Acoustic tweezers manipulate cells with sound waves

An illustration of the surface acoustic wave generators, with the generated 3-D trapping nodes. The inset indicates a single particle within a 3-D trapping node, which can be manipulated independently along x, y, or z axes.

Technique could enable 3-D printing of cellular structures for tissue engineering.

Engineers at MIT, Penn State University, and Carnegie Mellon University have devised a way to manipulate cells in three dimensions using sound waves. These “acoustic tweezers” could make possible 3-D printing of cell structures for tissue engineering and other applications, the researchers say.

Designing tissue implants that can be used to treat human disease requires precisely recreating the natural tissue architecture, but so far it has proven difficult to develop a single method that can achieve that while keeping cells viable and functional.

“The results presented in this paper provide a unique pathway to manipulate biological cells accurately and in three dimensions, without the need for any invasive contact, tagging, or biochemical labeling,” says Subra Suresh, president of Carnegie Mellon and former dean of engineering at MIT. “This approach could lead to new possibilities for research and applications in such areas as regenerative medicine, neuroscience, tissue engineering, biomanufacturing, and cancer metastasis.”

Suresh, Ming Dao, a principal research scientist in MIT’s Department of Materials Science and Engineering, and Tony Jun Huang, a professor of engineering science and mechanics at Penn State, are senior authors of a paper describing the device, published the week of Jan. 25. in the Proceedings of the National Academy of Sciences.

The paper’s lead author is Penn State graduate student Feng Guo. The team also includes Penn State researchers Zhangming Mao, Yuchao Chen, James Lata, Peng Li, Liqiang Ren, Jiayang Liu, Zhiwei Xie, and Jian Yang.

3-D control

The new acoustic tweezers are based on a microfluidic device that the researchers previously developed to manipulate cells in two dimensions. This device produces two acoustic standing waves, which are waves with a constant height. Where the two waves meet, they create a “pressure node” that can trap single cells. By altering the wavelength and another wave property known as the phase, the researchers can move the node and the cell trapped within it.

The research team previously used a similar approach to separate cancer cells from healthy cells, which could be useful for detecting rare tumor cells in a patient’s bloodstream and predicting whether the tumor will spread.

In the new study, the researchers added a third dimension of control: Once the cells are trapped in a horizontal plane, they can be moved up and down by altering the acoustic waves’ power, that is, the rate at which sound energy is emitted. Boosting the power allows the researchers to lift the cells from the surface in a type of “acoustic levitation,” then place them in a specific location, Dao says.

The researchers also developed equations that allow them to accurately predict how changes in the wavelength, phase, and acoustic power will affect cells’ positions.

“We now have a good idea of what to expect and how to control the 3-D positioning of the acoustic waves and the pressure nodes, enabling validation of the method as well as system optimization,” Dao says.

“Innovative approach”

In this study, the researchers demonstrated their device on polystyrene particles as well as mouse fibroblast cells. They were able to move the cells, one at a time, into specific positions on a surface and create patterns. They could also stack cells on top of each other.

“This is an exceptionally innovative approach of manipulating particles and single cells in 3-D in fluids,” says Taher Saif, a professor of mechanical science and engineering at the University of Illinois at Urbana-Champaign, who was not part of the research team. “Since acoustic energy is used for this manipulation, the approach is noninvasive and the cells maintain their viability. Overall, the method presented will be of significant interest for a broad community, from biologists to bioengineers.”

The researchers have filed for a patent on the technology and plan to continue developing it for tissue engineering and other applications.

ORIGINAL: MIT News

Anne Trafton | MIT News Office 

January 25, 2016

Researchers find how ancient Egyptian practice cheaply purify dirty water

Image: Penn State

And scientists have finally worked out how.

The seeds of the Moringa oleifera tree have been used to purify water and clean crockery since the days of ancient Egypt, but up until now scientists weren't sure exactly how they worked. Thanks to a new paper published in the journal Langmuir by researchers at Pennsylvania State University, part of the mystery has now been solved.

It had already been established that a protein inside the Egyptian seeds caused bacteria to clump together in the water and die, sinking to the bottom of the container to leave the water largely clear. But the latest discovery reveals how this is done: the academics found that the seeds actually fuse the membranes of said bacteria together. As those membranes are the main protection the bacteria have, disrupting them causes the cells to die.

That's not all though. The Penn State researchers have also worked out the best time to harvest the Moringa oleifera seeds: during the rainy season, when the seeds have reached full maturity. Previously, harvesting the seeds to capture them at the peak of their powers was largely guesswork, which meant it was difficult to assess to what extent the water they treated was purified.

These new breakthroughs are another step along the way to having this type of seed grown in areas where it is most needed, rather than just the areas where it occurs naturally. Because other parts of the seed are edible, it can be a useful food source for those in remote or impoverished areas, as well as a potentially vital way of cleaning drinking water.

According to the Water.org organisation, some 769 million people across the globe don't have access to safe and clean drinking water - this leads to around 840,000 deaths each year that could be prevented with improved water supplies. Most of these people (82 percent) live in rural areas, and it's here where the properties of the Moringa oleifera seed could make such a difference.

The scientists from Pennsylvania State University teamed up with botanist Bashir Abubakar, from Ahmadu Bello University in Zaria, Nigeria, as part of the research. Abubakar provided some of the seeds used in testing, and he says that their benefits go way beyond cleaning water. "[Local] farmers will have an additional income, because not only will they be growing Moringa for food, but they can also grow large plantations of Moringa for the seed," he said in a press release. "You can divert the money for other infrastructural and societal needs, either to improve the farmlands or to construct roads."

Further research is required before the seeds can be used to remove contaminations and leave water that's 100 percent clean and drinkable, but the end goal is now much closer, and could ultimately have a huge impact in developing nations. The researchers at Penn State are now seeking funding for additional studies.

ORIGINAL: Science Alert

DAVID NIELD
13 JUN 2015

Super-sponge polymer turns oil spill into floating gel

ORIGINAL: New Scientist

Following the Deepwater Horizon disaster, many new ways of cleaning up oil have been proposed. Now Mike Chung from Pennsylvania State University in University Park and colleagues have developed a novel approach using a super-absorbent material that turns an oil slick into a gel.

The material is a kind of polymer called a polyolefin, and can quickly soak up crude oil without mopping up water, absorbing up to 45 times its own weight (see video above). The gel that forms can then be removed and shipped to a refinery, where about 19 litres of oil can be recovered from a pound of the material. This is an advantage over existing absorbents, which become industrial waste after use.

According to Chung, the material's low cost makes it a viable solution. "Polyolefin products are inexpensive, with a large production capability around the world," he says.

If you enjoyed this post, watch a forked boom scoop up an oil spill or see a micro-submarine clean up motor oil.

Scientists use microbes to make 'clean' methane

ORIGINAL: Science Daily

ScienceDaily (July 27, 2012) — Microbes that convert electricity into methane gas could become an important source of renewable energy, according to scientists from Stanford and Pennsylvania State universities. 

Researchers at both campuses are raising colonies of microorganisms, called methanogens, which have the remarkable ability to turn electrical energy into pure methane -- the key ingredient in natural gas. The scientists' goal is to create large microbial factories that will transform clean electricity from solar, wind or nuclear power into renewable methane fuel and other valuable chemical compounds for industry.

"Most of today's methane is derived from natural gas, a fossil fuel," said Alfred Spormann, a professor of chemical engineering and of civil and environmental engineering at Stanford. "And many important organic molecules used in industry are made from petroleum. Our microbial approach would eliminate the need for using these fossil resources."

While methane itself is a formidable greenhouse gas, 20 times more potent than CO2, the microbial methane would be safely captured and stored, thus minimizing leakage into the atmosphere, Spormann said.

"The whole microbial process is carbon neutral," he explained. "All of the CO2 released during combustion is derived from the atmosphere, and all of the electrical energy comes from renewables or nuclear power, which are also CO2-free."

Methane-producing microbes, he added, could help solve one of the biggest challenges for large-scale renewable energy: What to do with surplus electricity generated by photovoltaic power stations and wind farms.

"Right now there is no good way to store electricity," Spormann said. "However, we know that some methanogens can produce methane directly from an electrical current. In other words, they metabolize electrical energy into chemical energy in the form of methane, which can be stored. Understanding how this metabolic process works is the focus of our research. If we can engineer methanogens to produce methane at scale, it will be a game changer."

'Green' methane

Burning natural gas accelerates global warming by releasing carbon dioxide that's been trapped underground for millennia. The Stanford and Penn State team is taking a "greener" approach to methane production. Instead of drilling rigs and pumps, the scientists envision large bioreactors filled with methanogens -- single-cell organisms that resemble bacteria but belong to a genetically distinct group of microbes called archaea.

By human standards, a methanogen's lifestyle is extreme. It cannot grow in the presence of oxygen. Instead, it regularly dines on atmospheric carbon dioxide and electrons borrowed from hydrogen gas. The byproduct of this microbial meal is pure methane, which methanogens excrete into the atmosphere.

The researchers plan to use this methane to fuel airplanes, ships and vehicles. In the ideal scenario, cultures of methanogens would be fed a constant supply of electrons generated from emissions-free power sources, such as solar cells, wind turbines and nuclear reactors. The microbes would use these clean electrons to metabolize carbon dioxide into methane, which can then be stockpiled and distributed via existing natural gas facilities and pipelines when needed.

When the microbial methane is burnt as fuel, carbon dioxide would be recycled back into the atmosphere where it originated from -- unlike conventional natural gas combustion, which contributes to global warming.

"Microbial methane is much more ecofriendly than ethanol and other biofuels," Spormann said. "Corn ethanol, for example, requires acres of cropland, as well as fertilizers, pesticides, irrigation and fermentation. Methanogens are much more efficient, because they metabolize methane in just a few quick steps."

Microbial communities

For this new technology to become commercially viable, a number of fundamental challenges must be addressed.

"While conceptually simple, there are significant hurdles to overcome before electricity-to-methane technology can be deployed at a large scale," said Bruce Logan, a professor of civil and environmental engineering at Penn State. "That's because the underlying science of how these organisms convert electrons into chemical energy is poorly understood."

In 2009, Logan's lab was the first to demonstrate that a methanogen strain known as Methanobacterium palustre could convert an electrical current directly into methane. For the experiment, Logan and his Penn State colleagues built a reverse battery with positive and negative electrodes placed in a beaker of nutrient-enriched water.

The researchers spread a biofilm mixture of M. palustre and other microbial species onto the cathode. When an electrical current was applied, the M. palustre began churning out methane gas.

"The microbes were about 80 percent efficient in converting electricity to methane," Logan said.

The rate of methane production remained high as long as the mixed microbial community was intact. But when a previously isolated strain of pure M. palustre was placed on the cathode alone, the rate plummeted, suggesting that methanogens separated from other microbial species are less efficient than those living in a natural community.

"Microbial communities are complex," Spormann added. "For example, oxygen-consuming bacteria can help stabilize the community by preventing the build-up of oxygen gas, which methanogens cannot tolerate. Other microbes compete with methanogens for electrons. We want to identify the composition of different communities and see how they evolve together over time."

Microbial zoo

To accomplish that goal, Spormann has been feeding electricity to laboratory cultures consisting of mixed strains of archaea and bacteria. This microbial zoo includes bacterial species that compete with methanogens for carbon dioxide, which the bacteria use to make acetate -- an important ingredient in vinegar, textiles and a variety of industrial chemicals.

"There might be organisms that are perfect for making acetate or methane but haven't been identified yet," Spormann said. "We need to tap into the unknown, novel organisms that are out there."

At Penn State, Logan's lab is designing and testing advanced cathode technologies that will encourage the growth of methanogens and maximize methane production. The Penn State team is also studying new materials for electrodes, including a carbon-mesh fabric that could eliminate the need for platinum and other precious metal catalysts.

"Many of these materials have only been studied in bacterial systems but not in communities with methanogens or other archaea," Logan said. "Our ultimate goal is to create a cost-effective system that reliably and robustly produces methane from clean electrical energy. It's high-risk, high-reward research, but new approaches are needed for energy storage and for making useful organic molecules without fossil fuels."

The Stanford-Penn State research effort is funded by a three-year grant from the Global Climate and Energy Project at Stanford.

NASA Researchers: DNA Building Blocks Can Be Made in Space

ORIGINAL: NASA

08.08.11

NASA-funded researchers have evidence that some building blocks of DNA, the molecule that carries the genetic instructions for life, found in meteorites were likely created in space. The research gives support to the theory that a "kit" of ready-made parts created in space and delivered to Earth by meteorite and comet impacts assisted the origin of life.

"People have been discovering components of DNA in meteorites since the 1960's, but researchers were unsure whether they were really created in space or if instead they came from contamination by terrestrial life," said Dr. Michael Callahan of NASA's Goddard Space Flight Center, Greenbelt, Md. "For the first time, we have three lines of evidence that together give us confidence these DNA building blocks actually were created in space." Callahan is lead author of a paper on the discovery appearing in Proceedings of the National Academy of Sciences of the United States of America.

NASA-funded researchers have evidence that some building blocks of DNA, the molecule that carries the genetic instructions for life, found in meteorites were likely created in space. The research gives support to the theory that a "kit" of ready-made parts created in space and delivered to Earth by meteorite and comet impacts assisted the origin of life. (Credit: NASA's Goddard Space Flight Center) › Download this and related videos from NASA Goddard's Scientific Visualization Studio

The discovery adds to a growing body of evidence that the chemistry inside asteroids and comets is capable of making building blocks of essential biological molecules. For example, previously, these scientists at the Goddard Astrobiology Analytical Laboratory have found amino acids in samples of comet Wild 2 from NASA’s Stardust mission, and in various carbon-rich meteorites. Amino acids are used to make proteins, the workhorse molecules of life, used in everything from structures like hair to enzymes, the catalysts that speed up or regulate chemical reactions.

In the new work, the Goddard team ground up samples of twelve carbon-rich meteorites, nine of which were recovered from Antarctica. They extracted each sample with a solution of formic acid and ran them through a liquid chromatograph, an instrument that separates a mixture of compounds. They further analyzed the samples with a mass spectrometer, which helps determine the chemical structure of compounds.

Meteorites contain a large variety of nucleobases, an essential building block of DNA. (Artist concept credit: NASA's Goddard Space Flight Center/Chris Smith)

The team found adenine and guanine, which are components of DNA called nucleobases, as well as hypoxanthine and xanthine. DNA resembles a spiral ladder; adenine and guanine connect with two other nucleobases to form the rungs of the ladder. They are part of the code that tells the cellular machinery which proteins to make. Hypoxanthine and xanthine are not found in DNA, but are used in other biological processes.

Also, in two of the meteorites, the team discovered for the first time trace amounts of three molecules related to nucleobases: purine, 2,6-diaminopurine, and 6,8-diaminopurine; the latter two almost never used in biology. These compounds have the same core molecule as nucleobases but with a structure added or removed.

It's these nucleobase-related molecules, called nucleobase analogs, which provide the first piece of evidence that the compounds in the meteorites came from space and not terrestrial contamination. "You would not expect to see these nucleobase analogs if contamination from terrestrial life was the source, because they're not used in biology, aside from one report of 2,6-diaminopurine occurring in a virus (cyanophage S-2L)," said Callahan. "However, if asteroids are behaving like chemical 'factories' cranking out prebiotic material, you would expect them to produce many variants of nucleobases, not just the biological ones, due to the wide variety of ingredients and conditions in each asteroid."

The second piece of evidence involved research to further rule out the possibility of terrestrial contamination as a source of these molecules. The team also analyzed an eight-kilogram (17.64-pound) sample of ice from Antarctica, where most of the meteorites in the study were found, with the same methods used on the meteorites. The amounts of the two nucleobases, plus hypoxanthine and xanthine, found in the ice were much lower -- parts per trillion -- than in the meteorites, where they were generally present at several parts per billion. More significantly, none of the nucleobase analogs were detected in the ice sample. One of the meteorites with nucleobase analog molecules fell in Australia, and the team also analyzed a soil sample collected near the fall site. As with the ice sample, the soil sample had none of the nucleobase analog molecules present in the meteorite.

Thirdly, the team found these nucleobases -- both the biological and non-biological ones -- were produced in a completely non-biological reaction. "In the lab, an identical suite of nucleobases and nucleobase analogs were generated in non-biological chemical reactions containing hydrogen cyanide, ammonia, and water. This provides a plausible mechanism for their synthesis in the asteroid parent bodies, and supports the notion that they are extraterrestrial," says Callahan.

"In fact, there seems to be a 'goldilocks' class of meteorite, the so-called CM2 meteorites, where conditions are just right to make more of these molecules," adds Callahan.

The team includes Callahan and Drs. Jennifer C. Stern, Daniel P. Glavin, and Jason P. Dworkin of NASA Goddard's Astrobiology Analytical Laboratory; Ms. Karen E. Smith and Dr. Christopher H. House of Pennsylvania State University, University Park, Pa.; Dr. H. James Cleaves II of the Carnegie Institution of Washington, Washington, DC; and Dr. Josef Ruzicka of Thermo Fisher Scientific, Somerset, N.J. The research was funded by the NASA Astrobiology Institute, the Goddard Center for Astrobiology, the NASA Astrobiology: Exobiology and Evolutionary Biology Program, and the NASA Postdoctoral Program.

Related Link

› Related videos from NASA Goddard's Scientific Visualization Studio

Bill Steigerwald
NASA's Goddard Space Flight Center, Greenbelt, Md.

El hongo de la "Hormiga Zombie" es atacado por otro hongo

ORIGINAL: NatGeo

Christine Dell'Amore. National Geographic News

04 de mayo 2012

Un cuerpo fructífero del hongo Ophiocordyceps se extiende desde la cabeza de una hormiga infectada.
Fotografía cortesía de David Hughes, Universidad de Penn State

Escuchando a David Hughes decir, las plantas de la selva tropical están llenas de cadáveres de un hongo infectado "hormigas zombi". Esto hizo que el entomólogo se extrañara: ¿Cómo logran escapar las hormigas afortunadas de la zombificación?

La respuesta, la encontró el equipo, es que las hormigas tienen un aliado involuntario: un hongo que "castra" el hongo de zombi hormiga.

La zombificación de la hormiga comienza cuando un hongo Ophiocordyceps dispara las esporas en un insecto. El hongo parásito poco a poco se apodera del cerebro de la hormiga y dirige el insecto a un lugar fresco y húmedo. Luego el hongo mata a la hormiga, y los cuerpos fructíferos brotan de la cabeza de la hormiga ydiseminan más esporas.

"Cuando uno entra en el bosque, se encuentran los cementerios de estos [infectados] cadáveres", dijo el líder del estudio Hughes, de Penn State.

"Esto sugiere que, para las hormigas andando por el suelo del bosque, es terriblemente precaria-que deban estar cubiertas con esporas de estos hongos."

Pero Hughes y su equipo descubrieron que no es así.

La combinación de los nuevos datos de cementerios brasileños de hormigas zombi con los estudios anteriores de los cementerios de Tailandia, los científicos se dieron cuenta de que un hongo aún sin nombre mantiene el hongo de zombis de hormigas en jaque.

"La gran mayoría [de las esporas de las hormigas zombis] han quedado fuera del ciclo" por el hongo, dijo Hughes.

(Ver fotos: "Fotos: Las hormigas 'Zombie' encontramos con el nuevo control de la mente los hongos.")

El hongo mata-hongos destruye químicamente su primo crea-zombies "castrándolo", Hughes explicó- y es altamente eficaz, por cierto.

Los análisis del equipo mostraron que sólo el 6,5 por ciento de las muestras de hongos de hormigas zombis eran capaces de producir esporas, lo que significa que el hongo no identificado en gran medida limita la propagación de Ophiocordyceps.

Hughes compara la situación con la reproducción del roble. "De todas esas pequeñas bellotas, la gran mayoría mueren, sólo unas pocas llegan a madurar", dijo.

"Hay muchas de estas interacciones muy interesantes que van a diario en el bosque", añadió Hughes, "y creo que se debe a estudiar con más detalle."

El estudio de los hongos-contra-hongo aparecií en el 02 de mayo número de la revista PLoS ONE.