that the dopant concentration affects nanorod growth and thus the size of the ZnO: Al nanorods. The resistivity decreases with increasing substrate temperature, and the dopant concentration become a positive electricity transition to negative electricity positively correlated. The piezoelectric characteristics of a nanogenerator system fabricated with the nanorods are also discussed.

A novel one-step chemical reduction method is developed to fabricate nanofluids with very tiny spherical copper nanoparticles. Their chemical and colloidal stability is studied by adjusting their pH value with citric acid. Their thermal conductivity is also measured by the transient hot-wire method. The particle size can be varied from 6.4 nm to 2.9 nm by changing the surfactant concentration. The thermal conductivity data show the existence of a critical particle size below which the nanoparticles cannot significantly enhance fluid conductivity due to the particle conductivity reduction and the solid-liquid interfacial thermal resistance increase as the particle size decreases. By considering these two factors, we have also made some theoretical analysis to find the possible critical particle size.

Polyvinylidene fluoride (PVDF) nanocomposites with multiwalled carbon nanotubes (MWNTs), functionalized carbon nanotubes (FMWNTs) and nanofibers (CNFs) were fabricated via the solution processing route. The effect of temperature on the electrical conduction of PVDF-CNF, PVDF-MWNT, and PVDF-FMWNT nanocomposites was studied. The results showed that the DC conductivity of such nanocomposites at ambient temperature follows a percolation scaling law behavior. And the conductivity of nanocomposites tended to decrease with increasing temperature. Moreover, the current-voltage responses of these nanocomposites near the percolation threshold displayed nonlinear characteristics. This nonlinear behavior became more pronounced as the temperature was increased. The mechanism for nonlinearity of these nanocomposite systems is discussed.

Gas sensor technology has been developed remarkably in recent years due to its wide applications in modern society. To meet the demand of low-level detection, gas sensor is still required to minimize the size in order to match the uses in micro-/nano- devices. This article reviews the development of nano SnO2 gas sensors to H2, CO, NO2, and ethanol gas/vapour. The emphasis has been put upon the material preparations, sensing mechanisms and properties based on different kinds of SnO2 nanostructures (e.g. nanoparticles, nanowires & nanofibers, nanobelts & nanoribbons, and nanorods & nanocolumns). It is demonstrated that very high sensitivity and selectivity as well as fast response can be achieved when the n-type semiconductor SnO2 is in the form of nanostructures.

The potential application of nano-/microcrystals-based materials depends not just on the size, compositions and surface chemistry of the crystals, but also on their special morphologies and arrangements. Therefore, developing straightforward and controllable methods for self-assembly of nanostructures in 1 dimension and higher dimensions has attracted considerable attention. In this paper, cadmium sulfide 3 dimensional assemblies of nano-/microcrystals with controllable morphologies and arrangements were prepared through an efficient additive-free solvothermal process. The morphologies and arrangements of the 3 dimensional assemblies can be adjusted and controlled conveniently through the adjustment of the preparation conditions, such as the composition of the solvent, the ratio of reactants, the cadmium sources, and the pH values of the experiments. It presents a facile, efficient, and controllable method to prepare 3 dimensional architectures of nano-/micro-crystals with controlled morphologies and arrangements.

Electro-centrifuge spinning is a novel, innovative, high-performance, and simple method to produce polymeric nanofibers based on using electrical and centrifugal forces. In this paper, first the electro-centrifuge method is presented and then an experiment is conducted to explore the range of centrifugal speed for the production of polyacrylonitrile (PAN) polymer nanofibers at different concentrations and voltages. Finally, the effect of important parameters such as rotational speed of the apparatus, concentration, and applied voltage on the flow rate of the polymer solution is estimated analytically and compared with experimental results.

Improving the electrochemical stability of manganese oxide/multiwalled carbon nanotubes (MnO2/MWCNTs) nanocomposites is of great importance to many electrochemical supercapacitor applications. In this study, the electrochemical properties of MnO2 filled inside the cavity of MWCNTs were investigated for the first time. The prepared nanocomposite was characterized by means of X-ray photoelectron spectroscopy (XPS), X-ray diffraction patterns (XRD), transmission electron microscopy (TEM) images, scanning electron microscopy (SEM) together with energy dispersive X-ray spectroscopy (EDX) and thermogravimetric analyses (TGA). Electrochemical characterization has been performed using cyclic voltammetry (CV), galvanostatic charging/discharging (CD) test. The TEM image, XRD analysis confirmed the high structural stability and CD test complied the high electrochemical stability of the prepared nanocomposite. Besides, MnO2/MWCNTs nanocomposite supercapacitor showed superior cycling stability in the potential range of 0-1.0V due to the filling of the electroactive material inside the tubes and retained 96% of initial capacitance even over 200 cycles.