2011/06/30

Rust busting self-healing materials

30 June 2011

Scientists in Singapore have prepared a coating for metals that heals itself after being scratched to prevent corrosion of the metal underneath.

Unlike other examples of such coatings, this one, developed by Mingxing Huang and Jinglei Yang of Nanyang Technological University, requires no catalyst and can be used at 40 degrees Celsius.

The team prepared the coating by encapsulating the highly reactive compound hexamethylene diisocyanate (HDI) inside polymer shells to form microcapsules. They then dispersing the microcapsules into epoxy resin and applied this coating to steel. When the coating was scratched, the punctured microcapsules released the HDI, which reacted with water to form polyurea and this sealed the damaged region. 'What's more, HDI microcapsules can also trap and react with the water diffused into the coating, providing another way to retard the corrosion process on the undamaged coating,' says Yang. 'There are a few studies reporting that the annual cost of corrosion is roughly 1-5 per cent of each nation's gross domestic product in the US, Japan, China and Europe. It's a huge number,' he adds.

A scored section of a steel panel coated with the new coating (left) and with a pure epoxy coating (right) after 48 h in a 10 per cent wt solution of sodium chloride

However, both the authors and materials expert Fred Wudl of the University of California Los Angeles, US, agree that more work is needed before the system is ready for real applications. 'The vesicle membranes are too permeable to moisture and the shelf life, particularly in a humid environment, would be too low for immediate applications, particularly the anticorrosive application the authors have in mind,' says Wudl.

Huang and Yang are currently optimising the material system by looking into the effect of microcapsule concentration and coating thickness on the damage healing kinetics. 'We expect the optimised system to show both damage healing smart features and a great improvement in long-term anticorrosion capability,' says Yang.

Heather Montgomery
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Surgeons and patients breathe easy during surgery

30 June 2011

UK scientists have developed a way of continuously analysing the breath of unconscious patients undergoing surgery using mass spectrometry.

Monitoring exhaled gases allows an insight into a patient's metabolic state so that surgeons and anaesthetists can work out how stressed the patient's body is during an operation. Currently, breath analysis can only be done by off-line collection of samples, in which the breath is captured in a bag and taken for analysis elsewhere. The other option is using blood samples, which take a long time to analyse and so are of little use to the medical team.

Breath samples are taken up by the ventilator and sent along a sample line to the mass spectrometer

David Smith from Keele University and colleagues have made a significant advance by taking the measurements and viewing the results in the operating theatre as the surgery is taking place using a selected ion flow tube-mass spectrometer (SIFT-MS). 'Specific breath gases can be monitored that can indicate to the surgeon and anaesthetist the status of the patient, thus allowing more informed decision making and improve the outcome of the surgical procedure,' says Smith.

The team measured the concentrations of acetone, propofol and isoprene in the exhaled breath of patients throughout their operations. Acetone is generated from the metabolism of lipids, propofol is the chemical used to put the patient to sleep and isoprene is related to blood cholesterol levels. They took the breath sample from the ventilator and, using a sampling line, delivered it to the inlet of the SIFT-MS. Paul Monks, an expert in measuring trace gases from the University of Leicester, UK, comments: 'The experimental set-up means that the gases involved in gas-exchange with the lung are directly sampled.'

The technique used is so sensitive it can detect parts-per-billion by volume and it has potential application in 'real-time monitoring in pharmacokinetic - drug effects over time - studies,' says Monks.

'We only monitored two breath metabolites in this initial pilot study, so a major objective of the follow-up research is to include more metabolites, which might be indicative of stress on vital organs such as the lungs, liver, kidneys and heart,' says Smith.

Holly Sheahan
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Screening for Alzheimer's drugs in tandem

28 June 2011

A simple assay based on sequential enzymatic reactions and a fluorescent sensor could help scientists to discover new Alzheimer's disease drugs.

Some Alzheimer's drugs work by blocking the activity of acetylcholinesterase, an enzyme that degrades the neurotransmitter acetylcholine to choline. To find new enzyme inhibitors, researchers need to identify choline formation, or the loss of acetylcholine, so they can tell whether the enzymatic reaction has stopped. But, acetylcholine and choline are both quaternary ammonium ions with very similar structures, making it difficult to distinguish between them.

To overcome this problem, teams led by Werner Nau at Jacobs University Bremen, Germany, and Yu Liu at Nankai University, China, have combined two sequential enzymatic reactions with a calixarene macrocycle that binds to a fluorescent dye to make a tandem assay that can screen for new inhibitors. The enzymes are highly specific and only work on one substrate.

The tandem reaction involves a fluorescence ''switch-on'' displacement assay as a sensor for specific analytes

In their assay, they use acetylcholinesterase to turn acetylcholine to choline. A second enzyme - choline oxidase - turns the choline into betaine. While choline and betaine are similar, they have different affinities for binding within the calixarene. Because of this difference, the dye can replace the betaine inside the calixarene. This turns off the dye's fluorescence, which is easy to detect. If the enzymatic reactions are inhibited, no betaine will be produced and so the dye's fluorescence stays on.

Pablo Ballester, an expert in supramolecular chemistry at the Institute of Chemical Research of Catalonia, Spain, welcomes the research. He says it 'represents a clever implementation of the use of enzymes to overcome the reduced binding selectivity exhibited by the negatively charged synthetic receptors of the calixarene family in the recognition of quaternary ammonium ions.'

Nau's team demonstrated their assay with acetylcholinesterase and choline oxidase but the principle could be adapted to other enzymatic reactions. In the future, Nau hopes to 'set up a large library of calixarene and dye pairs that are useful for a large range of analytes and biochemical reactions.'

Russell Johnson
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A cool way to store hydrogen?

28 June 2011

Years of researching new ways to store hydrogen efficiently - a vital prerequisite for any 'hydrogen economy' - have resulted in numerous exotic potential storage systems, from metal-organic frameworks (MOFs) to carbon nanotubes. But now theoretical chemists in the US have suggested a rather more commonplace solution: ice.

William Goddard, of the California Institute of Technology, and colleagues Tod Pascal and Christopher Boxe used complex quantum mechanical modelling coupled with high-powered statistics to investigate. They have now concluded that the common form of ice, made up of hexagonal crystals, could store hydrogen more effectively than existing materials.

'It sounds like a crazy idea, and we were very nervous about publishing it,' Goddard says. 'But the simulations suggest that it could be a feasible approach.'

Hydrogen must be stored efficiently - without adding too much weight - if it is to be practical for cars

The idea came from modelling phase transitions of water. 'We noticed that when you heat crystalline ice, as it starts melting, a molecule of water comes out of the ice framework and whizzes along little channels present throughout the crystal structure. We wondered that, if these channels were big enough to accommodate water molecules, could they hold hydrogen?'

Goddard has used his modelling methods extensively in the past to accurately predict the hydrogen storage capacity of a range of new materials such as MOFs. The team's calculations suggest that hexagonal ice crystals can hold 3.8 per cent by weight of hydrogen if the crystals are loaded at a temperature of 150K. This compares with 1.3 per cent by weight for the current best performing MOF. The hydrogen can be stored at a few degrees below freezing then released by melting the ice.

There would be a range of engineering hurdles to overcome, Goddard says. For example at the surface of the ice, the crystalline structure breaks down so the ice would need to be crushed before loading with hydrogen to expose fresh crystals.

'Current hydrogen storage solutions either require high pressure to achieve sufficiently high hydrogen densities, high temperatures for hydrogen release, complex re-hydrogenation processes, or store low gravimetric densities of hydrogen,' says Martin Jones, who researches novel hydrogen storage materials at the University of Oxford in the UK. The ice approach would store reasonable amounts of hydrogen, release it at room temperature and work at moderate pressure. 'Above all, the storage material is cheap,' Jones adds.

But the systems needed to handle the ice and hydrogen would add weight and reduce the efficiency of the system, he says. 'Furthermore, creating a system with high surface area ice, and maintaining it, would not be straightforward,' he says. 'Clearly corroboratory experiments will need to be performed.'

Simon Hadlington
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2011/06/28

Photosystems made using '3D Tetris'

28 June 2011

Scientists in Switzerland have designed self-sorted multicomponent surface architectures for supramolecular organic photosystems that are 40 times more active at generating electrical current from light energy than their single-component counterparts. In the future, this concept could be used to design more efficient organic solar cells.

Building multi-component supramolecular organic systems that generate electricity is of interest because they have the potential to be cheap photovoltaic devices. However, building these systems on surfaces with high precision and control can be time consuming and expensive.

Now, Stefan Matile and colleagues at the University of Geneva believe they have a cheap and easy alternative. Using self-organising surface-initiated polymerisation (SOSIP),1 the team has developed 3D supramolecular structures mounted on oxide surfaces that make photosystems that are more efficient than those of other organic structures.2


SOSIP combines self-organisation of monomers and ring-opening disulfide exchange polymerisation to give highly ordered and oriented architectures. Lysine-derived diamide subunits organise monomers incorporating naphthalenediimde (NDI) subunits are held together using hydrogen bonds so that they form pi stacks. The resulting delocalised system can easily transport electrons. The self-organisation then facilitates intramolecular ring-opening disulfide exchange to freeze the desired surface architecture in place.

Matile explains that in order to efficiently convert light into energy (in this case electrical) photosystems need two channels of molecules adjacent to each other within the structure. One channel carries electrons in one direction and the other is used to carry the positive charge or 'hole transport' - holes created by the electrons in first channel - in the opposite direction.

Using SOSIP, Matile and his team have been able to incorporate this double channel concept into their supramolecular architectures. 'This is known as the supramolecular heterojunction, which is an important architecture for future organic solar cells,' says Matile. He goes on to explain that, using the approach, different component parts can be built into the structure in a uniform and alternate manner by remote control. Matile says that the process can be thought of as '3D Tetris' on the molecular level.

Tomas Torres, an expert in supramolecular structures at the Autonomous University of Madrid, in Spain, says: 'This method will provide new ideas for researchers and in this sense it is very significant in the field of supramolecular chemistry.' However, he adds that, 'it will not have a significant impact on the race for molecular photovoltaics'.

Frank Würthner, an expert in organic materials at the University of Würzburg, Germany, is more optimistic about direct application. 'Obviously, dye-sensitised solar cells on titanium dioxide will be the next step,' he says. 'If successful, this approach may advance the field of Gratzel-type solar cells to unprecedented efficiencies and thus to the market,' he adds.

Meanwhile, Matile explains he is only concerned with the conceptual innovation of his research. 'The gap between application and basic science - this is where this research sits,' he says. 'I am looking at conceptual innovation and then if we get good results at the very end, it could be used for solar cells,' he adds.

Mike Brown
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Rollerball writes electronics straight to paper

27 June 2011

Electronic circuits can be fiddly to make: engineers have to snap components onto a board or etch designs onto a copper surface. Now a US group of researchers has demonstrated that all you really need is a pen and some paper.

A regular, shop bought rollerball pen was filled with conductive ink
© Advanced Materials / Wiley VCH

The new method, which uses a rollerball pen to be filled with conductive ink, could enable engineers to create one-off circuits that are cheap, flexible and disposable. 'Pen-based printing allows one to construct electronic devices "on-the-fly",' says group leader Jennifer Lewis, at the University of Illinois at Urbana-Champaign.

There has been a lot of interest in so-called desktop electronics manufacturing in recent years. Researchers have demonstrated that, using conductive ink, it is possible to create circuits using airbrushes or even inkjet printers. As a result, devices such as LED displays, antennae and even batteries have been printed onto various surfaces, from fabric to paper.

The pen-on-paper technique might be the most straightforward and accessible method yet. Lewis's group made a conductive ink from silver nanoparticles, produced in solution by reducing silver nitrate and using a capping agent (poly-acrylic acid) to prevent the particles growing too big. The researchers then removed the capping agent and tailored the viscosity of the ink by adding hydroxyethyl cellulose, before loading it into a store bought rollerball pen.

Using this pen, Lewis's group was able to draw working circuits for an LED display and an antenna, which they folded into a spherical shape. At times, the components had to be attached using an extra blob of ink and superglue, but at other times the only tools necessary were the pen and paper, says Lewis. Once dry, the researchers found that they could bend the paper circuits several thousand times before any breaks appeared.

Henning Sirringhaus, a specialist in microelectronics at the University of Cambridge, UK, and chief scientist at Plastic Logic, a technology start-up company commercialising printed organic transistor technology, says it is a 'novel approach'. But he doubts whether it could create high-resolution or highly integrated circuits. Still, he says the method 'offers very interesting opportunities for simple applications of flexible electronics on paper substrates.'

The system can be used for conductive electronic art drawn on Xerox paper
© Advanced Materials / Wiley VCH

In fact, Lewis's group has shown that it can write the conductive ink on other surfaces besides paper, such as polymer films, wood and ceramics. The next step for the researchers is to expand their ink palette to include other conductive substances. 'This is an important step towards enabling desktop manufacturing using very low cost, ubiquitous printing tools,' says Lewis.

Jon Cartwright
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Mystery of how plutonium enters cells solved

27 June 2011

It's been known for years that once plutonium is ingested it remains in the body for a long time, but what no one knew was how the plutonium is absorbed. Now, US scientists have found a cellular uptake pathway for plutonium, confirming a previous hypothesis but with a caveat.

Mark Jensen at Argonne National Laboratory and colleagues showed that plutonium hijacks the machinery used to deliver iron to mammalian cells - the transport protein transferrin.

That's maybe not so surprising, says Sarah Heath, a chemist at the University of Manchester, UK, who moved on to working with plutonium after first working with iron. She says that the two metals can often react in the same way.

'The charge density of the two ions is very similar,' says Heath, and this means the ions behave similarly.

Jensen and colleagues were interested in separating plutonium ions and decided to investigate how living organisms differentiate between metal ions in such different ways to chemists. To do that they tried to trick transferrin receptor protein to bind plutonium containing transferrin, but though plutonium can replace iron in the complex, only one form of plutonium containing transferrin binds with the receptor.

Plutonium hitches a ride into cells on an iron transporting protein

'At this point we realized that our fundamental studies of metal ion recognition by this pair of proteins had important implications for the cellular uptake of plutonium,' says Jensen.

Usually transferrin (Tf) forms a complex with two iron ions, one sit at the N-terminal end of the protein and one at the C-terminal end. If both of these irons are replaced by plutonium, the transferrin is too distorted to be recognised by the transferrin receptor protein. Using synchrotron X-ray fluorescence microscopy, the team showed that this means the plutonium cannot be absorbed by cells.

It turns out that only transferrin with plutonium bound to the C-terminal end and iron bound to the N-terminal end is a good enough match to be carried into cells. So although plutonium can use an iron uptake system to infiltrate cells, it can only do so with the help of iron.

There are probably other pathways for plutonium uptake Jensen says. 'However,' he adds 'the great majority of plutonium that gets into the blood stream is bound to transferrin, and the largest fraction of iron-transferrin in human blood (FeNTf) is the precursor to the form of iron-plutonium-transferrin that can be taken up by cells. This suggests that the transferrin pathway is important even if it is not the only way plutonium can infiltrate cells.'

The team have shown various targets to block plutonium uptake, which could prevent the metal getting into cells and causing damage.

Laura Howes
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A step forward for space power

27 June 2011

US scientists have gained insights into how to improve polymer solar cells' stability in space to power shuttles.

Inorganic solar cells have been investigated as power sources for spacecraft, and they are efficient, but they are heavy, so are costly to launch. Because of this, the power gains are marginal.

Organic polymer solar cells are light and flexible, making them attractive for use in satellites. But, these cells would degrade when exposed to the x-ray radiation present in space, making them inefficient. The x-rays pass through the relatively transparent polymer layer, causing a loss in voltage in the device.

Yang Yang from the University of California, Los Angeles, and Roderick Devine from the Air Force Research Laboratory at Kirtland Air Force Base, New Mexico, have discovered that the interface between the photoactive polymer layer and the electrode of the cell is the key to the cell's reaction to x-rays.


Polymer solar cells are lightweight so can be transported to space at a fraction of the cost of inorganic cells that are being investigated as power sources for spacecraft

The team saw that a charge accumulating at the interface after radiation exposure was causing the loss of voltage and that by modifying the interface, they could lessen this accumulation and improve the cell's stability. They tested different electrode interfaces - Ca/Al, Al and LiF/Al compared to TiO2:Cs/Al and ZnO/Al interfaces - and found that the metal-oxide/metal interfaces were less susceptible to radiation.

Jianyong Ouyang from the National University of Singapore, an expert in polymeric electronic materials and devices, is impressed by Yang's research. 'The work is practically significant in that it provides guidance for improving polymer solar cells,' he says.

'In the immediate future, we will continue to focus our efforts on the interface to gain a greater understanding and control of its properties,' concludes Yang.

Catherine Bacon
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EU looks to expand ban on phosphates in detergents

24 June 2011

Ned Stafford/Hamburg, Germany

Phosphate suppliers and dishwasher detergent producers have voiced strong opposition to a proposal by the European Parliament's Environment Committee to ban all but trace amounts of phosphates in household dishwasher detergents sold within the EU beginning in 2015.

The parliamentary committee approved the dishwasher recommendation on 15 June as part of a wider proposal that also calls for restricting phosphates in household laundry detergents beginning in 2013. Specifically, the committee recommended that phosphorus compounds in detergents not exceed 0.5 gram per standard load.

Few alternatives to phosphates in dishwasher detergents exist

The goal of the proposal is to reduce the discharge of phosphates into surface water, as phosphates can combine with other plant nutrients such as nitrogen and contribute to eutrophication. This results in excessive phytoplankton growth that kills off fish and other aquatic plant life. The largest source of phosphate discharge into surface water is agriculture, mainly from fertilisers, but also livestock feed, followed by human sewage and then detergents.

Parliament acts

The parliamentary committee was acting on a European Commission draft regulation announced last November to limit phosphorus content in laundry detergents by 1 January 2013. But instead of setting a firm date for restricting phosphate use in dishwasher detergents the Commission asked for a new study to be completed by the end of 2014.

'The Commission proposal is welcome, but not ambitious enough,' says Bill Newton Dunn, a member of the European Parliament from the UK Liberal Democrats party. 'The Commission's proposal for only a report would have delayed progress, whereas setting a date for a ban will require manufacturers to step up their efforts to produce less polluting formulations.'

The Environment Committee's phosphate recommendations will be debated in the European Parliament with a vote expected this November. Any new phosphate regulations would require dual approval of parliament and the European Council of Ministers, which directly represent all EU member nations. The Committee's recommendations also include assessing whether phosphate restrictions should be extended to industrial and institutional detergents by the end of 2016.

Most western European nations, including the UK, France, Germany, Italy, Belgium and the Netherlands, have already either banned or restricted the use of phosphates in household laundry detergents. France will ban dishwasher detergent phosphates beginning in 2012, while Sweden and Finland are considering dishwasher bans.

Sylvie Lemoine, director of technical and regulatory affairs at the Brussels-based International Association for Soaps, Detergents and Maintenance Products (AISE), tells Chemistry World that the requirements for dishwasher detergents, which are directed at hard surfaces, such as metal, glass, ceramic and plastic, are very different to laundry detergents used to clean textiles. While the basic scientific know-how to manufacture effective phosphate-free laundry detergents is 'pretty much a done deal,' technology for phosphate-free dishwasher detergents is 'not yet fully developed,' says Lemoine.

Phosphates serve numerous functions in detergents, such as neutralising hard water, dispersing dirt and preventing incrustation. Lemoine says that most laundry detergent manufacturers use zeolites - microporous aluminosilicate minerals - as a substitute in low phosphate products. But zeolites are abrasive and cannot be used in dishwasher detergents, she adds.

The European polyphosphate industry research group (CEEP) a sector group of the European Chemical Industry Council (Cefic) states that dishwasher detergent manufacturers are focusing on two approaches for phosphate free products. The first uses 'classic' chemicals, such as citrates and carbonates. But the CEEP says these are 'ineffective, even if boosted by significant doses of additives such as phosphonates, polymers and bleaches'.

The second approach uses new 'high tech' aminocarboxylates or derivatives. 'To our knowledge, only one of these new molecules has been successfully used to replace phosphates in a significant market share detergent,' CEEP says. The environmental and health impacts of the new chemicals and their co-additives have not yet been fully assessed, CEEP states.

Challenging targets

The Environment Committee's target date of 1 January 2015 for banning dishwasher detergent phosphates would be 'very challenging for industry to meet in order to deliver products which perform well, both in terms of cleaning efficiency as well as total environmental profile,' Lemoine says, adding that 2018 at the earliest would be a more realistic target date.

That said, the AISE is not officially opposed to phosphate restrictions on either laundry or dishwasher detergents, Lemoine says, adding that manufacturers would rather have one set of EU rules restricting phosphates than a jigsaw puzzle of various national regulations.

CEEP is opposed to phosphate restrictions in detergents, arguing that phosphates are non-toxic, safe to humans and more effective than substitutes. In a position paper the CEEP says that whether or not phosphates are used in detergents, adequate sewage collection and treatment is necessary. 'We believe that phosphorus removal in sewage works, combined with phosphorus recycling, is the way forward for both water quality protection and sustainable resource stewardship.'

While opposing a phosphate ban in both laundry and dishwasher detergents, CEEP, like AISE, appears to be focusing on stopping the proposed 2015 dishwasher ban. Caroline Andersson, CEEP sector group manager, tells Chemistry World that the potential impacts of phosphate free dishwasher detergents on hygiene, household energy use, water consumption and waste water treatment needs further study before a ban is legislated.

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2011/06/25

Scream ... The latest technology to charge the mobile phone

Korean scientists to develop new technology for mobile phone battery by shouting rather than electricity, where the technical conversion of audio frequencies to power, in the context of mobile companies compete to develop methods of shipment provided, clean and environmentally friendly.

Scream ... The latest technology to charge the mobile phone

According to the Daily Telegraph ” to “ expert at the University of sonkion Kwan in charge of research, Dr. sang Koo Kim, said: “ we tried to find a way to convert the audio energy around us, such as speech and music, to power and exploitation of shipping mobile phones ”.

And already produced ” “ company Samsung in April 2011 a phone works on its own battery by oxygen, by converting wind into electrical energy ayonath, where the new phone battery for direct methanol fuel operating oxygen instead of lithium ion rechargeable.

Nokia has recently been chanting: friends of the environment, the one on the exploitation of thermal energy into electrical energy, whereas the second battery shipped water, gas or water sweetened drinks sures shift to electric energy used in the operation of the phone.

2011/06/24

Pharma pollution is out of control in China

24 June 2011

By Hepeng Jia/Beijing, China

Harbin Pharmaceutical Group, a major pharmaceutical company in northeast China's Heilongjiang Province that specialises in antibiotics, has signed an agreement with Acheng District government (a suburb of Harbin) to build a new production plant. The agreement follows a recent pollution scandal involving the company that resulted in its active pharmaceutical ingredients (API) workshop being closed.

The pollution scandal - waste gases and water that exceeded legal pollution limits were released into the environment by Harbin - highlights pollution from China's booming API manufacturing business as a major environmental challenge. According to China's official Xinhua News Agency, Harbin's new production plant will not emit pollutants above the national standard, and the first phase of the project should be completed by 2013 and should cost Yuan2 billion (£193.3 million)

API pollution problems seem to continue even after the Chinese government's increased efforts to reduce the environmental pollution from the pharmaceutical industry. In July 2010, the Chinese Ministry of Environmental Protection (MEP) released a new, harsher set of standards for the discharge of pharmaceutical pollutants into water, after it identified the industry as one of the key polluting sources. However, the fast developing API making business is frustrating the government's efforts.

Pharmaceutical pollution in China is on the increase and it's getting harder to control
© Thinkstock

Ren Liren, director for Hebei Province-based National Engineering Centre for Pharmaceutical Pollution Water Discharges, was quoted by local media as saying that it is easier to meet the new discharge standards for conventional end drugs, but most API makers are finding it difficult to fulfill this goal.

China has become the world's largest API maker, with its two million tonnes of annual output accounting for 20 per cent of the world's total. 'Compared with other chemical industries, the costs to control pharmaceutical pollution are much higher, as many more materials are required to produce the same unit of end products, says Yu Zailin, president of Beijing-based Weiming Fortune Gene Drug Research Centre. 'There is much more diversity of pollutants in the pharmaceutical industry. This is particularly true for the API industry,' he adds.

Domestic pharma companies are reluctant to increase investment in environmental protection, as severe industry competition has pushed prices of products lower, therefore affecting profits. 'API exports are becoming the main new profit source for Chinese pharma companies, given the lack of output of innovative drugs,' Yu tells Chemistry World.

As it is hard for the average pharma company to invest in ways to reduce pollution, Ren suggests that a solution could be to group companies within pharmaceutical industrial parks. Every company's polluting discharges could then be processed in one place and in large amounts, he says. Yu agrees with this solution and adds that local government should invest in these common environmental facilities to reduce pollution while alleviating individual company's costs.

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Nanogenerators for environmental sensors

24 June 2011

A nanomaterial-based, self-powered sensor that detects mercury in water has been developed by teams from the US and Korea.

Most environmental sensors need to be wired to a power supply, which can be expensive in terms of parts and labour. There is also the potential for contamination from batteries. Solar energy is a more attractive, and greener, alternative, but it relies on weather conditions and time of day.

Instead, Zhong Lin Wang, from the Georgia Institute of Technology, Atlanta, US, and colleagues have made a standalone sensor that harvests energy from movements occurring in its surroundings. They created a nanogenerator to harvest the energy using zinc oxide nanowires (ZnO NW). The nanowires are piezoelectric, which means that they accumulate charge when they are moved, and they're environmentally friendly.

Left: zinc oxide nanowires on a flexible substrate (top) with a gold film electrode (bottom); right: zinc oxide nanowires

The team made the device by placing the nanowires onto a flexible substrate, with the ends of the wires in contact with a gold film electrode. When the nanowires were compressed as a result of movement, electrons flowed along the wires to the gold conductor. With successive compression and release, the electrons flowed back and forth, producing an electrical current. The output was stored in a capacitor to power the sensor to detect pollutants periodically. The sensor was made from single walled carbon nanotubes that turn on an LED indicator. Wang tested the device in water and found that the LED lit up in the presence of mercury ions, and the mercury concentration was indicated by the intensity of the LED.

'What's most exciting is that we have built a self-powered system that is driven by energy harvested from the environment that can work independently and sustainably,' says Wang. In the future, Wang hopes to apply the nanogenerators in other areas besides environmental sensing. 'There are potential applications in wireless biosensing, sensor networks, personal electronics and even national security,' he says. His team is also looking at harvesting energy from the environment in other ways such as turbulence in water or air flow and sonic waves.

Jun Liu, from the Pacific Northwest National Laboratory, Richland, US, who works on the synthesis and applications of nanostructured materials for energy was impressed with the device and says that the research has great potential for practical applications. 'Some biomedical applications or remote area sensing make it difficult to provide the power for very small devices. Fully functional and standalone nanodevices will be handy for these applications,' he says.

Rebecca Brodie
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An NMR machine in a fume hood

24 June 2011

Scientists in Germany have demonstrated a portable nuclear magnetic resonance (NMR) spectrometer that's small enough to be placed in a fume cupboard to monitor the progress of a reaction in situ.

NMR spectrometers are used to determine compound structures. They are typically installed in dedicated laboratories because they are large and their superconducting electromagnets - which split the spin states to create energy gaps, the transition energy of which makes up the final spectrum - need cryogenic coolers, which restrict their mobility. This means that the technique can't be used in situ, which would provide valuable insights into reactions.

Federico Casanova and coworkers at RWTH Aachen University have overcome this limitation by using a permanent magnet the size of a fist instead of an electromagnet. The cylindrical magnet consists of three rings, each made up of an array of eight samarium-cobalt magnets, separated by parallel gaps. Eight smaller rectangular magnets can be moved in or out of the gaps to ensure a consistent field. The magnet is connected to a portable NMR spectrometer, which is controlled by a laptop computer.

The reaction mixture is circulated through the NMR and back to the reaction vessel using tubing and a peristaltic pump and NMR spectra are produced on a laptop computer

To demonstrate the device and its flexibility, the team used it to follow the hazardous trimerisation of toxic propionaldehyde using an indium trichloride catalyst. As the reaction proceeded, the mixture was circulated through the magnet and back to the reaction vessel using tubing and a peristaltic pump. The team monitored the reaction's progress online by determining the concentrations of reactant and product from the NMR spectra. 'The advantage here is that during the reaction, we are getting information online,' says Casanova. 'The problem with a traditional spectrometer is that there are long time delays between sampling and measurements, and during this time the sample is not under controlled conditions.'

'Having a handy way to monitor a reaction - how far it's gone, how fast it's proceeding, whether it's following the right pathway or going off to produce some side product that's not wanted - rapidly and conveniently in situ in the right place in the process line is potentially very important,' explains Tim Claridge, director of NMR spectroscopy for organic chemistry at the University of Oxford, UK.

However, both scientists agree that the technique could be improved and Casanova plans to develop better magnets to improve sensitivity and resolution.

Yuandi Li
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2011/06/23

Dinosaur smile reveals secret to staying cool

23 June 2011

The levels of rare carbon and oxygen isotopes in fossilised dinosaur teeth suggest that some dinosaurs had body temperatures comparable to modern mammals. The technique used in the studies could now be applied to other species of dinosaur to help solve a long running debate over whether the animals were warm or cold blooded.

For decades, palaeontologists have arguing over whether dinosaurs were endothermic - 'warm blooded' - like mammals, or ectothermic - 'cold blooded' - like reptiles. Endotherms stay warm by burning food, while ectotherms get their heat from their surroundings - lizards, for example, bask in the sun. Some larger animals like leatherback turtles stay warm just by virtue of their small surface area to volume ratio, a phenomenon referred to as gigantothermy. But some dinosaurs were so large they must have risked overheating.

John Eiler (foreground) and Rob Eagle analysed fossilised dinosaur teeth to try to solve the age old question of whether dinosaurs were cold or hot blooded
© Caltech / Bill Youngblood

Recent models based on dinosaur growth rates have been used to estimate that the body temperature of the largest sauropods got as high as 40ºC. Now a team of US and German researchers led by Robert Eagle at the California Institute of Technology has made novel use of a recently developed isotopic technique to show that at least some dinosaurs were probably slightly cooler - between 36-38ºC. This suggests they had physiological adaptations to help them regulate their body temperatures - just as mammals do.

Eagle's team focused on 13C and 18O isotopes that bond more stably or 'clump' together at lower temperatures. 'People first started looking at the clumping of these two heavy isotopes in CO­2 gas in the atmosphere - to track where it came from,' says Eagle. 'I started working on this mineral that makes up bones and teeth and contains a very small component of carbonate.' Measurements of the clumping can be used to estimate the temperature at which the carbonates originally precipitated.

Camarasaurus tooth from the Jurassic Morrison Formation of North America that was analysed for carbon and oxygen isotopes levels
© Thomas Tutken, Bonn University

The researchers estimated average body temperatures for different sauropods - Brachiosaurus, Camarasaurus and another in the Diplodocus family. The temperature range they obtained suggests some of these large dinosaurs were neither cold like modern crocodiles and alligators, nor excessively hot. 'The numbers we got are striking because they're very similar to most modern mammals,' says Eagle.

The technique effectively does away with one of the unknown variables involved in reconstructing past temperatures, says Stephen Grimes, a geochemist at the University of Plymouth. 'Previously you had to model the isotopic composition of the fluid from which the tooth grew and use that in combination with what you measured on the tooth to reconstruct the temperature,' he says. 'Now you can work out temperatures just by measuring something directly and plugging it into an equation.' However, because clumping of the two isotopes is so rare, there is a reasonably large margin for error - about 1 or 2°C, he adds.

Penny Higgins, a specialist in isotope geochemistry at the University of Rochester, New York, says it is now up to the palaeontology community to combine the results with other interpretations of growth rate, body mass and behaviour to determine whether dinosaurs were warm blooded. 'The methods used in this paper cannot distinguish between a truly warm blooded organism versus one utilising gigantothermy to maintain body temperature,' she says.

Eagle agrees the results don't put an end to the debate, but thinks they provide more than just proof of concept, placing upper and lower limits on body temperatures. 'We might be able to say something more definitive if we made similar measurements over a big range of sizes, for example, by looking at juveniles or dwarf species,' he says. 'If you thought they were gigantotherms, you might expect to see their body temperature differ across the sizes. If they were like mammals, you'd expect to see the same temperature.'

Hayley Birch
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Breaking the carbon-fluorine bond

23 June 2011

US chemists have discovered a new way to break the bond between carbon and fluorine atoms - the strongest carbon bond there is. The reaction, which is mediated by an iridium complex and proceeds in an unexpected way, is important because many pharmaceuticals and agrichemicals incorporate C-F bonds. The research suggests possible routes for the development of new catalysts to promote reactions that make or break C-F bonds.

An unexpected route
© Science / AAAS

Bonds between fluorine and carbon atoms in aromatic rings or with double-bonds can be made and broken by using oxidative addition mediated by transition metals. But this approach has failed with the kinetically less reactive bond between fluorine and alkyl carbon atoms. Now, researchers at Rutgers University in New Jersey have cracked the problem by using a catalyst based on an iridium centre clamped between two bulky dialkylphosphino groups - a so-called pincer-ligated complex.

The research team had previously shown that similar catalysts attacked C-O bonds in an unusual way. 'The metal centre first attacks the C-H bond, which is oxidatively added, with the oxygen then migrating from the carbon to the metal and the hydrogen returning to the carbon,' says team member Alan Goldman. 'With that in mind we wondered if something similar might happen with a C-F bond, and to our pleasant surprise it did.'

As the carbon approaches the complex, the metal centre inserts itself into a C-H bond. The fluorine then migrates to the metal, with the displaced hydrogen returning to the carbon. 'At first sight it looks as though the hydrogen never left and that the iridium inserted itself directly into the C-F bond,' says Goldman. 'But this is not the case, and I do not think anyone would have anticipated how the reaction proceeds.'

Goldman adds: 'What I think we have done is provide an important piece of information which could help people to design new catalysts for making and breaking this type of C-F bond.'

Mike Whittlesey, who researches C-F bond activation at the University of Bath, UK, says: 'While significant progress has been made in activating sp2 hybridised C-F bonds, activation of aliphatic C-F bonds has been performed on exceptionally few occasions and then not with the very simplest substrates reported here, fluoromethane and trifluoromethane. Furthermore, the strong track record of the types of pincer metal complexes that Goldman has employed raises the real possibility of being able to utilise the stoichiometric chemistry he has now described for the development of catalytic C-F functionalisation reactions - a very exciting prospect.'

Simon Hadlington
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Graphene goes 3D

23 June 2011

Scientists in China have developed a quick and easy procedure for preparing 3D graphene in water, enhancing graphene's properties so that it can be used in supercapacitors, to store hydrogen and as a catalyst support.

Graphene, a single sheet of carbon atoms patterned in a honeycomb lattice can, via self-assembly, form 1D and 2D structures that have many potential applications. However, the graphene obtained is usually small, which limits its use as a functional material. 3D microporous and mesoporous carbon materials (hydrogels and aerogels) are lightweight; have high porosities and storage capacities; large surface areas; high electrical conductivity and thermal stability. Preparing such structures is challenging under mild conditions and current methods are not scalable or cost efficient.

By combining the reduction of graphene oxide and self-assembly of the products, it's possible to prepare 3D graphene structures in a one-pot process, igniting ideas for novel materials

Lifeng Yan and colleagues at the University of Science and Technology of China, Heifei, have prepared 3D graphene structures by self-assembly from graphene oxide using mild chemical reduction in water at 95 degrees Celsius at atmospheric pressure without stirring. The graphene shapes were controlled by using reactor vessels of differing shapes. The team were able to produce cylinder-, pear- and sphere-like shapes. 'The process is quite simple - any macroscopic 3D graphene shapes can be prepared at room temperature and pressure,' explains Yan.

In tests, the team found that the materials had high electrical conductivity, and high mechanical and thermal stability. The values for specific capacitance were similar to graphene hydrogels prepared by a hydrothermal method. The materials' mechanical stability, measured by a compression test, was comparable to chemically cross-linked polymer hydrogels.

Yan's team plans to investigate the applications of their materials in super-capacitance, biosensors and catalysis, as well as preparing different types of novel 3D graphene composites.

'These macroscopic multi-pore materials will be very interesting if they can be used for reducing greenhouse gases by developing new catalysts,' says Xiaobo He, an expert in graphene materials at Louisiana State University, US.

Carl Saxton
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One in the eye for diabetes

23 June 2011

A team in Canada has made a device that could be implanted behind the eye to release drugs on demand to treat retinal damage caused by diabetes.

Diabetic retinopathy can lead to blindness. A current treatment is laser therapy, which is destructive and results in side effects, such as diminished side and night vision, and unwanted laser burns. Another therapy is to administer antiproliferative drugs, such as docetaxel (normally a cancer drug), but the compounds clear from the blood quickly, so high doses are needed to produce the desired effect, which increases toxicity to other tissues.

Mu Chiao and colleagues from the University of British Columbia in Vancouver have made a device to be implanted behind the eye that releases drugs when triggered by an external magnet. This means that the device doesn't need a battery and lower doses can be used. Implantable devices have been made before but drug release is done by diffusion and the release rates can't be controlled, which is a problem if the dosage rate needs to be adjusted when a patient's condition changes.

The device is loaded with a drug then sealed with a polydimethylsiloxane membrane. Applying a magnetic field causes the membrane to deform, triggering the release of the drug.

The team made the device from a reservoir loaded with the drug, sealed by an elastic magnetic polydimethylsiloxane membrane. Applying a magnetic field causes the membrane to deform, triggering the release of the drug.

The team loaded the device with docetaxel at a dosage suitable for treating diabetic retinopathy over 35 days and found that background leakage of the drug was negligible. They also monitored the drug's biological activity over time by testing it against two cell lines, including prostate cancer cells. They found that they were able to achieve reproducible release rates and the docetaxel retained its pharmacological efficacy for more than two months in the device.

'The device is intended to improve the quality of life for patients suffering from chronic diseases,' says Chiao whose motivation was personal as he has family members that have diabetic retinopathy.

'This is an interesting approach towards developing therapeutically useful ophthalmic delivery systems,' says John Tsibouklis who studies biomaterials and drug delivery at the University of Portsmouth in the UK. 'It represents a significant advance towards device based drug delivery.'

Chiao hopes to pin down the exact medical applications for the device so that he can tailor the mechanical design to particular diseases. However, he does envisage challenges ahead, involving biocompatibility, performance optimisation and degree of controllability.

Elinor Richards
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2011/06/22

Synthesising red wine's overlooked chemical secrets

22 June 2011

US chemists have discovered how to selectively synthesise a wide range of natural polyphenol compounds based on resveratrol, a stilbenoid consisting of three phenols on two aromatic rings linked by a short hydrocarbon chain. Controlled synthesis of these compounds will allow researchers to probe their possible health benefits.

Resveratrol and its many derivatives are present in the skin of grapes, for example, and are thought to be responsible for some of the apparent health benefits of red wine. These health benefits may help to explain the 'French paradox' - a low incidence of coronary heart disease in the population, despite a diet high in saturated fat.

Resveratrol and its oligomers may help to explain the health benefits of red wine

However, while much effort has been devoted to studying resveratrol, its oligomers, consisting of a number of resveratrol units linked in various configurations, have not been as thoroughly probed. This is partly because isolating the oligomers is both costly and time-consuming - processing hundreds of kilograms of dried plant material often yields only a few milligrams of a single product.

Now, Scott Snyder, Andreas Gollner and Maria Chiriac at Columbia University in New York have shown how a variety of resveratrol oligomers can be selectively produced, some in quantity, which will enable a much more focused and systematic study of their potential as medicines.

In earlier work, the team developed a way to create many of the dimeric members of the resveratrol family. However, each of these dimers has multiple potential points of attack for the subsequent attachment of additional resveratrol monomers. One dimer, for example, has four apparently identical hydrogens available for reaction. The team discovered, however, that these hydrogens behave differently when presented with electrophilic bromine reagents. Reacting the dimeric core with N-bromosuccinimide resulted in a bromine substitution at one specific hydrogen, followed by another specific hydrogen. In this way a bromine 'handle' for adding extra resveratrol units can be placed in one position or in two positions in a controlled manner.

Joining up resveratrol units in a controlled manner will allow researchers to investigate their potential health benefits

In an attempt to add resveratrol monomers at different locations, the team experimented with a range of brominating reagents. Eventually a compound called bromodiethylsulfide bromopentachloroantimonate (BDSB) was found to solve this problem. Using this reagent, a single resveratrol dimer can be primed to accept further monomers in multiple positions in a controlled and directed way.

'Unlike many syntheses which result in only a single product, this approach allows us to generate an entire family of structures,' says Snyder. 'This may allow people to move beyond looking solely at resveratrol and extend biochemical studies to rationally probe these more complex natural products,'

Sharon Rossiter, a medicinal chemist at the University of Hertfordshire in the UK, says that the Snyder group's approach 'has enormous potential both for the synthesis of other complex architectures and for evaluation of these exciting natural products in drug discovery'.

Simon Hadlington
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US approves cancer drugs twice as fast as Europe

22 June 2011

Cancer drugs are, on average, approved nearly twice as fast in the US than they are in Europe. Analysis by Friends of Cancer Research (FOCR) in Washington DC, US, indicates the median gap between a pharma company filing for approval for a new cancer medicine and the Food and Drug Administration (FDA) giving it the go-ahead was 182 days between 2003 and 2010. In Europe, the median time to gain European Medicines Agency (EMA) approval was 350 days.

This was not what the authors expected to find. 'We had heard a lot of criticism that the FDA was performing poorly compared to Europe in getting cancer medicines to patients,' explains Samantha Roberts, science policy analyst at FOCR. 'We started looking at the approval times to find ways to improve the FDA process, and what we found surprised us. It went against everything else we'd been hearing.'

The US approves cancer drugs almost twice as fast as Europe
© F. Hoffmann-La Roche

Greater collaboration

One reason for the US's faster approval times appears to be that cancer drugs are more likely to qualify for the FDA's priority and accelerated review systems. However, greater collaboration between the two agencies may address the difference in approval times. 'There seems to be a desire to make sure the policies around specific endpoints [of drug trials] are as similar as possible between the regulatory agencies,' says FOCR executive director Jeff Allen. 'I think there's an acknowledgement that it's not in anyone's interests to have a [pharma company] go through two extremely disjointed systems.'

The authors believe such initiatives will lead to the differences in approval times between the two agencies decreasing in future. It might also address whether a drug is approved or not - of the 35 drugs studied, 32 were approved in the US, compared to just 26 in Europe. The three the FDA turned down were all approved by the EMA.

Joshua Cohen, research assistant professor at Tufts Center for Drug Development in Boston, US, was less surprised. 'The results are consistent with several studies we've done recently,' he says. 'Cancer is an area in which the US still has a comparative advantage. Many products are biotechnologically derived and, generally speaking, biotechnology still does better in the US than Europe. Cancer advocacy is very powerful in the US, and there is still a lot of market upside in cancer therapeutics here, while many other therapeutic categories are saturated.'

Access over time

Cohen wishes access to cancer drugs was interpreted more broadly than simply looking at approvals, as well as taking into account the realities facing drug developers, patients, providers and payers today. 'Regulatory approval is half the battle, but it tells you little about real patient access to these drugs, and whether or not having access to certain drugs is even appropriate,' he says.

He thinks any discussion about cancer medicine availability must be done in the context of paying for them. 'In the US, we have a tiered system, and the patient's ability to pay out of pocket or buy good insurance plays an important role in determining access,' he says. 'Many do indeed have speedier and greater access to oncology drugs, but a significant group is not so lucky. In the US, some payers are explicitly and openly taking a closer look at all newly approved medicines, including cancer drugs... Nevertheless, in the US cancer remains a protected therapeutic class, especially for Medicare patients. In Europe, payers are definitely taking a harder line, in particular with expensive but marginally beneficial therapies.'

Cohen also believes lag times between approval and reimbursement decisions in Europe are shortening a little, and health technology agencies such as NICE should be praised for their honest and forthright approach to rationally allocating resources. 'They make mistakes, but at least they're mostly transparent about them,' he says. 'In the US, there is little transparency in the decision making process, and a lot of implicit rationing. We can no longer pretend we have unlimited resources. We don't. Hard decisions need to be made with a long-term view to benefiting society as a whole.'

Speed should not come at the expense of safety, however. According to Meg McArthur, senior policy and information officer at non-profit Breakthrough Breast Cancer, it is difficult to directly compare the FDA and the EMA and the processes they use as they are required to adhere to different laws and regulations. 'Patient safety is of the utmost importance,' she stresses. 'Therefore, it is necessary that the appropriate measures and time required are taken to ensure approvals for new drugs are safe.'

Allen also says it is important that financial resources are available to support rigorous review. 'During this time of increasingly difficult budget environments, we have advocated that US Congress provides the resources necessary to support rigorous review at the FDA,' he says. 'This isn't to say that the current system is perfect - but it's worth examining ways in which it could be improved.'

Sarah Houlton
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2011/06/21

Nanotubes inject stroke therapy into rats' brains

21 June 2011

Carbon nanotubes (CNTs) have been used as a delivery vehicle for tiny pieces of RNA to minimise brain cell death during and after a stroke. Rats given the nanotube therapy performed better than controls in physical skills tests after a stroke was induced and the researchers believe that this treatment could be used to tackle other neurodegenerative diseases, although questions remain over the safety of the nanotube vehicle.

Stroke is the second biggest killer worldwide. When a patient has a stroke it results in traumatic brain injury. This injury leads to increased activity of an enzyme, which results in a concomitant rise in programmed cell death. Inhibiting this enzyme would result in fewer neurons dying after a stroke, which would, in theory, help the stroke victim to avoid some of the debilitating physical effects, such as difficulty walking. Unfortunately, it is very difficult to target the enzyme at the site of injury in the brain.

Carbon nanotubes act as a delivery vehicle for small pieces of RNA that help to prevent cell death in the brain after stroke

Now, scientists led by Tommaso Pizzorusso at the National Neuroscience Research Institute in Pisa, Italy and Kostas Kostarelos at the University of London, UK, think they have found a way to inhibit this enzyme in the brain. They used ammonium-functionalised multi-walled CNTs to deliver small interfering RNAs - nucleic acids which block gene expression - to stop production of this enzyme. Rats that received an injection of the CNT-siRNA complex directly into the brain performed better in food retrieval tests than controls, after a stroke was induced. Although the effects were more pronounced if the siRNAs were administered before the stroke, injecting them after the stroke is still beneficial.

Pizzorusso believes that the work proves nanocarriers can deliver siRNAs to treat stroke. 'The type of nanocarrier is not so important, we need chemists to prepare nano-vehicles with the best biocompatibility, and the best abilities to carry and release the siRNA once in the cells,' he says. He says that protecting neurons in this manner should be combined with research to obtain better function from the remaining neurons after stroke damage. This combination should preserve more brain cells and enable the preserved cells to work better.

'Our overarching hypothesis is that if we take CNTs coated or conjugated with small molecules and inject them directly into tissue, these materials are capable of piercing the cells as if they were an extension of the syringe,' Kostarelos says. While there may be debate about the carrier, this is one of the first CNT-based treatments to have piqued the interest of clinicians and it is an important step forward for nanomedicine, he adds. Kostarelos's group is now looking at what happens to the CNTs after the treatment is administered, and says that this therapy could be used in other neurodegenerative diseases.

Vincent Rotello, an expert in nanomaterial drug delivery at the University of Massachusetts, Amherst, US, says that 'localised administration provides a means of increasing therapeutic efficacy while minimising collateral effects. Questions of long-term toxicity of the CNTs remain; however, this therapeutic strategy could be readily applied to other vehicles.'

Carol Stanier
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Making smell-o-vision a reality using a polymer matrix

21 June 2011

A polymeric matrix of cells, which can be opened and closed individually, could bring personal 'smell-o-vision' a step closer to reality.

Virtual reality experiences are becoming more and more realistic thanks to both audio and visual advancements. Smell-o-vision, as it's often called, can enhance these experiences, by releasing odours to match visual clues. However, attempts to create it often fail to impress due to a narrow range of smells that can only be deployed once.

Now, researchers at the University of California, San Diego, US, and Samsung in Korea, think they have found a solution. They used the polymer polydimethylsiloxane (PDMS) to create a square matrix of cells, which can each hold a different fragrance. The scientists then used heat to release an odour from a cell on cue.

Polymer matrix that releases odours to order could help to create a more realistic virtual reality environment

'We wanted to be one of the pioneers to demonstrate that the sense of smell - odours - can be generated on command,' says Sungho Jin at the University of California, San Diego. The team placed a set of heated elements both horizontally and vertically under the cells to control whether each cell was open or closed. A cell only opens if both its horizontal and vertical elements are switched on - the heat causes the polymer to expand and the odour escapes through a puncture hole.

'In the past other people have used a single reservoir of some smell and tried to activate it, but in real life we are dealing with thousands of smells,' says Jin. The matrix system enables the researchers to use and control thousands of different cells relatively simply. For example a square of 10,000 cells - which can hold 10,000 different odours - needs only 200 controllers.

Takamichi Nakamoto, who combines odours with technology at the Tokyo Institute of Technology, Japan, is impressed with the matrix system. 'The basic principle of heating PDMS to release and stop an odour is not new,' he says. '[However], with a matrix many kinds of smells can be emitted, so [if the work] is realised it would be very interesting.'

The system can be used with cells ranging in size from nanometres through to micrometres, and shows no signs of leakage over a couple of days. The work is currently proof of concept, but the researchers say they could potentially develop the system for use in TVs or phones to enhance virtual reality experiences.

Manisha Lalloo
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Controversy over academy membership in China

20 June 2011

By Hepeng Jia/Beijing, China

Controversy has arisen in China regarding the candidates short-listed for membership of the Chinese Academy of Engineering (CAE) this year, as they include a group of executives from leading state-owned petrochemical firms.

CAE membership is commonly awarded to distinguished people in the: engineering, materials, transportation, chemical, energy, construction, agricultural, medicine and management sectors. However, criticisms have arisen as a group of state-owned enterprises (SOEs) and government leaders have been listed as membership candidates, mainly for management sciences. They include: Sinopec president Fu Chengyu, vice president of Sinopec Cao Yaofeng, former vice-president of PetroChina Hu Wenrui, and Zhang Xiaolu, vice president of China Power Investment Corp.

Though most of the above candidates have research and development experience in engineering fields, it is argued that their positions of leadership have taken them far from the frontier of research. At present, the CAE has 739 members, 44 of which are from the management sciences sector, including a former railways minister, former deputy health minister, and former energy minister.

Membership of the CAE represents a high social status for senior scientists
© ieeexplore

'Although these top leaders have been ranked with high positions, their academic work may not make them qualified for CAE membership,' says Gu Haibing, an outspoken professor of management at Beijing-based China Renmin University. He adds that in Chinese society, academy members remain quite powerful when deciding funding and influencing research projects.

The CAE has not responded to the criticism. But on its website, it has posted an open letter to member candidates, warning them against improper behaviour regarding membership issues. According to the letter, some existing members, who have voting rights, have already reported there are candidates trying to bribe them.

Zhan Zhengmao, a research fellow of science policy at the China Association for Science and Technology, says that the rush among senior leaders to become academicians is also because of the very high honour associated with the position. According to the China Science Communication Report 2011, of which Zhan is the first author, the Chinese public has low confidence in the government and public sector. But the science sector enjoys a trusted position, only second to the military.

'The fact indicates the very high social status of senior scientists such as academy members. This is a legacy that can be inherited even after their retirement from their official positions. I think this could be the major attraction for those who are already top leaders in SOEs or the government,' Zhan told Chemistry World.
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Chatty nanoparticles signal the attack on tumours

20 June 2011

Researchers in the US have shown how drugs can be directed to a tumour using two different nanoparticles that can talk to each other: one nanoparticle homes in on the tumour then loudly broadcasts its location to a second, drug-carrying particle that responds to the signal and accumulates at the target site. Early studies show that the system can result in 40 times more drug reaching the target than when non-communicating controls are used.

Conventional approaches to administering drugs typically involve swamping tissues with excessive amounts of drug to ensure that the target receives a therapeutic dose. Sangeeta Bhatia of the Massachusetts Institute of Technology and colleagues focused on how to generate a signal at the site of a tumour and then amplify it so that it can be easily received by a circulating drug carrier.

The researchers decided to use the blood's coagulation response as the signal. Here, a small stimulus that results in damage to a blood vessel is massively amplified by a biochemical cascade into a huge response resulting in vast quantities of the protein fibrin being manufactured to repair the wound.

Nanoparticles harness the body's blood clotting system to signal to each other and home in on tumour cells
© Gary Carlson/Nature Materials

The team devised one nanoparticle system to enter the tumour and cause damage to the blood vessels, resulting in excessive production of fibrin. The presence of fibrin would act as the 'transmitting' signal. A second nanoparticle circulating in the blood would then be tailored to seek out the fibrin, as a 'receiver' of the signal.

The team developed two types of nanoparticle that preferentially accumulate in tumours: small gold nanorods and a protein that attaches to blood vessels in the tumour. Once in the tumour, the nanorods can be heated by infrared irradiation to cause damage and trigger the coagulation response. The protein-based nanoparticles spontaneously prompt fibrin release when they arrive at the tumour.

Two drug-carrying nanoparticles were used as 'receivers', one consisting of dextrin-coated iron oxide nanocrystals, the other based upon a hollow lipid sphere called a lysosome. The first of these was fitted with a peptide that makes it stick to fibrin; the second with a peptide that interacts with an enzyme in the coagulation pathway, which 'staples' it to the fibrin sheet.

Experimenting with mice, the research team observed that tumour uptake of drugs carried by the 'receiving' nanoparticle was around 40 times greater than in the absence of the 'transmitting' nanoparticle and six times more efficient than nanoparticles designed to target receptors on tumour blood vessels. 'These early demonstration systems show a substantial improvement in efficiency,' says team member Geoffrey von Maltzahn.

Francesca Greco, who researches nanotechnological approaches to anti-cancer agents at the University of Reading, UK, says that the approach is ' interesting and versatile, with potential applications both in tumour diagnostics, as well as in tumour treatment'. Greco adds that signal amplification is of particular importance, as early tumour detection is the key to improving overall prognosis.


Simon Hadlington
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2011/06/18

Nanoboxes given optoelectronic function

17 June 2011

Scientists in the US have folded a nanoscale wafer of aluminium oxide, with a pattern of gold on its surface, into a hollow cube, creating a tiny optoelectronic device. They have made the smallest ever 3D split-ring resonator, a device widely used in new metamaterials that have unusual physical and electronic properties.

The researchers say that the 3D device is more active than its 2D counterpart, and that the work demonstrates the feasibility of creating functional, precisely engineered devices at the nanoscale.

© Small / Wiley VCH

David Gracias and colleagues at Johns Hopkins University in the US showed previously how nanoscale origami could be used to fold a sheet into a cube. They have now taken the process a step further by functionalising the product.

To make the cube the team first deposits a layer of polymethylmethacrylate on to a silicon substrate. They then use electron beam lithography to carve out a mould into a cruciform shape consisting of the six sides of the final cube. The mould is filled with aluminium oxide. A second layer of polymer is deposited and portions etched out at the meeting point of the individual panels, where tin is laid down to form the hinges for the box. The polymer is then removed and the silicon etched away with activated fluorine. This process is exothermic, and the heat generated melts the tin. As the molten tin coalesces it creates twisting forces that cause the alumina panels to fold inwards, creating the cube.

The team put gold on to the surface in the pattern for a split-ring resonator before overlaying the cube's panels to create the optoelectronic properties.

'In nanotechnology, it is relatively easy to make particles, but introducing patterning is less straightforward,' says Gracias. 'Here we have shown that we can engineer precise geometries and introduce patterns which have function.'

Mark Morrison, chief executive of UK educational charity the Institute of Nanotechnology, says that the combination of top down lithography and deposition and bottom up self assembly methods is of 'particular interest'. The devices, he adds, could have applications in a range of fields from computing to medicine. 'This is clearly cutting edge, fundamental research which still needs a lot of development before it could find real life applications,' says Morrison. 'One major issue will be scaling up this technology to manufacturing levels.'

Gracias says that the process has limitations. 'It is expensive, and we can only make a few structures at a time. But what we are doing is pushing the limits of this type of engineering.'

Simon Hadlington
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2011/06/16

Plasmon rulers measure in 3D

16 June 2011

Researchers in the US and Germany have used a plasmon ruler to show in principle how to measure the three dimensional position of objects at the nano-scale. The ruler, which consists of a stack of gold nano-rods, could one day be used to improve understanding of soft matter processes, such as protein folding.

Plasmon rulers made out of gold nanorods could help researchers understand how DNA or proteins fold
© Science/AAAS

Plasmon rulers consist of metal nanoparticles that are attached to biomolecules. Like tiny antennae, the nanoparticles create plasmon resonances - waves of electrons - that absorb or scatter light at specific visible or infrared frequencies. Because the exact frequency depends on the proximity of other particles, the nanoparticles offer a way to measure inter-particle distance.

In the past, such distance measuring has been limited to one dimension, which has generally ruled out determining the relative orientation of the particles. But now Paul Alivisatos and Na Liu of the University of California at Berkeley, US, together with colleagues at the University of Stuttgart in Germany, have found a way to explore the other two dimensions. 'Compared with 1D plasmon rulers, our 3D plasmon ruler offers additional degrees of freedom, such as rotating, twisting, tilting and any conformational changes,' says Liu.

The researchers created their plasmon ruler from five gold rods, each less than 350 nm long, in an 'H' arrangement, with one horizontal rod sandwiched between two vertical rods at either end. They used electron-beam lithography to create several such arrangements, subtly varying the position of the central, horizontal rod in each one. By examining the energy of the resonance dips in the transmission spectrum, the researchers found they could determine this central-rod position with accuracy.

'I'd say this takes the plasmon ruler concept - which [Alivisatos and his group] have helped pioneer - to a new level of sophistication and complexity,' says David Ginger, a chemist at the University of Washington in Seattle, US, who has worked with plasmon rulers. Ginger says there will be hurdles for practical applications, such as incorporating the rulers into biochemical systems, something the authors also point out. But he adds that this is 'within reach and, in the long term, variations of this approach are likely going to find many applications.'

Liu says that one application of 3D plasmon rulers could be understanding why proteins fold in a certain way - an important topic in biology because incorrectly folded proteins are linked to diseases like Alzheimer's and Parkinson's disease.

Jon Cartwright
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Nanomaterial dust no worse than the rest

16 June 2011

A team of researchers in Germany has brought some good news to the debate on nano-material safety. The team took four materials containing nanoparticles or nanotubes and subjected them to high speed sanding, gentle abrasion and UV radiation, and found that the resulting dust was no finer than that from conventional materials. What's more, rats exposed to the fine dust fared no worse whether the material contained nano-components or not.

With an eye on likely consumer exposure, Wendel Wohlleben and his colleagues at German chemical group BASF, in Ludwigshafen, studied two thermoplastic materials - polyoxymethylene (POM) and polyamide - as well as two cements infused with different nanostructures.

The POM contained carbon nanotubes (5 per cent by weight) for anti-static properties; the carbon nanotubes in the cement (2 per cent) shielded the material from high-frequency radiation; the polyamide contained silicon dioxide particles (4 per cent) for increased strength; and the calcium silicate hydrate nanoparticles in the second cement (4 per cent) accelerated its hardening.

Cement with embedded carbon nanotubes
© Small / Wiley VCH

The researchers did not find significant release of nano-components into the air as a result of sanding. They collected the dust and measured the particle sizes and chemical identities using microscopy, spectroscopy, laser diffraction, fractionation by centrifuge and filtration. In all cases, the nanomaterial powders were not significantly smaller than the control powders.

By rolling wheels over the materials, the researchers simulated the gentler abrasions of everyday wear and tear. As with the sanding, the sizes of particles released through this treatment appear to be independent of the material's nano-component content.

Andrew Maynard, professor of environmental health sciences at the University of Michigan, US, says these results were expected as the nano-components are very tightly bound to the plastic and cement. But he adds: 'We cannot be complacent and assume that there is no release or subsequent risk here - there need to be studies, and this is one that helps inch the state of knowledge forward.'

A dose of UV light equivalent to nine months outdoors degraded the POM and exposed the network of carbon nanotubes, an effect which Wohlleben says is known. In contrast, the researchers saw no differences in UV weathering between the nano-engineered and plain versions of the polyamide or either cement.

The team then studied the biological effects of the powders, using only particles small enough for absorption by lung tissue. They injected suspensions of powder into the lungs of 48 rats. Three days after the dose, and again after three weeks, the researchers examined the rats for damage to tissues or DNA. None of the rats experienced general or organ targeted toxicity or mutagenic effects. Although the powders caused some inflammation in the lungs of the rats, the nano-materials were no more detrimental than their conventional counterparts.

Wohlleben calls the rat study preliminary as it was limited by the amount of powder available, but the results suggest that the nano-components do not increase the hazards of inhaling the material. 'The statistics will be improved in further studies, but for the first time, we have experimentally determined all elements of a risk assessment of nano-composites,' he says.

Kate McAlpine
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Forming the first sugars with formose reactions

16 June 2011

While studying the formose reaction under hydrothermal conditions, scientists in Germany may have replicated the formation of the first sugars on prebiotic Earth.

In the formose reaction, formaldehyde undergoes self-condensation to give a mixture of sugars. The precursors are simple compounds so scientists have speculated that the reaction could have played a role in the origin of biomolecules. But, the reaction normally takes place under alkaline conditions in the presence of a catalyst.

Daniel Kopetzki and Markus Antonietti from the Max-Planck-Institute of Colloids and Interfaces in Potsdam carried out the reaction at high temperature and pressure - 200 degrees Celsius and 100 bar - to emulate conditions that would have been present in hydrothermal vents and on prebiotic Earth. They found that the sugars were produced under these conditions, too, without a catalyst or alkaline conditions.

Hydrothermal synthesis could provide greener synthesis methods as well as information about the origin of life
© NOAA

'The origin of life has been studied for well over a century but if we mean to define it as the emergence of a self-reproducing complex chemistry that is capable of evolving and sustaining itself, it is still utterly unknown,' says Sandra Pizzarello who studies prebiotic catalysis at Arizona State University, US. 'Darwin was among the first to touch upon the theme and foretold our current working hypothesis - that biological evolution was preceded and may have its roots in abiotic chemical evolution.'

'We do not claim that this reaction did contribute to the formation of the first biomolecules,' says Kopetzki, 'but the research is of interest, as it is unclear how life emerged and therefore important to explore plausible pathways.'

So far, model systems have not shown the selectivity and specificity of life's molecules. 'This work reminds us of this again and points out that hydrothermal conditions might not be useful either,' says Pizzarello.

Kopetzki says that the findings could be applied to green synthesis. 'Water at high temperature is a beneficial solvent. Our experiments have shown that catalysts can be simplified under such conditions,' he says. 'Saving catalysts by employing high temperature and simple salts adds another sustainable feature.'

Amaya Camara-Campos
RSC

2011/06/14

A new spin on protein NMR

14 June 2011

Smart lateral thinking by scientists in Italy and Germany has potentially opened an entirely new field in the study of the structure of proteins. The researchers have described a new technique for rapidly obtaining solid samples of protein for nuclear magnetic resonance interrogation without needing to crystallise the protein. The method, which combines solid-state NMR with ultracentrifugation, could become a versatile way to study transient proteins or to monitor how the structure of proteins changes in the presence of other molecules.

New technique will allow researchers to study protein structure in greater detail using NMR

NMR has been used for decades to measure the distance between pairs of nuclei in proteins, which can then be built up into a picture of the molecule's structure. The method is well-suited to soluble proteins - but is limited by the protein's molecular weight. As proteins get above a molecular weight of around 30,000 the signals become almost impossible to interpret. NMR can be used on larger proteins in their crystalline form - solid-state NMR - but obtaining crystals can be difficult and time consuming.

Solid state NMR requires the sample to be rotated at high speed in the sample tube, which has the side-effect of producing forces of up to 1 million g. Ivano Bertini and Claudio Luchinat of the University of Florence had a 'lightbulb moment' when they realised that this spinning tube was remarkably similar to an ultracentrifuge - used for almost a century to draw soluble proteins into a solid pellet of sediment. 'We wondered what would happen if we put a soluble protein in the sample tube and spun it - would the protein form a sediment and would this provide an NMR signal?' Luchinat tells Chemistry World.

Working with colleagues from Florence and the Technical University of Munich, the researchers experimented with the soluble protein ferritin, which has a molecular weight of 480,000. 'As soon as the sample started spinning we could see a signal of the solid protein as it formed a precipitate on the wall of the cylinder,' Luchinat says. The signal was of the same quality as that from crystalline ferritin. As the spinning stopped, the protein sediment reverted back to solution.

The sample tube can also become a reaction vessel: small molecules could be added to the protein and the effect on the structure observed when the sediment is formed. 'It also allows us the possibility to look at species that are transient and difficult to isolate in any other way,' Luchinat suggests.

Mark Lorch, who uses NMR to study proteins at the University of Hull in the UK, is impressed by the finding. 'This cuts out the need for laborious - and potentially damaging - preparations and so has the potential to make many more proteins accessible to structural studies by NMR. Like so many good ideas it now seems so obvious.'

Simon Hadlington
RSC