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Nanoparticles boost performance of cancer drugs

Adding nanoparticles to the surface of tumour cells could make them more susceptible to treatment with particular cancer drugs, according to new research at MIT. The study showed that nanoparticles tethered to the cell surface can increase the effects of forces exerted on the tumour cells by physiological fluids flowing within the body, which makes the cells much more vulnerable to attack by certain therapeutics.

Scientists have recently been exploring the physical properties of tumours and their microenvironment, with recent research showing that tumours can exploit the forces in their surroundings to enhance their survival and promote the progression of the cancer. But researchers at MIT believe that increasing the forces exerted on tumour cells can make certain therapeutics more effective in killing cells and controlling the cancer.

The study, which was led by Robert Langer, used an experimental drug known as TRAIL (a TNF-related apoptosis-inducing ligand), which exerts a cytotoxic effect on tumour cells without damaging healthy cells. TRAIL also avoids many of the debilitating effects of more commonly used therapies.

The researchers found that when used to target tumour cells, TRAIL was more successful in killing cancerous cells once they had been exposed to the shear forces generated by physiological fluids such as blood flow in the body (Nat. Commun. 8 14179). The MIT team set out to optimize the forces required for cell death, and they found that increasing the force on the cells made them more susceptible to TRAIL.

Nanoparticles strengthen forces

To produce these forces, Langer and his colleagues have pioneered the use of nanoparticles made from biodegradable polymers known as PLGA (poly(lactic-co-glycolic acid)). When injected into the bloodstream, the nanoparticles attach to the tumour cell surface and increase the force on the cell from the flow of physiological fluids.

Members of the MIT research team: Michael Mitchell, Amanda Chung, and Pedro Guimaraes

The nanoparticles are coated with PEG (polyethylene glycol), which is tagged with a specific ligand that interacts with proteins found on the surface of the tumour cells. These ligands, and therefore the nanoparticles, are attached to the tumour cell like a ball tied to a string. The shear forces from the flow of physiological fluids cause the nanoparticles to bump and bash the tumour cells, causing them to become more susceptible to the effects of the therapeutics.

The MIT team found that attaching the nanoparticles to tumour cells prior to treatment with TRAIL killed metastatic tumours and reduced the progression of tumours in mice. The researchers also found that the treatment appeared to be specific to tumour cells and that healthy cells remained unaffected. Nanoparticle size and quantity were also found to have an effect on cell death. Larger particles, around one micrometre across, and a higher quantity of particles were found to have the most positive effect.

The researchers believe that the mechanism the nanoparticles induce on the tumour cells may cause the molecules surrounding the tumour cells to compress, enabling the therapeutics to interact more efficiently with receptors on the cell surface.

Langer and his research team are now exploring the possibilities of using this technique in combination with other drugs. This is a key strategy to prevent drug resistance in cancer treatment since tumours often regrow and become unaffected by drugs that had previously been effective. The MIT team is particularly interested in drug combinations that induce cytokines, which stimulate signalling chemicals that trigger an immune response to the site that helps destroy the tumour.

Flash Physics: Wiggling keeps bats on target, pressure helps supercooled water flow, BELLE II rolls into place

Wiggling ears and noses keep bats on target

Horseshoe bats wiggle their ears and noses to boost their ability to navigate using ultrasound. That is the conclusion of Rolf Müller of Virginia Tech and colleagues, who have done mechanical and computer simulations that show that the wiggles could improve the bats’ ability to resolve direction by up to a factor of 1000. A horseshoe bat emits ultrasound from its nose and detects the reflected signal using its ears. The creature’s nose and ears have complex external structures – called noseleaves and pinnae, respectively – that diffract sound waves upon emission and reception. Bat experts also know that the shapes of the noseleaves and pinnae can change rapidly and that this has an effect on the sound used for echolocation. To understand why, Müller’s team created robotic models of noseleaves and pinnae and measured their acoustic properties when they were wiggled to mimic living bats. When combined with computer simulations, the measurements suggest the wiggling can result in a 100–1000 fold improvement in direction resolution over what can be achieved with static noseleaves and ears. Writing in Physical Review Letters, the researchers point out that very little is known about how bats use echolocation to navigate in complex natural environments. They suggest that a better understanding of the dynamic nature of the noseleaves and pinnae could boost our understanding of these incredible creatures and also lead to navigation technology inspired by bats.

Pressure helps supercooled water flow

The viscosity of supercooled water decreases by 42% when under pressure, according to scientists in France. Usually liquids become thicker when pressure is increased, but more than a century ago the opposite was observed to happen for water below 32 °C. This occurs because the application of pressure breaks the intermolecular hydrogen bonds that provide the water with its unusual properties. As the network of hydrogen bonds increases with cooling, the effect of pressure should be stronger. Frédéric Caupin and colleagues at the University of Lyon have studied this phenomenon in supercooled water – liquid water below the freezing point – which is a difficult feat as the liquid is liable to crystallize. Using a time-of-flight viscometer, the team measured water flow for temperatures down to –29 °C and pressures up to 3000 atmospheres. Finding that the viscosity decreased by nearly a half, Caupin and colleagues propose a model that treats water as a mixture of two species – a high-density “fragile” liquid and a low-density “strong” liquid. As described in PNAS, the ratio of these fluids explains water’s unusual thermodynamic and dynamic properties.

BELLE II detector rolls into collision point

Photograph of SuperKEKB showing BELLE II under construction — Starting point: BELLE II before it started its voyage. (Courtesy: KEK)

The BELLE II particle detector has been moved 13 m from its place of assembly to a collision point on the SuperKEKB collider in Japan. The SuperKEKB accelerator is an electron–positron collider that is designed to create large numbers of B-mesons. It is a major upgrade to the KEKB collider, which operated in 1998–2010 and included the Belle detector. In 2001, Belle discovered the existence of charge–parity symmetry violation (CP violation) with B-mesons. This confirmed the theoretical prediction of Makoto Kobayashi and Toshihide Maskawa, who shared the 2008 Nobel Prize for Physics for that work. SuperKEKB will achieve a collision rate that is about 40 times higher than KEKB, and BELLE II is designed to collect much more data than Belle and operate at a much improved measurement precision. Standing 8 m tall and weighing 1400 tonnes, BELLE II is expected to start taking data in 2018. It will do further studies of CP violation as well as perform searches for physics beyond the Standard Model.

You can find all our daily Flash Physics posts in the website’s news section, as well as on Twitter and Facebook using #FlashPhysics.

How to weigh tiny objects using sound

A $12 device that can measure the mass of microgram-sized objects in fluid has been developed by researchers in the US. The sensor is driven by a piezoelectric speaker and measures the change in the resonant frequency of a glass tube as the object passes through it. The team used the device to measure mass changes in several biological samples and says that the sensor has applications in a wide range of fields, such as developmental biology, toxicology, materials science and plant science.

Mass is an important physical measurement that can provide crucial information about the nature of an object. However, weighing microgram-sized biological samples such as embryos in liquid, can be very tricky indeed. While mass measurements can offer valuable insights into the biological state and health of such specimens, they cannot be easily made with standard laboratory equipment.

Nanogram resolution

To tackle this shortcoming, William Grover and colleagues at the University of California, Riverside, have created a simple mass sensor from off-the-shelf electronics and a short length of glass tubing bent into a “U” shape. The glass tube is attached to a small speaker and the bottom of the “U” passes through a photointerrupter – a device that uses an LED and a light sensor to detect the presence, or not, of an object. This simple set-up cost around US$12, yet can determine the mass of a microgram-sized object with a resolution of a few hundred nanograms.

It provides a pretty complete picture of the physical properties of a sample
William Grover, University of California, Riverside

The speaker keeps the glass tube vibrating at its resonant frequency using a simple feedback circuit from the photointerrupter, which detects the oscillation rate. As the object being weighed is pumped through the tube it changes the tube’s resonance frequency. This change is detected by the photointerrupter and can be used to calculate the objects mass, volume and density.

“If the object has a different density than the fluid, then it will change the sensor’s mass when it flows through,” explains Grover. “If the object is denser than the fluid around it, it’ll make the sensor slightly heavier and that makes the sensor’s frequency go down. If the object is less dense than the fluid, it makes the sensor slightly lighter and that makes the sensor’s frequency go up. By measuring these frequency changes, we measure the buoyant mass of the object.”

Germinating seeds

The sensor was calibrated with microbeads of known mass. The team then demonstrated that it can measure changes in the mass of zebra-fish embryos – a common model for embryological development studies – as they react to toxins. The device was also used to measure the degradation rates of nano-sized biomaterials used in medical implants, as well as mass and density changes in germinating seeds.

“It’s fundamentally a mass sensor, so at the most basic level it can weigh tiny objects in fluid,” says Grover. “But by using a method that Archimedes first described over 2000 years ago, we can also use it to measure the volume and density of the objects. So it provides a pretty complete picture of the physical properties of a sample.”

Grover expects the sensor to have many applications, but he is especially interested in using it to “study the development of organisms, measure biodegradable materials, and monitor the environment”. The new device is described in PLOS ONE.

Flash Physics: Quantum diamonds are coupled, metal ions on Mars, Canada should spend more on science

Quantum diamonds coupled using microwaves

Nitrogen-vacancy (NV) centres on two different diamonds have been coupled coherently by physicists in Austria. NV centres occur whenever two neighbouring carbon atoms in diamond are replaced by a nitrogen atom and an empty lattice site. NV centres are being used to develop quantum technologies because they have spin states with very long quantum-coherence times, even at room temperature. Another important benefit of NV centres is that they interact with both light and microwave radiation and could therefore act as a transducer between quantum devices based on the two types of radiation. Now, Johannes Majer and colleagues at the Technical University of Vienna have created quantum-coherent interactions between NV centres in two different pieces of diamond separated by about 5 mm. The diamonds are placed on two different microwave cavities, which are connected by a microwave-resonator transmission line. A static magnetic field is applied to the system and this tunes the transition energies of the NV spins to correspond to the microwave energy of the cavity – causing the NV spins to couple to the cavity. Because microwave radiation can travel through the transmission line between the two cavities, the NV centres in both diamonds can be coupled to each other. The team showed that when the crystalline structures of both diamonds are aligned, then the NV centres in both diamonds are coupled in a quantum-coherent manner. “This interaction is mediated by the microwave resonator in the chip in between; here, the resonator plays a similar role to that of a data bus in a regular computer,” says Majer. The coupling can also be switched off, allowing the NV centres of each diamond to be manipulated independently. While the researchers were not able to show that the NV centres on different diamonds were entangled quantum-mechanically, they write in Physical Review Letters that achieving and measuring entanglement could be an “interesting future challenge”.

Martian metals unlike Earth’s

Artist's concept showing MAVEN spacecraft over Mars — Alien behaviour: Mars’ ionosphere has a structure unlike Earth’s. Artist’s concept showing MAVEN spacecraft over Mars. (Courtesy: NASA’s Goddard Space Flight Center)

Metal ions in Mars’ atmosphere have been directly detected for the first time, and the distributions are distinctly different to those on Earth. Scientists have extensive knowledge of Earth’s ionosphere – a region of high-energy electrons, ions and charged molecules in the upper atmosphere, resulting from the ionization of meteorite dust entering at high speed. Due to Earth’s magnetic fields, gravity and ionospheric winds, the metallic ions – mainly magnesium (Mg⁺) and iron (Fe⁺) – are forced into layers. Investigations into the ionospheres of other planets have been modelled upon Earth’s example and have been reliant upon indirect measurements from Earth or satellites. But now, NASA‘s Mars Atmosphere and Volatile Evolution (MAVEN) mission has not only made the first direct detection of ions on a planet other than Earth, but also found that they behave differently. MAVEN’s spectrometer has detected sodium (Na⁺), Mg⁺ and Fe⁺ continuously over the last two years, implying the ions are a permanent feature. But rather than Earth’s distinct layers, there is no separation of the light Mg⁺ and the heavy Fe⁺ with increasing altitude as expected because of gravity. Instead the metals are mixed with the neutral atmosphere at altitudes where no mixing process is expected. Joseph Grebowsky of NASA’s Goddard Space Flight Center in the US and team suggest this is because Mars only has localized magnetic fields in certain regions of the crust and so layering only occurs there. The aim of the MAVEN mission is to investigate how Mars lost most of its air, and the new results, published in Geophysical Research Letters give a new insight into predicting the atmospheres of other planets.

Canadian science panel calls for increased spending

Canadian science requires a billion dollar increase to avoid falling behind other nations in basic science. That is the main conclusion of a report released yesterday by a nine-strong panel led by David Naylor, former president of the University of Toronto, which also included the Nobel laureate Art McDonald and Blackberry co-founder Mike Lazaridis. The panel say that Canada needs to invest an additional C$1.3bn over the next four years to boost the science base – taking the county’s science budget to C$4.8bn – recommending that about C$500m of that increase should be diverted to basic research. The panel also calls on the government to set up a National Advisory Council on Research and Innovation that would advise the Canadian government on research priorities and also “provide broad oversight of the federal research and innovation ecosystem”. The Fundamental Science Review was commissioned last year by science minister Kirsty Duncan to review the state of science in Canada. The publication of the report comes after the Canadian government disappointed scientists last month with a flat budget for science in 2017.

You can find all our daily Flash Physics posts in the website’s news section, as well as on Twitter and Facebook using #FlashPhysics. Tune in to physicsworld.com later today to read today’s extensive news story on a $12 sensor that can weigh microgram-sized objects.

Flash Physics: Newborn stars collide, wind creates rogue waves, ion-trap pioneer Hans Dehmelt dies

Newborn stars collide in a cosmic firework

The explosive collision of newly born stars has been captured by astronomers in unprecedented detail. John Bally of the University of Colorado Boulder in the US and colleagues used the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile to observe the Orion Molecular Cloud 1 (OMC-1), located within the constellation of Orion 1350 light-years away. OMC-1 is an active star-formation factory – a massive, dense cloud of gas. As it collapses under its own gravity, OMC-1 produces stars and – in the densest regions of the cloud – protostars. Astronomers suggest that several protostars began to form about 100,000 years ago and, before they could escape their stellar nursery, gravity started to pull them together. A mere 500 years ago, two of the protostars collided, producing a dramatic and powerful explosion with as much energy as the Sun emits in 10 million years. The collision caused gas, dust and the other nearby protostars to be propelled out into space at over 150 km/s. The resulting cosmic firework in OMC-1 was first observed in 2009, but the latest high-resolution ALMA images have revealed details about the distribution and motion of carbon monoxide within the streamers. The results, published in the Astrophysical Journal, may provide greater understanding of how such events impact star formation. It is thought that although protostar collisions are relatively short-lived (lasting only centuries), they are probably fairly common and may regulate stellar formation in massive molecular clouds.

Wind creates rogue waves in the lab

Wind-driven rogue waves have been created in an experimental water tank for the first time. Rogue waves are huge walls of water that can emerge without warning on a relatively calm ocean. Long a part of seafaring lore, it has only been very recently that physicists have begun to study these dramatic events. Previous studies used paddles to create rogue waves in water tanks, and have shown that they can occur as a result of nonlinear self-focusing of smaller waves. However, ocean waves are created by the wind, and so these paddle-driven rogue waves may not offer a realistic model of the phenomenon. Now, an international team led by Alessandro Toffoli at the University of Melbourne in Australia has looked at the more realistic role of wind in rogue-wave formation using an annular water tank. The tank has an outside diameter of 5 m, an inside diameter of 1 m and a depth of 46 cm. Turbines drive the water around the tank and two large fans create a wind blowing over the surface at 16 km/h. The circular flow eliminates an important limitation of wind studies in linear wave tanks – the tanks are too short for wind-blown rogue waves to emerge. With water and air flowing in a circle, the distance that the wind travels over the water is essentially unlimited. After switching the experiment on, it takes about 30 min for that tank to reach a stable state in which most of the waves are about 5 cm tall. However, the team also observed rogue waves that were about 2.2 times higher than the stable waves. Most of the rogue waves appeared just before the tank reached the stable state. In general, taller than average waves became more common in the tank at this time – with their frequency falling after the steady state was reached. This suggests that strong nonlinear interactions are present in the tank at that time, affirming the findings of previous studies. The study is described in Physical Review Letters.

Ion-trap pioneer Hans Dehmelt dies at 94

Photograph of Hans Dehmelt — Hans Dehmelt: 1922–2017. (Courtesy: University of Washington)

Hans Dehmelt, the German-born US physicist who shared the 1989 Nobel Prize for Physics for the development of ion traps, has died at the age of 94. Dehmelt was born in Germany in 1922 and gained a Master’s degree in physics in 1948 and a PhD in 1950 from the University of Göttingen. In 1952 he then went to Duke University in the US, before moving to the University of Washington in 1955, where he remained for the rest of his career until retiring in 2002. It was during his time in the US that Dehmelt developed the Penning trap that used magnetic and electric fields to trap ions and electrons, allowing them to be studied to high precision. Today, such traps are used to study to properties of antimatter, such as antihydrogen. For this breakthrough, Dehmelt shared half the 1989 Nobel prize together with Wolfgang Paul from the University of Bonn, while US physicist Norman Ramsey was awarded the other half for his work probing the structure of atoms to high precision.

You can find all our daily Flash Physics posts in the website’s news section, as well as on Twitter and Facebook using #FlashPhysics.

Once a physicist: Z Aziza Baccouche

What sparked your interest in physics?

I’ve always had a passion for maths, but I lost most of my sight when I was nine years old. I grew up in Tunisia and went to a blind school there for a few years before my parents decided to come back to the US. My mom is African-American and my dad is from Tunisia. When we came to the US, I went to a regular high school and in my senior year I took physics and immediately fell in love with the subject. I had a fantastic teacher who never saw my physical limitations in terms of my sight. He never said “Oh no you can’t do this lab,” or “You shouldn’t do physics,” and this was crucial. I was a young person and I knew I would have to prove myself as a legally blind person.

What were some of the challenges you faced as a blind person in physics?

It was when I went to the College of William and Mary in Virginia to study physics that I really encountered difficulties. For the first time I found it tough trying to make my coursework accessible to me. I was the first blind person to study physics there so the books weren’t on tape, I had to find readers to record the coursework. There seemed to be all of these issues that I had to worry about that my colleagues didn’t even think about. This puts you a little behind. My peers could just pick up a book or go to the library to get information while I didn’t have that flexibility. As I would be listening to audio, something like turning back to page 10 wasn’t as easy for me as it was for a sighted person. This forced me to memorize as much as I could. I would memorize all the formulae and equations and in the long term this made physics easier for me. I think the biggest thing though was dealing with other people’s perceptions about what blind people can and can’t do. The first thing that people see is my disability. After that, they notice that I am a woman and also African-American so it’s like a three-strike situation. This was the reality, especially as I was in a predominantly white male department, so it was really hard for me to feel like I belonged. But I had a drive that came from within me – an ability to envision possibility.

How did you get into media and films?

When I was doing my PhD at the University of Maryland I applied for an American Physical Society Mass Media Fellowship, and when I got it, it was the most fantastic experience. They assigned me to CNN in Atlanta. Although the programme was meant to be only 10 weeks, I ended up doing more than three months and I even took a semester off my PhD because I wanted to focus on the fellowship. I had the opportunity to learn all about science communication and I found that I was really interested in the media. People often assume that as a blind person, you would not want to be in front of the camera, but that was what interested me most, along with producing media content. My time at CNN was great and I even got to meet then chief executive Tom Johnson. He was on the advisory board of the School of Journalism in Maryland and he took me under his wing. When the fellowship ended I continued to produce out of the Washington bureau, where I was a special science correspondent. I was the first blind on-air producer for the network and I really wanted to show that it didn’t take sight to do this. Who cares if my eyes don’t align properly to the camera lens – you should be paying attention to the content I am delivering. I then set up Aziza Productions, making short films for science-based non-profit organizations and focusing on minority communities in science.

Was it hard finding work after your fellowship?

As blind people we have to be part of changing the attitude that the general public has about us. Even today in the US, 70% of working-age blind people are unemployed. This is something I dealt with when I came out of my PhD and was trying to find work. You may have the credentials and the necessary skills and experience, but unfortunately people just see the blindness. There are many environments where people aren’t used to seeing blind people – physics was one and television was another. People think that it takes vision to do the work, but you could say that about any job. For me vision is a mindset, an attitude, and for that I don’t need sight. Of course it has been challenging and there have been roadblocks, but I have managed just fine without sight. I hope that my story inspires others with disability, especially in physics. The main barrier is dealing with people, not doing the physics.

How has your physics background been helpful in your media work?

I’m passionate about science and I love talking about it. My physics training helps me better communicate it because you have to understand it in order to effectively explain it to the general public. I also love working with people and storytelling, so journalism was an obvious path, but science was my first love.

What are you working on now?

I’m working on a documentary film called Seeking Vision. It’s about overcoming odds and not being able to see with your eyes. A little over 10 years ago I had my fifth brain operation and because I knew I wanted to produce a film that will connect with people, I had my camera crew in the operating room filming for nearly three hours of a seven-hour surgery. Although the hospital was worried about liabilities, my neurosurgeons allowed it. I want to show the reality of being blind and that we can do more than answer phones.

Do you have any advice for today’s students, especially those with any disabilities?

I like referring to the concept of disabilities as “different abilities”. I tell my sighted colleagues that while they see with their eyes, I do the same with my fingers while reading braille and with my ears while listening to audio. What drives me is my vision and my goals, both of which come from within. It’s important to know who you are and what you are capable of, so hold on to that vision.

LEGO acoustics, potato cannons go to war, personal politics and popular science

By Hamish Johnston

In the above video Brian Anderson of Brigham Young University shows how the acoustic concept of “time reversal” can be used to knock over a series of LEGO figures using sound. The idea is that sound waves are broadcast into an environment and captured by a sensor at a specific location. The signal is then used to work-out how the sound waves bounced about before reaching the location and this information is then used to target that specific location with subsequent sound waves. In the demonstration, sound knocks over 29 LEGO figures one-by-one. It’s very impressive and entertaining as well.

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Bell correlations measured in 500,000 atoms

Bell correlations – a hallmark of an entangled quantum system – have been spotted in an ensemble of 500,000 rubidium-87 atoms. The atoms were prepared in spin-squeezed states by physicists at Stanford University in the US and the correlations measured to a whopping statistical significance of 124σ.

In quantum mechanics, entangled particles have much stronger correlations than are allowed in classical physics – a property that can be exploited in quantum technologies including cryptography. In 1964 the physicist John Bell famously calculated an upper limit on how strong these correlations could be if they were caused by classical physics alone – what has become known as Bell’s inequality. Correlations stronger than this limit, Bell reasoned, could occur only if the particles are entangled.

In this latest work, Onur Hosten, Mark Kasevich and colleagues have measured these strong Bell correlations in an ensemble of 500,000 cold rubidium-87 atoms that are trapped by laser light. The atoms are put into an entangled state using a process called spin squeezing. The uncertainty principle dictates that the uncertainty in a measurement of the z-component of the total spin of the system multiplied by the uncertainty in the y-component must be larger than a certain value. Reducing (or squeezing) the uncertainty of the z-component increases the uncertainty of y-component, putting the system into a spin-squeezed state.

Not a fluke

It turns out that the technique used by Hosten and colleagues to create a spin-squeezed state in their atomic system also puts the atoms into an entangled state. The team then characterized this state by measuring two quantities. One is related to the total spin of the atoms in the z direction and the other is related to the total spin of the atoms in a direction n, which is in the z–x plane. Correlations between these two quantities can be expressed in terms of a Bell-like inequality. The team found that for certain values of n, the inequality was violated – showing that entanglement is present in the system. For some values of n, the statistical significance of the violation was 124σ, making it extremely unlikely that the measurement was a random fluke.

Kai Bongs of the University of Birmingham in the UK describes the work as “a very nice experiment done on a fantastic system”, and points out that the Stanford team has taken the atomic ensemble “deep into the quantum domain”. However, Bongs, who works in the field of quantum sensors, says that practical applications of the Bell correlation measurements are not obvious. Hosten concurs: “We do not know any immediate practical applications of the Bell correlation measurements. However the spin-squeezed states have immediate applications in improving the precision of atomic clocks and atom interferometers.”

Hosten points out that the team’s study differs from conventional Bell experiments because it does not look at correlations between measurements made at two different places. If the system could be adapted for atom interferometry – whereby the atoms can follow two different paths – it could be used to further test the predictions of quantum theory. The measurements are described in Physical Review Letters.

Leukosomes engage stealth mode by altering their protein shell

Leukosomes are a promising new type of nanoparticle for use in targeted drug and gene delivery. Preloaded with leukocyte proteins, the particles cloak themselves in a shroud of host protein. Researchers from the Houston Methodist Research Institute in Texas have investigated this coating to find out how they evade the host immune system.

Reaching your target behind enemy lines is easier if you can steal a uniform. Leukosomes are biomimetic lipid vesicles (liposomes) that are preloaded with host white blood cell proteins on their surface. When inside the body, they shroud themselves in host protein to slip past the immune system: it is this unknown shroud of host protein that makes them special.

When Ennio Tasciotti and colleagues in Texas and Italy compared how coated leukosomes and bare liposomes fared in the blood, they found that the liposomes were quickly swallowed up by the host immune system, whereas the leukosomes circulated far longer. In addition, the leukosomes reached sites of inflammation in greater numbers.

The researchers studied leukosomes sized from 80 to 1000 nm that coat themselves in a specific array of plasma proteins – a corona, which helps to conceal them from the deadly host immune system. This was what they investigated to find out how it might enable the stealth function of these vesicles.

Stealth mode

Tasciotti and colleagues imaged the leukosomes in mice by intra-vital microscopy. They found that the leukosomes were able to target inflamed tissue, while also circulating for longer in the blood. Moreover, the leukosomes had the ability to resist being swallowed by roaming phagocytic macrophages. In contrast, liposomes – while they did also pick up a protein corona – were more evenly spread from their point of origin and were quickly swallowed up. This induced ability to both turn on stealth mode and target specific organs was quite unexpected. Especially after the researchers analysed the protein corona and found that leukosomes adsorb fewer proteins to their surface than plain liposomes.

The final experiment of the paper seems to posit an answer: macrophage receptors. One possibility, the researchers argue, is that the macrophage receptors in the leukosome undergo receptor site–ligand binding with proteins in the blood. This effectively blocks the sites that macrophages would normally grab on to, so the leukosome goes on unimpeded.

Biomimetic particles like these have been described as Trojan horses, and were originally designed using erythrocyte membranes. Here, researchers have begun to characterize the corona – the “cloak of many colours” – an extra layer composed of hundreds of proteins that a leukosome takes on when it enters the blood of the host. Understanding this process might well help to make more bespoke, generally targeted nanoparticles, which can sneak through the immune system to deliver their precious cargo to a specific target.

Full details reported in ACS Nano.

Flash Physics: Superconductor is flexible, girls underestimate maths ability, super-Earth has atmosphere

Superconducting fabric is ultrathin, flexible and lightweight

A flexible fabric woven from plastic fibres and high-temperature superconductor nanowires has been unveiled by Uwe Hartmann, Volker Presser and colleagues at the University of Saarland in Germany. Potential applications of the material include coatings that screen objects form electromagnetic fields, flexible resistance-free electrical cables and friction-free motion through magnetic levitation. The material, which looks like charred paper, is a superconductor below about 73 K. However, unlike most other high-temperature superconductors – which are ceramics – the fabric is as flexible as plastic kitchen film. It has a density of just 0.05 g/cm³, which is just 1% of most supercomputing materials. “This makes the material very promising for all those applications where weight is an issue, such as in space technology,” says Hartmann, adding: “There are also potential applications in medical technology.” The superconducting nanowires are 300 nm or less in diameter and are made from yttrium-barium-copper-oxide or a similar material. The nanowire manufacturing process is described in Superconductor Science and Technology and the new material will be presented at the Hannover Messe industrial fair on 24–28 April.

Girls underestimate their mathematical ability, reveals study

Photograph of Lara Perez-Felkner — Confidence booster: Lara Perez-Felkner has found that girls underestimate their mathematical ability. (Courtesy: Florida State University)

A study by psychologists in the US has found that high-school girls rate their competence in mathematics lower than boys, even for those with similar abilities, according to research reported in Frontiers in Psychology. Carried out by Lara Perez-Felkner at Florida State University and colleagues, the study asked high-school students in the 10th and 12th grade to indicate their level of agreement to statements such as “I am certain I can understand the most difficult material presented in math texts”. For boys and girls who showed a high ability in mathematics, the researchers found that boys rated their ability 27% higher than girls. The authors say that this difference could explain why more boys go on to study mathematics and science at degree level and beyond. “The argument continues to be made that gender differences in the hard sciences is all about ability,” says Perez-Felkner. “But when we hold tests scores constant, we see boys still rate their ability higher, and girls rate their ability lower.” The authors suggest that initiatives such as regular science camps, extracurricular activity in science and increased access to female scientists could help to boost girls’ confidence in mathematics and science.

Super-Earth exoplanet has atmosphere

Artist's impression of GJ 1132b orbiting its host red dwarf — Steamy atmosphere: super-Earth may have atmosphere rich in water and methane. Artist’s impression of GJ 1132b orbiting its host red dwarf. (Courtesy: Max Plank Institute of Astronomy)

An atmosphere has been detected on an exoplanet that is slightly larger than Earth. Previous observations of atmospheres on planets outside the solar system have involved objects much more massive than Earth. But this is the first time an atmosphere has been detected on a planet only marginally bigger than ours – 1.6 times the mass of Earth and 1.4 times the radius. The planet in question, GJ 1132b, orbits a red-dwarf star 39 light-years away and is classified as a super-Earth because it is bigger than Earth but smaller than a gas giant. A European collaboration used the GROND imager at the MPG/ESO 2.2 m telescope of the European Southern Observatory in Chile to image the changing brightness of GJ 1132b’s host star as the planet passed in front of it. By looking at seven different wavelengths, the team saw that the planet appeared bigger when observed in the infrared. This suggests that GJ 1132b has an atmosphere that is opaque to infrared but transparent to other wavelengths. Using simulations, the researchers suggest this is because the atmosphere may be rich in oxygen and methane, but with the current data it is not possible to say how similar or dissimilar GJ 1132b is to Earth. It may be a water planet with a steam atmosphere, for example. Meanwhile, as the current method for detecting life on other planets is to look for fingerprint chemical imbalances in their atmospheres, the finding, published in the Astronomical Journal, is a step towards finding life outside the solar system.

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