Nanotechnology World - References

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Modeling the Loading and Unloading of Drugs into Nanotubes One of the most promising applications of nanotechnology is that of drug delivery, and in particular the targeted delivery of drugs using nanotubes. Functionalized nanotubes might be able to target specific cells, become ingested, and then release their contents in response to a chemical trigger. This will have significant implications for the future treatment of patients, particularly those suffering from cancer, for whom presently the nonspecific nature of chemotherapy often kills healthy normal cells. Research to date has largely been through experiments investigating toxicity, biocompatibility, solubility, functionalization, and cellular uptake. More recently, the loading and unloading of molecular cargo has gained momentum from both experimental and theoretical investigations. This Review focuses on the loading and unloading of molecular cargo and highlights recent theoretical investigations, which to date have received very little attention in the review literature. The development of nanotube drug-delivery capsules is of vital concern for the improvement of medical treatment, and mathematical modeling tends to facilitate such development and provides a quicker route to applications of the technology. This Review highlights the latest progress in terms of theoretical investigations and provides a focus for the development of the next generation of medical therapeutics. Micro- and Nanoprinting into Solids Using Reaction-Diffusion Etching and Hydrogel Stamps Micropatterned hydrogel stamps soaked in appropriate chemical etchants can imprint various types of micro- and nanoarchitectures into metals, conductive oxides, semiconductors, glasses, and crystals. Localized etching is mediated by a reaction-diffusion process initiated from the stamp microfeatures and gives lateral resolution down to approximately 300 nm. The method is well suited for the rapid prototyping of small-scale devices including multilevel microfluidic systems and curvilinear optical elements. Tailoring the Pore Size and Architecture of CeO2/TiO2 Core/Shell Inverse Opals by Atomic Layer Deposition No Abstract. Magnetolithography: From Bottom-Up Route to High Throughput No Abstract. Controlled Assembly of Vesicle-Based Nanocontainers on Layer-by-Layer Particles via DNA Hybridization No Abstract. Gecko-Inspired Directional and Controllable Adhesion No Abstract. Phase-Inversion Method for Incorporation of Metal Nanoparticles into Carbon-Nanotube/Polymer Composites No Abstract. CMOS-Compatible Nanowire Sensor Arrays for Detection of Cellular Bioelectricity No Abstract. Ultrafine ZnO Nanowire Electronic Device Arrays Fabricated by Selective Metal-Organic Chemical Vapor Deposition No Abstract. Fabrication of MnxFe1-xO Colloidal Solid Solution as a Dual Magnetic-Resonance-Contrast Agent No Abstract. Local Conformation of Confined DNA Studied Using Emission Polarization Anisotropy No Abstract. Tuning Electrical and Photoelectrical Properties of CdSe Nanowires via Indium Doping No Abstract. Friction Measurements of InAs Nanowires on Silicon Nitride by AFM Manipulation No Abstract Tröger's-Base-Derived Infinite Co-ordination Polymer Microparticles No Abstract. Multifunctional Silica Nanocapsule with a Single Surface Hole No Abstract. Fabrication and Functionalization of Supramolecular Microgel Arrays Through Complementary Hydrogen-Bonding Interactions No Abstract. Mesoporous Silica Nanoparticles for Reducing Hemolytic Activity Towards Mammalian Red Blood Cells No Abstract. Nanomechanical Mass Sensor for Spatially Resolved Ultrasensitive Monitoring of Deposition Rates in Stencil Lithography No Abstract. Hierarchical Self-Assembly of Metallo-Supramolecular Nanospheres No Abstract. Multifunctional Fe3O4@Au Nanoeggs as Photothermal Agents for Selective Killing of Nosocomial and Antibiotic-Resistant Bacteria No Abstract. Synthesis of Amphiphilic Graphene Nanoplatelets No Abstract. Transport Coefficients of InAs Nanowires as a Function of Diameter No Abstract. Synthesis of a Cagelike Hollow Aluminosilicate with Vermiculate Micro-Through-Holes and its Application to Ship-In-Bottle Encapsulation of Protein No Abstract. Development of Polymer-Encapsulated Metal Nanoparticles as Surface-Enhanced Raman Scattering Probes No Abstract. "Lock-and-Key" Geometry Effect of Patterned Surfaces: Wettability and Switching of Adhesive Force No Abstract. Biomolecular Nanopatterning by Electrophoretic Printing Lithography No Abstract. Aqueous Layer-by-Layer Epitaxy of Type-II CdTe/CdSe Quantum Dots with Near-Infrared Fluorescence for Bioimaging Applications No Abstract. Synthesis of Water-Soluble Blue Photoluminescent Silicon Nanocrystals with Oxide Surface Passivation No Abstract. Controlled Deposition of Silver Nanoparticles in Mesoporous Single- or Multilayer Thin Films: From Tuned Pore Filling to Selective Spatial Location of Nanometric Objects Silver nanoparticle assemblies are embedded within mesoporous oxide thin films by an in situ mild reduction leading to nanoparticle-mesoporous oxide thin-film composites (NP@MOTF). A quantitative method based on X-ray reflectivity is developed and validated with energy dispersive spectroscopy in order to assess pore filling. The use of dilute formaldehyde solutions leads to control over the formation of silver nanoparticles within mesoporous titania films. Inclusion of silver nanoparticles in mesoporous silica requires more drastic conditions. This difference in reactivity can be exploited to selectively synthesize nanoparticles in a predetermined layer of a multilayered mesoporous stack leading to complex 1D-ordered multilayers with precise spatial location of nanometric objects. The metal oxide nanocomposites synthesized have potential applications in catalysis, optical devices, surface-enhanced Raman scattering, and metal enhancement fluorescence. Layer-By-Layer Electropeeling of Organic Conducting Material Imaged In Real Time Soft materials comprising low-molecular-weight organic molecules are attracting increasing interest because of their importance in the development of a number of emerging areas in nanoscience and technology, including molecular electronics, nanosystems for energy conversion, and devices in the widest sense. Their interaction with electrodes and their behavior under electric fields is a topic of vital significance for these areas, and about which very little is known. Here unprecedented evidence is presented for the controlled peeling of organic molecular material when a voltage is applied between the conducting system and the conducting probe of a scanning force microscope. The rate of removal of the material from the surface of the bulk conducting supramolecular material can be tuned. It depends on the potential applied and is initiated only above a threshold value of 200 mV. The results indicate the importance of electric fields on the stability and performance of conducting organic systems at the nanoscale. Cancer-Cell-Phenotype-Dependent Differential Intracellular Trafficking of Unconjugated Quantum Dots A diverse array of nanoparticles, including quantum dots (QDs), metals, polymers, liposomes, and dendrimers, are being investigated as therapeutics and imaging agents in cancer diseases. However, the role of the cancer-cell phenotype on the uptake and intracellular fate of nanoparticles in cancer cells remains poorly understood. Reported here is that differences in cancer-cell phenotypes can lead to significant differences in intracellular sorting, trafficking, and localization of nanoparticles. Unconjugated anionic QDs demonstrate dramatically different intracellular profiles in three closely related human-prostate-cancer cells used in the investigation: PC3, PC3-flu, and PC3-PSMA. QDs demonstrate punctated intracellular localization throughout the cytoplasm in PC3 cells. In contrast, the nanoparticles localize mainly at a single juxtanuclear location ("dot-of-dots") inside the perinuclear recycling compartment in PC3-PSMA cells, where they co-localize with transferrin and the prostate-specific membrane antigen. The results indicate that nanoparticle sorting and transport is influenced by changes in cancer-cell phenotype and can have significant implications in the design and engineering of nanoscale drug delivery and imaging systems for advanced tumors. Strain-Driven Self-Assembled Network of Antidots in Complex Oxide Thin Films Structural strain due to lattice mismatch is used to promote the formation of a self-assembled network of antidots in highly epitaxial La2/3Sr1/3MnO3 thin films grown on (001) oriented SrTiO3 substrates by radiofrequency magnetron sputtering. Size, depth, and separation between antidots can be controlled by changing deposition parameters and the miscut angle of the substrate. This morphology exhibits a remarkable magnetic anisotropy and offers unique opportunities for versatile nanostencils for the preparation of nano-object networks that can be of major relevance for the fabrication of oxide-based magnetic and magnetoelectronic devices. Direct Magnetic Patterning due to the Generation of Ferromagnetism by Selective Ion Irradiation of Paramagnetic FeAl Alloys Sub-100-nm magnetic dots embedded in a non-magnetic matrix are controllably generated by selective ion irradiation of paramagnetic Fe60Al40 (atomic %) alloys, taking advantage of the disorder-induced magnetism in this material. The process is demonstrated by sequential focused ion beam irradiation and by in-parallel broad-beam ion irradiation through lithographed masks. Due to the low fluences used, this method results in practically no alteration of the surface roughness. The dots exhibit a range of magnetic properties depending on the size and shape of the structures, with the smallest dots (<100 nm) having square hysteresis loops with coercivities in excess of µ0HC = 50 mT. Importantly, the patterning can be fully removed by annealing. The combination of properties induced by the direct magnetic patterning is appealing for a wide range of applications, such as patterned media, magnetic separators, or sensors. Single Chain Epidermal Growth Factor Receptor Antibody Conjugated Nanoparticles for in vivo Tumor Targeting and Imaging Epidermal growth factor receptor (EGFR) targeted nanoparticle are developed by conjugating a single-chain anti-EGFR antibody (ScFvEGFR) to surface functionalized quantum dots (QDs) or magnetic iron oxide (IO) nanoparticles. The results show that ScFvEGFR can be successfully conjugated to the nanoparticles, resulting in compact ScFvEGFR nanoparticles that specifically bind to and are internalized by EGFR-expressing cancer cells, thereby producing a fluorescent signal or magnetic resonance imaging (MRI) contrast. In vivo tumor targeting and uptake of the nanoparticles in human cancer cells is demonstrated after systemic delivery of ScFvEGFR-QDs or ScFvEGFR-IO nanoparticles into an orthotopic pancreatic cancer model. Therefore, ScFvEGFR nanoparticles have potential to be used as a molecular-targeted in vivo tumor imaging agent. Efficient internalization of ScFvEGFR nanoparticles into tumor cells after systemic delivery suggests that the EGFR-targeted nanoparticles can also be used for the targeted delivery of therapeutic agents. Inhibition of Tumor-Cell Invasion with Chlorotoxin-Bound Superparamagnetic Nanoparticles Nanoparticles have been investigated as drug delivery vehicles, contrast agents, and multifunctional devices for patient care. Current nanoparticle-based therapeutic strategies for cancer treatment are mainly based on delivery of chemotherapeutic agents to induce apoptosis or DNA/siRNA to regulate oncogene expression. Here, a nanoparticle system that demonstrates an alternative approach to the treatment of cancers through the inhibition of cell invasion, while serving as a magnetic resonance and optical imaging contrast agent, is presented. The nanoparticle comprises an iron oxide nanoparticle core conjugated with an amine-functionalized poly(ethylene glycol) silane and a small peptide, chlorotoxin (CTX), which enables the tumor cell-specific binding of the nanoparticle. It is shown that the nanoparticle exhibits substantially enhanced cellular uptake and an invasion inhibition rate of [sim]98% compared to unbound CTX ([sim]45%). Significantly, the investigation from flow cytometry analysis, transmission electron microscopy, and fluorescent imaging reveals that the CTX-enabled nanoparticles deactivated the membrane-bound matrix metalloproteinase 2 (MMP-2) and induced increased internalization of lipid rafts that contain surface-expressed MMP-2 and volume-regulating ion channels through receptor-mediated endocytosis, leading to enhanced prohibitory effects. Since upregulation and activity of MMP-2 have been observed in tumors of neuroectodermal origin, and in cancers of the breast, colon, skin, lung, prostate, ovaries, and a host of others, this nanoparticle system can be potentially used for non-invasive diagnosis and treatment of a variety of cancer types. Alkyl-Capped Silicon Nanocrystals Lack Cytotoxicity and have Enhanced Intracellular Accumulation in Malignant Cells via Cholesterol-Dependent Endocytosis Nanocrystals of various inorganic materials are being considered for application in the life sciences as fluorescent labels and for such therapeutic applications as drug delivery or targeted cell destruction. The potential applications of the nanoparticles are critically compromised due to the well-documented toxicity and lack of understanding about the mechanisms involved in the intracellular internalization. Here intracellular internalization and toxicity of alkyl-capped silicon nanocrystals in human neoplastic and normal primary cells is reported. The capped nanocrystals lack cytotoxicity, and there is a marked difference in the rate and extent of intracellular accumulation of the nanoparticles between human cancerous and non-cancerous primary cells, the rate and extent being higher in the malignant cells compared to normal human primary cells. The exposure of the cells to the alkyl-capped nanocrystals demonstrates no evidence of in vitro cytotoxicity when assessed by cell morphology, apoptosis, and cell viability assays. The internalization of the nanocrystals by Hela and SW1353 cells is almost completely blocked by the pinocytosis inhibitors filipin, cytochalasin B, and actinomycin D. The internalization process is not associated with any surface change in the nanoparticles, as their luminescence spectrum is unaltered upon transport into the cytosol. The observed dramatic difference in the rate and extent of internalization of the nanocrystals between malignant and non-malignant cells therefore offers potential application in the management of human neoplastic conditions. Electronic-Type- and Diameter-Dependent Reduction of Single-Walled Carbon Nanotubes Induced by Adsorption of Electron-Donor Molecules The adsorption of the organic donor molecules tetrakis(dimethylamino)ethylene (TDAE) and cobaltocene (CoCp2) on high-pressure CO decomposition (HiPco) single-walled carbon nanotubes (SWNTs) is investigated using density functional theory (DFT), optical absorption, and Raman spectra methods. The selective reduction of SWNTs according to the electronic type and diameter of SWNTs is revealed. The reduction rate decreases in the order: metallic SWNTs [ge] large-diameter semiconducting SWNTs > small-diameter semiconducting SWNTs. Particle Size, Surface Coating, and PEGylation Influence the Biodistribution of Quantum Dots in Living Mice This study evaluates the influence of particle size, PEGylation, and surface coating on the quantitative biodistribution of near-infrared-emitting quantum dots (QDs) in mice. Polymer- or peptide-coated 64Cu-labeled QDs 2 or 12 nm in diameter, with or without polyethylene glycol (PEG) of molecular weight 2000, are studied by serial micropositron emission tomography imaging and region-of-interest analysis, as well as transmission electron microscopy and inductively coupled plasma mass spectrometry. PEGylation and peptide coating slow QD uptake into the organs of the reticuloendothelial system (RES), liver and spleen, by a factor of 6-9 and 2-3, respectively. Small particles are in part renally excreted. Peptide-coated particles are cleared from liver faster than physical decay alone would suggest. Renal excretion of small QDs and slowing of RES clearance by PEGylation or peptide surface coating are encouraging steps toward the use of modified QDs for imaging living subjects. Microreplication and Design of Biological Architectures Using Dynamic-Mask Multiphoton Lithography A strategy for rapidly printing three-dimensional (3D) microscopic replicas using multiphoton lithography directed by a dynamic electronic mask is reported. Morphological descriptions of 3D structures are encoded as stacks of 2D slices created from tomographic and computer-designed instruction sets. In this manner, digital images serve as input for a sequence of reflective photomasks on a digital micromirror device to direct replication of a structure. By scanning a laser focus across the face of the intrinsically aligned masks, tomographic and computed data can be translated into protein-based 3D reproductions with submicrometer feature sizes within 1 min. This straightforward and highly versatile approach may provide improved routes for the development of 3D cellular scaffolds, rapid prototyping of microanalytical devices, and production of custom tissue replacements. Photoelectrochemical Water Splitting Using Dense and Aligned TiO2 Nanorod Arrays Dense and aligned TiO2 nanorod arrays are fabricated using oblique-angle deposition on indium tin oxide (ITO) conducting substrates. The TiO2 nanorods are measured to be 800-1100 nm in length and 45-400 nm in width with an anatase crystal phase. Coverage of the ITO is extremely high with 25 × 106 mm-2 of the TiO2 nanorods. The first use of these dense TiO2 nanorod arrays as working electrodes in photoelectrochemical (PEC) cells used for the generation of hydrogen by water splitting is demonstrated. A number of experimental techniques including UV/Vis absorption spectroscopy, X-ray diffraction, high-resolution scanning electron microscopy, energy-dispersive X-ray spectroscopy, and photoelectrochemistry are used to characterize their structural, optical, and electronic properties. Both UV/Vis and incident-photon-to-current-efficiency measurements show their photoresponse in the visible is limited but with a marked increase around [ap]400 nm. Mott-Schottky measurements give a flat-band potential (VFB) of +0.20 V, a carrier density of 4.5 × 1017 cm-3, and a space-charge layer of 99 nm. Overall water splitting is observed with an applied overpotential at 1.0 V (versus Ag/AgCl) with a photo-to-hydrogen efficiency of 0.1%. The results suggest that these dense and aligned one-dimensional TiO2 nanostructures are promising for hydrogen generation from water splitting based on PEC cells. Oligothiophene Assemblies Defined by DNA Interaction: From Single Chains to Disordered Clusters The organization of conjugated polyelectrolytes (CPEs) interacting with biomolecules sets conditions for the biodetection of biological processes and identity, through the use of optical emission from the CPE. Herein, a well-defined CPE and its binding to DNA is studied. By using dynamic light scattering and circular dichroism spectroscopy, it is shown that the CPE forms a multimolecule ensemble in aqueous solution that is more than doubled in size when interacting with a small DNA chain, while single chains are evident in ethanol. The related changes in the fluorescence spectra upon polymer aggregation are assigned to oscillator strength redistribution between vibronic transitions in weakly coupled H-aggregates. An enhanced single-molecule spectroscopy technique that allows full control of excitation and emission light polarization is applied to combed and decorated [lambda]DNA chains. It is found that the organization of combed CPE-[lambda]DNA complexes (when dry on the surface) allows considerable variation of CPE distances and direction relative to the DNA chain. By analysis of the polarization data energy transfer between the polymer chains in individual complexes is confirmed and their sizes estimated.

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