2013: the year in review

C&I Issue 12, 2013

Super-repellent surfaces

In January, researchers reported developing new ‘superomniphobic’ surfaces that repel not just water but a wide range of liquids – an advance toward stain-proof, spill-proof clothing, protective garments and a host of other products (JACS, 2013, 135(2), 578). Scientists have previously reported ‘omniphobic’ surfaces, which can cause a range of different liquids to bead up and not spread on them. But typically very low surface tension liquids, such as some oils and alcohols, can adhere to those surfaces. Further, scientists have mostly focused on making surfaces that repel only one of the two families of liquids – Newtonian liquids. Instead, the surfaces made by researchers at the University of Michigan, US, display extreme repellency to both Newtonian and non-Newtonian liquids, including concentrated acids and bases, oils and alcohols with extremely low surface tension, solvents and various polymer solutions. It is claimed that virtually all liquids easily roll off and bounce on the new surfaces, making them ideal for protecting other materials from the effects of chemicals.

Hydrogel for heart repair

An injectable hydrogel that helps repair heart tissue after a heart attack was pronounced safe and ready for testing in humans, according to a study published in February (Sci. Transl. Med., doi: 10.1126/scitranslmed.3005503). University of California, San Diego, US, bioengineers demonstrated in a study in pigs that the hydrogel can help the heart grow new tissue and blood vessels, clearing the way for clinical trials in Europe.

A major problem after heart attacks is the loss of healthy heart muscle and an increase in scar tissue. The new material gels into a porous, fibrous scaffold once injected into damaged heart tissue. The scaffold provides a structural framework to encourage stem cells and new blood vessels to migrate into the damaged tissue, resulting in more cardiac muscle and less scar tissue. The researchers injected the hydrogel into pigs using a catheter, a procedure that does not requiring surgery or general anaesthesia.

There are an estimated 785,000 new heart attack cases in the US each year, with no established treatment for repairing the resulting damage to cardiac tissue. ‘Our data show that this hydrogel can increase cardiac muscle and reduce scar tissue in the region damaged by the heart attack, which prevents heart failure,’ said lead researcher Karen Christman. ‘These results suggest this may be a novel minimally invasive therapy to prevent heart failure after a heart attack in humans.’

A company called Ventrix, founded by Christman, is finalising manufacture of the hydrogel into a clinical-grade product.

Towards high-quality graphene

In February, C&I reported the story that researchers have made a major step forward towards developing a reliable method to produce uniform, high quality graphene – needed for applications in the electronics industry (C&I, 2013, 2, 9).

Currently, the most favoured method to make graphene involves chemical vapour deposition (CVD) via the decomposition of methane on copper foil at temperatures >900°C. However, the growth of graphene from different nucleation sites on the copper surface results in defects in the material that hinder electron transport and reduce its strength.

Now, analytical studies by an international team of scientists have found that the orientation the individual graphene domains depends on the crystallographic orientation of the copper foil (ACS Nano, doi: 10.1021/nn402489v). ‘We found that the graphene domains actually align on particular surfaces of the copper – Cu[111] and Cu [101], explained University of Oxford researcher Adrian Murdoch. ‘When we looked different orientations of copper, for example Cu [001], which is used by most suppliers, the graphene domains do not align.’

‘These findings offer new mechanisms for tailoring electronic properties of graphene nanostructures and using graphene in electronic devices,’ commented Andrei Khlobystov at the University of Nottingham, UK.

Solar cell world record

A new world record for the conversion of sunlight into electricity using a new solar cell structure with four solar subcells has been achieved by researchers in France and Germany. Impressively, the new cell converts nearly half of the energy of sunlight (44.7%), from ultraviolet through to the infrared, into electrical energy – a major step towards reducing further the costs of solar electricity.

The German-French team of Fraunhofer ISE, Soitec, CEA-Leti and the Helmholtz Center Berlin had already announced a solar cell with 43.6% efficiency back in May. They announced the new record, measured at a concentration of 297 suns, in October.

The new cells were originally developed from space technology. They are used in concentrator photovoltaics (CPV), which achieves more than twice the efficiency of conventional PV power plants in sun-rich locations. Several different III-V semiconductor materials are stacked on top of each other to create a multi-junction solar cell, in which the individual subcells absorb different wavelength ranges of the solar spectrum.

The cells were created by using a new procedure called wafer bonding, explained Frank Dimroth, project leader at Fraunhofer ISE. ‘With this technology, we are able to connect two semiconductor crystals, which otherwise cannot be grown on top of each other with high crystal quality. In this way we can produce the optimal semiconductor combination to create the highest efficiency solar cells.’

Sleep mutations and migraine

An enzyme that alters sleep patterns also causes changes in brain activity which may trigger migraines, according to a study in May. Researchers in the UK, US and Finland found that casein kinase alters the activity of multiple brain proteins in a way that may cause migraines (Sci. Transl. Med., doi: 10.1126/scitranslmed.3005784). The researchers looked at a single family with a history of migraines and saw that many family members also had a sleep condition called advanced sleep phase disorder caused by a mutation in the casein kinase gene, which alters the circadian clock. This mutation also occurred in individuals with migraines.

The researchers also investigated casein kinase mutations expressed in animals and found that the mice showed patterns of brain activity similar to those seen in migraine patients. Treating the mice with migraine medications seemed to decrease some of these symptoms. The findings suggest that the enzyme could be a potential target for treating these debilitating headaches.

Stretchable electronics

Flexible electronics have a wide variety of possibilities, from bendable displays and batteries to medical implants that move with the body. However, finding good conductors that still work when pulled to twice their length is a tall order – scientists have tried wires in tortuous zigzag or spring-like patterns, liquid metals, nanowire networks and more. In July, however, researchers at the University of Michigan, US, reported finding that polyurethane studded with gold nanoparticles can conduct electricity even when stretched to more than twice its original length (Nature, doi: 10.1038/nature12401).

‘Essentially the new nanoparticle materials behave as elastic metals,’ said Nicholas Kotov, professor of engineering. ‘As we stretch, they rearrange to maintain the conductivity, and this is the reason why we got the amazing combination of stretchability and electrical conductivity.’

The team made two versions of their material – by building it in alternating layers or filtering a liquid containing polyurethane and nanoparticle clumps to leave behind a mixed layer. Even when close to its breaking point, at a little more than twice its original length, the layer-by-layer material still conducted at 2400 S/cm. Pulled to an unprecedented 5.8 times its original length, the filtered material had an electrical conductance of 35 S/cm – enough for some devices.

Kotov is especially interested in seeing his stretchable conductors used as electrodes for brain implants that would not damage cells. They could also be used in displays that can roll up or in the joints of life-like ‘soft’ robots.

Flexible electronic ‘skin’

Also in July, researchers reported further progress in the area of flexible electronics by developing an artificial ‘skin’ with which to assess the position and intensity of a finger touch instantaneously (Nature Materials, doi:10.1038/nmat3711). The group at the University of California, Berkeley, US, combined a matrix of organic light-emitting diodes with a conductive rubber that, when compressed, allows electric current to flow. They showed that the force applied to each diode can control the intensity of the light emitted. This integrated sensor-and-display device rests on a flexible plastic substrate that can adapt to curved surfaces. In the prototypes, arrays of coloured pixels were generated on a plastic substrate and worked without the need for external connections to human-readable interfaces. The researchers suggest that this device is an example of the complexity that can be achieved using plastic substrates. The availability of technologies to realise electronic circuits, light-emitting devices and sensors on flexible substrates, and also on very large areas, may inspire the design of a broad range of integrated systems for automotive, robotics or medical applications.

Ultrafast electrical switch

Researchers from the US Department of Energy’s SLAC National Accelerator Laboratory have clocked the fastest-possible electrical switching in magnetite, a naturally magnetic mineral. Reporting their results in July, the researchers claim their results could drive innovations in the tiny transistors that control the flow of electricity across silicon chips, enabling faster, more powerful computing devices.

By using the Linac Coherent Light Source (LCLS) X-ray laser at the SLAC laboratory in California, US, the researchers found that it takes only 1 trillionth of a second to flip the on-off electrical switch in samples of magnetite, which is thousands of times faster than in transistors now in use. The results were published in Nature Materials (doi:10.1038/nmat3718).

The experiment also showed researchers how the electronic structure of the sample rearranged into non-conducting ‘islands’ surrounded by electrically conducting regions, which began to form just hundreds of quadrillionths of a second after a laser pulse struck the sample. The study shows how such conducting and non-conducting states can coexist and create electrical pathways in next-generation transistors.

Scientists first hit each sample with a visible-light laser, which fragmented the material’s electronic structure at an atomic scale, rearranging it to form the islands. The laser blast was followed closely by an ultra-bright, ultra-short X-ray pulse that allowed them to study, for the first time, the timing and details of changes in the sample excited by the initial laser strike.

By slightly adjusting the interval of the X-ray pulses, they precisely measured how long it took the material to shift from a non-conducting to an electrically conducting state, and observed the structural changes during this switch.

Building a new liver

Scientists reported in July the creation of a functional human liver made from stem cells (Nature, doi: 10.1038/nature12271). The team at the Yokohama City University Graduate School of Medicine in Japan made the liver by transplanting ‘liver buds’ produced in the lab into mice, where the buds matured into tissue resembling the adult liver. After transplantation, the organ developed a vascular system and performed liver-specific functions. A liver bud is an early structure seen when livers form, produced by recreating cellular interactions that normally take place during bud development. Earlier attempts to create complex vascularised organs from stem cells have been fraught with challenges. However, the researchers believe their work highlights the therapeutic potential for using transplantation of organ buds grown from induced pluripotent stem cells for treating organ failure.

Lab grown burger eaten

The world’s first lab-grown burger was served up ready to eat at a news conference in London in August, and received a mixed reaction from food critics. ‘What was consistently different was the flavour,’ food writer Josh Schonwald was quoted as saying in a BBC news report.

Scientist Mark Post of Maastricht University, who created the burger, believes that ‘cultured meat’ could be an answer to future food shortages and provide a sustainable answer to food production (C&I, 2011, 22, 16). ‘I hope it will show cultured beef has the answers to major problems that the world faces,’ said Post, whose work was funded by Sergey Brin, co-founder of Google (C&I, 2013, 9, 14). Commercial production of cultured beef could begin within 10-20 years, Post added. Once a production system is developed and the technology refined, he says it could be cheaper than conventionally-farmed beef.

Post’s research involves using myoblast cells from which muscle cells develop, which ‘reproduce very easily and in tremendous quantities, and they’re tissue specific, which means that they automatically differentiate into muscle tissue’. The cells are taken from living cows and then soaked in nutrient-rich gel and left to multiply for several days, before being attached to a biodegradable polymer scaffold and trained to form muscle tissue. After a few weeks, the team can harvest the first muscles; around 3000 are enough to create a hamburger.

Malaria vaccine saves lives

Newspapers in autumn carried the story that a new malaria vaccine could stop millions of cases of malaria every year and save hundreds of thousands of lives. The news followed the results of a large scale Phase 3 trial of the vaccine candidate, RTS,S, in Durban, South Africa, announced by developer GlaxoSmithKline. Over 18 months of follow-up, RTS,S was shown to almost halve the number of malaria cases in young children (aged 5-17 months at first vaccination) and to reduce by around a quarter the malaria cases in infants (aged 6-12 weeks at first vaccination).

Based on these data, GSK says it now intends to submit, in 2014, a regulatory application to the European Medicines Agency (EMA). The World Health Organization has indicated that a policy recommendation for the malaria vaccine candidate is possible as early as 2015 if it is granted a positive scientific opinion by EMA.

Eleven African research centres in seven African countries are conducting the trial, together with GSK and the PATH Malaria Vaccine Initiative (MVI), with grant funding from the Bill & Melinda Gates Foundation to MVI.

‘In Africa we experience nearly 600,000 deaths annually from malaria, mainly children under five years of age,’ says Halidou Tinto, principal investigator from the Nanoro, Burkina Faso, trial site and chair of the Clinical Trials Partnership Committee (CTPC), which oversees the RTS,S Phase 3 programme. ‘Many millions of malaria cases fill the wards of our hospitals. Progress is being made with bed nets and other measures, but we need more tools to battle this terrible disease.’

Automated organic synthesis

Automated synthesiser machines to make DNA, peptides and oligoncucleotides have been around for years, and have dramatically accelerated medical progress. In October, C&I reported the development of an automated synthesis machine for small molecules – responsible for the activities of 90% of drugs (C&I, 2013, 10, 11). Presenting the work at the ACS meeting in Indianapolis, US, in September, Martin Burke and coworkers at the University of Illinois at Urbana-Champaign reported the development of a synthesiser to make a class of small molecules called polyenes. Some years ago, Burke’s team developed special building blocks – MIDA boronates – to improve the utility of the Nobel-prizewinning Suzuki-Miyaura cross-coupling reaction to make polyenes (C&I, 2008, 1, 7). The group extrapolated this idea to produce the long-sought-after synthesiser, by using iterative cycles of deprotection, coupling and purification. The work is described in a patent (WO2012/149182A2) in November 2012.

Brain cell death halted

In October, UK researchers reported that a chemical has been used for the first time to prevent the death of brain tissue in a neurodegenerative disease. Researchers at the Medical Research Council (MRC) toxicology unit at the University of Leicester used an orally-administered compound to block a major pathway leading to brain cell death in mice.

The team had found previously that the build-up of misfolded proteins in the brains of mice with prion disease over-activates a natural defence mechanism in cells, which switches off the production of new proteins. In this original study, published in Nature (doi:10.1038/nature11058), the researchers were able to restore protein production by injecting a protein that blocked this ‘off’ switch into a small region of the brain, and so halt neurodegeneration.

In the new study, reported in Science Translational Medicine (doi: 10.1093/hmg/ddq546), the researchers were able to block the off-switch by giving the prion-infected mice an alternative compound, originally developed by GlaxoSmithKline for a different purpose. Unfortunately, this compound also had the unfortunate side effect of producing weight loss in the mice and mild diabetes.

‘We’re still a long way from a usable drug for humans – this compound had serious side effects,’ said Giovanna Mallucci, who led the MRC team. ‘But the fact we have established that this pathway can be manipulated to protect against brain cell loss first with genetic tools and now with a compound, means that developing drug treatments targeting this pathway for prion and other neurodegenerative diseases is now a real possibility.’

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