Monday, May 30, 2011

New biomaterial more closely mimics human tissue

 A new biomaterial designed for repairing damaged human tissue doesn’t wrinkle up when it is stretched. The invention from nanoengineers at the University of California, San Diego marks a significant breakthrough in tissue engineering because it more closely mimics the properties of native human tissue.

Shaochen Chen, professor in the Department of NanoEngineering at the UC San Diego Jacobs School of Engineering, hopes future tissue patches, which are used to repair damaged heart walls, blood vessels and skin, for example, will be more compatible with native than the patches available today. His findings were published in a recent issue of the journal Advanced Functional Materials.

The new was created using a new biofabrication platform that Chen is developing under a four-year, $1.5 million grant from the National Institutes of Health. This biofabrication technique uses light, precisely controlled mirrors and a computer projection system -- shined on a solution of new cells and polymers -- to build three-dimensional scaffolds with well-defined patterns of any shape for tissue engineering.

“We are also exploring other opportunities,” said Chen. “It’s a new material. I think it’s just a matter of time before more people will pick up and find applications for it in defense, energy and communications, for instance.”

Although Chen’s team is focused on creating biological materials, he said the manufacturing technology could be used to engineer many other kinds of materials including metal parts used in ships and spacecraft, for example.

Shape turned out to be essential to the new material’s mechanical property. While most engineered tissue is layered in scaffolds that take the shape of circular or square holes, Chen’s team created two new shapes called “reentrant honeycomb” and “cut missing rib.” Both shapes exhibit the property of negative Poisson’s ratio (i.e. not wrinkling when stretched) and maintain this property whether the tissue patch has one or multiple layers. One layer is double the thickness of a human hair, and the number of layers used in a tissue patch depends on the thickness of the native tissue that doctors are trying to repair. A single layer would not be thick enough to repair a heart wall or skin tissue, for example.  The next phase of research will involve working with the Department of Bioengineering at the Jacobs School of Engineering to make grafts to repair damaged blood vessels.

Provided by UC Davis (news : web)

Quantum sensor tracked in human cells could aid drug discovery

Groundbreaking research has shown a quantum atom has been tracked inside a living human cell and may lead to improvements in the testing and development of new drugs.

Professor Lloyd Hollenberg from the University of Melbourne's School of Physics who led the research said it is the first time a single atom encased in nanodiamond has been used as a sensor to explore the nanoscale environment inside a living human cell.

"It is exciting to see how the atom experiences the biological environment at the nanoscale," he said.

"This research paves the way towards a new class of quantum sensors used for biological research into the development of new drugs and nanomedicine."

The sensor is capable of detecting biological processes at a molecular level, such as the regulation of chemicals in and out of the cell, which is critical in understanding how drugs work.

The paper has been published in the journal Nature Nanotechnology.

Funded by the ARC Centre of Excellence for Quantum Computation and Communication Technology, the research was conducted by a cross-disciplinary team from the University of Melbourne's Physics, Chemistry, and Chemical and Biomolecular Engineering departments.

The researchers developed state of the art technology to control and manipulate the atom in the nanodiamond before inserting it into the human cells in the lab.

Biologist Dr Yan Yan of the University's Department of Chemical and Biomolecular Engineering who works in the field of nanomedicine, said the sensor provides critical information about the movement of the nanodiamonds inside the living cell.

"This is important for the new field of nanomedicine where drug delivery is dependant on the uptake of similar sized nanoparticles into the cell."

Quantum physicist and PhD student Liam McGuinness from the University's School of Physics said that monitoring the atomic sensor in a living cell was a significant achievement.

"Previously, these atomic level quantum measurements could only be achieved under carefully controlled conditions of a physics lab," he said.

It is hoped in the next few years, that following these proof of principle experiments, the researchers will be able to develop the technology and provide a new set of tools for drug discovery and nanomedicine.

Story Source:

The above story is reprinted (with editorial adaptations ) from materials provided by University of Melbourne.

Journal Reference:

L. P. McGuinness, Y. Yan, A. Stacey, D. A. Simpson, L. T. Hall, D. Maclaurin, S. Prawer, P. Mulvaney, J. Wrachtrup, F. Caruso, R. E. Scholten, L. C. L. Hollenberg. Quantum measurement and orientation tracking of fluorescent nanodiamonds inside living cells. Nature Nanotechnology, 2011; DOI: 10.1038/nnano.2011.64

Matter-matter entanglement at a distance: Quantum mechanical entanglement of two remote quantum systems

Because of its strange consequences the quantum mechanical phenomenon of entanglement has been called "spooky action at a distance" by Albert Einstein. For several years physicists have been developing concepts how to use this phenomenon for practical applications such as absolutely safe data transmission. For this purpose, the entanglement which is generated in a local process has to be distributed among remote quantum systems.

A team of scientists led by Prof. Gerhard Rempe, Director at the Max Planck Institute of Quantum Optics and head of the Quantum Dynamics Division, has now demonstrated that two remote atomic quantum systems can be prepared in a shared "entangled" state (Physical Review Letters, Advance Online Publication, May 26, 2011): one system is a single atom trapped in an optical resonator, the other one a Bose-Einstein condensate consisting of hundreds of thousands of ultracold atoms. With the hybrid system thus generated, the researchers have realized a fundamental building block of a quantum network.

In the quantum mechanical phenomenon of "entanglement" two quantum systems are coupled in such a way that their properties become strictly correlated. This requires the particles to be in close contact. For many applications in a quantum network, however, it is necessary that entanglement is shared between two remote nodes ("stationary" quantum bits). One way to achieve this is to use photons ("flying" quantum bits) for transporting the entanglement. This is somewhat analogous to classical telecommunication, were light is used to transmit information between computers or telephones. In the case of a quantum network, however, this task is much more difficult as entangled quantum states are extremely fragile and can only survive if the particles are well isolated from their environment.

The team of Professor Rempe has now taken this hurdle by preparing two atomic quantum systems located in two different laboratories in an entangled state: on the one hand a single rubidium atom trapped inside an optical resonator formed by two highly reflective mirrors, on the other hand an ensemble of hundreds of thousands of ultracold rubidium atoms which form a Bose Einstein condensate (BEC). In a BEC, all particles have the same quantum properties so that they all act as a single "superatom."

First, a laser pulse stimulates the single atom to emit a single photon. In this process, internal degrees of freedom of the atom are coupled to the polarisation of the photon, so that both particles become entangled. The photon is transported through a 30 m long optical fibre into a neighbouring laboratory where it is directed to the BEC. There, it is absorbed by the whole ensemble. This process converts the photon into a collective excitation of the BEC. "The exchange of quantum information between photons and atomic quantum systems requires a strong light-matter interaction," explains Matthias Lettner, a doctoral student working on the experiment. "For the single atom, we achieve this by multiple reflections between the two resonator mirrors, whereas for the BEC the light-matter interaction is enhanced by the large number of atoms."

In a subsequent step, the physicists prove that the single atom and the BEC are really entangled. To this end, the photon absorbed in the BEC is retrieved with the help of a laser pulse and the state of the single atom is read out by generating a second photon. The entanglement of the two photons reaches 95 % of the maximally possible value, thus showing that the entanglement of the two atomic quantum systems must have been equally good, or even better. Moreover, the entanglement is detectable for approximately 100 microseconds.

"A BEC is very well suited as a quantum memory because this exotic state does not suffer from any disturbances caused by thermal motion," says Matthias Lettner. "This makes it possible to store and retrieve quantum information with high efficiency and to conserve this state for a long time."

In this experiment, the team of Professor Rempe has realized a building block for a quantum network consisting of two remote, entangled, stationary nodes. This is a milestone on the way to large-scale quantum networks in which, for example, quantum information can be transmitted absolutely safe. In addition, such networks might help realizing a universal quantum computer in which quantum bits can be exchanged with photons between nodes designed for information storage and processing.

Story Source:

The above story is reprinted (with editorial adaptations ) from materials provided by Max Planck Institute of Quantum Optics, via AlphaGalileo.

Journal Reference:

M. Lettner, M. Mücke, S. Riedl, C. Vo, C. Hahn, S. Baur, J. Bochmann, S. Ritter, S. Dürr, and G. Rempe. Remote Entanglement between a Single Atom and a Bose-Einstein Condensate. Physical Review Letters, 2011; DOI: 10.1103/PhysRevLett.106.210503

Common fire retardant harmful to aquatic life

ScienceDaily (May 24, 2011) — A new study by Baylor University environmental health researchers found that zebra fish exposed to several different technical mixtures of polybrominated diphenyl ethers (PBDEs) -- a common fire retardant -- during early development can cause developmental malformations, changes in behavior and death.

The study will appear in the June issue of the journal Environmental Toxicology and Chemistry and is the first to test multiple PBDE mixtures for changes in behavior, physical malformations and mortality on zebra fish.

PBDEs are found in many common household products from blankets to couches to food wrappers. Lab tests have shown that PBDEs have been found in human breast milk and cord blood. Previous studies have showed children with high levels of PBDEs in their umbilical cord at birth scored lower on tests between one and six years of age. In 2006, the state of California started prohibiting the use of PBDEs.

The family of PBDEs consists of more than 200 possible substances, which are called congeners. Congeners are considered low if they average between 1 to 5 bromine atoms per molecule.

The Baylor researchers tested six PBDE congeners for developmental effects on embryonic zebra fish. Changes in behavior, physical malformations and mortality were recorded daily for seven days.

The results showed:

Lower brominated congeners were more toxic than higher brominated congeners.Embryos were most sensitive to two particular types of PBDE exposures, the two lowest brominated congeners of the six tested. Both induced a curved body axis and eventually death.In all, four of the six congeners tested caused developmental malformations, such as a curved body axis and pulmonary edema. Five of the six caused alterations in behaviors, such as decreased swimming rates and increased spontaneous movement in the embryo.

"While most PBDEs have either been banned or phased out throughout the world, it may be more beneficial to identify congeners of concern rather than replacing these compounds with chemicals of unknown biological interactions," said Dr. Erica Bruce, assistant professor of environmental science at Baylor who is an expert in environmental chemicals and their effects on public health. "Alterations in early behavior may potentially be due to disruption of thyroid hormones. Thyroid hormones play a vital role in the development of the cholinergic system and this study gives insight into biological interaction within a few hours of exposure. The observed hyperactivity may be due to overstimulation of the cholinergic system," Bruce said.

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by Baylor University.

Journal Reference:

Crystal Y. Usenko, Eleanor M. Robinson, Sascha Usenko, Bryan W. Brooks, Erica D. Bruce. PBDE developmental effects on embryonic zebrafish. Environmental Toxicology and Chemistry, 2011; DOI: 10.1002/etc.570

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

Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.

Droplets for detecting tumoral DNA

New research suggests it may be possible, in the near future, to detect cancer by a simple blood or urine test.

Biologists from CNRS, Inserm, Paris Descartes and Strasbourg universities have developed a technique capable of detecting minute traces of tumoral DNA present in the biological fluids of patients suffering from cancer. The method consists in carrying out ultra-sensitive molecular analyses in microscopic droplets. Successfully tested on genes involved in various cancers, including cancer of the colon and leukemia, it has the potential of becoming a powerful tool for oncologists, both in making a diagnosis and in prescribing a treatment. A clinical study is already envisaged to evaluate this technique.

The work is published on the website of the journal Lab on a Chip.

When tumoral cells die, they spill their contents into the extracellular medium. These contents, in particular the DNA of cells, are then found in the biological fluids of the patient: blood, lymph, urine, etc. Since the development of most cancers involves genetic factors, a simple blood or urine test could in theory reveal the presence of tumoral DNA and thus cancer as soon as the first cancerous cells die, in other words at a very early stage.

Despite this great promise, there is a snag which explains why physicians cannot yet track down cancers in biological fluids: tumoral DNA is only present in trace amounts in these fluids. In blood, for example, it represents less than 0.01% of the total DNA found in diluted form. However, conventional DNA analysis methods are not sensitive enough to detect such small amounts. Hence the interest of the technique developed by researchers from CNRS, Inserm, the Université de Strasbourg and the Université Paris Descartes, in collaboration with a German team from the Max Planck Institute (Göttingen) and an American company (Raindance Technologies). The considerable advantage of this technique is that it makes it possible to detect DNA thresholds 20,000 times lower than was previously the case in clinics.

How does it work? A first step consists in distributing the DNA extracted from a biological sample into millions of droplets, which are sufficiently small to contain only a single target gene each. Then, this DNA is amplified by means of modern molecular multiplication methods. Simultaneously, fluorescent molecules specific to each gene interact with the DNA. This key phase provides a sort of gene color code. The droplets are then guided, one by one, into microscopic grooves where they are analyzed by laser: the color of the fluorescent molecules then indicates which gene is present in the droplet. If the droplet emits red fluorescence, for example, the DNA is healthy. If it is green, it is tumoral. If the droplet does not emit any fluorescence, it does not contain the targeted gene. A simple count of the colored spots then makes it possible to determine the tumoral DNA concentration.

The researchers have successfully applied their method to an oncogene (a gene that has the potential of causing cancer) known as KRAS (associated with leukemia and various cancers, such as cancer of the colon, pancreas and lung). The DNA bearing this gene was derived from laboratory cell lines. This new analytical method now needs to be tested in a therapeutic context. A clinical study is already scheduled. If it is a success, physicians will have an efficient "anticancer weapon," not just for detecting the presence of tumors but also for proposing treatments. The aggressiveness of the cancer, its responsiveness to existing treatments and its risk of recurrence following local treatment: all this information is partly contained in the tumoral DNA. By deciphering it with the microdroplet technology, oncologists could benefit from a powerful diagnostic tool to help predict the evolution of the disease and determine a therapeutic strategy.

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by CNRS (Délégation Paris Michel-Ange).

Journal Reference:

Deniz Pekin, Yousr Skhiri, Jean-Christophe Baret, Delphine Le Corre, Linas Mazutis, Chaouki Ben Salem, Florian Millot, Abdeslam El Harrak, J. Brian Hutchison, Jonathan W. Larson, Darren R. Link, Pierre Laurent-Puig, Andrew D. Griffiths, Valérie Taly. Quantitative and sensitive detection of rare mutations using droplet-based microfluidics. Lab on a Chip, 2011; DOI: 10.1039/C1LC20128J