Small

Cover image for Vol. 7 Issue 14

Special Issue: C. A. Mirkin, 20 Years at Northwestern

July 18, 2011

Volume 7, Issue 14

Pages 1849–2119

  1. Cover Picture

    1. Top of page
    2. Cover Picture
    3. Inside Front Cover
    4. Editorial
    5. Contents
    6. Reviews
    7. Frontispiece
    8. Communications
    9. Full Papers
    1. Special Issue Dedicated to Chad A. Mirkin in Celebration of 20 Years of Influential Research at Northwestern University: (Small 14/2011) (page 1849)

      Article first published online: 14 JUL 2011 | DOI: 10.1002/smll.201190048

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      This issue's cover highlights the fields of nanofabrication and bio-nanotechnology, two areas where Chad Mirkin has made substantial contributions. The main image of the cover combines these two themes, depicting the capture of DNA-functionalized nanoparticles by a nanoelectrode. This image from the Mirkin group appeared in the first issue of Small (Volume 1, Issue 1 published in 2005), providing a fitting introduction to this issue commemorating the first 20 years of Chad's career.

  2. Inside Front Cover

    1. Top of page
    2. Cover Picture
    3. Inside Front Cover
    4. Editorial
    5. Contents
    6. Reviews
    7. Frontispiece
    8. Communications
    9. Full Papers
    1. 3D Nanofabrication: Nanoscale Origami for 3D Optics (Small 14/2011) (page 1850)

      Jeong-Hyun Cho, Michael D. Keung, Niels Verellen, Liesbet Lagae, Victor V. Moshchalkov, Pol Van Dorpe and David H. Gracias

      Article first published online: 14 JUL 2011 | DOI: 10.1002/smll.201190049

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      The cover image shows 500 nm scaled dielectric cubes with precise metal patterns (50 nm line width) including functional optical elements such as split-ring resonators (SRRs) on all faces. The cubes fold up spontaneously during the plasma etching of electron-beampatterned panels. This self-folding enables origami-inspired approaches to be extended to the nanoscale, allowing precisely patterned 3D structures to be self-assembled from flat (2D) panels in a parallel manner. Compared to planar patterns, arrangements of optically active elements in polyhedral geometries can augment functionality for optics and biosensing. For more information, please read the Communication “Nanoscale Origami for 3D Optics” by D. H. Gracias and co-workers, beginning on page 1943.

  3. Editorial

    1. Top of page
    2. Cover Picture
    3. Inside Front Cover
    4. Editorial
    5. Contents
    6. Reviews
    7. Frontispiece
    8. Communications
    9. Full Papers
    1. You have free access to this content
      Special Issue Dedicated to Chad Mirkin: 20 Years of Influential Research (page 1851)

      Nathan C. Gianneschi, David S. Ginger and Vincent M. Rotello

      Article first published online: 14 JUL 2011 | DOI: 10.1002/smll.201101142

  4. Contents

    1. Top of page
    2. Cover Picture
    3. Inside Front Cover
    4. Editorial
    5. Contents
    6. Reviews
    7. Frontispiece
    8. Communications
    9. Full Papers
    1. Contents: (Small 14/2011) (pages 1853–1862)

      Article first published online: 14 JUL 2011 | DOI: 10.1002/smll.201190050

  5. Reviews

    1. Top of page
    2. Cover Picture
    3. Inside Front Cover
    4. Editorial
    5. Contents
    6. Reviews
    7. Frontispiece
    8. Communications
    9. Full Papers
    1. Molecular Analysis of Blood with Micro-/Nanoscale Field-Effect-Transistor Biosensors (pages 1863–1875)

      Matthew S. Makowski and Albena Ivanisevic

      Article first published online: 3 JUN 2011 | DOI: 10.1002/smll.201100211

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      Rapid and accurate molecular blood analysis is essential for disease dia­gnosis and management. Field-effect transistor (FET) biosensors promise to advance blood point-of-care testing by offering desirable characteristics such as portability, high sensitivity, brief detection time, low manufacturing cost, multi­plexing, and label-free detection. By controlling device parameters, desirable FET biosensor performance and stability are obtained.

    2. Graphene-Based Materials: Synthesis, Characterization, Properties, and Applications (pages 1876–1902)

      Xiao Huang, Zongyou Yin, Shixin Wu, Xiaoying Qi, Qiyuan He, Qichun Zhang, Qingyu Yan, Freddy Boey and Hua Zhang

      Article first published online: 1 JUN 2011 | DOI: 10.1002/smll.201002009

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      Graphene-based materials may find applications in a variety of fields. Following a general introduction to graphene and its derivatives, the synthesis, characterization, properties, and applications of graphene-based materials are discussed.

    3. Beauty is Skin Deep: A Surface Monolayer Perspective on Nanoparticle Interactions with Cells and Bio-macromolecules (pages 1903–1918)

      Krishnendu Saha, Avinash Bajaj, Bradley Duncan and Vincent M. Rotello

      Article first published online: 14 JUN 2011 | DOI: 10.1002/smll.201100478

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      Functionalized nanoparticles provide a versatile platform for surface recognition of bio-macromolecules. This review highlights current advances in the tuning of nanoparticle monolayers for interaction with biomolecules and cells. The use of these engineered materials for delivery, hybrid nanomaterials, and biosensing applications is discussed.

    4. More Effective Nanomedicines through Particle Design (pages 1919–1931)

      Jin Wang, James D. Byrne, Mary E. Napier and Joseph M. DeSimone

      Article first published online: 22 JUN 2011 | DOI: 10.1002/smll.201100442

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      Nanomedicine is an emerging field that applies concepts in nanotechnology to the development of novel diagnostics and therapeutics. Physical and chemical properties of particles, including size, shape, modulus, surface charge, and surface chemistry, play important roles in the efficacy of nanomedicines. This review focuses on the effect of particle physical and chemical properties on their interactions with cells in vitro and their pharmacokinetics and biodistribution in vivo.

    5. Five Years of siRNA Delivery: Spotlight on Gold Nanoparticles (pages 1932–1937)

      Abigail K. R. Lytton-Jean, Robert Langer and Daniel G. Anderson

      Article first published online: 17 JUN 2011 | DOI: 10.1002/smll.201100761

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      The use of gold nanoparticles for intracellular delivery of siRNA has built up momentum over the last five years. The different strategies employed are described in detail. These strategies involve either direct conjugation of siRNA to the gold surface via a thiol/gold bond, or association via an electrostatic interaction.

  6. Frontispiece

    1. Top of page
    2. Cover Picture
    3. Inside Front Cover
    4. Editorial
    5. Contents
    6. Reviews
    7. Frontispiece
    8. Communications
    9. Full Papers
    1. Gold Superstructures: Size-Controlled Peptide-Directed Synthesis of Hollow Spherical Gold Nanoparticle Superstructures (Small 14/2011) (page 1938)

      Leekyoung Hwang, Gongpu Zhao, Peijun Zhang and Nathaniel L. Rosi

      Article first published online: 14 JUL 2011 | DOI: 10.1002/smll.201190051

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      The frontispiece image shows hollow spherical assemblies of nanoparticles arising from mixtures of metal salts, simple buffers, and carefully designed peptides. The structures are prepared in aqueous conditions at neutral pH. Importantly, small modifications of the peptide sequence leads to dramatic differences in the diameter of the nanoparticle superstructures, allowing one to construct either sub-50-nm hollow spherical structures or larger (>100 nm) hollow spherical structures. For more information, please read the Communication “Size-Controlled Peptide-Directed Synthesis of Hollow Spherical Gold Nanoparticle Superstructures” by N. L. Rosi and co-workers, beginning on page 1938.

  7. Communications

    1. Top of page
    2. Cover Picture
    3. Inside Front Cover
    4. Editorial
    5. Contents
    6. Reviews
    7. Frontispiece
    8. Communications
    9. Full Papers
    1. Size-Controlled Peptide-Directed Synthesis of Hollow Spherical Gold Nanoparticle Superstructures (pages 1939–1942)

      Leekyoung Hwang, Gongpu Zhao, Peijun Zhang and Nathaniel L. Rosi

      Article first published online: 3 JUN 2011 | DOI: 10.1002/smll.201100477

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      Choose your favorite size: Peptide conjugates, BP–Ax–PEPAu, direct the synthesis and assembly of gold nanoparticles into well-defined hollow spherical gold nanoparticle superstructures. The diameter of the superstructures can be dialed-in by choosing the proper number of alanine residues, x: x = 2 leads to superstructures with diameters larger than 100 nm while x = 3 leads to superstructures with sub-50-nm diameters.

    2. Nanoscale Origami for 3D Optics (pages 1943–1948)

      Jeong-Hyun Cho, Michael D. Keung, Niels Verellen, Liesbet Lagae, Victor V. Moshchalkov, Pol Van Dorpe and David H. Gracias

      Article first published online: 14 JUN 2011 | DOI: 10.1002/smll.201100568

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      Nanoscale self-folding of electron-beam lithography patterned templates is used to create 3D devices for optics and biosensing.

    3. Enhanced Electrical Conductivity of Individual Conducting Polymer Nanobelts (pages 1949–1953)

      Lin Jiang, Yinghui Sun, Haiyang Peng, Lain-Jong Li, Tao Wu, Jan Ma, Freddy Yin Chiang Boey, Xiaodong Chen and Lifeng Chi

      Article first published online: 3 JUN 2011 | DOI: 10.1002/smll.201100090

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      Afacile strategy for preparing 1D conducting polymer nanobelts with the width of the belts down to less than 50 nm is presented. Strong enhancement in the conductivity of individual polypyrrole (PPy) nanobelts is observed, due to lengthening of the π-conjugation length of PPy belts with decreasing belt width, as confirmed by micro-Raman measurements.

    4. Glyco-DNA–Gold Nanoparticles: Lectin-Mediated Assembly and Dual-Stimuli Response (pages 1954–1960)

      Katrin G. Witten, Claudia Rech, Thomas Eckert, Samir Charrak, Walter Richtering, Lothar Elling and Ulrich Simon

      Article first published online: 8 JUN 2011 | DOI: 10.1002/smll.201100492

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      The formation and properties of glyco-DNA–gold nanoparticles (NP) with a multivalent presentation of DNA-glyco ligands is presented. These particles are equipped with two reversible binding modes, which enable reversible dissociation by two independent external stimuli: temperature-induced DNA duplex melting and displacement of the DNA-glyco ligands from the carbohydrate recognition domains with free sugar.

    5. Mixed-Ligand Nanoparticles as Supramolecular Receptors (pages 1961–1966)

      Xiang Liu, Ying Hu and Francesco Stellacci

      Article first published online: 3 JUN 2011 | DOI: 10.1002/smll.201100386

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      The design of nanoparticle-based receptors has generally focused on the design of ligand molecules for the particles' ligand shell. This study focuses on the development of supramolecular nanoparticle receptors through the mixing of two types of ligand molecules. The nanoparticle receptor is achieved via the self-assembly of two ligands that together create binding sites, whereas each of the two homoligand particles has no appreciable binding capability.

    6. Mixed-Valence Nanoclusters: Fast Electron Transfer in Mixed-Valence Systems with a Gold Nanoparticle as the Bridge (pages 1967–1971)

      Gabriele Canzi and Clifford P. Kubiak

      Article first published online: 9 JUN 2011 | DOI: 10.1002/smll.201100483

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      Trinuclear ruthenium clusters attached to Au nanoparticles can be partially reduced to form mixed-valence nanoclusters. The nanoparticles are synthesized using a modified Brust method. IR-SEC shows dynamic coalescence of the stretching vibrations of the carbonyls, ν(CO), indicating the electron transfer between Ru clusters attached via a π-conjugated bridge to NPs occurs on the picosecond timescale. Simulation of IR spectra gives ket on the order of 1011 s−1.

    7. Rare-Earth Upconverting Nanobarcodes for Multiplexed Biological Detection (pages 1972–1976)

      Fan Zhang, Robert C. Haushalter, Robert W. Haushalter, Yifeng Shi, Yichi Zhang, Kunlun Ding, Dongyuan Zhao and Galen D. Stucky

      Article first published online: 4 JUL 2011 | DOI: 10.1002/smll.201100629

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      Rare-earth upconversion nanobarcodes (UPNBs) have been developed for multi­plexed signaling. There is no optical cross talk between the upconversion optical code and any reporter dyes. The midrange IR radiation used to excite the upconversion materials does not excite dyes that absorb in the visible and UV region and, conversely, the upconversion materials are not excited by the visible lasers used to excite the organic dyes.

    8. Hybridization-Induced “Off-On” 19F-NMR Signal Probe Release from DNA-Functionalized Gold Nanoparticles (pages 1977–1981)

      Alexander Kieger, Michael J. Wiester, Daniel Procissi, Todd B. Parrish, Chad A. Mirkin and C. Shad Thaxton

      Article first published online: 10 JUN 2011 | DOI: 10.1002/smll.201100566

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      Fluorine-19-DNA-functionalized gold nanoparticles (19F-DNA AuNPs) are demonstrated to provide a 19F-NMR off–on switch in response to target-specific DNA hybridization events. AuNP-bound 19F-DNA produces a low intensity signal that is undetectable above background. Upon complementary DNA hybridization and subsequent19F-DNA release, the 19F-NMR signal becomes detectable. This method has the potential to be used both in vitro and in vivo to non-invasively detect and image specific nucleic acid binding events of interest.

    9. Acrylate-Facilitated Cellular Uptake of Gold Nanoparticles (pages 1982–1986)

      Željka Krpetić, Paola Nativo, Ian A. Prior and Mathias Brust

      Article first published online: 7 JUN 2011 | DOI: 10.1002/smll.201100462

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      Uptake of PEGylated gold nanoparticles by HeLa cells in the presence of acrylate is described. Nanoparticles that are usually not taken up readily cross the plasma membrane into the cytosol in the presence of acrylate. In addition, a method is described that allows the introduction of large amounts of pre-aggregated gold nanoparticles into the cells without compromising the cell viability.

    10. EcoRI-Modified Gold Nanoparticles for Dual-Mode Colorimetric Detection of Magnesium and Pyrophosphate Ions (pages 1987–1992)

      Hongbo Wang, Wei Xu, Hao Zhang, Dawei Li, Zhaoqi Yang, Xiaoji Xie, Tianhu Li and Xiaogang Liu

      Article first published online: 14 JUN 2011 | DOI: 10.1002/smll.201100470

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      Rapid colorimetric detection of magnesium ions is demonstrated via a convenient approach, based on EcoRI-modified gold nanoparticles and a specifically designed DNA duplex. EcoRI is an enzyme obtained from certain strains of Escherichia coli.

    11. Optical Detection of Protein in Complex Media with Plasmonic Nanoparticle Dimers (pages 1993–1997)

      Jennifer I. L. Chen, Heather Durkee, Beth Traxler and David S. Ginger

      Article first published online: 14 JUN 2011 | DOI: 10.1002/smll.201100617

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      Actuatable gold nanoparticle dimers for protein sensing are presented. By monitoring the spectral blue shift in the hybridized bonding plasmon mode instead of the conventional refractive index changes on a single nanoparticle, dimers are shown to be able to detect target protein even in the presence of high levels of nonspecific binding in complex media such as serum.

    12. Influence of Nanostructure Morphology on Host Capacity and Kinetics of Guest Release (pages 1998–2003)

      Nam S. Lee, Lily Yun Lin, William L. Neumann, John N. Freskos, Amolkumar Karwa, Jeng J. Shieh, Richard B. Dorshow and Karen L. Wooley

      Article first published online: 16 JUN 2011 | DOI: 10.1002/smll.201100567

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      Morphology-dependent drug loading capacities and release kinetics are observed from pH-responsive diblock copolymer-based nano-objects, derived from the same block copolymer precursor. Shell-crosslinked, rod-shaped nanostructures exhibit a higher doxorubicin-loading capacity and rate of release than do their spherical counterparts. The extent of crosslinking and the type of crosslinker is also demonstrated to affect the rate of release.

    13. Helical Assemblies of Gold Nanoparticles (pages 2004–2009)

      G. Daniel Lilly, Ashish Agarwal, Sudhanshu Srivastava and Nicholas A. Kotov

      Article first published online: 22 JUN 2011 | DOI: 10.1002/smll.201100536

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      Chiral metallic nanohelices with periodicity in the submicrometer regime are made from twisted CdTe nanoribbons. These helices are highly effective in polarization rotation at wavelengths centered at their pitch length. Interestingly, the chiro-optical performance of helical nanoparticle assemblies is better than that of solid gold nanowires with similar geometries, which sets an important target for the design of metamaterials.

    14. Wet Nanoscale Imaging and Testing of Polymersomes (pages 2010–2015)

      Giuseppe Battaglia, Caterina LoPresti, Marzia Massignani, Nicholas J. Warren, Jeppe Madsen, Simon Forster, Cvetilin Vasilev, Jamie K. Hobbs, Steven P. Armes, Somoyot Chirasatitsin and Adam J. Engler

      Article first published online: 22 JUN 2011 | DOI: 10.1002/smll.201100511

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      A facile methodology for the immobilization of polymersomes is demo­nstrated using ad-hoc synthesized, biotinylated copolymers or commercially available biotinylated phospholipids on streptavidin-decorated substrates. This allows the imaging of polymersomes using high-resolution techniques such as stimulated emission depletion microscopy and atomic force microscopy. This latter allows the gathering of other important functional parameters such as mechanical properties and surface topology, enabling characterization of these water-borne nanoparticles in wet conditions and hence in their natural environment.

    15. Using Charge to Control the Functional Properties of Self-Assembled Nanopores in Membranes (pages 2016–2020)

      Michael X. Macrae, Diana Schlamadinger, Judy E. Kim, Michael Mayer and Jerry Yang

      Article first published online: 31 MAY 2011 | DOI: 10.1002/smll.201100394

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      Light sensitive, semisynthetic ion channels allow for the modulation of multi­ple channel properties. Covalent attachment of a photoswitchable spiropyran group to the entrance of a gramicidin A ion channel enables reversible control of both conductance and channel lifetime, which show opposite trends in behavior at high and low salt concentrations.

    16. Multicomponent DNA-Templated Nanoparticle Chains with Controllable Dimension and Composition (pages 2021–2026)

      Pengfei Wang, Hamsa Jaganathan and Albena Ivanisevic

      Article first published online: 31 MAY 2011 | DOI: 10.1002/smll.201100067

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      Multicomponent DNA-templated nanoparticle chains with controllable dimension and composition are fabricated by joining nanoparticle (NP)-coated DNA fragments with asymmetric sticky overhangs in a specific pattern. Nuclear magnetic resonance spectroscopy is used to investigate the proton relaxation properties for two- segmented multicomponent structures. The position, composition, and the pattern of the NP chains has an influence on proton relaxation.

    17. Growth Inhibition of Staphylococcus aureus by Mixed Monolayer Gold Nanoparticles (pages 2027–2031)

      Jamee Bresee, Keith E. Maier, Amy E. Boncella, Christian Melander and Daniel L. Feldheim

      Article first published online: 1 JUN 2011 | DOI: 10.1002/smll.201100420

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      A library of 120 nanoparticle conjugates is produced by simple one-pot thiol exchange reactions. The antibiotic activity of the conjugates toward Staphylococcus aureus is found to depend upon the combination of thiols assembled on the nanoparticles.

    18. Optical Properties of Tipless Gold Nanopyramids (pages 2032–2036)

      Christina M. Sweeney, Christopher L. Stender, Colleen L. Nehl, Warefta Hasan, Kevin L. Shuford and Teri W. Odom

      Article first published online: 9 JUN 2011 | DOI: 10.1002/smll.201100758

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      Small structural changes in the shape of nanostructures have profound effects on their optical properties. As the tip of Au nanopyramidal shells is removed, the complex plasmon modes shifted to lower wavelengths.

    19. Templated Synthesis of Shape-Controlled, Ordered TiO2 Cage Structures (pages 2037–2040)

      Yonghui Deng, Harun Tüysüz, Joel Henzie and Peidong Yang

      Article first published online: 14 JUN 2011 | DOI: 10.1002/smll.201100579

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      Based on a combination of colloidal self-assembly and atomic layer deposition, a facile approach is developed to create novel, high-quality, ordered cage structures of anatase TiO2 with shape and morphology control using Ag nanocrystals of different shapes as templates.

    20. A Morphology-Dependent Bio-organic Template for Inorganic Nanowire Synthesis (pages 2041–2046)

      Miao-Ping Chien and Nathan C. Gianneschi

      Article first published online: 16 JUN 2011 | DOI: 10.1002/smll.201101014

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      Morphology-dependent templates for crystalline Au nanowire synthesis are prepared from programmable DNA–block-copolymer micelles, in which DNA serves as the polar head group of amphiphilic polymers. Intriguingly, successful templation depends on the morphology of the micelles, with nanowire formation only observed in the case where the soft template is in the ordered cylindrical phase.

  8. Full Papers

    1. Top of page
    2. Cover Picture
    3. Inside Front Cover
    4. Editorial
    5. Contents
    6. Reviews
    7. Frontispiece
    8. Communications
    9. Full Papers
    1. Hybrid Nanomotor: A Catalytically/Magnetically Powered Adaptive Nanowire Swimmer (pages 2047–2051)

      Wei Gao, Kalayil Manian Manesh, Joe Hua, Sirilak Sattayasamitsathit and Joseph Wang

      Article first published online: 31 MAY 2011 | DOI: 10.1002/smll.201100213

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      The design and dual-mode locomotion of a parallel hybrid nanowire motor, powered by two sources–chemical and magnetic–are described. The hybrid nanomotor relies on a multisegment nanowire, with different portions responsible for catalytic and magnetic propulsion. Such hybrid nanomotors hold promise for the design of self-regulated nanovehicles that adapt their operation according to unexpected events.

    2. Tumor Targeting and Imaging Using Cyclic RGD-PEGylated Gold Nanoparticle Probes with Directly Conjugated Iodine-125 (pages 2052–2060)

      Young-Hwa Kim, Jongho Jeon, Su Hyun Hong, Won-Kyu Rhim, Yun-Sang Lee, Hyewon Youn, June-Key Chung, Myung Chul Lee, Dong Soo Lee, Keon Wook Kang and Jwa-Min Nam

      Article first published online: 20 JUN 2011 | DOI: 10.1002/smll.201100927

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      Highly stable and tumor-specific SPECT/CT imaging nanoparticle probes are described. Cyclic RGD-PEGlyated gold nanoparticle probes with directly conjugated iodine-125 can specifically target αvβ3 integrin-expressing tumor cells and can be taken up by tumor cells via integrin αvβ3-receptor-mediated endocytosis with almost no cytotoxicity. The probes can target tumor sites in vivo only 10 min after intravenous injection. These probes can be excreted after tumor targeting.

    3. Cisplatin-Loaded Porous Si Microparticles Capped by Electroless Deposition of Platinum (pages 2061–2069)

      Jennifer S. Park, Joseph M. Kinsella, Danielle D. Jandial, Stephen B. Howell and Michael J. Sailor

      Article first published online: 1 JUN 2011 | DOI: 10.1002/smll.201100438

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      Porous silicon-based microparticles are used to load cisplatin, an anti-cancer drug, using reductive chemistry that caps the drug into the pores by partially converting cisplatin into metallic platinum. Cellular toxicity with ovarian cancer cells demonstrates an enhanced toxic effect in comparison to free drugs.

    4. Self-Assembly of Hydrophilic Homopolymers: A Matter of RAFT End Groups (pages 2070–2080)

      Jianzhong Du, Helen Willcock, Joseph P. Patterson, Ian Portman and Rachel K. O'Reilly

      Article first published online: 7 JUN 2011 | DOI: 10.1002/smll.201100382

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      The remarkable effect of end groups on the self-assembly of RAFT hydrophilic homopolymers is explored. These hydrophobically end-functionalized homopolymers assemble in solution to afford well-defined aggregates, which are characterized by dynamic and static light scattering and transmission electron microscopy.

    5. Measurement of Mass Transfer during Dip-Pen Nanolithography with Phospholipids (pages 2081–2086)

      Soma Biswas, Michael Hirtz and Harald Fuchs

      Article first published online: 8 JUN 2011 | DOI: 10.1002/smll.201100381

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      The amount of lipid ink transferred during dip-pen lithography (DPN) is determined by measuring the harmonic oscillation of the microcantilever used for lithography before and after the writing process. From the measured frequency shift, picogram mass sensitivity is obtained for the determination of transferred lipid mass.

    6. Anodic Deposition of Colloidal Iridium Oxide Thin Films from Hexahydroxyiridate(IV) Solutions (pages 2087–2093)

      Yixin Zhao, Nella M. Vargas-Barbosa, Emil A. Hernandez-Pagan and Thomas E. Mallouk

      Article first published online: 16 JUN 2011 | DOI: 10.1002/smll.201100485

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      The facile anodic deposition of colloidal iridium oxide (IrOx·nH2O) thin films from [Ir(OH)6]2− solutions is described. The stable IrOx·nH2O nanoparticle films exhibit the lowest-reported overpotential, 0.20 V at 1.5 mA cm−2 current density, for the oxygen evolution reaction (OER) and have an exchange current density for the OER of 4–8 × 10−10 A cm −2 at a 4 mC cm−2 coverage of electroactive Ir.

    7. Polymer Nanoneedle-Mediated Intracellular Drug Delivery (pages 2094–2100)

      Poornima Kolhar, Nishit Doshi and Samir Mitragotri

      Article first published online: 22 JUN 2011 | DOI: 10.1002/smll.201100497

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      Intracellular delivery using needles: Needle-shaped particles made from a biodegradable polymer, PLGA, are shown to deliver siRNA into cells with minimal toxicity. The particles lead to higher intracellular delivery compared to spheres by direct penetration into the cell membrane resulting in higher gene knockdown. The particles are engineered to switch to spherical shape on demand mitigating the toxicity due to continuous permeabilization.

    8. Single-Molecule Colocalization Studies Shed Light on the Idea of Fully Emitting versus Dark Single Quantum Dots (pages 2101–2108)

      Thomas Pons, Igor L. Medintz, Dorothy Farrell, Xiang Wang, Amy F. Grimes, Douglas S. English, Lorenzo Berti and Hedi Mattoussi

      Article first published online: 28 JUN 2011 | DOI: 10.1002/smll.201100802

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      The coexistance of permanently “dark” and emitting quantum dots (QD) is established using the correlation between the enhancement in the QD photoemission yield that occurs when self-assembled with polyhistidine-appended proteins and the fraction of individual “bright” QDs in a macroscopic sample.

    9. Polymersome-Loaded Capsules for Controlled Release of DNA (pages 2109–2119)

      Hannah Lomas, Angus P. R. Johnston, Georgina K. Such, Zhiyuan Zhu, Kang Liang, Martin P. Van Koeverden, Siripong Alongkornchotikul and Frank Caruso

      Article first published online: 4 JUL 2011 | DOI: 10.1002/smll.201100744

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      A layer-by-layer capsule system subcompartmentalized with pH-responsive polymersomes loaded with Cy5-labeled plasmid DNA is formed for use as a novel drug-delivery carrier for the controlled release of DNA. The DNA is released from the capsules in response to pH changes between physiological and endocytic conditions.

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