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. Lewis^1,*

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 Foston^1,3, 
3. Dr. Udaya C. Kalluri², 
4. Dr. Gerald A. Tuskan²,
5. Prof. Dr. Arthur J. Ragauskas^1,*

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

Xun Hong , Dingsheng Wang , Shuangfei Cai ,Hongpan Rong , and Yadong Li *

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

• Christian P. Canlas,
• Junling Lu,
• Natalie A. Ray,
• Nicolas A. Grosso-Giordano,
• Sungsik Lee,
• Jeffrey W. Elam,
• Randall E. Winans,
• Richard P. Van Duyne,
• Peter C. Stair
• & Justin M. Notestein

Nature Chemistry

 

(2012)

 

doi:10.1038/nchem.1477

Received

 

15 June 2012 

Accepted

 

11 September 2012 

Published online

 

28 October 2012

New porous materials such as zeolites, metal–organic frameworks and mesostructured oxides are of immense practical utility for gas storage, separations and heterogeneous catalysis. Their extended pore structures enable selective uptake of molecules or can modify the product selectivity (regioselectivity or enantioselectivity) of catalyst sites contained within. However, diffusion within pores can be problematic for biomass and fine chemicals, and not all catalyst classes can be readily synthesized with pores of the correct dimensions. Here, we present a novel approach that adds reactant selectivity to existing, non-porous oxide catalysts by first grafting the catalyst particles with single-molecule sacrificial templates, then partially overcoating the catalyst with a second oxide through atomic layer deposition. This technique is used to create sieving layers ofAl₂O₃ (thickness, 0.4–0.7 nm) with ‘nanocavities’ (<2 nm in diameter) on a TiO₂ photocatalyst. The additional layers result in selectivity (up to 9:1) towards less hindered reactants in otherwise unselective, competitive photocatalytic oxidations and transfer hydrogenations.

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

Surface Plasmon Resonance Chemical Sensing on Cell Phones

1. Pakorn Preechaburana^1,2,*, 
2. Marcos Collado Gonzalez¹, 
3. Dr. Anke Suska¹, 
4. Dr. Daniel Filippini^1,*

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

Xiaonao Liu †, Yi Shen ‡, Ruoting Yang §, Shihui Zou†, Xiulei Ji , Lei Shi †, Yichi Zhang , Deyu Liu ,Liping Xiao †, Xiaoming Zheng †, Song Li ‡, Jie Fan*†, and Galen D. Stucky *

^† 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. Anseth^1,2,3,*

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.

Construction of a 4 Zeptoliters Switchable 3D DNA Box Origami

Reza M. Zadegan †‡§, Mette D. E. Jepsen †‡§, Karen E. Thomsen §, Anders H. Okholm †‡§, David H. Schaffert †‡§, Ebbe S. Andersen †‡§, Victoria Birkedal ‡§, and Jørgen Kjems †‡§*

^†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 Zhou^1,*,
4. Deyue Yan¹,
5. Xinyuan Zhu^1,2,*

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 Sentic^1,2,
2. Gabriel Loget¹,
3. Prof. Dragan Manojlovic²,
4. Prof. Alexander Kuhn¹,
5. Prof. Neso Sojic^1,*

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 12 October 2012:
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 12 October 2012:
Vol. 338 no. 6104 pp. 260-263
DOI: 10.1126/science.1222376
 

Functionalized multiwalled carbon nanotubes as ultrasound contrast agents

1.  Published online before print September 24, 2012, doi: 10.1073/pnas.1208312109 PNAS October 9, 2012 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.

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.