Monday, August 15, 2011

New model predicts environmental effect of pharmaceutical products

 Most synthetic chemical products used in consumer goods end up unchanged in the environment. Given the risks this could pose for the environment and human health, researchers from the Autonomous University of Barcelona (UAB) have developed a new tool to effectively predict what will happen to current and future pharmaceutical products.

Thousands of pharmaceutical products, which are increasingly diverse and increasingly used, are "partially" metabolised by the human body. Those that remain unchanged pass into the waste water treated at sewage plants, which are not always designed to eliminate synthetic organic compounds.

"Sometimes, some substrates can even revert to the original drug within the water treatment plant itself, increasing the concentration of the drug in the effluent discharged, as is the case with carbamazepine (a psychotropic anti-epilepsy drug)," says Xavier Domenech, co-author of the study and a researcher at the Department of Chemistry of the UAB.

The result is that a great variety of drugs that could be harmful to wildlife end up in the environment. "This is of greater concern in the case of water treated for human consumption, in which we are increasingly detecting a cocktail of drugs at low concentrations (nanograms per litre), the long-term effect of which is unknown," explains Domenech.

Pinpointing the effect of a drug

The study, which has been published in Water Air and Soil Pollution, has made it possible to develop a new tool to determine the likelihood of drugs ending up in the environment, and at what concentrations, thereby fulfilling the European Medicines Agency (EMEA) requirement to evaluate the environmental risk of new drugs that are being proposed for marketing.

The new tool, developed by Marc Ribera, lead author of the study, uses some physical-chemical properties of pharmaceuticals and the rate of growth in their use in Spain between 1999 and 2006 to determine how they will behave in the environment. The drugs analysed are those that are most commonly consumed in Spain (more than 1 mg of active substance per person and year), including, among many others, ibuprofen, diazepam, naproxen, omeprazole and paracetamol.

In order to validate the model, the research team compared the model's prediction results on water with values measured by authors in rivers and lakes. "The model used is good at predicting the experimental data, and can be seen as a good predictive model for evaluating the environmental risks of current drugs and those that may be marketed in future," concludes Domenech.

Story Source:

The above story is reprinted (with editorial adaptations) from materials provided by Plataforma SINC, via AlphaGalileo.

Journal Reference:

Xavier Domenech, Marc Ribera, José Peral. Assessment of Pharmaceuticals Fate in a Model Environment. Water, Air, & Soil Pollution, 2010; 218 (1-4): 413 DOI: 10.1007/s11270-010-0655-y

Polymer's hunt for nicotine

Newly synthesized polymer, fitted with molecular pincers of carefully tailored structure, effectively captures nicotine molecules and its analogues. The polymer can be used for fabrication of sensitive and selective chemical sensors to determine nicotine in solutions, and in the near future also in gases. Moreover, the polymer is suitable for slow, controlled release of nicotine, e.g., for therapeutic purposes.

The collaboration of researchers of the Institute of Physical Chemistry of the Polish Academy of Sciences (IPC PAS) and of the Department of Chemistry, Wichita State University, Wichita, KS, has resulted in fabrication of a polymer trap for nicotine. Bearing molecular pincers, the polymer effectively captures nicotine molecules and its analogues, and can also release them in a controlled way. The compound will be used in reusable chemical sensors for determination of nicotine for industrial and biomedical purposes as well as in patches for smokers to evenly release nicotine to the body for a prolong time.

"The first nicotine trap has been synthesized by our US partner, Prof. Francis D'Souza, several years ago. It was a sort of molecular pincers, molecules that freely move in solution and form complexes with nicotine therein. Recently, our US-Polish team has been able to fix the pincers inside a polymer. The substance is solid, and that's why we could use it to construct chemosensors," says Prof. Włodzimierz Kutner from IPC PAS.

The core of the polymer nicotine trap, which has been recently filed for a patent, is a metalloporphyrin derivative, a substance present, i.a., in human blood. The molecule contains a ring (a macrocycle) with a centrally located zinc atom and amide pincers attached to this ring. Nicotine binds to this polymer with its two nitrogen atoms: one binds to the zinc atom, whereas the other to the pincers. "It is due to the specific two-point binding that we are surer that the captured molecule is nicotine," stresses Dr. Krzysztof Noworyta from IPC PAS, adding that in one of the devised polymers the pincers are located on both sides of the zinc containing-ring plane. "Such a design clearly increases the efficiency of nicotine trapping," says Dr. Noworyta.

Beside nicotine, the polymer captures also a cotinine alkaloid produced in the metabolism of nicotine and other alkaloids often accompanying nicotine, e.g., myosmine. Polymer binding to nicotine is durable but reversible. It is the property why the new chemosensors for determination of nicotine and its analogues can be used repeatedly.

Nicotine is detected by means of a piezoelectric resonator coated by electropolymerization with a submicrometer thick polymer film. The captured nicotine increases the mass of the film resulting in a decrease in the resonant frequency of the resonator that is easy to measure. "It can be said that we are weighing a film of our polymer all throughout the experiment. Because we know the initial polymer mass and we know that the polymer selectively captures nicotine and its analogues, an increased mass of the film means that these compounds are present in solution," explains Dr. Noworyta.

Quartz acoustic bulk wave resonators used in experiments with the new polymer allow determining nicotine in solutions. In the near future, the researchers from IPC PAS plan to establish collaboration with manufacturers of surface acoustic wave resonators. These resonators oscillate at significantly higher frequencies, thus being more sensitive, and after coating with the nicotine capturing polymer film could detect nicotine also in gases.

In the method described herein, the detection and determination of nicotine do not need to be confined to weighing. Because nicotine is electroactive, the researchers from IPC PAS are going to measure oxidation current of nicotine trapped in the polymer in parallel with the resonant frequency measurement. Simultaneous measurement with these two methods will increase the detection reliability.

The polymer with pincers for nicotine can be used, among others, in chemosensors devised to analyze nicotine content in tobacco leaves and in biomedical studies to determine nicotine metabolites in patients' body fluids. Another potential application is nicotine patches to help quit smoking. The new polymer could be used for prolong and smooth release of nicotine.

Story Source:

The above story is reprinted (with editorial adaptations ) from materials provided by Institute of Physical Chemistry of the Polish Academy of Sciences.

Journal References:

Gollapalli R. Deviprasad, Francis D’Souza. Molecular recognition directed porphyrin chemosensor for selective detection of nicotine and cotinine. Chemical Communications, 2000; (19): 1915 DOI: 10.1039/B006055KFrancis D'Souza, Gollapalli R. Deviprasad, Melvin E. Zandler, Mohamed E. El-Khouly, Mamoru Fujitsuka, Osamu Ito. Photoinduced Electron Transfer in “Two-Point” Bound Supramolecular Triads Composed ofN,N-Dimethylaminophenyl-Fullerene-Pyridine Coordinated to Zinc Porphyrin. The Journal of Physical Chemistry A, 2003; 107 (24): 4801 DOI: 10.1021/jp030363w

Biology, materials science get a boost from robust imaging tool: Collaborators give a new view of macromolecular systems

Shape and alignment are everything. How nanometer-sized pieces fit together into a whole structure determines how well a living cell or an artificially fabricated device performs. A new method to help understand and predict such structure has arrived with the successful use a new imaging tool.

Coupling laser-driven, two-dimensional fluorescence imaging and high-performance computer modeling, a six-member team -- led by University of Oregon chemist Andrew H. Marcus and Harvard University chemist Alan Aspuru-Guzik -- solved the conformation of self-assembled porphyrin molecules in a biological membrane.

Porphyrins are organic compounds that are ubiquitous in living things. They carry mobile electrical charges that can hop from molecule-to-molecule and allow for nanoscale communications and energy transfer. They are also building blocks in nanodevices.

The new technique -- phase-modulation 2D fluorescence spectroscopy -- is detailed in a paper scheduled to appear online this week ahead of regular publication in the Proceedings of the National Academy of Sciences. The breakthrough skirts the often-needed step of obtaining crystals of molecules that are being studied, said Marcus, a member of the Oregon Center for Optics, Materials Science Institute and Institute of Molecular Biology. Most functional biological molecules don't easily form crystals.

"Our technique is a workable way to determine how macromolecular objects assemble and form the structures they will in biological environments," Marcus said. "It's robust and will provide a means to study biological protein-nucleic acid interactions."

Work already is underway to modify the experimental instrumentation in the UO's stable and temperature-controlled High Stability Optics Lab to apply the research on DNA replication machinery -- one category of the best-known macromolecular complexes, which consist of nucleic acids and proteins that must be properly aligned to function correctly. "It's a strategy that will allow us to do two things: Look at these complexes one molecule at a time, and perform experiments at short ultraviolet wavelengths to look at DNA problems," he said.

In addition, the approach should be useful to materials scientists striving to understand and harness the necessary conformation of polymers used in the production of nanoscale devices. "In biology, large molecules assemble to form very complex structures that all work together like a machine," Marcus said. "The way these nanoscale structures form and become functional is an actively pursued question."

The technique builds on earlier versions of two-dimensional (2D) optical spectroscopy that emerged in efforts to get around limitations involved in applying X-ray crystallography and nuclear magnetic resonance to such research. The previous 2D approaches depended on the detection of transmitted signals but lacked the desired sensitivity.

The new approach can be combined with single-molecule fluorescence microscopy to allow for research at the tiniest of scales to date, Marcus said. "With fluorescence, you can see and measure what happens one molecule at time. We expect this approach will allow us to look at individual molecular assemblies."

Oregon Nanoscience and Microtechnologies Institute (ONAMI), the National Science Foundation and U.S. Department of Energy supported the research. Marcus is a researcher in ONAMI, a collaboration involving the UO, Oregon State University, Oregon Health and Science University, Portland State University, the Pacific Northwest National Laboratory, the state of Oregon and private industry.

The laboratory where the laser work opened in 2005, built with a $510,500 grant from the M.J. Murdock Charitable Trust and a $600,000 investment by the UO. Initially named the Laboratory for Quantum Control as part of the UO's Center for Optics, the basement lab allows researchers to probe and control the behavior of atoms, semiconductors and nanometer-thin metal films.

Geoffrey A. Lott, who earned a doctorate at the UO and is now with Boise Technology Inc. in Nampa, Idaho, and Alejandro Perdomo-Ortiz, a doctoral student in Harvard's department of chemistry and chemical biology, were lead authors on the paper. Additional co-authors were James K. Utterback, an UO undergraduate student in physics and 2009 Barry M. Goldwater Scholarship recipient, and Julia R. Widom, a UO doctoral student and a 2010 recipient of a Rosario Haugland Chemistry Graduate Research Fellowship.

Story Source:

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

Student turns paper mill waste into ‘green’ material for industrial applications

A method to use paper mill waste to produce ecologically friendly, industrial foams from renewable resources has been developed by a graduate student in agriculture at the Hebrew University of Jerusalem.

Foams are used for numerous day-to-day uses, including in the manufacture of furniture and car interiors. In many composite material applications, they are used as core material in "sandwich" panels to achieve high strength, weight reduction, energy dissipation and insulation. Conventional foams are produced from polymers such as polyurethane, polystyrene, polyvinyl chloride (PVC) and polyethylene terephthalate (PET). Since all of these current foams rely on fossil oil, they present a clear environmental disadvantage.

Shaul Lapidot, a Ph.D. student of Prof. Oded Shoseyov, along with his laboratory colleagues at the Robert H. Smith Faculty of Agriculture, Food and Environment of the Hebrew University in Rehovot, has formulated a procedure for production of nano-crystalline cellulose (NCC) from paper mill waste. NCC is further processed into composite foams for applications in the composite materials industry as bio-based replacement for synthetic foams.

The process of paper production involves loss of all fibers with dimensions lower than the forming fabric mesh. Consequently around 50% of the total fibers initially produced are washed away as sludge. In Europe alone, 11 million tons of waste are produced annually by this industry, creating an incentive for finding alternative uses and different applications for the wastes.

Lapidot has found that fibers from paper mill sludge are a perfect source for NCC production due to their small dimensions which require relatively low energy and chemical input in order to process them into NCC. He also developed the application of NCC into nano-structured foams. This is further processed into composite foams for applications in the composite materials industry to be used as bio-based replacement for synthetic foams.

NCC foams that Lapidot and his colleagues have recently developed are highly porous and lightweight. Additional strengthening of the foams was enabled by infiltration of furan resin, a hemicellulose-based resin produced from raw crop waste, such as that remaining from sugar cane processing, as well as oat hulls, corn cobs and rice hulls.

The new NCC reinforced foams display technical performance which matches current high-end synthetic foams. The technology was recently licensed from Yissum, the technology transfer company of the Hebrew University, by Melodea Ltd., an Israeli-Swedish start-up company which aims to develop it for industrial scale production.

Lapidot's development has led to his being awarded one of the Barenholz Prizes that were presented on June 21 at the Hebrew University Board of Governors meeting. The award is named for its donor, Prof. Yehezkel Barenholz of the Hebrew University-Hadassah Medical School.

Story Source:

The above story is reprinted (with editorial adaptations) from materials provided by Hebrew University of Jerusalem, via AlphaGalileo.

Dream screens from graphene: Indium-free transparent, flexible electrodes developed

Flexible, transparent electronics are closer to reality with the creation of graphene-based electrodes at Rice University. The lab of Rice chemist James Tour lab has created thin films that could revolutionize touch-screen displays, solar panels and LED lighting. The research was reported in the online edition of ACS Nano.

Flexible, see-through video screens may be the "killer app" that finally puts graphene -- the highly touted single-atom-thick form of carbon -- into the commercial spotlight once and for all, Tour said. Combined with other flexible, transparent electronic components being developed at Rice and elsewhere, the breakthrough could lead to computers that wrap around the wrist and solar cells that wrap around just about anything.

The lab's hybrid graphene film is a strong candidate to replace indium tin oxide (ITO), a commercial product widely used as a transparent, conductive coating. It's the essential element in virtually all flat-panel displays, including touch screens on smart phones and iPads, and is part of organic light-emitting diodes (OLEDs) and solar cells.

ITO works well in all of these applications, but has several disadvantages. The element indium is increasingly rare and expensive. It's also brittle, which heightens the risk of a screen cracking when a smart phone is dropped and further rules ITO out as the basis for flexible displays.

The Tour Lab's thin film combines a single-layer sheet of highly conductive graphene with a fine grid of metal nanowire. The researchers claim the material easily outperforms ITO and other competing materials, with better transparency and lower resistance to electric current.

"Many people are working on ITO replacements, especially as it relates to flexible substrates," said Tour, Rice's T.T. and W.F. Chao Chair in Chemistry as well as a professor of mechanical engineering and materials science and of computer science. "Other labs have looked at using pure graphene. It might work theoretically, but when you put it on a substrate, it doesn't have high enough conductivity at a high enough transparency. It has to be assisted in some way."

Conversely, said postdoctoral researcher Yu Zhu, lead author of the new paper, fine metal meshes show good conductivity, but gaps in the nanowires to keep them transparent make them unsuitable as stand-alone components in conductive electrodes.

But combining the materials works superbly, Zhu said. The metal grid strengthens the graphene, and the graphene fills all the empty spaces between the grid. The researchers found a grid of five-micron nanowires made of inexpensive, lightweight aluminum did not detract from the material's transparency.

"Five-micron grid lines are about a 10th the size of a human hair, and a human hair is hard to see," Tour said.

Tour said metal grids could be easily produced on a flexible substrate via standard techniques, including roll-to-roll and ink-jet printing. Techniques for making large sheets of graphene are also improving rapidly, he said; commercial labs have already developed a roll-to-roll graphene production technique.

"This material is ready to scale right now," he said.

The flexibility is almost a bonus, Zhu said, due to the potential savings of using carbon and aluminum instead of expensive ITO. "Right now, ITO is the only commercial electrode we have, but it's brittle," he said. "Our transparent electrode has better conductivity than ITO and it's flexible. I think flexible electronics will benefit a lot."

In tests, he found the hybrid film's conductivity decreases by 20 to 30 percent with the initial 50 bends, but after that, the material stabilizes. "There were no significant variations up to 500 bending cycles," Zhu said. More rigorous bending test will be left to commercial users, he said.

"I don't know how many times a person would roll up a computer," Tour added. "Maybe 1,000 times? Ten thousand times? It's hard to see how it would wear out in the lifetime you would normally keep a device."

The film also proved environmentally stable. When the research paper was submitted in late 2010, test films had been exposed to the environment in the lab for six months without deterioration. After a year, they remain so.

"Now that we know it works fine on flexible substrates, this brings the efficacy of graphene a step up to its potential utility," Tour said.

Rice graduate students Zhengzong Sun and Zheng Yan and former postdoctoral researcher Zhong Jin are co-authors of the paper.

The Office of Naval Research Graphene MURI program, the Air Force Research Laboratory through the University Technology Corporation, the Air Force Office of Scientific Research and the Lockheed Martin Corp./LANCER IV program supported the research.

Story Source:

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

Journal Reference:

Yu Zhu, Zhengzong Sun, Zheng Yan, Zhong Jin, James M. Tour. Rational Design of Hybrid Graphene Films for High-Performance Transparent Electrodes. ACS Nano, 2011; : 110729133414013 DOI: 10.1021/nn201696g