Saturday, October 15, 2011

A breath-takingly simple test for human exposure to potentially toxic substances


The search for a rapid, non-invasive way to determine whether people have been exposed to potentially toxic substances in their workplaces, homes and elsewhere in the environment has led scientists to a technology that literally takes a person's breath away. Their report identifying exhaled breath as an ideal indicator of such exposure appears in ACS' Environmental Science & Technology.

Andrea M. Dietrich, Masoud Agah, and their students Heather Vereb and Bassam Alfeeli explain that scientists have known since the late 1970s that contains traces of any potentially that people may have inhaled. Research has shown that those amounts are an accurate reflection of the levels that exist in a person's blood. Those advances have positioned exhaled breath as the ideal substance to use in rapid, non-invasive, simple testing for to potentially harmful substances in the air. Sampling breath is less invasive than drawing blood, more convenient than taking urine samples and "shows promise as an inexpensive method with a fast turnaround time," they state.

The article describes how advances in microelectronics have helped position breath analysis for more extensive use in the 21st century. Equipment for analyzing substances in human breath that once had to be housed in laboratories, for instance, have shrunk to hand-held size. The technology can detect minute amounts of substances in the breath and do so quickly — offering the promise of helping limit human exposure and improve health.

More information: The Possibilities Will Take Your Breath Away: Breath Analysis for Assessing Environmental Exposure, Environ. Sci. Technol., Article ASAP. DOI: 10.1021/es202041j

Human breath is the gaseous exchange with the blood and thus contains trace organic contaminants and metabolites representative of environmental doses. Sampling and analysis of gaseous components in human breath offers a noninvasive and quick means of qualitatively and quantitatively assessing internalized doses of environmental contaminants. Although the humid and complex nature of breath is a challenge for detection of part-per-trillion to part-per-billion concentrations of environmental contaminants, recent advances in chemical analysis and instrumentation are allowing determination of environmental exposure and disease detection.

Provided by American Chemical Society (news : web)

'Low tech' light in neutron beam illuminates photosynthesis in bacteria

Researchers at the Bio-SANS instrument at the High Flux Isotope Reactor are getting a leg up in their research from an ingenious "low tech" lighting tool that can be fixed to their samples and then pushed directly into the neutron beam, to illuminate the response of layers of cyanobacteria to changes in light.

"It's really low tech," says Volker Urban, lead instrument scientist on the Bio-SANS, with a grin. "You can buy the parts anywhere." The lighting tool is the work of graduate student Brad O'Dell, a visiting intern from Cambridge University in the United Kingdom. The device combines with the electronics that drive the illumination.

Parts off the shelf it may be, but the device facilitates research into biologically inspired solar cell devices, important alternative energy-related research being conducted with funding from the Photosynthetic Antenna Research Center one of the Energy Frontier Research Centers in the US.

Photosynthesis is the process by which plants convert sunlight into energy. Bacteria, algae and plants have natural sensors called light-harvesting antenna systems that capture the sun's light and transfer the energy to reaction centers, where the electron transfer for photochemistry occurs. Such are highly specialized in nature, allowing organisms to capture the maximum available in their environment.

Researchers at the Bio-SANS are now using the new tool to study the light response of the membrane stacks in , a blue-green algae found in almost every environment, from oceans to fresh water to bare rock to soil.

At the Bio-SANS, the bacteria are loaded into cuvettes, small sample holders that resemble tiny transparent banjos. An LED is fixed to the top of each cuvette. The array is then pushed into the sample holder and the passes through a window, taking "pictures" of the response of the layers of the bacteria to variations in light from the attached LEDs.

"We push the samples into the neutron beam - and then from the neutron scattering we can observe how the structure changes, depending on how much light of which color we shine on the samples," Urban said. "Ultimately, we want to find out how nature has solved the problem of optimizing the efficient use of solar energy through these intricate architectures of antennas. These collect sunlight and funnel the light energy to reaction centers, where it is converted into chemical energy that can be stored for further use," he said. "If those fundamental principles are better understood then they can be used to create new, more efficient solar panels." They have already made some observations. "In a preliminary experiment, we could see with neutrons that the membrane stacking in the cycnobacteria changes in response to light on/ light off," Urban said. "With this new light in place, we can now study this response more precisely, and in more detail: How does it depend on the intensity and the color of the light?"

In related recent work, also funded by PARC, Urban and his collaborators performed small-angle neutron scattering studies to obtain structural information about the photosynthetic apparatus of the light-harvesting chlorosome complex, the light-harvesting B808-866 complex, and the bacterium Chloroflexus aurantiacus. "To our knowledge, this was the first SANS report regarding the overall photosynthetic machinery of Cfx. Aurantiacus," Urban said.

Subsequently, the researchers studied in greater detail the light harvesting antenna chlorosome. Chlorosomes, from green photosynthetic bacteria, are the largest and one of the most efficient light-harvesting antenna complexes found in nature. The chlorosome is able to absorb solar energy and convert it into chemical energy under both low and high light conditions. Its unique properties make it an attractive candidate for developing biohybrid solar cell devices.

The paper that resulted was the first to investigate the ionic strength effects of chlorosomes, whose size, shape, and orientation of the light-harvesting complexes are critical to understand for the phenomenon of to semiconductor electrodes in solar devices.

"These studies are useful for developing biomimetic and bioanalytical solar cell devices, and for demonstrating that chlorosomes are alternatives to other protein_pigment complexes produced in photosynthetic organisms," Urban said.

Provided by Oak Ridge National Laboratory (news : web)

Potential treatment for 'pink eye' epidemic

 Scientists are reporting discovery of a potential new drug for epidemic keratoconjunctivitis (EKC) -- sometimes called "pink eye" -- a highly infectious eye disease that may occur in 15 million to 20 million people annually in the United States alone. Their report describing an innovative new "molecular wipe" that sweeps up viruses responsible for EKC appears in ACS's Journal of Medicinal Chemistry.

Ulf Ellervik and colleagues note that there is no approved treatment for EKC, which is caused by viruses from the same family responsible for the common cold. EKC affects the cornea, the clear, dome-shaped tissue that forms the outer layer of the eye. It causes redness, pain, tearing, and may reduce visions for months. "Patients are usually recommended to stay home from work or school, resulting in substantial ," the scientists write.

They describe discovery of a potential new drug that sweeps up the viruses responsible for EKC, preventing the viruses from binding to and infecting the cornea. The drug removes viruses already in the eye and new viruses that are forming. In doing so, it would relieve symptoms, speed up healing (potentially avoiding impaired vision, and reduce and the risk of infecting the patient's other eye or spreading the infection within families, schools and work places, the scientists suggested.

The authors acknowledge funding from Adenovir Pharma AB, The Swedish Research Council, The Crafoord Foundation, and The Royal Physiographic Society in Lund.

More information: Molecular Wipes: Application to Epidemic Keratoconjuctivitis, J. Med. Chem., Article ASAP. DOI: 10.1021/jm200545m

Epidemic keratoconjunctivitis (EKC) is a severe disease of the eye, caused by members of the Adenoviridae (Ad) family, with symptoms such as keratitis, conjunctivitis, pain, edema, and reduced vision that may last for months or years. There are no vaccines or antiviral drugs available to prevent or treat EKC. It was found previously that EKC-causing Ads use sialic acid as a cellular receptor and demonstrated that soluble, sialic acid-containing molecules can prevent infection. In this study, multivalent sialic acid constructs based on 10,12-pentacosadiynoic acid (PDA) have been synthesized, and these constructs are shown to be efficient inhibitors of Ad binding (IC50 = 0.9 µM) and Ad infectivity (IC50 = 0.7 µM). The mechanism of action is to aggregate virus particles and thereby prevent them from binding to ocular cells. Such formulations may be used for topical treatment of adenovirus-caused EKC.

Provided by American Chemical Society (news : web)

Lessons to be learned from nature in photosynthesis

Photosynthesis is one of nature's finest miracles. Through the photosynthetic process, green plants absorb sunlight in their leaves and convert the photonic energy into chemical energy that is stored as sugars in the plants' biomass. If we can learn from nature and develop an artificial version of photosynthesis we would have an energy source that is absolutely clean and virtually inexhaustible.

" is forecasted to provide a significant fraction of the world's energy needs over the next century, as is the most abundant source of energy we have at our disposal," says Graham Fleming, Vice Chancellor for Research at the University of California (UC) Berkeley who holds a joint appointment with Lawrence Berkeley National Laboratory (Berkeley Lab). "However, to utilize solar energy harvested from sun¬light efficiently we must understand and improve both the effective cap¬ture of photons and the transfer of electronic excitation energy."

Fleming, a physical chemist and authority on the quantum phenomena that underlie , is one of four international co-authors of a paper in Nature Chemistry, entitled "Lessons from nature about solar light harvesting." The other co-authors are Gregory Scholes, of the University of Toronto, Alexandra Olaya-Castro, of London's University College, and Rienk van Grondelle, of the University of Amsterdam. The paper describes the principles behind various natural antenna complexes and explains what research needs to be done for the design of effective artificial versions.

Solar-based energy production starts with the harvesting of the photons in sunlight by the molecules in antenna complexes. Energy from the photons excites or energizes electrons in these light-absorbing molecules and this excitation energy is subsequently transferred to suitable acceptor molecular complexes. In natural photosynthesis, these antenna complexes consist of light-absorbing molecules called "chromophores," and the captured solar energy is directed to chemical reaction centers – a process that is completed within 10–to-100 picoseconds (a picosecond is one trillionth of second).

"In solar cells made from organic film, this brief timescale constrains the size of the chromophore arrays and how far excitation energy can travel," Fleming says. "Therefore energy-transfer needs and antenna design can make a significant difference to the efficiency of an artificial photosynthetic system."

Scientists have been studying how nature has mastered the efficient capture and near instantaneous transfer of the sun's energy for more than a century, and while important lessons have been learned that can aid the design of optimal synthetic sys¬tems, Fleming and his co-authors say that some of nature's design principles are not easily applied using current chemical synthesis procedures. For example, the way in which light harvesting is optimized through the organization of chromophores and the tuning of their excitation energy is not easily replicated. Also, the discovery by Fleming and his research group that the phenomenon of quantum coherence is involved in the transport of electronic excitation energy presents what the authors say is a "challenge to our understanding of chemical dynamics."

In their paper, Fleming and his international colleagues say that a clear framework exists for the design and synthesis of an effective antenna unit for future artificial photosynthesis systems providing several key areas of research are addressed. First, chromophores with large absorption strengths that can be conveniently incorporated into a synthetic protocol must be developed. Second, theoretical studies are needed to determine the optimal arrangement patterns of chromophores. Third, experiments are needed to elucidate the role of the environment on quantum coherence and the transport of electronic excitation energy. Experiments are also needed to determine how light-harvesting regulation and photo protection can be introduced and made reasonably sophisticated in response to incident light levels.

"There remains a number of outstanding questions about the mechanistic details of energy transfer, especially concerning how the electronic system interacts with the environment and what are the precise consequences of quantum coherence," Fleming says. "However, if the right research effort is made, perhaps based on synthetic biology, artificial photosynthetic systems should be able to produce on a commercial scale within the next 20 years."

Provided by Lawrence Berkeley National Laboratory (news : web)

Game-changing microfluidics

The development of miniaturization strategies that integrate several laboratory functions on a single chip is benefiting many areas of biomedical research, making even complex experiments faster and cheaper to perform. These ‘lab on a chip’ systems, generally known as microfluidic devices, are typically composed of small polymer wafers patterned with precisely engineered microscopic channels, reservoirs and valves that can transport tiny volumes of fluid with remarkable precision.

offers key advantages for bioanalytical and diagnostic applications, including faster analysis and response times, better process control and high throughput on a cost-effective, disposable chip,” explains Zhiping Wang, manager of the Microfluidics Manufacturing Programme at the Singapore Institute of Manufacturing Technology (SIMTech).

Putting principles into practice

SIMTech is just one of several A*STAR centers exploring microfluidics, and A*STAR recently demonstrated its commitment to this technology with the launch of the Microfluidics Systems Biology (MSB) laboratory at the Institute of Materials Research and Engineering (IMRE). To head up the project, they turned to Stephen Quake, a Stanford University researcher who has focused on developing cutting-edge for biological applications.

Quake already had strong ties to the Singapore research community through his company Fluidigm, which bases its manufacturing operations in the country, but he also recognized the MSB as a new opportunity for interdisciplinary collaboration. “The initial idea was to start applying some of the technologies we developed at Stanford, and using them to advance the frontiers of science,” he says. “I wanted to make contact with people working on biology and genomics and materials science.”

Game-changing microfluidics

The 3D HepaTox chip, devised by Hanry Yu?s team at the IBN, enables researchers to assess the physiological effects of eight different compounds on cultured liver cells simultaneously. Credit: IBN, A*STAR

Quake collaborated with Stanford colleague William Burkholder, a microbiologist who is co-principal investigator at the MSB alongside IMRE scientist Yin Thai Chan, and the three have been working on a variety of projects since August 2010. One of the primary objectives of the MSB is to transform experimental microfluidic devices into a working engine for scientific discovery. “Our key performance indicators are going to be publications, because we really want to keep the focus of the group on doing high-impact biology,” says Burkholder.

The majority of MSB projects emphasize the use of microfluidic tools to generate large quantities of high-quality biological data, such as mapping the way that proteins interact with each other or with chromosomal DNA, or generating high-quality genomic sequence data from single cells. One current project focuses on optimizing the ‘MITOMI’ chip, a device developed in the Quake lab that offers a high-throughput platform for measuring the binding affinity of proteins known as transcription factors for target DNA sequences. “We invented the device to observe how biological molecules stick to each other and how strongly they do so, and to run experiments in parallel using tiny amounts of sample,” says Quake. Current versions of the device can screen up to 4,000 sets of interactions at a time, and he and Burkholder are now using such devices to characterize the function of key gene regulators within human cells.

Chips for every occasion

A growing number of laboratories in Singapore are investigating the far-reaching applications of microfluidics. Some of the most advanced applications of the technology currently involve analyzing environmental or biological samples in order to detect infectious agents or toxic contaminants. A*STAR scientists have already made considerable progress in this field.

A research group at the Institute of Biotechnology and Nanotechnology (IBN) has designed an all-in-one chip that can be used in the diagnosis of influenza from a patient nasal swab sample within a couple of hours. This MicroKit technology, which was selected as a finalist for the Wall Street Journal’s Asian Innovation Awards in 2011, has already been licensed for commercial development, and the IBN is now engaged in trials to test its efficacy at detecting pathogenic bacteria in clinical settings.

Meanwhile, Abdur Rub Abdur Rahman and colleagues at the Institute of Microelectronics (IME) are using microfluidics to hunt another kind of threat—the circulating tumor cells (CTCs) that lay the groundwork for metastatic invasion in cancer. “CTC detection is a proverbial ‘needle in the haystack’ problem,” explains Rahman. “CTCs are extremely rare in blood—there may be one CTC per milliliter as opposed to one billion red blood cells per milliliter—and harvesting these cells reliably and reproducibly is a challenge.”

The system being developed at the IME uses magnetic beads to capture and enable the detection of these extremely scarce CTCs with relative ease. The present prototype platform delivers results in less than half a day. Rahman also points out that this approach eliminates many of the ‘moving parts’ that can confound conventional analysis. “We want to avoid all manual processing steps, including optical microscopy for cell recognition and enumeration, which is a mainstay in many contemporary systems,” he says.

A research team led by Hanry Yu at the IBN is investigating how to manipulate the flow of liquid and nutrients within a microfluidic cell culture system to create conditions that mimic the natural environment of tissues within the human body. The IBN team seeded liver cells within a microfluidic system, creating a ‘microtissue’ that can be used to characterize the liver’s capacity to metabolize and process different drugs and other compounds. “This method saves precious human liver cells, as it requires only a few thousand cells per assay,” says Yu. “It is easy to change the media to test complex drug treatment schemes in order to design optimal treatment strategies.” The method might also be useful early on in the drug discovery process by reducing the amount of a drug candidate that is required for screening. The current generation of the IBN’s three-dimensional HepaTox chip features eight channels, enabling investigators to screen multiple compounds in parallel.

Although the liver is a major destination for drugs, Yu envisions similar three-dimensional culture systems being used to model other organs, such as the kidney and pancreas. Yu and his colleagues have already begun experimenting with a ‘human-on-a-chip’ prototype, which enables cultivation of four different cell types, each of which resides within its own channel but can simultaneously be exposed to the same fluid environment.

Small chips ready for the big time

While commercialization is often the best way for research seeds to achieve maximum impact, transitioning from a functional prototype to a mass-produced device presents numerous logistical challenges. “The biggest challenge in the area of microfluidics device manufacturing is reducing the production cost from several dollars per device to a few tens of cents per device,” says Wang. His team at SIMTech is focusing heavily on large-scale manufacturing, and has already developed a chip for monitoring water quality and a ‘micromixer’ device that can efficiently combine polymers, which is currently being tested by a major pharmaceutical company.

In September, SIMTech launches a new Microfluidics Foundry operation, a dedicated center for microfluidic device research, development and manufacturing. “The Foundry will provide design, prototyping and production services to laboratories in universities and research institutions as well as companies worldwide,” says Wang.

Optimization for consumer use is another key objective of the MSB. “The most basic goal of the lab is to give fresh life to devices that have been prototyped but are not widely available to the biological community,” says Burkholder. “We aim to transform devices that can work with expert assistance on a benchtop into user-friendly products that can be purchased from a catalogue.” MSB scientists have begun investigating the potential of adapting their MITOMI chip for use in drug discovery applications.

With the growing number of laboratories across Singapore now exploring microfluidic tool development, an increasing amount of collaborative research is expected to advance the field further. “We organized the first community-wide microfluidics conference in Singapore earlier this year,” says Quake. “I was very impressed with the breadth of the research that’s going on—there is really a wonderful community that has sprung up.”

More information: Maerkl, S. J. & Quake, S. R. A systems approach to measuring the binding energy landscapes of transcription factors. Science 315, 233–237 (2007).

Toh, Y. C., et al. A microfluidic 3D hepatocyte chip for drug toxicity testing. Lab Chip 9, 2026–2035 (2009).

Zhang, C., et al. Towards a human-on-chip: culturing multiple cell types on a chip with compartmentalized microenvironments. Lab Chip 9, 3185–3192 (2009).

Xia, H. M., et al. A microfluidic mixer with self-excited ‘turbulent’ fluid motion for wide viscosity ratio applications. Lab Chip 10, 1712–1716 (2010).

Provided by Agency for Science, Technology and Research (A*STAR)