Sunday, October 28, 2012

High-Throughput Printing via Microvascular Multinozzle Arrays


  1. Christopher J. Hansen1
  2. Rajat Saksena2,
  3. David B. Kolesky1
  4. John J. Vericella1,
  5. Stephen J. Kranz1
  6. Gregory P. Muldowney3,
  7. Kenneth T. Christensen2
  8. Jennifer A. Lewis1,*
Article first published online: 26 OCT 2012
DOI: 10.1002/adma.201203321


Microvascular multinozzle arrays are designed and fabricated for high-throughput printing of functional materials. Ink-flow uniformity within these multigeneration, bifurcating microchannel arrays is characterized by computer modeling and microscopic particle image velocimetry (micro-PIV) measurements. Both single and dual multinozzle printheads are produced to enable rapid printing of multilayered periodic structures over large areas (≈1 m2).

3D Chemical Image using TOF-SIMS Revealing the Biopolymer Component Spatial and Lateral Distributions in Biomass


  1. Seokwon Jung1
  2. Dr. Marcus Foston1,3
  3. Dr. Udaya C. Kalluri2
  4. Dr. Gerald A. Tuskan2,
  5. Prof. Dr. Arthur J. Ragauskas1,*
Article first published online: 25 OCT 2012
DOI: 10.1002/anie.201205243


Show me inside: 3D time-of-flight secondary-ion mass spectrometry (TOF-SIMS) with a dual-beam mode allows detecting the characteristic biopolymers from surface to subsurface in plant cell walls. Lateral and vertical distribution of major components can thereby be mapped to understand the structural architecture of plant cell walls at under sub-micrometer scales (see picture: green=cellulose, red=lignin).

Single-Crystalline Octahedral Au–Ag Nanoframes


Department of Chemistry and State Key Laboratory of Low-Dimensional Quantum Physics, Tsinghua University, Beijing 100084, China
J. Am. Chem. Soc., Article ASAP
DOI: 10.1021/ja3076132
Publication Date (Web): October 22, 2012
Copyright © 2012 American Chemical Society



We report the formation of single-crystalline octahedral Au–Ag nanoframes by a modified galvanic replacement reaction. Upon sequential addition of AgNO3, CuCl, and HAuCl4 to octadecylamine solution, truncated polyhedral silver nanoparticles formed first and then changed into octahedral Au–Ag nanoframes, without requiring a conventional Ag removal step with additional oxidation etchant. The nanoframes have 12 sides, and all of the eight {111} faces are empty. The side grows along the [110] direction, and the diameter is less than 10 nm. The selective gold deposition on the high-energy (110) surface, the diffusion, and the selective redeposition of Au and Ag atoms are the key reasons for the formation of octahedral nanoframes.

Shape-selective sieving layers on an oxide catalyst surface


  • Nature Chemistry
     
    (2012)
     
    doi:10.1038/nchem.1477
    Received
     
    Accepted
     
    Published online
     
  • Versatile nanomop


    doi:10.1038/nindia.2012.157; Published online 25 October 2012 

    Researchers have synthesized a new kind of curcumin-modified nanocomposite that inhibits the growth of cervical cancer cells and breaks down methylene blue (MB), a potentially harmful chemical in the presence of visible irradiation.1
    Composite nanomaterials have shown promise as drug carriers and cancer killer

    Sunday, October 21, 2012

    Surface Plasmon Resonance Chemical Sensing on Cell Phones


    1. Pakorn Preechaburana1,2,*
    2. Marcos Collado Gonzalez1
    3. Dr. Anke Suska1
    4. Dr. Daniel Filippini1,*
    Article first published online: 16 OCT 2012
    DOI: 10.1002/anie.201206804

    Chemosensing based on angle-resolved surface plasmon resonance is demonstrated on intact cell phones using a disposable optical coupler and software to configure illumination and acquisition. This coupler operates on different cell phones and is applied for classical affinity assays with commercial chips and custom-made tests with embedded calibration. Measured performance (2.14x10−6 refractive index units) is comparable with compact SPR systems.

    Inkjet Printing Assisted Synthesis of Multicomponent Mesoporous Metal Oxides for Ultrafast Catalyst Exploration


     Department of Chemistry, Zhejiang University, Hangzhou, Zhejiang Province 310027, China
     Department of Mathematics, Zhejiang University, Hangzhou, Zhejiang Province 310027, China
    § Institute for Collaborative Biotechnologies, University of California, Santa Barbara, California 93106, United States
     Department of Chemistry and Biochemistry, University of California, Santa Barbara, California 93106, United States
    Nano Lett., Article ASAP
    DOI: 10.1021/nl302992q
    Publication Date (Web): October 10, 2012
    Copyright © 2012 American Chemical Society

    We describe an inkjet printing assisted cooperative-assembly method for high-throughput generation of catalyst libraries (multicomponent mesoporous metal oxides) at a rate of 1 000 000-formulations/hour with up to eight-component compositions. The compositions and mesostructures of the libraries can be well-controlled and continuously varied. Fast identification of an inexpensive and efficient quaternary catalyst for photocatalytic hydrogen evolution is achieved via a multidimensional group testing strategy to reduce the number of performance validation experiments (25 000-fold reduction over an exhaustive one-by-one search).

    Resolving Sub-Molecular Binding and Electrical Switching Mechanisms of Single Proteins at Electroactive Conducting Polymers


    1. A. Gelmi, 
    2. M. J. Higgins*
    3. G. G. Wallace*
    Article first published online: 17 OCT 2012
    DOI: 10.1002/smll.201201686

    Polymer-based electrodes for interfacing biological tissues are becoming increasingly sophisticated. Their many functions place them at the cross-roads of electromaterials, biomaterials, and drug-delivery systems. For conducting polymers, the mechanism of conductivity requires doping with anionic molecules such as extracellular matrix molecules, a process that distinguishes them as biomaterials and provides a means to control interactions at the cellular–electrode interface. However, due to their complex structure, directly observing the selective binding of target molecules or proteins has so far eluded researchers. This situation is compounded by the polymer's ability to adopt different electronic states that alter the polymer–dopant interactions. Here, the ability to resolve sub-molecular binding specificity between sulfate and carboxyl groups of dopants and heparin binding domains of human plasma fibronectin is demonstrated. The interaction exploits a form of biological ‘charge complementarity’ to enable specificity. When an electrical signal is applied to the polymer, the specific interaction is switched to a non-specific, high-affinity binding state that can be reversibly controlled using electrochemical processes. Both the specific and non-specific interactions are integral for controlling protein conformation and dynamics. These details, which represent the first direct measurement of biomolecular recognition between a single protein and any type of organic conductor, give new molecular insight into controlling cellular interactions on these polymer surfaces.

    In Situ Control of Cell Substrate Microtopographies Using Photolabile Hydrogels


    1. Chelsea M. Kirschner1
    2. Kristi S. Anseth1,2,3,*
    Article first published online: 17 OCT 2012
    DOI: 10.1002/smll.201201841

    Substratum topography can play a significant role in regulating cellular function and fate. To study cellular responses to biophysical cues, researchers have developed dynamic methods for controlling cell morphology; however, many of these platforms are limited to one transition between two predefined substratum topographies. To afford the user additional control over the presentation of microtopographic cues to cell populations, a photolabile, PEG-based hydrogel system is presented in which precisely engineered topographic cues can be formed in situ by controlled erosion. Here, the ability to produce precisely engineered static microtopographies in the hydrogel surface is first established. Human mesenchymal stem cell (hMSC) response to topographies with features of subcellular dimensions (∼5 to 40 μm) and with various aspect ratios increasing from 1:1 to infinity (e.g., channels) are quantified, and the dynamic nature of the culture system is demonstrated by sequentially presenting a series of topographies through in situ modifications and quantifying reversible changes in cell morphology in response to substratum topographies altered in real time.

    Multi-Fuel Driven Janus Micromotors


    1. Wei Gao, 
    2. Mattia D'Agostino, 
    3. Victor Garcia-Gradilla, 
    4. Jahir Orozco, 
    5. Joseph Wang*
    Article first published online: 11 OCT 2012
    DOI: 10.1002/smll.201201864

    Here the first example of a chemically powered micromotor that harvests its energy from the reactions of three different fuels is presented. The new Al/Pd Janus microspheres—prepared by depositing a Pd layer on one side of Al microparticles—are propelled efficiently by the thrust of hydrogen bubbles generated from different reactions of Al in strong acidic and alkaline environments, and by an oxygen bubble thrust produced at their partial Pd coating in hydrogen peroxide media. High speeds and long lifetimes of 200 μm s−1 and 8 min are achieved in strong alkaline media and acidic media, respectively. The ability to autonomously adapt to the presence of a new fuel (surrounding environment), without compromising the propulsion behavior is illustrated. These data also represent the first example of a chemically powered micromotor that propels autonomously and efficiently in alkaline environments (pH > 11) without additional fuels. The ability to use multiple fuel sources to power the same micromotor offers a broader scope of operation and considerable promise for diverse applications of micromotors in different chemical environments.

    Sunday, October 14, 2012

    Construction of a 4 Zeptoliters Switchable 3D DNA Box Origami

    Department of Molecular Biology and Genetics, Danish National Research Foundation: Centre for DNA Nanotechnology (CDNA) and § Interdisciplinary Nanoscience Center (iNANO), Aarhus University, DK-8000 Aarhus, Denmark
    ACS Nano, Article ASAP
    DOI: 10.1021/nn303767b
    Publication Date (Web): October 2, 2012
    Copyright © 2012 American Chemical Society
    The DNA origami technique is a recently developed self-assembly method that allows construction of 3D objects at the nanoscale for various applications. In the current study we report the production of a 18 × 18 × 24 nm3 hollow DNA box origami structure with a switchable lid. The structure was efficiently produced and characterized by atomic force microscopy, transmission electron microscopy, and Förster resonance energy transfer spectroscopy. The DNA box has a unique reclosing mechanism, which enables it to repeatedly open and close in response to a unique set of DNA keys. This DNA device can potentially be used for a broad range of applications such as controlling the function of single molecules, controlled drug delivery, and molecular computing.
     

    Breathing” Vesicles with Jellyfish-like On–Off Switchable Fluorescence Behavior†

    1. Dr. Ruijiao Dong1,
    2. Prof. Bangshang Zhu2,
    3. Prof. Yongfeng Zhou1,*,
    4. Deyue Yan1,
    5. Xinyuan Zhu1,2,*
    Article first published online: 12 OCT 2012
    DOI: 10.1002/anie.201206362
    Controlled, deep breathing: Polymeric vesicles that exhibit reversible pH-induced “breathing” behavior accompanied by switchable fluorescence (see picture) were prepared through the aqueous self-assembly of an amphiphilic block copolymer. Mechanistic studies showed that this jellyfish-like breathing and light-emitting behavior originates from protonation- or deprotonation-induced changes in the conformation of the azobenzene chromophores.


    Light-Emitting Electrochemical “Swimmers

    1. Milica Sentic1,2,
    2. Gabriel Loget1,
    3. Prof. Dragan Manojlovic2,
    4. Prof. Alexander Kuhn1,
    5. Prof. Neso Sojic1,*
    Article first published online: 8 OCT 2012
    DOI: 10.1002/anie.201206227

      Propulsion of a conducting object is intrinsically coupled with light emission using bipolar electrochemistry. Asymmetric redox activity on the surface of the swimmer (black bead; see picture) causes production of gas bubbles to propel the swimmer in a glass tube with simultaneous electrochemiluminescence (ECL) emission to monitor the progress of the swimmer.

    The Right Choice?

     Science
    Vol. 338 no. 6104 p. 169
    DOI: 10.1126/science.338.6104.169-g


    Every day people make new choices between alternatives that they have never directly experienced. Yet, such decisions are often made rapidly and confidently. Here, we show that the hippocampus, traditionally known for its role in building long-term declarative memories, enables the spread of value across memories, thereby guiding decisions between new choice options. Using functional brain imaging in humans, we discovered that giving people monetary rewards led to activation of a preestablished network of memories, spreading the positive value of reward to nonrewarded items stored in memory. Later, people were biased to choose these nonrewarded items. This decision bias was predicted by activity in the hippocampus, reactivation of associated memories, and connectivity between memory and reward regions in the brain. These findings explain how choices among new alternatives emerge automatically from the associative mechanisms by which the brain builds memories. Further, our findings demonstrate a previously unknown role for the hippocampus in value-based decisions.

    Feeling the Light


    Phototransduction in Drosophila microvillar photoreceptor cells is mediated by a G protein–activated phospholipase C (PLC). PLC hydrolyzes the minor membrane lipid phosphatidylinositol 4,5-bisphosphate (PIP2), leading by an unknown mechanism to activation of the prototypical transient receptor potential (TRP) and TRP-like (TRPL) channels. We found that light exposure evoked rapid PLC-mediated contractions of the photoreceptor cells and modulated the activity of mechanosensitive channels introduced into photoreceptor cells. Furthermore, photoreceptor light responses were facilitated by membrane stretch and were inhibited by amphipaths, which alter lipid bilayer properties. These results indicate that, by cleaving PIP2, PLC generates rapid physical changes in the lipid bilayer that lead to contractions of the microvilli, and suggest that the resultant mechanical forces contribute to gating the light-sensitive channels.

     Science
    Vol. 338 no. 6104 pp. 260-263
    DOI: 10.1126/science.1222376

     

    Functionalized multiwalled carbon nanotubes as ultrasound contrast agents

    1.   PNAS vol. 109 no. 41 16612-16617  
    2. Ultrasonography is a fundamental diagnostic imaging tool in everyday clinical practice. Here, we are unique in describing the use of functionalized multiwalled carbon nanotubes (MWCNTs) as hyperechogenic material, suggesting their potential application as ultrasound contrast agents. Initially, we carried out a thorough investigation to assess the echogenic property of the nanotubes in vitro. We demonstrated their long-lasting ultrasound contrast properties. We also showed that ultrasound signal of functionalized MWCNTs is higher than graphene oxide, pristine MWCNTs, and functionalized single-walled CNTs. Qualitatively, the ultrasound signal of CNTs was equal to that of sulfur hexafluoride (SonoVue), a commercially available contrast agent. Then, we found that MWCNTs were highly echogenic in liver and heart through ex vivo experiments using pig as an animal model. In contrast to the majority of ultrasound contrast agents, we observed in a phantom bladder that the tubes can be visualized within a wide variety of frequencies (i.e., 5.5–10 MHz) and 12.5 MHz using tissue harmonic imaging modality. Finally, we demonstrated in vivo in the pig bladder that MWCNTs can be observed at low frequencies, which are appropriate for abdominal organs. Importantly, we did not report any toxicity of CNTs after 7 d from the injection by animal autopsy, organ histology and immunostaining, blood count, and chemical profile. Our results reveal the enormous potential of CNTs as ultrasound contrast agents, giving support for their future applications as theranostic nanoparticles, combining diagnostic and therapeutic modalities.

    Sunday, October 7, 2012

    Reading Disc-Based Bioassays with Standard Computer Drives


    Hua-Zhong Yu *Yunchao Li *, and Lily M.-L. Ou 
     Department of Chemistry, Simon Fraser University, Burnaby, British Columbia V5A 1S6, Canada
     Department of Chemistry, Beijing Normal University, Beijing 100875, People's Republic of China
    Acc. Chem. Res., Article ASAP
    DOI: 10.1021/ar300104b
    Publication Date (Web): October 1, 2012
    Copyright © 2012 American Chemical Society

    Traditional methods of disease diagnosis are both time-consuming and labor-intensive, and many tests require expensive instrumentation and trained professionals, which restricts their use to biomedical laboratories. Because patients can wait several days (even weeks) for the results, the consequences of delayed treatment could be disastrous. Therefore, affordable and simple point-of-care (POC) biosensor devices could fill a diagnostic niche in the clinic or even at home, as personal glucose meters do for diabetics. These devices would allow patients to check their own health conditions and enable physicians to make prompt treatment decisions, which could improve the chances for rapid recovery and cure.
    Compact discs (CDs) provide inexpensive substrate materials for the preparation of microarray biochips, and conventional computer drives/disc players can be adapted as precise optical reading devices for signal processing. Researchers can employ the polycarbonate (PC) base of a CD as an alternative substrate to glass slides or silicon wafers for the preparation of microanalytical devices. Using the characteristic optical phenomena occurring on the metal layer of a CD, researchers can develop biosensors based on advanced spectroscopic readout (interferometry or surface plasmon resonance). If researchers integrate microfluidic functions with CD mechanics, they can control fluid transfer through the spinning motion of the disc, leading to “lab-on-a-CD” devices.
    Over the last decade, our laboratory has focused on the construction of POC biosensor devices from off-the-shelf CDs or DVDs and standard computer drives. Besides the initial studies of the suitability of CDs for surface and materials chemistry research (fabrication of self-assembled monolayers and oxide nanostructures), we have demonstrated that an ordinary optical drive, without modification of either the hardware or the software driver, can function as the signal transducing element for reading disc-based bioassays quantitatively.
    In this Account, we first provide a brief introduction to CD-related materials chemistry and microfluidics research. Then we describe the mild chemistry developed in our laboratory for the preparation of computer-readable biomolecular screening assays: photochemical activation of the polycarbonate (PC) disc surface and immobilization and delivery of probe and target biomolecules. We thoroughly discuss the analysis of the molecular recognition events: researchers can “read” these devices quantitatively with an unmodified optical drive of any personal computer. Finally, and critically, we illustrate our digitized molecular diagnosis approach with three trial systems: DNA hybridization, antibody–antigen binding, and ultrasensitive lead detection with a DNAzyme assay. These examples demonstrate the broad potential of this new analytical/diagnostic tool for medical screening, on-site food/water safety testing, and remote environmental monitoring.