Microscale garbage “collectors” cleans polluted water

Dec2

(Nanowerk Spotlight) The construction of artificial micro- and nanomotors is a high priority in the nanotechnology field owing to their great potential for diverse potential applications, ranging from targeted drug delivery, on-chip diagnostics and biosensing, or pumping of fluids at the microscale to environmental remediation.

Particular attention has been given to self-propelled chemically-powered micro/nanoscale motors, such as catalytic nanowires (read more: “”Another nanotechnology step towards ‘Fantastic Voyage'”), microtube engines (read more: “Microbots transport, assemble and deliver micro- and nanoscale objects”) or spherical Janus microparticles (read more: “Novel motor system powered by polymerization”). In new work, researchers in Germany have now reported the first example of micromotors for the active degradation of organic pollutants in solution.

The novelty of this work lies in the synergy between internal and external functionality of the micromotors. “Previously, some groups tried to demonstrate the use of catalytic nanomotors for biomedical applications – including ours – on-chip biosensors and capture of bio species,” Dr. Samuel Sánchez, Group Leader Smart Nano-Bio-Systems, Max Planck Institute for Intelligent Systems, tells Nanowerk. “However, the toxicity of the fuel employed still limits their real applications. We imagined that environmental applications might be another field to explore, where the use of hydrogen peroxide is not controversial.” In that direction, Wang’s group reported the removal of oil droplets (“‘Microsubmarines’ designed to help clean up oil spills”) from solution, not degrading them.

Now, Sánchez and his collaborators went one step beyond that and demonstrated the total removal of contaminants using micromotors. Indeed, the chemical is used for the self-propulsion and for the remediation when interacts with the outer layer of the micromachine. “We have demonstrated the ability of self-propelled micromotors to oxidize organic pollutants in aqueous solutions through a Fenton process,” explains Sánchez.

“The combination of mixing and releasing iron ions in liquids results in a rate of removal of model pollutant (rhodamine 6G) ca. 12 times higher than when the Fenton oxidation process is carried out with nonpropelling metallic iron tubes.” Reporting their results in The November 1, 2013 online edition of ACS Nano (“Self-Propelled Micromotors for Cleaning Polluted Water”), the research team from Max Planck, the Leibniz Institute for Solid State and Materials Research Dresden, and the Chemnitz University of Technology demonstrates that micromotors boost the Fenton oxidation process (read more about Fenton reactions at the bottom of this article) without applying external energy, and complete degradation of organic pollutants is achieved.

Schematic process for the degradation of polluted water into inorganic products by multifunctional micromotors

Schematic process for the degradation of polluted water (rhodamine 6G as model contaminant) into inorganic products by multifunctional micromotors. The self propulsion is achieved by the catalytic inner layer (Pt), which provides the motion of the micromotors in H2O2 solutions. The remediation of polluted water is achieved by the combination of Fe2+ ions with peroxide, generating OH• radicals, which degrade organic pollutants. (Reprinted with permission from American Chemical Society)

Sánchez notes that, if desired, the micromotors can be easily recovered using a magnet once the water purification process has been completed and the excess of hydrogen peroxide can be easily decomposed to pure water and oxygen under visible light. The team fabricated their tubular bubble-propelled micromotors containing small amounts of metallic iron (from 20 to 200 nm layer thickness) as outer layer and platinum as inner layer. The mechanism of degradation is based on Fenton reactions relying on spontaneous acidic corrosion of the iron metal surface of the micromotors in the presence of hydrogen peroxide, which acts both as a reagent for the Fenton reaction and as main fuel to propel the micromotors.

Moreover, the ability of self-propelled, tubular micromotors to improve mixing results in a synergetic effect that enhances water remediation without applying external energy. This work can pave the way for the use of multifunctional micromotors for environmental applications where the use of hydrogen peroxide is not a major drawback but a co-reagent. Sánchez adds that the high efficiency of the oxidation of organic pollutants achieved by the Fe/Pt catalytic micromotors reported in this work is of importance for the design of new and faster water treatments, such as the decontamination of organic compounds in wastewaters and industrial effluents. The aim of this study was to fabricate an autonomous microscopic cleaning system that is working without external energy input in a much faster and convenient way.

The micromotors offer this ability to move the catalyst around without external actuation or addition of catalyst (iron salts) to achieve water remediation, removal of organic dyes, etc. However, as the researchers point out, this is an application especially for microscale environments. “It is, unfortunately, clear that we would not use the micromotors in a large reactor vessel to clean huge amounts of water,” says Sánchez. Nevertheless, the high efficiency of the oxidation of organic pollutants achieved by the Fe/Pt catalytic micromotors reported here is of importance for the design of new and faster water treatments, such as the decontamination of organic compounds in wastewaters and industrial effluents.

“We have proven that the usefulness of the micromotors lies not solely in their capacity to move, but to exploit their motion using their external surface to enhance useful catalytic reactions,” says Sánchez. “This work could open a new research line towards coupling a variety of catalytic reactions in self-propelled devices where the presence of hydrogen peroxide is not a disadvantage. We expect that a rich variety of contaminants can be in the next years be cleaned.”

Watch the micromotor in action. A synergetic effect is achieved taking advantage of the release of the iron ions from the outer layer of the micromotors and their active motion in the solution.

About Fenton reactions The Fenton method is one of the most popular advanced oxidation processes for the degradation of organic pollutants, utilizing the hydroxyl radical (OH•) as its main oxidizing agent. The generation of OH• in the Fenton method occurs by reaction of H2O2 in the presence of Fe(II). However, one disadvantage of these processes is that Fe ions in solution must be removed after the treatment to meet regulations for drinking water. In order to diminish and, in the best scenario, solve the problems caused by the presence of Fe ions in treated effluents and decrease the costs of recovery, the use of heterogeneous Fenton catalysts is a promising strategy that could allow for the degradation of pollutants by Fenton processes without the requirement of dissolved iron salts. The micromotors fabricated in this work can be included as a new type of heterogeneous Fenton catalyst. With this method the remaining iron in the solution is one to three orders of magnitude lower than in conventional Fenton processes.

Automated and scalable inline two-stage synthesis process for high quality colloidal quantum dots

Oct28

(Nanowerk Spotlight) Colloidal quantum dot (CQD) nanocrystals are attractive materials for optoelectronics, sensing devices and third generation photovoltaics, due to their low cost, tunable bandgap – i.e. their optical absorption can be controlled by changing the size of the CQD nanocrystal – and solution processability. This makes them attractive candidate materials for cheap and scalable roll-to-roll printable device fabrication technologies.

One key impediment that currently prevents CQDs from fulfilling their tremendous promise is that all reports of high efficiency devices were from CQDs synthesized using manual batch synthesis methods (in classical reaction flasks).

Researchers have known that chemically producing nanocrystals of controlled and narrow size-distributions requires stringent control over the reaction conditions – e.g. temperature and reactant concentration – which is only practical for small-scale reactions.

Such a synthesis is extremely difficult to scale up, hence very costly to mass produce without severely compromising quality. The reason for this is that, just like rain droplets, nanocrystals form sequentially by ‘nucleation’ and ‘growth’. Both these phenomena are highly sensitive to temperature and reagent concentration. Moreover, nucleation and growth must occur at substantially different temperatures and, in fact, to obtain nanocrystals of uniform sizes, one must be able to rapidly cool down the reaction from the nucleation temperature to the growth temperature.

Hence, the quality of the product is contingent upon how well and fast one can homogenize the reactor, both chemically and thermally. Unfortunately, the only way to scale up batch reactors is by increasing their volume, whereupon it becomes difficult to homogenize the reactor and impractical to rapidly cool. The end result is nanocrystals of low-quality and broad size distributions, which are not useful for fabricating devices.

Some researchers have sought to circumvent this limitation by conducting the reactions in narrow fluidic channels (less than a 1 mm in diameter) while the reactants are continuously pumped through the channels, so called ‘continuous-flow reactors’.

Conceptually, this scheme has several advantages. Narrow-width channels afford uniform heating and mixing of the reaction, while the reaction is scalable by simply increasing channel length and pump rate of the reagents. This sort of scaling does not effect the quality of the product, because the channel width, and hence the effective reaction volume, remains the same. Despite these advantages, most attempts to use continuous-flow reactors in the past have resulted in nanocrystals with a much lower quality than the batch produced ones.

“We have analyzed the nucleation and growth of CQDs in continuous-flow reactors and realized that, in order to achieve controllable size and narrow size-distributions, one must employ two temperature stages in the reactor: one for nucleation, and another for growth,” Osman Bakr, an assistant professor in the Solar & Photovoltaics Engineering Research Center at King Abdullah University of Science and Technology (KAUST), tells Nanowerk.

“By separating these two crucial steps in the formation of the CQDs in time, temperature, and space, we were able to obtain very high quality nanocrystals, as good as the best batch synthesis, by a process that is low-cost, mass-producible, and automated.”

Schematic of a conventional batch synthesis setup and a dual-stage continuous flow reactor setup

Schematic of (a) a conventional batch synthesis setup and (b) a dual-stage continuous flow reactor setup with precursor A (Pb-oleate, octadecene) and precursor B (bis(trimethylsilyl) sulfide in octadecene). (Reprinted with permission from American Chemical Society)

Reporting their findings in ACS Nano (“Automated Synthesis of Photovoltaic-Quality Colloidal Quantum Dots Using Separate Nucleation and Growth Stages”), Bakr and his team demonstrated the quality of the CQDs produced by their method by using them to make CQD-based solar cells that showed very high efficiencies.

“In this paper, we developed an automated, scalable, in-line synthesis methodology of high-quality CQDs based on a flow-reactor with two temperature-stages of narrow channel coils,” says Professor Ted Sargent from the University of Toronto who, together with Bakr, led this work. “The flow-reactor methodology not only enables easy scalability and cheap production, but also affords rapid screening of parameters, automation, and low reagent consumption during optimization.

Moreover, the CQDs are as good in quality and device performance as the best CQDs that are produced in the traditional batch methodology.” The team also developed a general theory for how one can use the flow-reactors to finely tune the quality and size distribution of the CQDs, and explained why previous attempts of using flow-reactors based on a single-temperature-stage, as opposed to a dual-temperature-stage, necessarily produce CQDs of low-quality and broad size distribution.

This work paves the way towards the large-scale and affordable synthesis of high-quality CQD nanocrystals in tunable sizes, enabling photovoltaics, light-emitting diodes, photodetectors, and biological tagging technologies that take advantage of the nanoscale properties of those promising materials.

“Over the last ten years we have seen tremendous advancements in software and computer integration, in items that we use in our everyday lives,” says Bakr. “Flow-reactors as a platform are ideally placed to take advantage of this trend. Software that automates the routines of flow-reactors already exists. In the near future, researchers will be able to run and monitor hundreds of experiments to produce CQDs from home using a mobile app.

Moreover, because flow-reactors contain very few moving parts, essentially just programmable pumps, I expect that it will become an automated research platform that most labs studying nanocrystals can afford.” “Our work has shown that flow-reactors can produce nanocrystals that are as good as the best batch produced reactions, with exquisite control over reaction conditions,” he adds. “We believe that this will encourage the nanomaterials community to take advantage of the enormous productivity gains in R&D afforded by flow-reactors, which other chemical industries, such as pharmaceuticals, are currently utilizing earnestly.”

Nanoparticle Super Antioxidant Developed at Rice University

Oct16

Scientists create a super antioxidant with nanoparticles
(Nanowerk News) Scientists at Rice University are enhancing the natural antioxidant properties of an element found in a car’s catalytic converter to make it useful for medical applications.
Rice chemist Vicki Colvin led a team that created small, uniform spheres of cerium oxide and gave them a thin coating of fatty oleic acid to make them biocompatible. The researchers say their discovery has the potential to help treat traumatic brain injury, cardiac arrest and Alzheimer’s patients and can guard against radiation-induced side effects suffered by cancer patients.
Their nanoparticles also have potential to protect astronauts from long-term exposure to radiation in space and perhaps even slow the effects of aging, they reported.
The research appears this month in the American Chemical Society journal ACS Nano (“Antioxidant Properties of Cerium Oxide Nanocrystals as a Function of Nanocrystal Diameter and Surface Coating”).

Oleylamine (red dots) and oleac acid (blue) layers serve to protect a cerium oxide nanosphere that catalyzes reactive oxygen species by absorbing them and turning them into less-harmful molecules. The finding could help treat injuries, guard against radiation-induced side effects of cancer therapy and protect astronauts from space radiation. (Credit: Colvin Group/Rice University)
Cerium oxide nanocrystals have the ability to absorb and release oxygen ions — a chemical reaction known as reduction oxidation, or redox, for short. It’s the same process that allows catalytic converters in cars to absorb and eliminate pollutants.
The particles made at Rice are small enough to be injected into the bloodstream when organs need protection from oxidation, particularly after traumatic injuries, when damaging reactive oxygen species (ROS) increase dramatically.
The cerium particles go to work immediately, absorbing ROS free radicals, and they continue to work over time as the particles revert to their initial state, a process that remains a mystery, she said. The oxygen species released in the process “won’t be super reactive,” she said.
Colvin said cerium oxide, a form of the rare earth metal cerium, remains relatively stable as it cycles between cerium oxide III and IV. In the first state, the nanoparticles have gaps in their surface that absorb oxygen ions like a sponge. When cerium oxide III is mixed with free radicals, it catalyzes a reaction that effectively defangs the ROS by capturing oxygen atoms and turning into cerium oxide IV. She said cerium oxide IV particles slowly release their captured oxygen and revert to cerium oxide III, and can break down free radicals again and again.
Colvin said the nanoparticles’ tiny size makes them effective scavengers of oxygen.
“The smaller the particles, the more surface area they have available to capture free radicals,” Colvin said. “A gram of these nanoparticles can have the surface area of a football field, and that provides a lot of space to absorb oxygen.”
None of the cerium oxide particles made before Rice tackled the problem were stable enough to be used in biological settings, she said. “We created uniform particles whose surfaces are really well-defined, and we found a water-free production method to maximize the surface gaps available for oxygen scavenging.”
Colvin said it’s relatively simple to add a polymer coating to the 3.8-nanometer spheres. The coating is thin enough to let oxygen pass through to the particle, but robust enough to protect it through many cycles of ROS absorption.
In testing with hydrogen peroxide, a strong oxidizing agent, the researchers found their most effective cerium oxide III nanoparticles performed nine times better than a common antioxidant, Trolox, at first exposure, and held up well through 20 redox cycles.
“The next logical step for us is to do some passive targeting,” Colvin said. “For that, we plan to attach antibodies to the surface of the nanoparticles so they will be attracted to particular cell types, and we will evaluate these modified particles in more realistic biological settings.”
Colvin is most excited by the potential to help cancer patients undergoing radiation therapy.
“Existing radioprotectants have to be given in incredibly high doses,” she said. “They have their own side effects, and there are not a lot of great options.”
She said a self-renewing antioxidant that can stay in place to protect organs would have clear benefits over toxic radioprotectants that must be eliminated from the body before they damage good tissue.
“Probably the neatest thing about this is that so much of nanomedicine has been about exploiting the magnetic and optical properties of nanomaterials, and we have great examples of that at Rice,” Colvin said. “But the special properties of nanoparticles have rarely been leveraged in medical applications.
“What I like about this work is that it opens a part of nanochemistry — namely catalysis — to the medical world. Cerium III and IV are electron shuttles that have broad applications if we can make the chemistry accessible in a biological setting.
“And of all things, this humble material comes from a catalytic converter,” she said.

Source: Rice University

Making Inorganic Solar Cells with an Airbrush Spray

Sep25

(Nanowerk Spotlight) There is currently a tremendous amount of interest in the solution processing of inorganic materials. Low cost, large area deposition of inorganic materials could revolutionize the fabrication of solar cells, LEDs, and photodetectors. The use of inorganic nanocrystals to form these structures is an attractive route as the ligand shell that surrounds the inorganic core allows them to be manipulated and deposited using organic solvents.

The most common methods currently used for film formation are spin coating and dip coating, which provide uniform thin films but limit the geometry of the substrate used in the process. The same nanocrystal solutions used in these procedures can also be sprayed using an airbrush, enabling larger areas and multiple substrates to be covered much more rapidly.

The trade-off is the roughness and uniformity of the film, both of which can be substantially higher. Reporting their findings in a recent online edition of ACS Applied Materials & Interfaces (“Inorganic Photovoltaic Devices Fabricated Using Nanocrystal Spray Deposition”), researchers have now attempted to quantify these differences for a single-layer solar cell structure, and found the main difference to be a reduction in the open circuit voltage of the device. deposited films of CdTe nanocrystals SEM images of the top surface of the deposited films following deposition and sintering, showing (a) CdTe spin coated and (b) CdTe spray coated. The scale bar in both images represents 200 nm. (Reprinted with permission from American Chemical Society)

“Our work was motivated by a desire to coat larger substrate areas more efficiently,” Edward Foos, a research scientists in the Materials Synthesis and Processing Section of the Chemistry Division at the Naval Research Laboratory, and first author of the paper, tells Nanowerk. “Our initial work indicated that if the layers were thick enough to cover the substrate completely and avoid pinhole formation that would lead to shorting of the device, then the increased surface roughness might be tolerable.”

He adds that this is the first time the impact of this surface roughness on the performance characteristics has been directly compared for these types of devices.

The team prepared single-layer Schottky-barrier solar cells using spray deposition of inorganic (CdTe) nanocrystals with an airbrush. The spray deposition results in a rougher film morphology that manifests itself as a 2 orders of magnitude higher saturation current density compared to spin coating. “We’re currently working to improve the spray coating process to improve the layer uniformity,” says Foos. “If the surface roughness can be reduced, then the overall device performance should increase.” The team is confident that further optimization of the spray process to reduce this surface roughness and limit the Voc suppression should be possible and eventually lead to comparable performances between the two deposition techniques. “Importantly” Foos points out, “the spray-coating process enables larger areas to be covered more efficiently, reducing waste of the active layer components, while enabling deposition on asymmetric substrates.

These advantages should be of substantial interest as inorganic nanocrystal-based solar cells become increasingly competitive as third-generation devices.” The team’s next step will be the fabrication of more complex device architectures that incorporate multiple solution processed layers. These structures will have an even smaller tolerance for variation. In addition, the deposition chemistry used must not interfere with the material applied in the previous step.

Nanotechnology Today – Fuel Cells, Buckyballs and Carbon Nanotubes

Aug30

To celebrate the 25th anniversary of National Chemistry Week, we visited the Maryland Nanocenter at the University of Maryland (UMD) to check out the latest research in nanotechnology — this year’s theme for NCW.

Three UMD researchers explain how their work in the nano-scale could lead to better fuel cells, solar cells, cancer treatments and super strong materials made from carbon nanotubes. Check out the video for a first hand look at the exciting applications of nanotechnology available today, and those that are just around the corner.

Drs. Eichhorn and Reutt-Robey at the University of Maryland ‘illuminate’ for us some of the current nano-technology being developed for commercial applications.

Video by Kirk Zamieroski Produced by the American Chemical Society

NANOTECHNOLOGY – Photons to Electricity Nano Based Solar Cells

Aug23

“Dr. Sargent provides us with a very detailed presentation on integrating ‘nanotechnology’ and photovoltaics. It is well recognized the ‘solar energy model’ will require advancements to lower manufacturing (production) costs and …

… “harvest” with greater efficiencies the available (and abundant) renewable source of energy from our sun.” – GenesisNanoTechnology

Published on Jul 9, 2013

What is Nanotechnology? A basic definition: Nanotechnology is the engineering of functional systems at the molecular scale. This covers both current work and concepts that are more advanced. In its original sense, ‘nanotechnology’ refers to the projected ability to construct items from the bottom up, using techniques and tools being developed today to make complete, high performance products.

Nanotechnology (sometimes shortened to “nanotech”) is the manipulation of matter on an atomic and molecular scale. The earliest, widespread description of nanotechnology referred to the particular technological goal of precisely manipulating atoms and molecules for fabrication of macroscale products, also now referred to as molecular nanotechnology.

A more generalized description of nanotechnology was subsequently established by the National Nanotechnology Initiative, which defines nanotechnology as the manipulation of matter with at least one dimension sized from 1 to 100 nanometers.

This definition reflects the fact that quantum mechanical effects are important at this quantum-realm scale, and so the definition shifted from a particular technological goal to a research category inclusive of all types of research and technologies that deal with the special properties of matter that occur below the given size threshold.

It is therefore common to see the plural form “nanotechnologies” as well as “nanoscale technologies” to refer to the broad range of research and applications whose common trait is size. Because of the variety of potential applications (including industrial and military), governments have invested billions of dollars in nanotechnology research. Through its National Nanotechnology Initiative, the USA has invested 3.7 billion dollars. The European Union has invested 1.2 billion and Japan 750 million dollars

Inexpensive, Flexible Solar Cells: Rice & Penn State Collaborate

Aug22

(Phys.org) —Work by a team of chemical engineers at Penn State and Rice University may lead to a new class of inexpensive organic solar cells.

Work by a research team at Penn State and Rice University could lead to the development of flexible solar cells. The engineers’ technique centers on control of the nanostructure and morphology to create organic solar cells made of block polymers. Credit: Curtis Chan

Most solar cells today are inorganic and made of crystalline silicon. The problem with these, Gomez explained, is that inorganic solar cells tend to be expensive, rigid and relatively inefficient when it comes to converting sunlight into electricity.

But organic solar cells offer an intriguing alternative that’s flexible and potentially less expensive.

Not many organic solar cells currently exist. He said, “There are a bunch of prototypes floating around. You see them in places like in solar-powered laptop bags and on the top of some bus depots.”

The problem is that the bulk of organic solar cells employ fullerene acceptors—a carbon-based molecule that’s extremely difficult to scale up for mass production.

Gomez’s approach skips the fullerene acceptor altogether and seeks to combine

The idea of utilizing molecular self-assembly for solar cells isn’t new, but Gomez said, “It’s not been well executed.”

He continued, “It’s like trying to mix oil and water.” The issue is that weak intermolecular interactions and disorder at junctions of different organic materials limited the performance and stability of previous organic solar cells.

But by controlling the nanostructure and morphology, the team essentially redesigned the molecules to link together in a better way.

The engineers were able to control the donor-acceptor heterojunctions through microphase-separated conjugated block copolymers.

“We have not only demonstrated control of the microstructure, but also control of the interface responsible for the initial steps in charge photogeneration in a way never achieved before,” Gomez said.

The result, which was detailed in a recent issue of the American Chemical Society‘s Nano Letters journal, is an organic solar cell made of block copolymers that’s three percent efficient.

The team included Penn State chemical engineering graduate student Changhe Guo; undergraduate student Matt Witman; Rafael Verduzco, the Louis Owen Assistant Professor of Chemical and Biomolecular Engineering at Rice University; Joseph Strzalka, research scientist at Argonne National Laboratory; and research scientists Cheng Wang and Alexander Hexemer of Lawrence Berkeley National Laboratory.

Though the team’s prototype is not as efficient as some solar cells that are commercially available, Gomez explained the work shows flexible organic solar cells are indeed possible.

“Our cells right now don’t capture a lot of light. We need to look back and redesign the molecule. We think we can do better than 3 percent,” he said.

Read more at: http://phys.org/news/2013-08-chemical-inexpensive-flexible-solar-cells.html#jCpmolecules in a solution.

Nano-storage wires

Aug13

(Nanowerk Spotlight) Nanowires are considered a major building block for future nanotechnology devices, with great potential for applications in transistors, solar cells, lasers, sensors, etc. (see for instance: “Nanowires for the electronics and optoelectronics of the future” and “Nanotechnology explained: Nanowires and nanotubes”).

Now, for the first time, nanotechnology researchers have utilized nanowires as a ‘storage’ device for biochemical species such as ATP. Led by Seunghun Hong, a professor of physics, biophysics and chemical biology at Seoul National University, the team developed a new nanowire structure – which they named ‘nano-storage wire’ – which can store and release biomolecules.

Reporting their findings in the July 16, 2013 online edition of ACS Nano (“Nano-Storage Wires”), Hong’s group demonstrated that their nano-storage wire structure can be deposited onto virtually any substrate to build nanostorage devices for the real-time controlled release of biochemical molecules upon the application of electrical stimuli.

“Our nano-storage wires are multisegmented nanowires comprised of three segments and each segment plays a role in extending the applications of the nanowire,” Hong explains to Nanowerk: “1) the conducting polymer segment stores biomolecules; 2) the nickel segment allows the utilization of magnetic fields to drive the nanowires and place them onto a specific location for device applications; and 3) the gold segment enables a good electrical contact between the deposited nano-storage wires and the electrodes. The polymer segment is utilized for the controlled release of ATP molecules. The nickel segment enables the magnetic localization of nano-storage wires, while the gold segment provides a good electrical contact with electrodes.”

Left: Schematics of a nano-storage wire. Right: SEM image of a single nano-storage wire. The dark, intermediate, and bright regions represent PPy-ATP (conducting polymer with ATP molecules), nickel, and gold segments, respectively. (Images: Dr. Seunghun Hong, Seoul National University) The released biomolecules from such a nanowire-storage system can be used for instance to control the activity of biosystems. As a proof of concept, the researchers stored ATP in their nano-storage wires and released it by electrical stimuli, which activated the motion of motor protein systems. The team also demonstrated flexible nanostorage devices. Here, nano-storage wires were driven by magnetic fields and deposited onto nickel/gold films on a transparent and flexible polyimide film. The device transmitted some light, and it can be easily bent. They also showed that the nanowires could be deposited onto curved surfaces such as the sharp end of a micropipet.

nano-storage wires deposited on tip of a micropipette

SEM image of nano-storage wires deposited on a micropipet. (Reprinted with permission from American Chemical Society)

“Nano-storage wires will allow the fabrication of advanced biochips which can activate or deactivate the activities of biosystems in real time,” Hong points out. “The activation and deactivation of biosystems such as biomotors, are controlled by specific biomolecules. In our method, we can selectively control the biomolecular activities related with ATP or any released chemical species while leaving other biomolecular activities unaltered.”

Having demonstrated the storage of ATP, the team is now planning to store other biomolecules in our nano-storage wires. Examples are drugs to control the activity of cells and tissues, enzymes to activate specific signal pathways in biosystems etc. “Eventually, we would like to build an advanced biochip which can be utilized to control the activities of desired biosystems in real-time,” says Hong.

Tumor Targeting platform with Nanoghosts

Aug2

By Marcelle Machluf, Associate Professor, The Faculty of Biotechnology & Food Engineering, Technion – Israel Institute of Technology, Haifa, Israel.

(Nanowerk Spotlight) The field of drug discovery is growing at a remarkable pace, leading to the development of many new drugs, most of which are generally more potent than their predecessors, yet suffer from poor solubility and/or high toxicities.

Targeted drug-delivery vehicles (e.g., liposomes, nano-particles) have often been proposed in an effort to reduce the side effects of such drugs and improve their overall efficacy for treating genetic, viral and malignant diseases. Three main considerations must be addressed when designing any such delivery system: It should be biocompatible; bioavailable; and highly selective to its specific target.

Targeting may be improved by conjugating drug carrying vehicles with targeting moieties that substantially improve their selectivity. For example, antibodies, proteins etc. have been incorporated into nano-sized drug-carriers made from polymeric particles, micelles or liposomes, yet their relatively short circulation time and the complexity of their production render them too costly and inefficient.

The need for drug delivery vehicles is particularly stressed in cancer treatment, where high doses of toxic drugs are often required. Passively-targeted drug-loaded vehicles are still the predominantly used delivery systems for cancer therapy. Because of their nano-size and physical properties, such systems were shown to achieve extended circulation times, and retention in the tumor microenvironment—owing to the Enhanced Permeability and Retention (EPR) effect of tumor vasculature and microenvironment.

These systems, nonetheless, are limited by tumor vascularization and permeability that are largely dependent on the stage of the malignancy and tumor type. Consequently, active targeting vehicles, once a promising therapeutic approach, have almost exhausted their potential, particularly in the area of cancer therapy where such solutions are desperately needed.

In our recent paper (“Reconstructed Stem Cell Nanoghosts: A Natural Tumor Targeting Platform”) we report on a novel targeted drug-delivery vehicle for cancer therapy, which can selectively target the tumor niche while delivering an array of therapeutic agents. This targeting platform is based on unique vesicles (‘nanoghosts’) that are produced, for the first time, from intact cell membranes of stem cells with inherent homing abilities, and which may be loaded with different therapeutics.

Binding of nanoghosts to cells Binding of nanoghosts (white arrow) to PC3 cells; cell, green (GFP); nucleolus, blue (DAPI) evaluated using confocal microscopy over short (3 h) incubation times. (Reprinted with permission from American Chemical Society)

We have shown that such vesicles, encompassing the cell surface molecules and preserving the targeting mechanism of the cells from which they were made, can outperform conventional delivery systems based on liposomes or nanoparticles. These vesicles leverage the benefits related to the size, and chemical and physical properties of nano-liposomes, allowing them to efficiently entrap various hydrophilic and hydrophobic drugs, and be administered through different routes while exhibiting versatile and controllable release profiles.

The prior art pertaining to the design of this unique and novel drug-delivery platform is drawn from and associated with the production and utilization of cell-derived vesicles, and the inherent tumor-targeting abilities of mesenchymal stem cells (MSCs). A similar therapeutic effect, to what we have achieved, was previously demonstrated for prostate cancer, using monoclonal antibodies against N-cadherin, which is highly expressed in castration-resistant prostate cancer; however, it requires more frequent and higher dosing.

Our therapeutic outcome is comparable to that demonstrated by De Marra et al. (“New self-assembly nanoparticles and stealth liposomes for the delivery of zoledronic acid: a comparative study”) who used no less than three administrations per week of liposomes encapsulating Zoledronic acid and exceeded the effect achieved by a weekly administration of an imatinib–mitoxantrone liposomal formulation.

The efficiency of our delivery system is even more compelling in light of the results reported by Srivastava et al. (“Effects of sequential treatments with chemotherapeutic drugs followed by TRAIL on prostate cancer in vitro and in vivo”), which demonstrated no inhibition of tumor growth after two weeks and as many as four IV administrations of similar quantities of free sTRAIL. The efficacy of our system also exceeded that of previously reported liposomal formulations containing sTRAIL tested on glioblastoma and lung cancer.

Till now, nanoghosts made from mammalian cells have been used to study cell membranes and were utilized for cancer immunotherapy but have never been tested as targeted drug-delivery vehicles. Recently, we reported a novel concept describing a targeted drug-delivery system based on nanoghosts, which were prepared from the outer cell membranes of a non-human cells engineered to express the human receptor (CCR5) of a viral ligand (gp120) found on the surface of HIV-infected cells (“Cell derived liposomes expressing CCR5 as a new targeted drug-delivery system for HIV infected cells”).

Drug-loaded nanoghosts selectively targeted HIV-infected cells in vitro, achieving over 60% reduction in their viability compared to empty nanoghosts, free drug, or nanoghosts applied on control uninfected cells that were not affected at all. This intrinsically-targeted system, which does not entail the elaborate production of targeting molecules and their incorporation into passive vehicles, represents a simpler and more clinically relevant approach than existing particulate drug-delivery vehicles.

Our success in using nanoghosts to target HIV-infected cells has prompted us to devise a more sophisticated universal and non-immunogenic delivery platform, in which the nanoghosts will be produced from stem cells that are known to naturally target various tumors. Insights gained from this work may pave the way for new research utilizing nanoghosts’ inherent targeting to treat not only tumors but also sites of inflammations, wound healing, and trauma.

The knowledge accumulated on the entrapment of diverse drugs can facilitate the loading of nanoghosts with nucleic acid (DNA, siRNA etc.) for gene therapy. Nanoghosts loaded with MRI contrast agents (Indocyanine or magnetite nano-crystals) can open unique research avenues in imaging and diagnosis. Their small size and specific targeting abilities may enable the nanoghosts to freely travel in the body possibly detecting small and sub-metastatic cancer nuclei and lesions, which are otherwise undetectable using conventional methodologies.

Owing to MSCs natural role in regenerative medicine, nanoghosts can be also investigated in tissue engineering applications for delivering growth factors for regenerating tissues. Finally, MSCs can be engineered to express additional targeting molecules and used to treat other diseases manifested by the expression of unique targetable ligands.

This work was conducted by PhD students Naama Ester Toledano-Furman, Yael Lupu-Haber, Limor Kaneti, and the Lab manager Dr. Tomer Bronshtein.

By Marcelle Machluf, Associate Professor, The Faculty of Biotechnology & Food Engineering, Technion – Israel Institute of Technology, Haifa, Israel.

Nanowires: Major Building-block for Nanotechnology Devices: Transistors, Solar Cells, Lasers and More

Aug2

(Nanowerk Spotlight) Nanowires are considered a major building block for future nanotechnology devices, with great potential for applications in transistors, solar cells, lasers, sensors, etc.

*** Read articles explaining how ‘nanowires and nanotubes’ differ from other quantum materials, such as quantum dots, and their potential applications here:

http://www.nanowerk.com/news2/newsid=29945.php

http://www.nanowerk.com/news/newsid=16857.php

The released biomolecules from such a nanowire-storage system can be used for instance to control the activity of biosystems. As a proof of concept, the researchers stored ATP in their nano-storage wires and released it by electrical stimuli, which activated the motion of motor protein systems. The team also demonstrated flexible nanostorage devices. Here, nano-storage wires were driven by magnetic fields and deposited onto nickel/gold films on a transparent and flexible polyimide film. The device transmitted some light, and it can be easily bent. They also showed that the nanowires could be deposited onto curved surfaces such as the sharp end of a micropipet.

nano-storage wires deposited on tip of a micropipette

SEM image of nano-storage wires deposited on a micropipet. (Reprinted with permission from American Chemical Society)

“Such probe-shaped storage devices can be used for the delivery of chemicals to individual cells through a direct injection,” says Hong. “Basically, our results show that nano-storage wires are quite versatile structures and we can deposit them onto virtually any structure to create nanoscale devices for the controlled release of biochemical materials.” “Nano-storage wires will allow the fabrication of advanced biochips which can activate or deactivate the activities of biosystems in real time,” Hong points out. “The activation and deactivation of biosystems such as biomotors, are controlled by specific biomolecules.

In our method, we can selectively control the biomolecular activities related with ATP or any released chemical species while leaving other biomolecular activities unaltered.” Having demonstrated the storage of ATP, the team is now planning to store other biomolecules in our nano-storage wires. Examples are drugs to control the activity of cells and tissues, enzymes to activate specific signal pathways in biosystems etc. “Eventually, we would like to build an advanced biochip which can be utilized to control the activities of desired biosystems in real-time,” says Hong.

Genesis Nanotechnologyo and l o

Great Things From Small Things

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Scientists create a super antioxidant with nanoparticles

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