Current Nanoscience - Volume 8, Issue 5, 2012

We present a magnetic study of lithium ferrite nanoparticles of composition Li0.5Fe2.5O4, synthesized by a citrate gel decomposition method. The as prepared sample was composed of nearly spherical nanoparticles with an average particle size TEM∼12 nm. Further annealing at 573 K and 673 K for 4 hours did not increase particle size noticeably, while annealing at 973 K led to morphology changes and significant increase in size ranging from 40 to above 200 nm. The magnetic properties of samples have been studied using Mossbauer specroscopy, and static magnetic measurements. The hyperfine parameters obtained from Mossbauer data at T = 10 K are in agreement to the bulk lithium ferrite phase. Annealed samples showed an evolution from monodomain structure to polycrystalline behaviour, what is evident from TEM imagines, as well as the evolution of the coercive filed, HC, and the saturation magnetization, MS, with particle size increase. The exchange interactions have been observed in the single-domain nanoparticles, which probably originate from their core-shell structure. At low temperatures and in high enough magnetic fields, the cubic magnetic anisotropy stays preserved and the magnetic moments in the particle core are aligned along (111) directions of the spinel structure.

We have investigated the magnetic and transport properties of nanoscaled Fe3O4 films obtained from Chemical Vapor Deposition (CVD) technique using [FeIIFe2 III(OBut)8] and [Fe2 III(OBut)6] precursors. Samples were deposited on different substrates (i.e., MgO (001), MgAl2O4 (001) and Al2O3 (0001)) with thicknesses varying from 50 to 350 nm. Atomic Force Microscopy analysis indicated a granular nature of the samples, irrespective of the synthesis conditions (precursor and deposition temperature, Tpre) and substrate. Despite the similar morphology of the films, magnetic and transport properties were found to depend on the precursor used for deposition. Using [FeIIFe2 III(OBut)8] as precursor resulted in lower resistivity, higher MS and a sharper magnetization decrease at the Verwey transition (TV). The temperature dependence of resistivity was found to depend on the precursor and Tpre. We found that the transport is dominated by the density of antiferromagnetic antiphase boundaries (AF-APB's) when [FeIIFe2 III(OBut)8] precursor and Tpre = 363 K are used. On the other hand, grain boundary-scattering seems to be the main mechanism when [Fe2 III(OBut)6] is used. The Magnetoresistance (MR(H)) displayed an approximate linear behavior in the high field regime ( H > 796 kA/m), with a maximum value at room-temperature of ∼ 2-3 % for H = 1592 kA/m, irrespective from the transport mechanism.

Kinesin motor proteins can hydrolyze ATP and unidirectionally transport specific cargo molecules along microtubule tracks (MTs). Engineering scientists interested in nanotechnology have used kinesin and MTs to build shuttles of 2 geometries. In the bead geometry, the kinesin shuttles transport cargos along the MTs. In the gliding geometry, cargos are carried by MTs, which glide on a kinesin lawn. To realize the goal of building in vitro protein shuttles with real utilities, the issue of how to allow the shuttles specifically, yet easily, to transport the designated cargos has not been completely resolved. Popular methods, such as non-specific bead attachments, or biotinylation of tubulin subunits by covalent tagging with reactive chemicals, have limitations. In this study, we focus on developing a bead geometry protein shuttle to transport specific DNA. Because numerous DNA-binding proteins must form homodimers to bind DNA, we created kinesin fusion proteins KIF5-cro proteins. These proteins were made by genetically fusing the tail of a truncated kinesin with the cro protein, which is a DNA-binding protein derived from the λ bacteriophage. We showed that the resultant kinesin fusion proteins transport DNA with specificity and high affinity (Kd 60 nM). This study provides a discussion on the plausible approaches of applying the recombinant DNA technology to the shuttles of the gliding geometry.

Viscoelastic and other physical properties of cancerous cells are particularly important since cells interact with the extracellular matrix and other cells constantly during malignant proliferation, adhesion, invasion and metastasis process. Atomic force microscope (AFM) has an unparalleled advantage in the measurement of viscoelastic properties of living cells. In this paper, a stress relaxation test using atomic force microscopy was conducted to obtain viscoelastic characteristics of lung cancer cells. The experimental data obtained were well fitted with a special theoretical model which is appropriate to samples with infinite thickness, such as cells. This theoretical model takes into account the thin thickness of the measured sample and the substrate effect generated by a relatively larger indention of AFM probe can be avoided. Two different non-small cell lung cancer cell lines with varying metastatic potential show distinct stress relaxation characteristics. The metastatic NCI-H1299 cells, which are originally isolated from a patient's lymph node metastases, appeared a lower viscoelastic response compared to the non-metastatic A549 tumorous cells. When cancerous cells release from the primary tumor site, intravasate into lymphatic or blood circulation, and squeeze through a variety of cell gaps to transfer other where, they become easily deformed and thus show lower viscoelastic properties. The emerging insight into these viscoelastic properties may promote the understanding of the underlying mechanism for cancer metastatic and invasive progress.

In the present study, polyethylenimine (PEI, 1800 Da) and liposome were combined in order to improve gene expression. A new gene delivery system (polycationic liposome) was developed by modification of liposomes with lipoploymers constructed from acrylate or bromoalkane derivatives. The polycationic liposome-plasmid DNA (pDNA) complexes were characterized for their size, zeta potential and ability for DNA condensation. Luciferase reporter gene was used for the determination of transfection efficiency in Neuro2A cells. While mean particle size of prepared vectors ranged from 75 to 520 nm, the zeta potential varied from 11-35 mV. Transfection activity of selected non-viral vectors was higher than that of PEI 1800 Da and PEI 25 KDa. The transfection activity of polycationic liposomes was reduced after replacement of bromoalkane derivatives by acrylates in the structure of lipopolymers. Furthermore, gene carriers described in this study showed low cytotoxicity. The results show that inclusion of hydrophobic PEI derivatives in liposome structure can improve the transfection efficiency but the lipopolymer structure determines the gene expression efficiency of vectors.

Pseudomonas aeruginosa is a common cause of nosocomial infections and severe infections in burn patients. It is one of the most important extended spectrum β-lactamase (ESBLs) producing bacteria. ESBLs can cause bacteria to resist antibiotics containing a β-lactam group. Problems due to antibiotic resistance have renewed trends toward using silver, because it has bactericidal properties, and there is a significant increase in this property at very low concentrations. Nanosilver in particular, because of its small size and increase in surface/volume ratio compared with bulk silver, makes more contacts with the surrounding space and has more impact on the bacterial environment. In this study, we investigated the antibacterial activity of a nanosilver colloidal (NSC) solution on ESBL-producers and non-ESBL strains of P. aeruginosa using the MIC and MBC methods. The morphology of the bacterial cells was evaluated after treatment with NSC using scanning electron microscopy (SEM). The in vitro cytotoxicity test with the Chinese Hamster Ovary (CHO) cell line was used to evaluate the cytotoxic potential of the NSC solution. The experimental results indicated that 0.312μg ml-1 of NSC could completely inhibit the growth of 107cfu/ml ESBL-producing P. aeruginosa cells in brain heart infusion broth (BHI Broth) and the MBC was determined to be 0.0625μg ml-1. NSC solution in concentrations of 0.03125 up to 0.5μg ml-1 showed no cytotoxicity. It was concluded that NSC solution could be considered as a good candidate for the treatment of infections caused by P. aeruginosa, especially by ESBL-producing strains.

The purpose of this study was to investigate the effect of PEG-PBA-PEG nanoparticles as a carrier of quercetin and hyperthermia on the clonogenicity and DNA damages in spheroid model of DU 145 prostate carcinoma cell lines. Therefore, DU145 cells were cultured as spheroids and treated with different concentrations of quercetin / or nanoparticles as quercetin carriers for 24 hours and hyperthermia at 43°C for 60 minutes. After hyperthermic treatment, the colony forming ability and the induced DNA damages were examined. Our results showed that colony number decreased and DNA damages increased along with the increase of the concentration of free quercetin and quercetin encapsulated in the nanoparticles in combination with hyperthermia. However, the extent of reduction of clonogenicity and induction of DNA damages caused by quercetin encapsulated in nanoparticles in combination with hyperthermia significantly increased compared with free quercetin. Since drug loaded nanoparticles could deliver quercetin more efficiently into the cells, PEG-PBAPEG nanoparticles are stable and effective drug delivery vehicles for quercetin.

Nanoparticles synthesized from sodium alginate are economically useful due to their wide applicability in various fields such as food, tissue engineering, biomedical implants and drug delivery. Sodium alginate used for synthesis of silver nanoparticles was extracted from the marine seaweed Padina tetrastromatica. The silver nanoparticles were synthesized by optimizing different parameters such as pH, temperature, time and concentration of AgNO3. Synthesized silver nanoparticle stability was successfully maintained at room temperature up to 72 hr. The synthesized silver nanoparticles were characterized for their size, morphology and surface plasmon resonance (SPR), using UV-Vis spectrum, FTIR, XRD SEM-EDX and AFM. Biosynthesized silver nanoparticles showed antibacterial activity against multidrug resistant human pathogens such as Staphylococcus aureus and Pseudomonas aeruginosa. These results suggest that silver nanoparticles can be used as effective growth inhibitors against various microorganisms, making them applicable to diverse medical devices and antimicrobial control systems. These biologically synthesized nanoparticles can also offer compatibility in pharmaceutical and biomedical applications.

Biosynthesis of silver nanoparticles using the leaf extract of Amaranthus tristis was evaluated in the present report. The biosynthetic approach of nanoparticles synthesis deserves merit in biomedical applications due to its better biocompatibility. The biosynthesized silver nanoparticle was embedded in PVA polymer matrix as dispersed phase to craft an Ag/PVA nanocomposite membrane. The silver nanoparticles and the Ag/PVA nanocomposite membrane were characterized by UV–Vis, FTIR, AFM, SEM and TEM analyses. The membrane was fabricated by varying the ratios of Ag nanoparticles and PVA. Further, these membranes were tested against airborne microbes by exposing in air and compared with the control PVA membrane. 2:8 ratio of Ag: PVA nanocomposite membrane was found to possess a good activity in prevention of microbial growth and hence was studied further and characterized. UV-Vis spectra exhibited the characteristic Surface Plasmon Resonance (SPR) peak at 452 nm for Ag nanoparticle and 442 nm for Ag/PVA nanocomposite membrane (2:8). The AFM analysis of the nanoparticles showed the presence of uniform sized nanoparticles with an average size of 20- 40 nm. This size was further confirmed with TEM analysis and nanoparticles were found to exist in the same size range of 20-40nm. The membrane was further characterized by Energy Dispersive X-ray Spectroscopy (EDS) which confirmed the presence of Ag nanoparticles (24.3 weight% of Ag) in Ag/PVA nanocomposite membrane. The antimicrobial efficiency of Ag/PVA nanocomposite membrane and Ag nanoparticles were tested against Pseudomonas fluorescens and Klebsiella pneumonia.

Nanodimensional Zn1-xMnxS particles were synthesized with x=5, 10 and 15 wt % of Mn2+ ions by wet chemical method. Synthesized Zn1-xMnxS nanoparticles were characterized with X-ray diffraction (XRD) method, High resolution transmission electron microscopic (HRTEM) analysis, UV-Visible absorption spectroscopic method, Fourier transform infrared (FT-IR) analysis and vibrating sample magnetometer method. The XRD analysis showed that upon increasing the dopant concentration from 10% to 15%, hexagonal wurtzite phase changed into cubic zinc blende structure and it was originated by large level replacement of Zn2+ with Mn2+. HRTEM analysis confirmed the nanophase formation with partial mono dispersity and less amalgamation of particles. Blue shift was observed in UVVisible spectra which further established the reduced particle size (30 nm) and its subsequent increase in bandgap was estimated. The strong Mn-S and weak Zn-S interactions were indentified from FT-IR analysis. The superparamagnetism was inferred from VSM analysis for the samples of three doping concentrations, and further, alteration in the aligned paramagnetic grains with respect to the applied field was also indentified for heavily doped sample.

A characteristic comparison approach between Al/Cr and Cu/Cr nano-interfaces is developed for investigation of the potential probability to change the mechanical properties in the metal-matching nano-interface by considering thermal cycling and no-thermal cycling modes. The Cu/Cr interface and Al/Cr interface are prepared by using the magnetron sputtering. The nanoindentation method is used to test the mechanical properties of these metal-matching nano-interfaces. The elastic modulus and the hardness of Cu/Al are improved by the thermal cycling loading; but the thermal cycling has no effect on the Al/Cr nano-interfaces. The investigation reveals a potential probability that the mechanical properties of the Cu/Cr nano-interface can be enhanced by changing the thermal cycling loading mode. It builds a basis for the future work to explore the property and application of metal nano-interface.

Centimeter-scale well-aligned SiC/SiO2 core-shell nanowires were fabricated by a novel interlaminar vapor-diffusion reaction method in a double-channel quartz tube. The synthesized nanowires grew in a uniform direction perpendicular to a porous graphite substrate and were parallel to one another. The core-shell nanowires are 10 millimeters long and consist of β-SiC crystalline core of with diameters of 30-60 nm wrapped with an amorphous silica layer of about 20 nm. The formation mechanism of the well-aligned nanostructure is probably ascribed to the downward vapor-solid growth process and gravity revulsive effect that plays an important role because of super high aspect ratio of the as-received nanowires.

In this paper, N-(3-Trimethoxysilylethyl)ethylenediamine (TMSEEDA) has been immobilized on silica nanoparticles (NPs) with diameter smaller than 100 nm by covalent bond grafting technique. The as-made particles can be used as cores to prepare core-shell mesoporous silica composites, which are encapsulated with a layer of ordered mesoporous silica through a surfactant-assembly method, resulting to uniform core-shell NPs denoted as SiO2-NH2@mSiO2. Low angle X-ray diffraction (XRD), scanning, electron microscopy (SEM), transmission electron microscopy (TEM), N2 adsorption-desorption, and photoluminescence (PL) spectra were used to characterize the sample, respectively. The results show that the nanocomposites with 74 nm core size and 7 nm shell thickness have typical ordered mesoporous characteristics (2.8 nm) and spherical morphology with the surface area as high as 445 m2/g and the pore volume as large as 0.29 cm3/g. Additionally, a broad and faint blue emission at 410 nm was observed for silica NPs under 300 nm exaction at room temperature. Importantly, it is found that a quantitative comparison of PL intensity of silica NPs covalently grafted with TMSEEDA to the only silica NPs yields an enhancement of approximately an order of magnitude with the same peak position. This observation indicates, most likely, formation of more defect centers due to the functionalization of small molecules TMSEEDA. On the other hand, luminescence intensity is enhanced 3 times again after coating of mesoporous silica shells. The origin of the PL and enhanced mechanism are also discussed.

Functional polyvinylidene fluoride based composites filled with two-dimensional clay platelets and graphite nanosheets were prepared by means of solution mixing process. The dielectric responses of binary PVDF-clay and ternary graphite doped PVDF-clay nanocomposites were determined using broad band AC impedance spectroscopy. The results showed that the clay additions enhance permittivity of PVDF due to the formation of beta-phase polymorph. The permittivity of PVDF-clay nanocomposites can be further increased by adding conductive graphite nanosheet (GN). The hybrid composite with 3 wt% GN exhibited dielectric permittivity of 195 and low tangent loss of 0.45.

This work investigates the possible chemical bond formation between functionalized carbon nanotubes and alumina, in multiwall carbon nanotubes/alumina nanocomposite (MWCNT/Al2O3), with the aid of spectroscopic analysis. For this purpose, the nanocomposite MWCNT/alumina was synthesized via hydrothermal treatment. Different characterization techniques, scanning electron microscopy, energy dispersive X-ray spectroscope, X-ray diffraction, Fourier transformed infrared spectroscope and high-resolution transmission electron microscopy, have been used to investigate the interaction of the nanocomposite. XRD data confirmed the main alumina phase on the nanotube was α - Al2O3, with 12 nm average crystallite size. The presence of a shift in the carbonyl peak between oxidized nanotube and the nanocomposite, from 1710 cm-1 to 1630 cm-1 indicates the formation of chemical bond between alumina and CNT tips. The study predicts the possibility of covalent chemical bonding between alumina and the nanotube.

The free-radical graft polymerization of methacrylic acid onto surface activated nano silica particles was studied experimentally. Activated silica nanoparticle were modified using different concentration of 3-Chloropropyltrimethoxysilane (3-CTMS) to load the Chlor group by bonding with the organic functional group contained in 4-hydroxybenzoic acid (4-HBA). The carboxyl group of 4-HBA was then converted to vinyl ester group by reacting nano silica-bound benzoic acid (NSBA) and vinyl acetate as an acylating agent in the presence of catalyst. Methacrylic-type nano composites were synthesized by free radical copolymerization of methacrylic acid and vinyl ester derivative of modified nano silica. The nano composites were characterized by the FTIR and SEM techniques. The equilibrium swelling studies were carried out in enzyme-free simulated gastric and intestinal fluids (SGF and SIF, respectively). Naproxen was entrapped in the as-prepared nano composites and the in vitro release profiles were established separately in both (SGF, pH 1) and (SIF, pH 7.4).

Organic light-emitting diodes provide an excellent artificial illumination for greenhouse because it enables one to tailor the entire relevant spectral range from near infrared to near ultraviolet for optimal growth. We have fabricated a novel device to obtain the emission spectra that contained a deep blue and red emission, which fit well with the absorption peaks of chlorophylls a and b. The blue and red emission were produced from 4'-bis[N-(1-naphthyl)-N-phenyl-amino]biphenyl emitter and excimer emission of platinum [1,3- difluoro- 4,6-di(2-pyridinyl)benzene] chloride, respectively. The maximum external quantum efficiency of device reached 9.35 % with a CIEx, y coordinates (0.566, 0.317).

Biodegradable polymeric nanofibrosus meshes have emerged as a choice of scaffolds for cells to attach and grow as they mimic closely the nanoscale morphology of native extracellular proteins and promote cell-growth. Electrospun fibrous nanocomposite scaffolds of biodegradable synthetic polymer polycaprolactone (PCL) with surface modified carbon nanofibers (mCNFs) were successfully fabricated using the electrostatic co-spinning process. Structural and morphological properties of the nanofibrous composite scaffolds were characterized using, SEM, TEM, TGA and XRD. Microscopic analyses showed bead-free nanofibrous morphology with the presence of mCNFs in the electrospun scaffolds. The overall scaffolds' crystallinity and degree of orientation were assessed using XRD. The mechanical properties of the electrospun scaffolds as evaluated with tensile test, showed a marked increase in strength and stiffness with nanofiber alignment and with addition of mCNFs (0.1 and 0.5 wt %). Human mesenchymal stem cells (hMSCs) cultured onto PCL/mCNFs scaffold showed successful attachment and spreading of the cells.

In order to study the in vivo performance and in vitro cytotoxicity of 10-hydroxycamptothecin (10-HCPT) nanosuspension developed in our previous work. For investigating the pharmacokinetics in rats and the tissue distribution in mice with10-HCPT nanosuspension and the 10-HCPT solution, 10-HCPT nanosuspension and 10-HCPT solution were intravenously administered to rats via caudal vein, respectively. And 10-HCPT nanosuspension was intravenously injected to mice to study tissue distribution as compared to 10- HCPT solution. Serum samples and tissue homogenates were analyzed by HPLC-FD, then pharmaceutics parameters were calculation. In vitro cytotoxicity was also carried out with MCF-7/Ard and PC-3 as cell models. The results showed 10-HCPT nanosuspension could decrease plasma peak concentration and extend plasma circulating time compared to 10-HCPT solution. And the biodistribution test indicated that 10-HCPT nanosuspension can markedly change in vivo distribution pattern in comparison to 10-HCPT solution, and had considerable passive targeting capability to the mononuclear phagocyte systems. The in vitro cytotoxicity test demonstrated 10-HCPT nanosuspension had greater cytotoxicity to cancer cells than the solution, especially for adriamycin-sensitive cells. So the nanosuspensions will be a promising formulation strategy to resolve questions on solubility and increase anti-tumor activity of the poorly soluble anticancer compounds.

In this paper, scandia, yttria stabilized zirconia (SYSZ) nanoparticles were prepared by a wet chemistry method based on the Pechini-type sol-gel method. In this approach, zirconium oxynitrate, scandium and yttrium nitrate, citric acid (CA) and ethylene glycol mono butyl ether (EGM) were used as the source of Zr4+, Sc3+, Y3+, the chelating and solvent agent, respectively. In this study, the effect of EGM:CA ratios and calcination temperatures on the structure, morphology and the particle size of SYSZ have been investigated. The microstructure of the products was characterized by X-ray diffractometry (XRD), thermogravimetric and differential thermal analysis (TG/DTA), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), transmission electron microscopy (TEM), selected area electron diffraction (SAED), inductively coupled plasma emission spectroscopy (ICP), Fourier transform infrared spectroscopy (FTIR) and Raman spectroscopy. The SYSZ nanoparticles synthesized with EGM:CA mole ratio 4:1 and calcined at 700 °C, have average diameter of ∼15 nm and purity of 97.58%. Also, the optical properties of the as-prepared samples at different calcinations temperatures have been investigated.