Biosynthesis of luminescent quantum dots in an earthworm

• S. R. Stürzenbaum,
• M. Höckner,
• A. Panneerselvam,
• J. Levitt,
• J-S. Bouillard,
• S. Taniguchi,
• L-A. Dailey,
• R. Ahmad Khanbeigi,
• E. V. Rosca,
• M. Thanou,
• K. Suhling,
• A. V. Zayats
• & M. Green

• Nature Nanotechnology

   

  8,

   

  57–60

   

  (2013)

   

  doi:10.1038/nnano.2012.232

  Received

   

  24 September 2012 

  Accepted

   

  16 November 2012 

  Published online

   

  23 December 2012

  
  

Not only do earthworms fertilize soil and help catch fish, but the wriggly creatures are also capable of manufacturing semiconductor nanoparticles called quantum dots, according to researchers at King’s College London (Nat. Nanotechnol., DOI:10.1038/nnano.2012.232). Scientists have previously biosynthesized nanoparticles by hijacking the cellular machinery inside bacteria, viruses, and fungi, but “we’re pretty sure this is the first time this has been intentionally achieved in a higher animal,” says Mark Green, who led the research team. To prove the worms capable of the feat, Green, Stephen R. Stürzenbaum, and coworkers put the animals in soil laced with cadmium chloride and sodium tellurite. When they later cut the worms open, they found 2-nm-diameter CdTe quantum dots. The researchers think the earthworms sequester the heavy metals as part of a detoxification mechanism. After harvesting the worm-made dots, the team demonstrated their utility as imaging agents: The particles are taken up by ovarian cancer cells and emit green light after being excited at blue wavelengths.

Electrical Method to Quantify Nanoparticle Interaction with Lipid Bilayers

Randy P. Carney †, Yann Astier ‡, Tamara M. Carney†, Kislon Voïtchovsky †, Paulo H. Jacob Silva †, andFrancesco Stellacci †*

^† Institute of Materials, École Polytechnique Fédérale de Lausanne, EPFL-STI-IMX-SuNMIL, Lausanne CH-1015, Switzerland

^‡ ITQB, Universidade Nova de Lisboa, Avenida Da Republica, Oeiras, Portugal

ACS Nano, Article ASAP

DOI: 10.1021/nn3036304

Publication Date (Web): December 26, 2012

Copyright © 2012 American Chemical 

Understanding as well as rapidly screening the interaction of nanoparticles with cell membranes is of central importance for biological applications such as drug and gene delivery. Recently, we have shown that “striped” mixed-monolayer-coated gold nanoparticles spontaneously penetrate a variety of cell membranes through a passive pathway. Here, we report an electrical approach to screen and readily quantify the interaction between nanoparticles and bilayer lipid membranes. Membrane adsorption is monitored through the capacitive increase of suspended planar lipid membranes upon fusion with nanoparticles. We adopt a Langmuir isotherm model to characterize the adsorption of nanoparticles by bilayer lipid membranes and extract the partition coefficient, K, and the standard free energy gain by this spontaneous process, for a variety of sizes of cell-membrane-penetrating nanoparticles. We believe that the method presented here will be a useful qualitative and quantitative tool to determine nanoparticle interaction with lipid bilayers and consequently with cell membranes.

A near-infrared fluorophore for live-cell super-resolution microscopy of cellular proteins

• Gražvydas Lukinavičius,
• Keitaro Umezawa,
• Nicolas Olivier,
• Alf Honigmann,
• Guoying Yang,
• Tilman Plass,
• Veronika Mueller,
• Luc Reymond,
• Ivan R. Corrêa Jr,
• Zhen-Ge Luo,
• Carsten Schultz,
• Edward A. Lemke,
• Paul Heppenstall,
• Christian Eggeling,
• Suliana Manley
• & Kai Johnsson

• 
  

The ideal fluorescent probe for bioimaging is bright, absorbs at long wavelengths and can be implemented flexibly in living cells and in vivo. However, the design of synthetic fluorophores that combine all of these properties has proved to be extremely difficult. Here, we introduce a biocompatible near-infrared silicon–rhodamine probe that can be coupled specifically to proteins using different labelling techniques. Importantly, its high permeability and fluorogenic character permit the imaging of proteins in living cells and tissues, and its brightness and photostability make it ideally suited for live-cell super-resolution microscopy. The excellent spectroscopic properties of the probe combined with its ease of use in live-cell applications make it a powerful new tool for bioimaging.

Stimuli Responsive Materials: Biopsy with Thermally-Responsive Untethered Microtools

1. Evin Gultepe¹, 
2. Jatinder S. Randhawa¹,
3. Sachin Kadam¹, 
4. Sumitaka Yamanaka²,
5. Florin M. Selaru², 
6. Eun J. Shin², 
7. Anthony N. Kalloo², 
8. David H. Gracias^1,3

1. 
   

1. 
   

The first biopsy with untethered, sub-millimeter scale grippers is described by David H. Gracias and co-workers on page 514. The cover shows the retrieval of cells from the bile duct of a live pig using thermally responsive tether-free m-grippers. The retrieved tissue was of a high enough quality and quantity to enable both histological and molecular biology analyses which forms the basis of diagnostics. Image created by Martin Rietveld.

The pH Taxis of an Intelligent Catalytic Microbot

1. Krishna Kanti Dey², 
2. Satyapriya Bhandari¹,
3. Dipankar Bandyopadhyay^2,3, 
4. Saurabh Basu⁴, 
5. Arun Chattopadhyay^1,2,*

Article first published online: 14 JAN 2013

DOI: 10.1002/smll.201202312

A Pd nanoparticle-containing polymer microsphere moves with increasing speed across a pH gradient, following differential catalytic decomposition of aqueous hydrogen peroxide. The directional motion is akin to the pH taxis of living microorganisms. The artificial pH taxis exhibits random walk, translation, vertical, hopping, and pulsed motion, when the size of the motor and the imposed pH gradient are modulated

Inside Back Cover: Light-Triggered Sequence-Specific Cargo Release from DNA Block Copolymer–Lipid Vesicles

Dr. Alberto Rodríguez-Pulido¹, Alina I. Kondrachuk¹, Dr. Deepak K. Prusty¹, Jia Gao²,  Prof. Dr. Maria A. Loi², Prof. Dr. Andreas Herrmann^1,*

^{Sequence-specific cargo release from DNA-encoded lipid vesicles through the stable tagging of a liposome surface with amphiphilic DNA block copolymers (DBCs) is reported by A. Herrmann and co-workers in their Communication on page 1008 ff. Hybridization of anchored DBCs with an oligonucleotide photosensitizer is the key to light-induced singlet oxygen generation close to the lipid membrane, which results in the oxidation of polymer anchors and/or unsaturated phospholipids, leading to release of the vesicle payload.}

On-Chip Protein Biosynthesis

M. Sc. Christopher Timm,
Prof. Dr. Christof M. Niemeyer^*
Article first published online: 10 JAN 2013
DOI: 10.1002/anie.201208880

 Spot on! Cell-free protein expression on surfaces can be implemented in biosensors and in microfluidic devices like that shown in the picture. Here, proteins are generated and immobilized successively on separated spots in a microfluidic reactor. This approach opens up novel opportunities for basic and applied biomedical research.

Movies of Molecular Motions and Reactions: The Single-Molecule, Real-Time Transmission Electron Microscope Imaging Technique

Prof. Eiichi Nakamura^*
Article first published online: 17 DEC 2012
DOI: 10.1002/anie.201205693

 “The truth is, the Science of Nature has been already too long made only a work of the Brain and the Fancy: It is now high time that it should return to the plainness and soundness of Observations on material and obvious things,” proudly declared Robert Hooke in his highly successful picture book of microscopic and telescopic images, “Micrographia” in 1665. Hooke’s statement has remained true in chemistry, where a considerable work of the brain and the fancy is still necessary. Single-molecule, real-time transmission electron microscope (SMRT-TEM) imaging at an atomic resolution now allows us to learn about molecules simply by watching movies of them. Like any dream come true, the new analytical technique challenged the old common sense of the communities, and offers new research opportunities that are unavailable by conventional methods. With its capacity to visualize the motions and the reactions of individual molecules and molecular clusters, the SMRT-TEM technique will become an indispensable tool in molecular science and the engineering of natural and synthetic substances, as well as in science education.

Electrically Controlled Nanoparticle Synthesis inside Nanopores

Kimberly Venta , Meni Wanunu , and Marija Drndić *

Department of Physics and Astronomy, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States

Nano Lett., Article ASAP

DOI: 10.1021/nl303576q

Publication Date (Web): December 18, 2012

Copyright © 2012 American Chemical Society

From their realization just over a decade ago, nanopores in silicon nitride membranes have allowed numerous transport-based single-molecule measurements. Here we report the use of these nanopores as subzeptoliter mixing volumes for the controlled synthesis of metal nanoparticles. Particle synthesis is controlled and monitored through an electric field applied across the nanopore membrane, which is positioned so as to separate electrolyte solutions of a metal precursor and a reducing agent. When the electric field drives reactive ions to the nanopore, a characteristic drop in the ion current is observed, indicating the formation of a nanoparticle inside the nanopore. While traditional chemical synthesis relies on temperature and timing to monitor particle growth, here we observe it in real time by monitoring electrical current. We describe the dynamics of gold particle formation in sub-10 nm diameter silicon nitride pores and the effects of salt concentration and additives on the particle’s shape and size. The current versus time signal during particle formation in the nanopore is in excellent agreement with the Richards growth curve, indicating an access-limited growth mechanism.

 

Composite Materials: Robotic Tentacles with Three-Dimensional Mobility Based on Flexible Elastomers

Ramses V. Martinez¹, Jamie L. Branch¹, Carina R. Fish¹, Lihua Jin⁴, Robert F. Shepherd¹, Rui M. D. Nunes¹, Zhigang Suo^2,4, George M. Whitesides^1,2,3,*

Article first published online: 7 JAN 2013

DOI: 10.1002/adma.201370008

The front cover image illustrates a soft robotic tentacle with a textured surface fabricated by composing flexible elastomers using soft lithographic molding. These soft tentacles can manipulate delicate objects and house functional components that extend their capabilities (for example, a video camera).

Tuning the Spring Constant of Cantilever-Free Tip Arrays

Daniel J. Eichelsdoerfer †‡, Keith A. Brown †‡, Radha Boya ‡§, Wooyoung Shim ‡§, and Chad A. Mirkin *†‡§

^†Department of Chemistry, ^‡International Institute for Nanotechnology, and ^§Department of Materials Science and Engineering, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, United States

Nano Lett., Article ASAP

DOI: 10.1021/nl304268u

Publication Date (Web): January 3, 2013

Copyright © 2013 American Chemical Society

A method to measure and tune the spring constant of tips in a cantilever-free array by adjusting the mechanical properties of the elastomeric layer on which it is based is reported. Using this technique, large-area silicon tip arrays are fabricated with spring constants tuned ranging from 7 to 150 N/m. To illustrate the benefit of utilizing a lower spring constant array, the ability to pattern on a delicate 50 nm silicon nitride substrate is explored

Electronically Programmable, Reversible Shape Change in Two- and Three-Dimensional Hydrogel Structures

1. Cunjiang Yu¹, 
2. Zheng Duan², 
3. Peixi Yuan³,
4. Yuhang Li⁵, 
5. Yewang Su^4,5, 
6. Xun Zhang¹,
7. Yuping Pan², 
8. Lenore L. Dai⁶, 
9. Ralph G. Nuzzo⁷, 
10. Yonggang Huang⁸, 
11. Hanqing Jiang^9,*, 
12. John A. Rogers^10,*

Article first published online: 19 DEC 2012

DOI: 10.1002/adma.201204180

Combining compliant electrode arrays in open-mesh constructs with hydrogels yields a class of soft actuator, capable of complex, programmable changes in shape. The results include materials strategies, integration approaches, and mechanical/thermal analysis of heater meshes embedded in thermoresponsive poly(N-isopropylacrylamide) (pNIPAM) hydrogels with forms ranging from 2D sheets to 3D hemispherical shells.