at the University of Ulm in Germany, and colleagues, have previously used red light with a wavelength of 670 nanometres to transport cancer drugs into cells. The laser light pushes water out of the cells and when the laser is switched off, the cells “suck in” water and any other molecules, including drugs, from their surroundings.

Now, Sommer’s team have found that the same technique can be used to destroy the beta-amyloid plaques in Alzheimer’s. These plaques consist of abnormally folded peptides, and are thought to disrupt communication between nerve cells, leading to loss of memory and other symptoms.

The team bathed brain cells containing beta-amyloid in epigallocatechin gallate (EGCG) – a green-tea extract known to have beta-amyloid inhibiting properties – at the same time as stimulating the cells with red light. Beta-amyloid in the cells reduced by around 60 per cent. Shining the laser light alone onto cells reduced beta-amyloid by around 20 per cent (, ).

It can be difficult getting drugs into the brain, but animal experiments show that the green-tea extract can penetrate the so-called blood-brain barrier when given orally together with red light. The light, which can penetrate tissue and bone, stimulates cell mitochondria to kick-start a process that increases the barrier’s permeability, says Sommer.

“This could form the basis of a therapy for Alzheimer’s, with or without complementary drugs”

There is no reason why other drugs that attack beta-amyloid could not be delivered to the brain in the same way, he adds.

“This important research could form the basis of a potential treatment for Alzheimer’s, with or without complementary drug treatment,” says Mario Trelles, medical director of the Vilafortuny Medical Institute in Cambrils, Spain.

“The technique described could help to regulate and even stop the appearance of this disease,” he adds.

This article has been edited since it was first posted.

A female mosquito sucks blood by flexing and relaxing certain muscles in its proboscis. This creates suction (or negative pressure) that draws blood into its mouthparts.

The new biocompatible microneedle, designed by of the Indian Institute of Technology in Kharagpur and Kazuyoshi Tsuchiya of in Kanagawa is based on the same principle.

In this case, the sucking action is provided by a microelectromechanical pump, which works using a piezoelectric actuator attached to the needle.

Contrary to popular belief, a mosquito bite does not hurt. It is the anticoagulant saliva that the creature injects to stop your blood clotting that causes inflammation and pain.

Snap safe

The new needle has an inner diameter of around 25 microns and an external diameter of 60 microns, which is about the same size as a mosquito’s mouthpart. Its size and the fact that it works by suction, makes it painless. To compare, a conventional syringe needle has an outer diameter of around 900 microns.

In contrast to previous microneedles, which were made of silicon dioxide, the new device is robust because it is made of stronger titanium and related alloys, which dramatically reduces the risk of it snapping during injections.

The needle is also strong enough to penetrate as far as 3 millimetres into skin and reach capillary blood vessels.

Its size compared to earlier models also means that surface tension effects are exploited further, and the same capillary flow that draws water up into trees helps draw blood into the microneedle.

The researchers have calculated that their needle can extract 5 microlitres of blood per second. This volume is sufficient for measuring blood-sugar levels in diabetics using a glucose sensor that can be attached to the needle in a “wristwatch” design.

Production challenges

The design uses a shape-memory alloy to drive the needle into skin and a micro-pump for delivering drugs. The latter could be used to inject insulin (or other drugs) into the patient when required.

“The working principle of this device follows on from our discovery that in a well-designed microneedle, surface tension forces may overcome resistance from friction and draw up blood with unprecedented efficiency,” Chakraborty told 91av.

Chakraborty and Tsuchiya hope to commercialise their needle, but there are still some challenges to overcome, including cost, scaling up the fabrication method, and making it more user-friendly.

“This new blood extraction is interesting, but I question its ability to be fabricated and initialised en masse,” said Geoffrey Thomas of the University of Calgary, Canada, who is working on a similar blood glucose sampling and analysis project.

Journal reference: Journal of Applied Physics (DOI: 10.1063/1.2936856)

A way to close off diseased blood vessels with unprecedented accuracy using a zap of laser light has been tested in mice.

The technique developed by Canadian, British and American researchers could be used to shut off blood vessels to treat certain tumours or a common eye disease.

It is a significant upgrade to an existing treatment called photodynamic therapy (PDT), which involves injecting a light-sensitive compound into diseased tissue. Exposing the compound to laser light generates a high-energy form of oxygen that is toxic to cells.

Using standard PDT, it is very difficult to focus the effect onto diseased cells without destroying adjacent healthy tissue. And the laser light needed can only penetrate 1 centimetre into the tissue.

A new compound made by and colleagues at Oxford University can tackle both those problems.

Extreme accuracy

Each molecule of the new drug is able to absorb two photons instead of just one, as for current PDT compounds. The drug displays a physical phenomenon known as , which means much less energy is needed to perform the procedure.

As a result, low-energy near-infrared light can be used, which can penetrate two or three times deeper into living tissue, depending on the particular tissue. That would allow many more uses for PDT.

The process is also more accurate, explains Anderson. The underlying physics means the amount of two-photon excitation declines extremely rapidly with increasing distance from the focus of the laser beam.

In tests on living mice, of the University of Toronto, Canada, and colleagues, were able to close blood vessels with “exquisite spatial selectivity”, using pulses of laser light to “draw” along vessels they wanted to close.

‘Many possibilities’

“The most immediate application is treating [advanced] age-related macular degeneration (AMD) by closing off unwanted blood capillaries,” Anderson told 91av. “It might also be used to treat certain tumours, particularly where improved accuracy is required.”

The team will now go on to investigate the toxicology of the new photosensitive drug, and test its efficacy against tumours. “We are also experimenting with related compounds in an attempt to improve uptake by cells,” adds Anderson.

“This paper is a breakthrough in two-photon PDT and I would mark it as in the top five important results for biophotonics in the past year,” commented David Cramb of the University of Calgary, Alberta, Canada, who also works on PDT.

Attempts to make drugs capable two-photon excitation have faltered in the past, says Cramb. “There are many possibilities for this [new] technique – with the most obvious being for treating AMD.”

Journal reference:

A new way to examine the composition of luminous jets of ionised gas known as “plasma needles” could speed their progress towards their use for dental treatment and other medical uses.

A plasma is a cloud of gas broken down into a mélange of free electrons and ions.

At atmospheric pressure and temperature most plasmas reach thousands of degrees Celsius. But in recent years physicists have created “plasma needles” that are cold enough to touch but deadly to bacteria.

Chinese researchers have now built a device that generates a cold plasma and can also measure the flow of electrons inside it. That could help reveal new insights into the nature of such plasmas so they can be fine-tuned for biomedical use.

This won’t hurt

Researchers are still trying to work out how to best control cold plasma.

Until now, most of plasma plumes created have been either been only millimetres long, or tens of degrees hotter than room temperature, and unsuitable for medical use, says XinPei Lu at , China.

Lu and colleagues’ latest device generates a room-temperature plasma plume a useful 4cm long that can safely be touched with a bare finger.

It consists of a high-voltage wire electrode inside a quartz tube. That ensemble is encased in a syringe, which can be used to channel nitrogen or helium gas.

When pulses of voltage are applied to the electrode, a luminous needle of plasma is created (see image, right). The plume’s length can be varied by changing the gas, its flow rate, and the applied voltage.

Open wide

Lu says the device could ultimately be used in a variety of applications, including sterilising medical instruments, and killing dental bacteria.

“We are focusing on dental hygiene applications, such as treating teeth cavities (caused by bacteria like Streptococcus mutans) and root canals,” he told 91av. Previous research has shown that oxygen, ozone and hydroxyl radicals generated by such plasma can kill bacteria.

The race to build better plasma plumes for biomedical uses is becoming competitive notes of Old Dominion University, Norfolk, Virginia, US, with Lu’s just the latest in a string of new variations being developed.

New insight

But Lu’s device has a feature that could lead to better understanding of what is happening inside the plasma, says John Goree of The University of Iowa, US. That could help tune them for peak bacteria-killing performance.

Monitoring the flow of electrons in a plasma is the usual way to get a handle on conditions inside, Goree explains. But small, cold plasmas have proved almost impossible to measure, because they contain few electrons compared to larger and hotter plasmas.

By powering their device using short electrical pulses, the Chinese group can measure electron flow, which could help tune them for peak bacteria-killing performance.

Journal reference:

A normal digital camera can take snaps of objects not directly visible to its lens, US researchers have shown. The “ghost imaging” technique could help satellites take snapshots through clouds or smoke.

Physicists have known for more than a decade that ghost imaging is possible. But, until now, experiments had only imaged the holes in stencil-like masks, which limited its potential applications.

Now of the University of Maryland, Baltimore, and colleagues at the , also in Maryland, have now taken the first ghost images of an opaque object – a toy soldier (see image, top right).

Quantum camera

Ghost imaging works a bit like taking a flash-lit photo of an object using a normal camera. There the image forms from photons that come out of the flash, bounce off an object and into the lens.

The new technique also uses a light source to illuminate an object. However, the image is not formed from light that hits the object and bounces back. Instead, the camera collects photons that do not hit the object, but are paired through a quantum effect with others that did.

In Shih’s experiments a toy soldier was placed 45 centimetres away from a light source, which was split into two beams. One was pointed at the toy and the other at a digital camera. A photon detector was placed near the soldier, able only to record when a photon bounced off.

Connected pairs

Photons from the light source constantly travel down both paths made by the splitter, either towards the soldier and the photon detector, or towards the camera. The detector and camera record a constant stream of those photons, and occasionally record a photon at exactly the same time.

When this happens, there is a direct relationship between where one of the photons hit the soldier, and where the other one hits the camera’s sensor, says Shih, because of a quantum effect called “two-photon interference”.

“If the first photon stops at one point on the object plane, the second photon can only be observed at the corresponding point on the image plane,” he says.

So when the camera records only pixels from photons that hit simultaneously with one reaching the detector, a “ghost image” of the object builds up. The soldier’s image appeared after around 1000 coincidental photons were recorded.

Sunny snaps

“It is clear that the experimental set-up can be directly applied to sensing applications,” Shih told 91av.

The same method could one day be employed to produce satellite images of objects hidden behind clouds or smoke, using the sun’s radiation as the photon source, says Shih. Doing that may require a photon counter beneath the clouds, but could allow a top-down view not possible using conventional methods.

Not everyone agrees that quantum effects are at work in ghost imaging, though. and of the Massachusetts Institute of Technology, Cambridge, US, point out in a recent paper that classical physics says light sources produce numbers of uncoordinated photons that are not correlated as Shih suggests.

They suspect ghost images might be produced without a quantum link between photon pairs, purely because some photons are just similar.

Journal reference: Physical Review A (DOI: 10.1103/PhysRevA.77.041801)

Quantum World – Learn more about a weird world in our comprehensive special report.

Next time you are lost in an unfamiliar city, console yourself with the knowledge that the layout of its roads are probably much the same as in any other.

French and US physicists have shown that the road networks in cities evolve driven by a simple universal mechanism despite significant cultural and historical differences. The resulting patterns are much like the veins of a leaf.

Marc Barthélemy of the French in Bruyères-le-Châtel and of Indiana University, US, analysed street pattern data from roughly 300 cities, including Brasilia, Cairo, Los Angeles, London, New Delhi, and Venice.

They found that cities’ road patterns have a lot in common mathematically, as well as looking similar to the eye.

‘Not just planning’

The researchers developed a simple mathematical model that can recreate the characteristic leaf-like patterns that develop, growing a road network from scratch as it would in reality.

The main influence on the simulated network as it grows is the need to efficiently connect new areas to the existing road network – a process they call “local optimisation”. They say the road patterns in cities evolve thanks to similar local efforts, as people try to connect houses, businesses and other infrastructures to existing roads.

Evolution has ensured that local efficiency also drives the growth of transport networks in biology – for example, in plant leaf veins and circulatory systems.

“Cities are not just the result of rational planning – in the same way that living organisms are not simply what is in their genetic code,” Barthélemy told 91av.

Growth predictions

“Beyond the economic, demographic and geographic “forces” that shape a town, there are a myriad of small “accidents” that contribute” he says. “Although these are unpredictable, they can be understood in terms of statistics and simple modelling.”

The team’s model also reveals that roads often bend, even in the absence of geographical obstacles, and that road intersections are generally perpendicular.

The study’s results might be important for understanding urban growth and “sprawl” says Barthélemy. More than half the world’s population lives in cities, a proportion that continues to increase.

“The approach could even help city planners to better predict how some street networks will evolve and to plan accordingly,” he adds.

Previous models of urban development assumed that efficient transport across the entire network motivated the system’s growth – as if planned from the top down. Focussing instead on the structure of local connections seems truer to real life, says Flammini.

Ancient roots

“Our study provides a first step in understanding and integrating such networks when modelling urban growth,” explains Flammini.

The researchers will now study how road networks developed over time in old cities, such as London and Paris. They hope to unearth other possible universal features that might be present to refine their model.

Despite the simplifications of the model, its results agree well with data from real city road networks, says complex systems specialist of Oxford University, UK.

Using the local efficiency of connections to drive road network growth looks to be a truer fit with reality than using the total cost of travelling across the network, says Onnela. “Especially given that the time scale of city growth (possibly thousands of years) and the time scale of urban planning (perhaps tens of years) are so clearly different.”

Journal reference:

Cars and Motoring – Learn more about the latest technologies in our comprehensive .

Vibrating people’s brains with laser beams could pinpoint the focus of epileptic seizures faster and more easily than the lengthy scans or surgery used today, US researchers say.

Epilepsy is the most common brain disorder and affects about 1% of the population. It occurs when nerve cells in a certain area of the brain fire more rapidly than usual, leading to seizures.

Only about two-thirds of people with epilepsy can be treated with drugs, with surgery the only option for the rest. Surgical cure rates are poor and recurrence rates high – especially for “neocortical seizures” that occur in the brain’s outer layers.

Cut it out

Surgery involves removing the part of the brain where the abnormal activity is centred so surgeons must know exactly where that is. Pinpointing it is difficult and often involves surgery to place a grid of electrodes directly onto the brain’s surface.

A scanner that fires laser light into the brain has the potential to find the focus of seizures without surgery. and colleagues at the University of Florida, Gainsville, US, have shown that their method works in tests on rats.

The technique is called laser-induced PAT, for photoacoustic tomography. A powerful laser is shone into the brain through the skull, causing tiny vibrations in the brain tissue. Listening to those vibrations using an ultrasound transducer makes it possible to map the brain, and its activity.

Vibrating brain

Active regions absorb the most light and thus create the most vibrations, making it possible to identify parts of the brain involved in a seizure.

Laser-induced PAT only takes a second or less to complete, compared with several minutes for CT and MRI scans, Jiang told 91av. “This is high speed, and the technique is low cost and potentially portable, so brain imaging might be performed in real time at the bedside of a patient.”

The rapidity of the technique also makes it suitable for children and babies, who often struggle to lie still during lengthy CT and MRI scans.

Laser hat

Having achieved good results with the rat version of the scanner, the team are now working on building a specially designed version for humans. A special hat will be used to deliver the laser pulses and pick up the vibrations they cause.

However, the researchers cannot simply scale up the scanner they used for rats. The human skull is around a centimetre thick, compared with tenths of a millimetre for a rat. That will make it hard for the laser beam to vibrate the brain inside the skull, and muddy the vibrations that can be picked up from outside.

Jiang and colleagues are confident they can overcome those problems by using laser light at longer wavelengths that can penetrate deeper into brain tissue. Using a special gel to ensure better transmission of laser light and vibrations should also help.

Journal reference: Physics in Medicine and Biology (DOI: )

The Human Brain – With one hundred billion nerve cells, the complexity is mind-boggling. Learn more in our cutting edge special report.

When temperatures drop, it can be tricky to judge road conditions accurately. Soon, however, some roads could give drivers clear icy warnings by turning themselves pink.

A new temperature-sensitive varnish developed by researchers at French company can be applied to road surfaces to warn drivers about dangerous conditions. The technique – still at the testing stage – might help prevent ice-related traffic accidents in future, the researchers say.

The varnish is made of a polymer containing a thermochromic pigment. The same type of coating is already used to make bath thermometers and frozen food packaging that responds to temperature change. However, it is the first time such a coating has been used to monitor road temperatures.

This winter, researchers at Eurovia tested the varnish on roads at different sites in France. They painted squares around a metre across onto the roads and observed how the normally transparent varnish turned dark pink when temperatures dropped below 1 °C (see image, right). When the temperature rose back above 2 °C, the coating became colourless again.

Tough coating

The beauty of the system, says project leader Thomas Devanne, is that information would be available in real time, allowing roads to be salted exactly where and when needed, or cautioning drivers to take extra care as roads start to become dangerous.

Devanne adds that the coating could be used anywhere that becomes icy in winter – on roads and highways, or even on pavements to warn pedestrians to watch their step.

“We have been proud to test this new coating, whose purpose is to make our roads safer,” Devanne told 91av.

“Our first on-site tests have produced some encouraging results – the coating is resistant to harsh weather conditions and is mechanically resistant too,” he says. “However, we have still have some work ahead of us to optimise the final product.”

Night visibility

The two most important challenges are improving the night visibility of the coating and ensuring it lasts throughout the summer months, when it would be exposed to higher levels of ultraviolet rays from the Sun.

“I think this is a very nice idea but the UV stability of the pigment used in these thermochromic materials will be one of the key issues to be addressed,” says of Case Western University in the US.

Rowan’s colleague points out that the team will also have to be certain of the accuracy of the temperature-induced colour changes.

“On beer bottles, thermochromics are really just a gimmick,” he adds. “However, Eurovia’s application, in contrast, strikes me as very useful and reflects some out-of-the-box thinking.”

Cars and Motoring – Learn more about the latest technologies in our comprehensive .

The device is placed inside the vas deferens – the duct which carries sperm from each testicle to the penis. When closed, it blocks the flow of sperm cells, allowing them to pass again when it is opened via a remote control. The valve could be a switchable alternative to vasectomy, the researchers say.

Although women can choose from several long-term contraceptive methods, for men vasectomy is really the only option. With this procedure, the vasa deferentia are cut or blocked, a process that requires surgery and can require a week of recovery. The procedure cannot be reliably reversed, leaving some men to later regret their decision.

Now, a team from the University of Adelaide, Australia, may have come up with a more easily reversed alternative. They have designed a small radio-controlled valve that would “push-fit” snugly inside the vas deferens and block the passage of sperm.

The silicone-polymer valve can be flipped between open and closed positions with a pulse of radio waves. A set of conducting “fingers” on the valve act as antennae and convert the signal’s energy into sound waves that travel through the polymer and create stresses inside the device.

Remote control

“Since it is flexible, the polymer either contracts or expands as a result, and this movement allows the valve to be opened or closed as needed,” explains team leader .

“It will be like turning a TV on and off with a remote control,” added team founder Derek Abbott, “except that the remote will probably be locked away in your local doctor’s office to safeguard against accidental pregnancy or potential misuse of the device.”

To secure the device against accidental activation, the device works in a similar way to a car’s remote key-fob. Each valve responds only to a radio-frequency signal with a unique code.

Another advantage of the microvalve is that would not require open surgery, unlike a vasectomy. The 800 micron-long device could simply be inserted using a hypodermic needle. “The procedure could be performed in a special clinic rather than in a hospital,” says Abbott.

The researchers have finished the design of all parts of the valve, and are convinced it will work effectively. The next step is to test it in the lab with a tube of pressurized water. After that, trials could begin in live sheep and pigs, they say.

‘Grace period’

One potential problem, however, is that after a while the valve may clog with protein and remain shut, rendering the man permanently infertile.

“We would only propose the device to men who were thinking of having a full vasectomy anyway,” said Abbott. “But, unlike in an actual vasectomy, he would have a ‘grace period’ where the procedure can easily be reversed.” How such a device affects gender politics would also make a fascinating social study, he added.

Men who regret a vasectomy can often only have children using donor sperm, says Natalie Gamble, associate with UK law firm .

“Although the law protects families conceiving with the help of a sperm donor, this type of conception has significant legal and emotional implications,” she adds. ” I am sure men will welcome the chance to control their fertility more flexibly, and to preserve the chance to have their own genetic child.”

Joe Hofmeister is president of US firm Shepherd Medical Company, which is also working on male contraceptive devices. “Consumer market research performed by an independent third party for Shepherd confirms a strong patient desire for a permanent-yet-reversible male contraceptive such as the microvalve or other such system.”

Journal reference: Smart Materials and Structures (DOI: )

The brightest quantum-dot LEDs yet made could provide lighting for displays that are clearer and richer in colour, as well as being cheaper to make, than existing ones.

The devices could be used to make better displays for mobile phones and PDAs, and to light larger flat-panel TV screens, say researchers based in China and the US.

Quantum dots are nanoscale semiconductors that confine electrons in three dimensions. In this case, the quantum dots have a cadmium selenide core and a zinc sulphide “shell”. Electrons are excited to higher energy levels in the core and the shell, then fall into the empty spaces, or “holes”, left behind. The dot then forms an “exciton” and emits a particle of light.

Changing the size of a QDLED makes it emit a different wavelength of light – producing red, orange, yellow, or green light. The devices also only need about 3 to 4 volts to operate and can run for over 300 hours without losing any brightness.

Although standard LEDs are far more efficient, QDLEDs could be better in other ways. The range of colours and intensity of light produced by QDLEDs promise to be better than alternative technologies.

“The brightness of the best LCD monitor on the market today is 500 candelas per square metre and the brightness of room light is about 2000 cd/m²,” says Andrew Wang of Ocean NanoTech in Fayetteville, Arkansas, which developed the quantum dots. “Our QDLEDs have reached 9000 cd/m² in brightness, which makes them the brightest in the world.”

Purer colours

QDLEDs are also relatively easy to make, using solution-processing techniques, such as spin coating, ink-jet printing and roll-to-roll printing, which is useful for flexible-screen applications. Organic LEDs, by contrast, are made using more complicated techniques like vacuum evaporation or vapour deposition.

Although similar devices were made by researchers at MIT in 2002, their QDLEDs had brightness values of around 7000 cd/m² and contained only a single layer of quantum dots. The new devices contain multiple quantum dot layers to make them brighter, Wang explains.

The Ocean NanoTech researchers, together with Yongfang Li and Qingjiang Sun at the , are now working hard to optimise the structures of the quantum dots to further increase the lifetime and power efficiency of the devices.

For the technology to be incorporated into a product, however, it may be necessary to demonstrate the same physical phenomena using a material other than cadmium, which is a highly toxic heavy metal.

Journal reference: