Thursday, January 12, 2012

New device creates lipid spheres that mimic cell membranes

Opening up a new door in synthetic biology, a team of researchers has developed a microfluidic device that produces a continuous supply of tiny spheres that are similar in many ways to a cell's .

"Cells are essentially small, complex bioreactors enclosed by phospholipid membranes," said Abraham Lee from the University of California, Irvine. "Effectively producing vesicles with lipid membranes that mimic those of natural cells is a for fundamental biology research, and it's also an important first step in the hoped-for production of an artificial cell."

The researchers have taken an important step in advancing this field by developing a single system that quickly and efficiently performs all the necessary steps to create stable lipid vesicles. Current multistep production methods create vesicles that have inconsistent sizes and layers and short usable lifespans, and they are often contaminated with solvents used in their production.

A paper accepted for publication in the AIP's journal.

Biomicrofluidics reports that the new microfluidic design overcomes these previous hurdles by generating and manipulating precisely sized droplets of water in an oil environment. This produces an oil-and-water membrane that serves as a scaffold around which lipids molecules assemble. As the membrane dissolves over time, the accumulated lipids form a stable, uniform vesicle that shares many of a natural cell membrane's chemical and .

More information: "Stable, Biocompatible Lipid Vesicle Generation by Solvent Extraction-based Droplet Microfluidics" is accepted for publication in the journal Biomicrofluidics.

Provided by American Institute of Physics

Hips that function better and last longer: Lubricant in metal-on-metal hip implants found to be graphite, not proteins

A team of engineers and physicians have made a surprising discovery that offers a target for designing new materials for hip implants that are less susceptible to the joint's normal wear and tear.

Researchers from Northwestern University, Rush University Medical Center, Chicago, and the University of Duisburg-Essen Germany found that graphitic carbon is a key element in a lubricating layer that forms on metal-on-metal hip implants. The lubricant is more similar to the lubrication of a combustion engine than that of a natural joint.

The study will be published Dec. 23 by the journal Science.

Prosthetic materials for hips, which include metals, polymers and ceramics, have a lifetime typically exceeding 10 years. However, beyond 10 years the failure rate generally increases, particularly in young, active individuals. Physicians would love to see that lifespan increased to 30 to 50 years. Ideally, artificial hips should last the patient's lifetime.

"Metal-on-metal implants can vastly improve people's lives, but it's an imperfect technology," said Laurence D. Marks, a co-author on the paper who led the experimental effort at Northwestern. "Now that we are starting to understand how lubrication of these implants works in the body, we have a target for how to make the devices better."

Marks is a professor of materials science and engineering at Northwestern's McCormick School of Engineering and Applied Science.

The ability to extend the life of implants would have enormous benefits, in terms of both cost and quality of life. More than 450,000 Americans, most with severe arthritis, undergo hip replacement each year, and the numbers are growing. Many more thousands delay the life-changing surgery until they are older, because of the limitations of current implants.

"Hip replacement surgery is the greatest advancement in the treatment of end-stage arthritis in the last century," said co-author and principal investigator Dr. Joshua J. Jacobs, the William A. Hark, M.D./Susanne G. Swift Professor of Orthopedic Surgery and professor and chair of the department of orthopedic surgery at Rush. "By the time patients get to me, most of them are disabled. Life is unpleasant. They have trouble working, playing with their grandchildren or walking down the street. Our findings will help push the field forward by providing a target to improve the performance of hip replacements. That's very exciting to me."

Earlier research by team members Alfons Fischer at the University of Duisburg-Essen and Markus Wimmer at Rush University Medical Center discovered that a lubricating layer forms on metallic joints as a result of friction. Once formed, the layer reduces friction as well as wear and corrosion. This layer is called a tribological layer and is where the sliding takes place, much like how an ice skate slides not on the ice but on a thin layer of water.

But, until now, researchers did not know what the layer was. (It forms on the surfaces of both the ball and the socket.) It had been assumed that the layer was made of proteins or something similar in the body that got into the joint and adhered to the implant's surfaces.

The interdisciplinary team studied seven implants that were retrieved from patients for a variety of reasons. The researchers used a number of analytical tools, including electron and optical microscopies, to study the tribological layer that formed on the metal parts. (An electron microscope uses electrons instead of light to image materials.)

The electron-energy loss spectra, a method of examining how the atoms are bonded, showed a well-known fingerprint of graphitic carbon. This, together with other evidence, led the researchers to conclude that the layer actually consists primarily of graphitic carbon, a well-established solid lubricant, not the proteins of natural joints.

"This was quite a surprise," Marks said, "but the moment we realized what we had, all of a sudden many things started to make sense."

Metal-on-metal implants have advantages over other types of implants, Jacobs said. They are a lower wear alternative to metal-on-polymer devices, and they allow for larger femoral heads, which can reduce the risk of hip dislocation (one of the more common reasons for additional surgery). Metal-on-metal also is the only current option for a hip resurfacing procedure, a bone-conserving surgical alternative to total hip replacement.

"Knowing that the structure is graphitic carbon really opens up the possibility that we may be able to manipulate the system in a way to produce graphitic surfaces," Fischer said. "We now have a target for how we can improve the performance of these devices."

"Nowadays we can design new alloys to go in racing cars, so we should be able to design new materials for implants that go into human beings," Marks added.

The next phase, Jacobs said, is to examine the surfaces of retrieved devices and correlate the researchers' observations of the graphitic layer with the reason for removal and the overall performance of the metal surfaces. Marks also hopes to learn how graphitic debris from the implant might affect surrounding cells.

The science of tribology is the study of friction, lubrication and wear. The term comes from the Greek word "tribos," meaning rubbing or sliding.

The National Institutes of Health (through American Recovery & Reinvestment Act of 2009 grant RC2-AR-058993) supported the research.

Story Source:

The above story is reprinted from materials provided by Northwestern University. The original article was written by Megan Fellman.

Note: Materials may be edited for content and length. For further information, please contact the source cited above.

Journal Reference:

Y. Liao, R. Pourzal, M. A. Wimmer, J. J. Jacobs, A. Fischer, L. D. Marks. Graphitic Tribological Layers in Metal-on-Metal Hip Replacements. Science, 2011; 334 (6063): 1687 DOI: 10.1126/science.1213902

Note: If no author is given, the source is cited instead.

E. coli packs a punch - an intestinal insight from ISIS

Commonly found in the intestines of humans and animals, E. coli is normally considered to be a ‘helpful’ bacterium that aids digestion.  However, it can also cause vomiting and diarrhoea, and can be a serious illness for young children, the elderly and those with vulnerable immune systems.  In 2010, 793 incidents of the O157 strain of E. coli were recorded by the Health Protection Agency, but this is thought to only represent a fraction of actual cases because most go unreported.

Discovering how antibacterial proteins attack harmful bacteria is important for establishing new methods of drug delivery. Antibacterial proteins often have to travel across a waterproof cell membrane to reach their target. E. coli bacteria use a similar mechanism when attacking each other so it makes a good comparable study for observing this behaviour.

A bacterial cell is surrounded by a cell membrane that acts as a barrier to hold nutrients and cell components inside, and protect the cell from attack.  The E. coli membrane is particularly difficult to pass through as it is a hydrophobic double layer making it twice as hard for the intruders to penetrate. To penetrate these barriers, E. coli bacteria secrete toxic proteins called Colicins. Just one Colicin can be enough to kill an E. coli bacterium – this is no mean feat as the E. coli bacterium is 400,000 times heavier than the Colicin protein.

For the first time, experiments carried out at ISIS by a team from Newcastle University and funded by the Wellcome Trust have revealed a ‘side view’ of the process that one type of Colicin (Colicin N) uses to kill E. coli bacteria.  The experiments allowed the progress of the Colicin N to be followed as it travelled through the membrane.  More conventional study methods only allow a surface-view of the membrane.  Colicin N specialises in punching a hole through the inner membrane of its target E. coli bacterium. Normally Colicin N would not be able to do this because it is too big to fit through the narrow food-entry pores in the outer membrane of the E. coli.  Results from these experiments have discovered that Colicin hijacks the pore-forming protein Ompf in the outer membrane of the and then squeezes down the side to reach the inner membrane which it then attacks.

“Neutron scattering techniques were able to show us the insertion of Colicin N into the hydrophobic . Using neutrons allowed us to get a side view of the process, which is important when following proteins across a barrier” said Jeremy Lakey, Professor of Structural Biochemistry at Newcastle University.

Professor Lakey and his team plan to conduct further studies at ISIS to observe later stages of the process.  The results of this research (published in the Journal of Biological Chemistry) will be used to develop new, more effective ways to treat life-threatening illnesses and ultimately help save lives.

Provided by Science and Technology Facilities Council (news : web)

N.E. Chemcat Corp. licenses Brookhaven Lab's electrocatalyst technology for fuel cells

Platinum is the most efficient electrocatalyst for fuel cells, but platinum-based catalysts are expensive, unstable, and have low durability. The newly licensed electrocatalysts have high activity, stability, and durability, while containing only about one tenth the platinum of conventional catalysts used in fuel cells, reducing overall costs.

The electrocatalysts consist of a palladium or a palladium alloy nanoparticle core covered with a monolayer – one-atom thick – platinum shell. This palladium-platinum combination notably improves oxygen reduction at the cathode of a hydrogen/oxygen . This type of fuel cell produces electricity using hydrogen as fuel, and forms water as the only byproduct.

Radoslav Adzic, the Brookhaven Lab senior chemist who led the team that developed the catalysts, said, "We are delighted that N.E. Chemcat Corporation has licensed our platinum electrocatalyst technology. We hope that it will facilitate the development of affordable and reliable fuel cell , which would be very beneficial for the environment since they produce no harmful emissions. Also, the use of nonrenewable fossil fuels for transportation that contribute to global warming would be greatly reduced, prolonging their availability for other uses in the future."

Provided by Brookhaven National Laboratory (news : web)

Relay race with single atoms: New ways of manipulating matter

 Thanks to a collaboration between scientists in San Sebastian and Japan, a relay reaction of hydrogen atoms at a single-molecule level has been observed in real-space. This way of manipulating matter could open up new ways to exchange information between novel molecular devices in future electronics. Dr. Thomas Frederiksen, presently working in the Donostia International Physics Center (DIPC) is one of the scientists that has participated in this research project. The results have been published in the journal Nature Materials.

An athletic relay race is a competition where each member of a team sprints a short distance with the baton before passing it onwards to the next team member. This collective way of transporting something rapidly along a well-defined track is not only a human activity and invention -- a similar relay mechanism, often refered to as structural diffusion, exists at the atomic scale that facilitate transport of hydrogen atoms and protons in hydrogen bonded networks, such as liquid water, biological systems, functional compounds, etc. However, direct visualization of this important transfer process in these situations is extremely difficult because of the highly complex environments.

Scientists in San Sebastian and Japan discovered that the relay reaction also occurs in well-defined molecular chains assembled on a metal surface. This new setup allowed the researchers to gain insight into the relay reactions at the level of single atoms and visualize the process using a scanning tunneling microscope (STM). By sending a pulse of electrons through a water molecule at one end of the chain, hydrogen atoms propagate one by one along the chain like dominoes in motion.

The result is that a hydrogen atom has been transferred from one end to the other via the relay mechanism.  The demonstrated control of the atom transfer along these molecular chains not only sheds new insight on a fundamental problem. It could also open up new ways to exchange information between novel molecular devices in future electronics by passing around hydrogen atoms.

Story Source:

The above story is reprinted from materials provided by Elhuyar Fundazioa, via AlphaGalileo.

Note: Materials may be edited for content and length. For further information, please contact the source cited above.

Journal Reference:

T. Kumagai, A. Shiotari, H. Okuyama, S. Hatta, T. Aruga, I. Hamada, T. Frederiksen, H. Ueba. H-atom relay reactions in real space. Nature Materials, 2011; DOI: 10.1038/NMAT3176

Note: If no author is given, the source is cited instead.