Current Nanoscience (v.6, #6)

Graphical Abstracts by Bentham Science Publishers (i-iv).
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Research into the targeting of drug substances to a specific disease site has enjoyed sustained activity for many decades. The reason for such fervent activity is the considerable clinical advantages that can be gained when the delivery system plays a pivotal role in determining where the drug is deposited. When compared to conventional formulations where no such control exists, such as parenteral and oral systems, the sophisticated targeting device can reduce side effects and limit collateral damage to surrounding normal tissue. No more so is this important than in the area of oncology when dose-limiting side effects are often encountered as an ever present difficulty. In this review, the types of colloidal carrier commonly used in targeted drug delivery are discussed, such as gold and polymeric colloids. In particular, the process of attaching targeting capabilities is considered, with reference to antibody technologies used as the targeting motifs. Nanotechnology has brought together a means to carry both a drug and targeting ligand in self-contained constructs and their applications to both clinical therapy and diagnosis are discussed.

Evaluation of In Vitro Dissolution and In Vivo Oral Absorption of Drug Nanopowders Prepared by Novel Wet-Milling Equipment by Yusuke Tanaka, Mitsugi Inkyo, Ryoko Yumoto, Junya Nagai, Mikihisa Takano, Shunji Nagata (571-576).
In vitro dissolution and in vivo oral absorption studies were carried out in order to evaluate the effects of nanoparticulation. Omeprazole, albendazole and danazol nanopowders were prepared using novel wet-milling equipment, an ULTRA APEX MILL, with Pluronic F-68 or F-108 as dispersing agents, followed by lyophilization. An in vitro dissolution study showed that the dissolution rates of all nanopowders were drastically improved compared to the corresponding bulk powders, and their apparent saturated solubilities also increased compared to mixed powders consisting of bulk powders and dispersing agents. The AUCs after oral administration to rats of omeprazole nanopowders with Pluronic F-68 and F-108, and albendazole nanopowder with Pluronic F-68, were 1.93, 2.90 and 10.3 times higher, respectively than those for the corresponding bulk powders. The ULTRA APEX MILL can be a very useful tool for pharmaceutical techniques to enhance the dissolution and oral bioavailability of poorly water-soluble drugs.

Nanomaterials: New Generation Therapeutics in Wound Healing and Tissue Repair by Ajay V. Singh, Aditi A.S, W. N. Gade, Tanushree Vats, Cristina Lenardi, Paolo Milani, Aditi A.S. (577-586).
Wound healing and ulcer management is a vast topic that stimulated clinical research due to its major socio economic impact on clinical practices. Last decade of research in clinical science has seen materials at microscale developments which significantly contributed to ulcer management and wound healing with their merits and limitations. The present review outlines the new materials at nanoscale that have been designed and manufactured to address the existing problems in wound care but comparatively less familiar to clinicians for tissue repair and ulcer management. Development in tissue engineering practices spanning from micro- to nano- dimension provided superior materials over traditional wound dressing materials mimicking tissue in vivo. Recent advances in material sciences and polymer chemistry have yielded an entire class of new nanomaterials, ranging from bioactive tissue scaffold to novel electrospun polymer and hydrogel for tissue repair and wound management. Nanoscale materials with biodegradable chemistries and molecular compositions assist wound healing as adhesive and bandages in specialized wound care. Moreover, new class of materials gives opportunity to engineer tissue substrate in vitro to support bio-responsive nanomedicine for wound healing. Soft nanomaterial design technology involving hydrogel and bio-scaffold revolutionized the wound management supplementing biophysical and biochemical considerations of tissue regeneration. In addition, this review addresses the immediate challenges and opportunities provided by nanoscale tissue engineering in designing synthetic biomaterials as instructive extracellular matrix (ECM) for tissue remodeling and morphogenesis.

Synthesis and Broad Spectrum Antibacterial Activity of Magnetite Ferrofluid by Charusheela Ramteke, Bijaya Ketan Sarangi, Tapan Chakrabarti, Sandeep Mudliar, Dewanand Satpute, Ram Avatar Pandey (587-591).
Magnetite (Fe3O4), is an extensively studied material because of several interesting properties and associated applications. However, synthesizing functional magnetite nano- and microstructures as ferrofluids for use in biomedical field still remains a challenge due to the technical limitations associated with the fabrication process. We have developed a one-step, low energy consumable process for the synthesis of highly monodisperse magnetite nanoparticles using thioglycerol as a stabilizing agent. The characterization of synthesized nanoparticles has been carried out using particle size analyzer, Transmission electron microscopy (TEM), X-ray diffractometry (XRD) and Fourier transform infrared spectrometry (FTIR). The antibacterial property of the synthesized magnetite nanoparticles has also been investigated and the results indicated that the tested pathogenic microorganisms are quite susceptible to very low concentrations of thioglycerol stabilized magnetite nanoparticles (TSMNs). The minimum inhibitory concentrations of synthesized TSMNs were found to be 0.041 mg/ml for E. coli and 0.047mg/ml for Staphylococcus aureus, Bacillus subtilis and Pseudomonas aeruginosa. Such antibacterial properties pose great promise for nanomaterials stabilized with organic molecules to be used in bio-medical applications.

Preparation of Ni-cysteine Hollow Spheres with Ferromagnetic Property and Good Biocompatibility by Chuanbao Caoa, Xiaoqiang An, Xuelian Yu, Xilan Ma (592-597).
In this work, magnetic Ni-cysteine hollow spheres were firstly fabricated by a facile room temperature self – assembly method. The most outstanding advantage of these hollow spheres is that the biocompatibility of amino acid and the magnetic property of metal nickel ions are successfully combined. Their coercivity in the magnetic measurement is 90 Oe at 80 K. This ferromagnetic performance and the satisfying blood compatibility in the anticoagulation test make them show promising applications in biological technique, especially the targeted drug delivery.

An Investigation of Mass Sensitivity of Fixed Free Single Walled Carbon Nanotube Based Nano Mechanical Sensors by Anand Y. Joshi, Aashish Bhatnagar, Satish C. Sharma, S. P. Harsha (598-603).
In the present paper, the simulation of the mechanical responses of individual carbon nanotubes treated as thin shells has been done using finite element method. The resonant frequencies of the fixed free single wall carbon nanotube have been investigated. This analysis explores the resonant frequency shift of Single Walled Carbon Nanotubes caused by the changes in the size of Carbon Nanotube in terms of length as well as the attached masses. The results showed the sensitivity of the single walled carbon nanotubes to different masses (attached to the tip and at the centre of Single Walled Carbon Nanotube) and different lengths. It has also observed that the mass sensitivity of carbon nanotube can reach upto 10-21 g of attached mass and the mass sensitivity increases when smaller size nanotubes resonators are used in mass sensors. In order to explore the suitability of the Single walled carbon nanotube as a mass detector device, the simulation results of the resonant frequency of fixed free Single Walled Carbon Nanotube are compared to the published experimental data. It is shown that the FEM simulation results are in good agreement with the experimental data and hence the current modelling approach is suitable as a coupled-field design tool for the development of Single Walled Carbon Nanotube -based NEMS applications.

A facile approach for the preparation of the photo-sensitive and degradable polymeric nanocapsules containing a number of hydroxyl groups was developed. The hyperbranched poly(amine ester) grafted silica nanoparticles (SN-HPAE) were cross-linked with 4,4and#180;-Azobenzene dibenzoyl chloride (ADC) by the reaction between the hydroxyl groups and benzoyl chloride groups. Then the silica templates were removed by being etched with HF to produce the photo-sensitive and degradable polymeric nanocapsules. The hollow structure of the polymeric nanocapsules with the inner diameter in the range of 20-100 nm was characterized by transmission electron microscopy (TEM). The solid-state UV-vis spectra of the cross-linked hyperbranched polymeric nanocapsules showed the photoresponsive behavior of the azobenzene type molecules.

Assembly of Silver Nanoparticles in Pearl-Necklace-Like Nanostructure Using a Polyelectrolyte by Qiang Cui, Lubin Zhong, Jiabao Ding, Jian Weng (610-618).
Pearl-necklace-like Ag nanostructures are prepared with microwave irradiation in a one-step process using polymethacrylic acid (PMAA) as a reducing agent, and AgNO3 as a silver precursor without other chemical agent in a 6.5and#x2264;pHand#x2264;8.0 aqueous solution. Derjaguin – Landau – Verwey – Overbeek theory is used to calculate the stability of Ag particles in the aqueous medium. The calculated results are fairly consistent with the experimental results. The formation mechanism of pearl-necklace-like silver nanostructures is suggested as three steps: immobilization of Ag+ ions with the PMAA template, reduction of Ag+ ions with PMAA under microwave irradiation, anisotropic self-assembly of silver particles capped by the negatively charged PMAA with electrostatic interactions and Van der Waals forces.

Absorption Spectral Simulation of the End-to-End Linked Gold Nanorods Chain Structure by Chia- Wen Kuo, C. R. Chris Wang, Chia-Wen Kuo (619-625).
A classical electrostatic simulation model was developed to study the absorption spectral features of the end-to-end linked and equally-spaced n gold nanorods system with n=2 to 20 for the first time. The model calculation takes into account the dipole-dipole interactions only and solved for the mean polarizability of such nano-chain. We modelled the evolution of the longitudinal surface plasmon (SPlong) absorption band of such system in terms of the interparticle spacings and the number of nanorods. In both cases, either the decrease of interparticle spacing or the increase of n, the evolution of the SPlong bands exhibits a clear spectral red-shift similar to other assembled forms reported in literature. The extent of such spectral shift can be as large as more than 100 nm before levelling off. The interparticle dipole-dipole interaction, characterized by the results in the spectral features of SPlong bands, evidences an effective spatial range of ca. 100 nm.

Variable Range Hopping in Carbon Nanotubes by Zishan H. Khan, Samina Husain, M. Husain (626-641).
Carbon nanotubes exhibit exceptional properties that are a consequence of their symmetric structure. Many properties of carbon nanotubes (CNTs) have been explained in the wider context of materials science, thereby highlighting the contribution from different researchers worldwide in this rapidly expanding field. Among various other properties of CNTs studied so far, the electrical transport properties are still unclear and needs a lot of attention. Due to high anisotropy of graphite, the electrical properties are strongly dependent on the structure of the nanotubes. Since, the CNTs can be metallic and semi-conducting in nature, their explanation to electrical conduction mechanism in these two cases would be different. During the last few years, efforts have been made to understand the electrical transport phenomenon in CNTs, aiming at the design of nanoelectronic devices made solely of carbon. Keeping in view the above, it is of great interest to present a state of art on the progress involving the research work on electrical conduction mechanism especially variable range hopping in CNTs. In the present paper, we have presented a review on electrical transport mechanism especially variable range hopping in carbon nanotubes. This review will provide a better understanding of variable range hopping in CNTs.

This study describes the fabrication of multilayer microporous alumina-titania self-assembled thin-film by dip-coating using sol – gel method on glass substrate. First layer of mesoporous alumina film was synthesized using alumina sol composed of aluminium trisec- butylate as precursor, 2-propanol, as solvent and ethyl acetoacetateas chelating agent. Titania overlayer nanoparticles (15-43 nm) were grown on alumina layer by the controlled hydrolysis of titanium (IV) isopropoxide. Thin films consisted of titania with extremely preferential (101) orientation as a novel means to enhance porosity. Thermogravimetry – differential thermal analyses, X-ray diffraction and scanning electron microscopy were employed to investigate the growth and morphology of the films. The results reveal that the thin films consist of stacked, nearly spherical, nanocrystalline particles, and that 500 and#176;C is optimal temperature for the smallest crystal size (15.2 nm) of TiO2 thin films. It is argued that the extremely preferential (101) orientation of anatase TiO2 is a result of self-assembly induced by interaction of titania/air and titania/alumina interfaces that force the titania micelles to align and to reorganise.

A MOSFET-Like Infrared Sensor for the Enhancement of Photoconductivity and Photoresponsivity by Chi- Guang Wang, Gou- Jen Wang, Chi-Guang Wang, Gou-Jen Wang (648-653).
In this study, a metal oxide semiconductor field effect transistor (MOSFET)-like infrared (IR) sensing method is presented. The orderly uneven barrier-layer surface of an anodic aluminum oxide (AAO) membrane was used as the substrate. The thickness of the barrier-layer was reduced by phosphoric acid etching following which a microchannel was transferred to the barrier-layer by the photolithographic technique. Single walled carbon nanotubes (SWNTs) were deposited into the microchannel as the sensing element. A gold thin film that served as the gate electrode was sputtered on the opposite side of the barrier-layer of the AAO substrate. A thin layer of polydimethylsiloxane (PDMS) was then cast on the SWNTs to insulate them from the surrounding ambiance. A thin film of indium tin oxide (ITO) was sputtered onto the PDMS layer to act as the counter electrode for the gate electrode. The conductance of the sensing element could be better controlled by the width of the microchannel and the amount of the deposited SWNTs. Experiments demonstrated that the proposed MOSFET-like IR sensor could effectively sense IR signals in the air at room temperature under a very weak power intensity (17 and#956;W/cm2) of IR illumination and an 0.01 V applied drain-source voltage. A 0.5 sec photocurrent response time and a 2.4and#x25; of conductivity enhancement were measured.

Efficient Loading and Controlled Release of Benzophenone-3 Entrapped into Self-Assembling Nanogels by Samia Daoud-Mahammed, Sunil A. Agnihotri, Kawthar Bouchemal, Stefanie Kloters, Patrick Couvreur, Ruxandra Gref (654-665).
Benzophenone-3 (BZ-3), was successfully entrapped into nanogels prepared by a simple one-step method based on selfassembly of two water soluble polymers: a hydrophobically modified dextran (MD) and a and#946;-Cyclodextrin polymer (pand#946;-CD). Isothermal titration microcalorimetry (ITC) and phase solubility experiments were performed at 4, 25 or 37and#176;C to investigate the interaction of the hydrophobic BZ-3 with MD and pand#946;-CD. The BZ-3 entrapment efficiency, yield of nanogels formation, particle size, and BZ-3 release were also evaluated. BZ-3/pand#946;-CD interaction was characterized by association constants K= 5180 M-1 and Kand#180;= 2700 M-1, as determined by phase solubility and ITC experiments, respectively. Differences obtained in association constants values were discussed critically. Results indicate that both K and Kand#180; decrease with increase in temperature. The strong interactions between BZ-3 and pand#946;-CD were characterized by a negative enthalpy change ( H) with entropic contribution (T S). Monodisperse nanogels were produced with an entrapment up to 75 and#x25; and yield up 84 and#x25;. BZ-3 was firmly entrapped into nanogels, as only the dilution of the nanogels led to its release. This system provides an advantage for sunscreen formulation to prevent systemic penetration of BZ-3. The and#x2018;greenand#x2019; (solvent free) preparation method, and the possibility of unlimited storage after freeze drying makes these nanogels valuable candidates for the entrapment of sun screen agents.

Hydrothermal Synthesis and Acidic Catalytic Activity of Nanometer Ce0.6Zr0.4O2 Solid Solution by Yucai Hu, Tao Liang, Li Zhou, Xuehua Yu, Ping Yin (666-668).
Nanometer Ce0.6Zr0.4O2 solid solution was prepared by hydrothermal method, using cerous nitrate and zirconium nitrate and hydrazine hydrate as raw materials at 250 and#176;C for 24h. The product was characterized by X-ray powder diffraction (XRD), Raman scattering spectrum, transmission microscopy (TEM) and infrared spectra (IR). Furthermore, its catalytic activity was measured in the synthesis of n-butyl acetate by the reaction of acetic acid and n-butyl alcohol. The XRD pattern and Raman scattering spectrum show that the sample formed homogeneous solid solution with CeO2 cubic structure. The TEM observation indicates that the as-synthesized Ce0.6Zr0.4O2 solid solution has the particle diameter less than 50 nm. In the esterification reaction, Ce0.6Zr0.4O2 solid solution possess high catalytic activity and can be easily separated from reaction liquid. According to Tanabe rules, its catalytic mechanism belongs to proton acid catalysis.