Science: July 2012

Sunday, July 22, 2012

Aerographite: Ultra Lightweight, Flexible Nanowall, Carbon Microtube Material with Outstanding Mechanical Performance

Matthias Mecklenburg¹,

Arnim Schuchardt²,

Yogendra Kumar Mishra²,

Sören Kaps²,

Rainer Adelung^2,*,

Andriy Lotnyk^3,†,

Lorenz Kienle³,

Karl Schulte¹

^{Article first published online: 12 JUN 2012

DOI: 10.1002/adma.201200491

An ultra lightweight carbon microtube material called Aerographite is synthesized by a novel single-step chemical vapor deposition synthesis based on ZnO networks, which is presently the lightest known material with a density smaller than μg/cm³. Despite its low density, the hierarchical design leads to remarkable mechanical, electrical, and optical properties. The first experiments with Aerographite electrodes confirm its applicability.}

Self-Replenishing Surfaces

T. Dikić²,

W. Ming³,

R. A. T. M. van Benthem⁴,

A. C. C. Esteves⁵,

G. de With^1,*

Article first published online: 14 JUN 2012

DOI: 10.1002/adma.201200807

Damaged surfaces self-replenish their chemical composition by the spontaneous re-orientation of functional groups chemically bonded to the polymer network. The repair of the surface chemistry leads to the recovery of surface functionality. This self-replenishing approach is suitable to recover many surface-related properties and constitutes a major breakthrough in extending the service life-time of functional materials.

A Whole-Cell Computational Model Predicts Phenotype from Genotype

Jonathan R. Karr¹^,⁴,

Jayodita C. Sanghvi²^,⁴,

Derek N. Macklin²,

Miriam V. Gutschow²,

Jared M. Jacobs²,

Benjamin Bolival Jr.²,

Nacyra Assad-Garcia³,

John I. Glass³,

Markus W. Covert²^,

Corresponding author contact information

¹ Graduate Program in Biophysics, Stanford University, Stanford, CA 94305, USA
² Department of Bioengineering, Stanford University, Stanford, CA 94305, USA
³ J. Craig Venter Institute, Rockville, MD 20850, USA

Received 8 March 2012. Revised 20 April 2012. Accepted 14 May 2012. Available online 19 July 2012. Published: July 19

Understanding how complex phenotypes arise from individual molecules and their interactions is a primary challenge in biology that computational approaches are poised to tackle. We report a whole-cell computational model of the life cycle of the human pathogen Mycoplasma genitalium that includes all of its molecular components and their interactions. An integrative approach to modeling that combines diverse mathematics enabled the simultaneous inclusion of fundamentally different cellular processes and experimental measurements. Our whole-cell model accounts for all annotated gene functions and was validated against a broad range of data. The model provides insights into many previously unobserved cellular behaviors, including in vivo rates of protein-DNA association and an inverse relationship between the durations of DNA replication initiation and replication. In addition, experimental analysis directed by model predictions identified previously undetected kinetic parameters and biological functions. We conclude that comprehensive whole-cell models can be used to facilitate biological discovery.

A tissue-engineered jellyfish with biomimetic propulsion

Janna C Nawroth,

Hyungsuk Lee,

Adam W Feinberg,

Crystal M Ripplinger,

Nature Biotechnology

(2012)

doi:10.1038/nbt.2269

Received: 07 December 2011
Accepted: 14 May 2012
Published online: 22 July 2012

Reverse engineering of biological form and function requires hierarchical design over several orders of space and time. Recent advances in the mechanistic understanding of biosynthetic compound materials^1, 2, 3, computer-aided design approaches in molecular synthetic biology^4, 5 and traditional soft robotics^6, 7, and increasing aptitude in generating structural and chemical microenvironments that promote cellular self-organization^8, 9, 10 have enhanced the ability to recapitulate such hierarchical architecture in engineered biological systems. Here we combined these capabilities in a systematic design strategy to reverse engineer a muscular pump. We report the construction of a freely swimming jellyfish from chemically dissociated rat tissue and silicone polymer as a proof of concept. The constructs, termed 'medusoids', were designed with computer simulations and experiments to match key determinants of jellyfish propulsion and feeding performance by quantitatively mimicking structural design, stroke kinematics and animal-fluid interactions. The combination of the engineering design algorithm with quantitative benchmarks of physiological performance suggests that our strategy is broadly applicable to reverse engineering of muscular organs or simple life forms that pump to survive.

Corking Carbon Nanotube Cups with Gold Nanoparticles

Yong Zhao, Yifan Tang, Yanan Chen, and AlexanderStar*

Department of Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, United States

ACS Nano, Article ASAP

DOI: 10.1021/nn3018443

Publication Date (Web): July 13, 2012

Nitrogen doping of carbon nanotubes during chemical vapor deposition synthesis can create unique stacked cup-shaped structures termed as nitrogen-doped carbon nanotube cups (NCNCs). These cups have semielliptical hollow cavities and elevated reactivity which could lead to various applications. In this work, by applying intense ultrasonication to the as-synthesized NCNCs, we demonstrated an effective mechanical method to isolate the individual cups with opened cavities from their stacks. The graphitic structures of the isolated cups and their inherent nitrogen functionalities were characterized by comprehensive microscopic and spectroscopic methods. In particular, we quantitatively determined the existence of amine functionalities on NCNCs and found that they were preferentially distributed at the open edges of the cups, providing localized reactive sites. Further, by thiolating the amine groups with 3-mercapto-propionic acid, we were able to effectively cork the isolated cups by gold nanoparticles with commensurate diameters. These cup-shaped carbon nanomaterials with controlled inner volumes and gold nanoparticle corks could find potential applications as nanoscale reaction containers or drug delivery vehicles.

Monday, July 16, 2012

The decades-long search for the Higgs

The discovery of the Higgs would be the start of a new era in physics. The puzzle is much bigger than just one particle; dark matter and dark energy and the possibility of supersymmetry will still beckon searchers even after the Standard Model is complete. Since the Higgs field is connected to all the other puzzles, we will not be able to solve them until we know its true nature. Is it the blue of the sea or the blue of the sky? Is it garden or pathway or building or boat? And how does it truly connect to the rest of the puzzle? The universe awaits.

Read more at: http://phys.org/news/2012-07-decades-long-higgs.html#jCp

Smart materials get SMARTer: Self-powered, homeostatic nanomaterials self-regulate in response to environmental change Read more at: http://phys.org/news/2012-07-smart-materials-smarter-self-powered-homeostatic

In the July 12 issue of Nature, a Harvard-led team of engineers presented a strategy for building self-thermoregulating nanomaterials that can, in principle, be tailored to maintain a set pH, pressure, or just about any other desired parameter by meeting the environmental changes with a compensatory chemical feedback response. Called SMARTS (Self-regulated Mechano-chemical Adaptively Reconfigurable Tunable System), this newly developed materials platform offers a customizable way to autonomously turn chemical reactions on and off and reproduce the type of dynamic self-powered feedback loops found in biological systems. The advance represents a step toward more intelligent and efficient medical implants and even dynamic buildings that could respond to the weather for increased energy efficiency. The researchers also expect that their methodology could have considerable potential for translation into areas such as robotics, computing, and healthcare.

Read more at: http://phys.org/news/2012-07-smart-materials-smarter-self-powered-homeostatic.html#jCp

1ms pan-tilt camera system tracks the flying balls

University of Japan researchers have worked on a camera system that tracks fast-moving objects in realtime, automatically keeping fast moving objects centered. The system can track fast-moving objects with high accuracy, called “amazing.” A video demo has been made that reveals their success. This is a pan-tilt system that keeps an object at the center of the field. The researchers started work based on a challenge they recognized in the broadcast of major sports events such as the World Cup and games at the Olympics, where videos that are powerful and of the highest quality are in demand.

Read more at: http://phys.org/news/2012-07-1ms-pan-tilt-camera-tracks-balls.html#jCp

http://www.k2.t.u-tokyo.ac.jp/mvf/SaccadeMirrorFullHD/index-e.html

Probing the Nature of Defects in Graphene by Raman Spectroscopy

Axel Eckmann†, Alexandre Felten‡§, ArtemMishchenko

, Liam Britnell

, Ralph Krupke§, Kostya S. Novoselov

, and Cinzia Casiraghi*†‡

^† School of Chemistry and Photon Science Institute,University of Manchester, United Kingdom

^‡ Physics Department, Freie Universität, Berlin, Germany

^§ Karlsruhe Institute of Technology, Karlsruhe, Germany

School of Physics and Astronomy,University of Manchester, United Kingdom

Nano Lett., Article ASAP

DOI: 10.1021/nl300901a

Publication Date (Web): July 5, 2012

Raman spectroscopy is able to probe disorder in graphene through defect-activated peaks. It is of great interest to link these features to the nature of disorder. Here we present a detailed analysis of the Raman spectra of graphene containing different type of defects. We found that the intensity ratio of the D and D′ peak is maximum (

13) for sp³-defects, it decreases for vacancy-like defects (

7), and it reaches a minimum for boundaries in graphite (

3.5). This makes Raman Spectroscopy a powerful tool to fully characterize graphene.

Separation of Nanoparticles in Aqueous Multiphase Systems through Centrifugation

Ozge Akbulut†, Charles R. Mace†, Ramses V.Martinez†, Ashok A. Kumar‡, Zhihong Nie†, Matthew R. Patton†, and George M. Whitesides*†§

^† Departments of Chemistry and Chemical Biology,Harvard University, 12 Oxford Street, Cambridge, Massachusetts 02138, United States

^‡ School of Engineering and Applied Sciences, Harvard University, 29 Oxford Street, Cambridge, Massachusetts 02138, United States

^§ Wyss Institute for Biologically Inspired Engineering,Harvard University, 60 Oxford Street, Cambridge, Massachusetts 02138, United States

Kavli Institute for Bionano Science and Technology, Harvard University, 29 Oxford Street, Cambridge, Massachusetts 02138, United States

Nano Lett., Article ASAP

DOI: 10.1021/nl301452x

Publication Date (Web): June 5, 2012

This paper demonstrates the use of aqueous multiphase systems (MuPSs) as media for rate-zonal centrifugation to separate nanoparticles of different shapes and sizes. The properties of MuPSs do not change with time or during centrifugation; this stability facilitates sample collection after separation. A three-phase system demonstrates the separation of the reaction products (nanorods, nanospheres, and large particles) of a synthesis of goldnanorods, and enriches the nanorods from 48 to 99% in less than ten minutes using a benchtop centrifuge.

Sunday, July 1, 2012

Rapid casting of patterned vascular networks for perfusable engineered three-dimensional tissues

& Christopher S. Chen

Nature Materials

(2012)

doi:10.1038/nmat3357

Received

25 October 2011

Accepted

15 May 2012

Published online

01 July 2012

In the absence of perfusable vascular networks, three-dimensional (3D) engineered tissues densely populated with cells quickly develop a necrotic core¹. Yet the lack of a general approach to rapidly construct such networks remains a major challenge for 3D tissue culture^2, 3, 4. Here, we printed rigid 3D filament networks of carbohydrate glass, and used them as a cytocompatible sacrificial template in engineered tissues containing living cells to generate cylindrical networks that could be lined with endothelial cells and perfused with blood under high-pressure pulsatile flow. Because this simple vascular casting approach allows independent control of network geometry, endothelialization and extravascular tissue, it is compatible with a wide variety of cell types, synthetic and natural extracellular matrices, and crosslinking strategies. We also demonstrated that the perfused vascular channels sustained the metabolic function of primary rat hepatocytes in engineered tissue constructs that otherwise exhibited suppressed function in their core.

Remotely Activated Protein-Producing Nanoparticles

Avi Schroeder†‡, Michael S. Goldberg†, ChristianKastrup†‡§, Yingxia Wang‡, Shan Jiang†‡, Brian J.Joseph‡, Christopher G. Levins†‡, Sneha T. Kannan†,Robert Langer†‡

, and Daniel G. Anderson*†‡

^†David H. Koch Institute for Integrative Cancer Research and ^‡Department of Chemical Engineering,Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States

^§ Michael Smith Laboratories and Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver V6T 1Z4 Canada

Harvard MIT Division of Health Science and Technology, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States

Nano Lett., 2012, 12 (6), pp 2685–2689

DOI: 10.1021/nl2036047

Publication Date (Web): March 20, 2012

The development of responsive nanomaterials, nanoscale systems that actively respond to stimuli, is one general goal of nanotechnology. Here we develop nanoparticles that can be controllably triggered to synthesize proteins. The nanoparticles consist of lipid vesicles filled with the cellular machinery responsible for transcription and translation, including amino acids, ribosomes, and DNA caged with a photolabile protecting group. These particles served as nanofactories capable of producing proteins including green fluorescent protein (GFP) and enzymatically active luciferase. In vitro and in vivo, protein synthesis was spatially and temporally controllable, and could be initiated by irradiating micrometer-scale regions on the time scale of milliseconds. The ability to control protein synthesis inside nanomaterials may enable new strategies to facilitate the study of orthogonal proteins in a confined environment and for remotely activated drug delivery.

On-chip manipulation of single microparticles, cells, and organisms using surface acoustic waves

Xiaoyun Ding^a,

Sz-Chin Steven Lin^a,

Brian Kiraly^a,

Hongjun Yue^b,

Sixing Li^c,

I-Kao Chiang^a,

Jinjie Shi^a,

Stephen J. Benkovic^b,¹, and

Tony Jun Huang^a,^c,¹

Published online before print June 25, 2012, doi:10.1073/pnas.1209288109PNAS June 25, 2012

Techniques that can dexterously manipulate single particles, cells, and organisms are invaluable for many applications in biology, chemistry, engineering, and physics. Here, we demonstrate standing surface acoustic wave based “acoustic tweezers” that can trap and manipulate single microparticles, cells, and entire organisms (i.e., Caenorhabditis elegans) in a single-layer microfluidic chip. Our acoustic tweezers utilize the wide resonance band of chirped interdigital transducers to achieve real-time control of a standing surface acoustic wave field, which enables flexible manipulation of most known microparticles. The power density required by our acoustic device is significantly lower than its optical counterparts (10,000,000 times less than optical tweezers and 100 times less than optoelectronic tweezers), which renders the technique more biocompatible and amenable to miniaturization. Cell-viability tests were conducted to verify the tweezers’ compatibility with biological objects. With its advantages in biocompatibility, miniaturization, and versatility, the acoustic tweezers presented here will become a powerful tool for many disciplines of science and engineering.