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30 abril 2015
Across the Sun
A long solar filament stretches across the relatively calm surface of the Sun in this telescopic snap shot from April 27. The negative or inverted narrowband image was made in the light of ionized hydrogen atoms. Seen at the upper left, the magnificent curtain of magnetized plasma towers above surface and actually reaches beyond the Sun's edge. How long is the solar filament? About as long as the distance from Earth to Moon, illustrated by the scale insert at the left. Tracking toward the right across the solar disk a day later the long filament erupted, lifting away from the Sun's surface. Monitored by Sun staring satellites, a coronal mass ejection was also blasted from the site but is expected to swing wide of our fair planet.
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A Smarter BandageThe injured soldiers had been treated well...
A Smarter Bandage
The injured soldiers had been treated well since their return from fighting in Afghanistan. At the San Antonio Military Medical Center in Texas, surgeons had carefully grafted healthy tissue over their burns and wounds, using microsurgery to connect their blood vessels to the new skin. But the patients still faced an uncertain recovery. The vessels might not supply enough oxygen for the transplants to thrive.
When Conor Evans visited San Antonio in 2010 and saw these soldiers, he realized that conventional techniques for monitoring oxygen levels did not work very well, and they often failed to give enough warning if the graft was failing. “What these physicians do is nothing short of amazing,” says Evans, a chemist at Harvard Medical School and the Wellman Center for Photomedicine at Massachusetts General Hospital. “But the sensors they had just weren’t cutting it.”
So Evans built a better bandage. He and his colleagues started with dyes that react to different oxygen levels, added nanosized molecules that control the dye activity, and used them to create a liquid bandage that indicates the health of the wound it covers. “The bandage changes color, just like a traffic light, from green through yellow and orange to red,” depending on the amount of oxygen present, Evans says. After success in laboratory animals in 2014, human trials are set to begin this year.
By taking advantage of newfound abilities to manipulate materials as small as a few billionths of a meter, scientists such as Evans can not only improve rapid health assessments, they can also turn wound dressings into precise drug-delivery systems “Nanotechnology plays a large role in being able to control the amounts released and how well formulations get to the area of a wound that we need them to reach,” says Paula Hammond, a chemist at the Massachusetts Institute of Technology. That precision has a major advantage over flooding body parts with drugs, only some of which find their targets.
COMING UP FOR AIR
poor wound healing caused by a lack of oxygen affects more than six million people in the U.S. every year, and the medical costs are estimated to reach $25 billion. Typically physicians stick needle electrodes into injured tissue to measure tissue oxygenation, but the needles can be painful and give readings from only a single point in a large wound. Evans’s bandage, in contrast, can provide an instant oxygen map of the entire injury.
It relies on two dyes mixed into a quick-drying liquid bandage that can be painted onto wounds. A brief burst of blue light energizes and illuminates both dyes: one glows bright red, the other green. Then oxygen molecules switch off the red dye’s phosphorescence, so the bandage will appear green if the adjacent tissue is bathed in oxygen and is healthy. But if areas of the wound are oxygen-starved, patches of yellow, orange and, finally, an alarming red shine through.
The key to the alert is a nanoscale addition to the red dye molecules. Evans coupled each of these molecules to a dendrimer, a treelike molecule with a branching structure up to two nanometers across. This molecular thicket prevents neighboring molecules from overlapping and quenching one another’s phosphorescence. They also physically block some—but not all—of the oxygen molecules from reaching the dye; starting with lower levels makes any changes more obvious.
In a hospital, the warning red would prompt a nurse to photograph the bandage, and doctors would to try to improve the blood and oxygen circulation in the trouble spots. In principle, the bandage could work at home, Evans says: patients could take their own bandage snapshots and send them to a doctor for assessment.
Evans’s team has also created alternative dyes that are much more efficient at converting blue light into red. “Our new bandage is so bright that it can be seen with very low dye loading, in a sunlit room,” Evans says. In the future, the bandage might even be engineered to dispense therapeutic drugs into wounds, he adds.
DRUG-DELIVERY DRESSING
in hammond’s lab, researchers have already loaded bandages with nanoengineered therapeutic substances. They have developed coatings that slowly release RNA or proteins, molecules that can shut down certain cell activities that might hamper wound recovery. Some RNA molecules, called small interfering RNAs, can hobble the ability of genes that give rise to problem-causing proteins, for example.
Her team encapsulated some of these RNAs within calcium phosphate shells, each about 200 nanometers wide, sandwiched the shells between two layers of a positively charged polymer made of biological molecules and then “buttered” one side of this sandwich with a negatively charged clay. (The opposite charges stick the layers to each other.) Stacking up 25 of these sandwiches formed a coating roughly half a micron thick, which Hammond placed on a conventional nylon bandage.
As natural enzymes in the body break down the layers, the dressing discharges the RNA molecules into the wound over the course of a week. The slow, steady release could reduce side effects caused by a single, large dose of a conventional drug; this release method could also ensure that the wound is constantly treated.
Hammond has also used this so-called layer-by-layer coating to supply a therapeutic protein that aids wound healing in diabetic mice. The protein is already available as an ointment, but she says that the formulation is not very effective—after initially delivering a huge burst of protein, its activity fades away within 24 hours. Hammond’s bandage, in contrast, sustains a steady flow over five to seven days to maintain the optimum dose of protein.
The layer-by-layer strategy could improve treatments for another ailment: coronary artery disease, which is caused by a buildup of plaque in vessels that carry blood through heart muscle. Treatment usually involves widening the artery with an inflatable balloon and keeping it open by inserting a small tube of stainless-steel mesh known as a stent. Some stents come loaded with therapeutic molecules to prevent the artery from narrowing again, but patients must then take more drugs to reduce the associated risks of blood clots that could break free from the area.
Treating the artery with doses of DNA, carefully delivered by devices with nanoscale coatings, could offer a better solution, according to David Lynn, a chemist at the University of Wisconsin– Madison. Inside the body, the DNA could make cells produce a protein that helps to stabilize and reconstruct blood vessel walls. To deliver such genetic therapies exactly when and where they are needed, Lynn has coated stents with successive layers of DNA and a biodegradable polymer, each several nanometers thick. By varying the number of layers, researchers can control the amount of DNA released into blood vessel walls. Experiments on pigs showed that the DNA gradually penetrated the surrounding tissue during the days after the stent was implanted. Fine-tuning the design of the coating, other tests show, can change the rate of release. “We now have reasonable control that allows us to time the release from seconds to months by modifying the structure of the polymer or how we put the film together,” Lynn says.
The basic nanoengineering behind these inventions could be adapted for a wide range of other applications. Lynn is using polymer coatings to deliver biological molecules called peptides that interrupt the chemical conversations among bacteria. Cut off from one another, the bacteria cannot team up to form tough biofilms that resist breakup by antibiotics. Evans, for his part, is using his phosphorescent dyes in tissue samples to identify oxygen-poor tumor cells, which can be particularly resistant to chemotherapy, and he plans to test the technique in animals later this year. The same dye approach could also be used to detect the presence of infectious bacteria in wound tissue or reveal other kinds of molecules. “Really, the sky’s the limit,” Evans says.
The only known photograph of a Chinese-American Union soldier,...
The only known photograph of a Chinese-American Union soldier, from the American Civil War. To read the almost unbelievable life story of a Chinese-American stowaway who eventually sat guard over Sitting Bull, check out historical-nonfiction.com’s latest post
This camel was buried in a tomb during the Northern...
This camel was buried in a tomb during the Northern Wei–Northern Qi dynasty, during the mid- to late-500s. Camels had first started appearing in northern Chinese tombs around the 200s and became increasingly popular. dapted to their natural habitat in the steppes and mountainous deserts north of China, camels were used to transport military goods to and from the harsh frontier, and as a mount for traders and even members of the upper classes. The tomb’s owner presumably hoped that this ceramic camel would continue work for them in the afterlife.
April 30th 1803: Louisiana PurchaseOn this day in 1803, the...
April 30th 1803: Louisiana Purchase
On this day in 1803, the United States purchased over 800,000 square miles of territory from France, known as the Louisiana Purchase. The purchase doubled the size of the young nation, opening the West to settlement by Americans. France had long controlled the territory, and despite ceding portions to Spain in 1762, soon re-purchased the Louisiana Territory in 1801. The United States were wary of this development, fearing that Napoleon would seek to expand French control further across the North American continent. For the bargain price of $15,000,000 - averaging at less than 42 cents per acre - the government of Thomas Jefferson purchased the land from France. The agreement was made on April 30th 1803 and the treaty signed on May 2nd. In October of the same year, the United States Senate ratified the treaty, and the transfer of authority was complete by December. Nine years after the agreement, on April 30th 1812, the first state from the territory - Louisiana - was admitted to the Union as the eighteenth state. The purchase is considered one of Jefferson’s greatest achievements.
In 2002, there were 397 civil offences and 608 penal offences in...
In 2002, there were 397 civil offences and 608 penal offences in Vatican City, which has 455 residents (the smallest number of any sovereign state). That comes to an average of 2.2 crimes per resident. Most of these offences were committed by some of the millions of tourists that visit annually.
Overview of MESSENGER Spacecraft's Impact Region on Mercury
On April 30th, this region of Mercury's surface will have a new crater! Traveling at 3.91 kilometers per second (over 8,700 miles per hour), the MESSENGER spacecraft will collide with Mercury's surface, creating a crater estimated to be 16 meters (52 feet) in diameter.
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With Destruction, Discovery
The Indian Ocean tsunami in 2004 uncovered parts of the lost port city Mahabalipuram, the capital of a powerful kingdom that traded with China, Roma, Greece, Arabia, and Egypt some 1,500 years ago. It is said that the capital was kodalkol or “swelled by the sea” at the height of its glory. The place was already being investigated by archaeologists when the receding waves before the tsunami revealed a temple structure and several rock sculptures.
Electronic Health Records InfographicHow do electronic health...
Electronic Health Records Infographic
How do electronic health records (EHRs) connect you and your doctor? In the past, medical data was only stored on paper, making it difficult for your health care providers to share your information. Between 2001 and 2011, the number of doctors using anEHRsystem grew about 57%, making it easier for you and all of your doctors to coordinate your care, and often reducing the chance of medical errors. Where are electronic health records headed? In this Infographic, view the history of electronic health records and see how they may improve your health and health care in the future.
(From HealthIT.gov)
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