Saturday, February 4, 2012

'Miracle tree' substance produces clean drinking water inexpensively and sustainably

Stephanie B. Velegol and colleagues explain that removing the disease-causing microbes and sediment from drinking water requires technology not always available in rural areas of developing countries. For an alternative approach, Velegol looked to Moringa oleifera, also called the "miracle tree," a plant grown in equatorial regions for food, and biofuel. Past research showed that a protein in Moringa seeds can clean water, but using the approach was too expensive and complicated. So Velegol's team sought to develop a simpler and less expensive way to utilize the seeds' power.

To do that, they added an extract of the seed containing the positively charged Moringa protein, which binds to sediment and kills microbes, to negatively charged sand. The resulting "functionalized," or "f-sand," proved effective in killing harmful E. coli bacteria and removing sediment from . "The results open the possibility that ... f-sand can provide a simple, locally sustainable process for producing storable drinking water," the researchers say.

More information: Antimicrobial Sand via Adsorption of Cationic Moringa oleifera Protein, Langmuir, Article ASAP. DOI: 10.1021/la2038262

Moringa oleifera (Moringa) seeds contain a natural cationic protein (MOCP) that can be used as an antimicrobial flocculant for water clarification. Currently, the main barrier to using Moringa seeds for producing potable water is that the seeds release other water-soluble proteins and organic matter, which increase the concentration of dissolved organic matter (DOM) in the water. The presence of this DOM supports the regrowth of pathogens in treated water, preventing its storage and later use. A new strategy has been established for retaining the MOCP protein and its ability to clarify and disinfect water while removing the excess organic matter. The MOCP is first adsorbed and immobilized onto sand granules, followed by a rinsing step wherein the excess organic matter is removed, thereby preventing later growth of bacteria in the purified water. Our hypotheses are that the protein remains adsorbed onto the sand after the functionalization treatment, and that the ability of the antimicrobial functionalized sand (f-sand) to clarify turbidity and kill bacteria, as MOCP does in bulk solution, is maintained. The data support these hypotheses, indicating that the f-sand removes silica microspheres and pathogens from water, renders adhered Escherichia coli bacteria nonviable, and reduces turbidity of a kaolin suspension. The antimicrobial properties of f-sand were assessed using fluorescent (live-dead) staining of bacteria on the surface of the f-sand. The DOM that can contribute to bacterial regrowth was shown to be significantly reduced in solution, by measuring biochemical oxygen demand (BOD). Overall, these results open the possibility that immobilization of the MOCP protein onto sand can provide a simple, locally sustainable process for producing storable drinking water.

Provided by American Chemical Society (news : web)

Microreactors: Improving manufacturing by going small

When perfumes, creams, shampoos and other similar products are manufactured, the chemical reactions involved typically take place in big, agitated containers called reactors. The various ingredients are mixed in the container, often along with catalysts that increase the reaction speed, while temperature, pressure and a variety of other parameters are carefully controlled. These reactors are usually quite large (several cubic meters in volume) in order to be able to produce large quantities of a product. They operate in discontinuous cycles, which means they must be stopped, emptied and cleaned before each new use.

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The GGRC team worked with the company Givaudan Suisse SA to rethink this process, and ended up taking a diametrically different approach – dividing up the substance into small volumes in order to produce it more efficiently. With their invention, the chemical reaction doesn’t take place in big containers, but in micro-channels, each with a diameter of a few hundred microns. Several thousand of these channels can be assembled together.

Continuous production

“The primary advantage is a much higher level of safety,” explains GGRC director Lioubov Kiwi. “Any problem or risk of explosion remains confined within a tiny volume. It’s also much easier to control the temperature and, in fact, the entire process. In addition, they function continuously, with reactants entering on one side of the micro-tubes and the final product continuously generated at the exit.”

In terms of efficiency, the new machine is advantageous because it reduces the loss of raw materials. “About 20% of raw materials, up to now wasted, can now be recuperated,” the professor explains. In addition, the size of installations can be reduced by a factor of ten. Finally, the procedure improves product quality, because there are fewer impurities and waste products produced in the procedure.

Provided by Ecole Polytechnique Federale de Lausanne

'Meating' a solution: Research finds that LED lights extend meat shelf life, save retailers money

Kyle Steele, recent master's graduate in and industry, Silver Lake, Kan., found that using light-emitting diode, or LED, lights in refrigeration units both saves energy for retailers and extends the shelf life of some beef products.

"By using LED lighting in meat retail display cases, Kansas retailers can save money by lowering the operational costs of refrigerated cases and extending the color shelf life of fresh ," Steele said. "Additionally, by extending the color shelf life, retailers have a greater opportunity to sell the product at full price, and the state of Kansas can gain tax revenue from the full retail price rather than a discounted price."

Steele compared the use of LED lights and fluorescent lights in meat refrigeration units because many meat retailers currently use fluorescent lights. He worked with Elizabeth Boyle and Melvin Hunt, both professors of animal sciences and industry, as well as with Melissa Weber, recent doctoral graduate in animal sciences and industry, Collinwood, Tenn.

During refrigerated display, the color of fresh meat changes because of its natural chemistry and exposure to oxygen. Because color is a large factor that influences customers in purchasing meat, some consumers discriminate against discolored meat. These discolored meat products must either be discounted or discarded, which has been estimated to cost the meat industry up to a billion dollars each year, Steele said.

For his research, Steele looked at five different meat products: pork loin chops, beef loin steaks, ground beef, and beef inside round steaks. Steele looked at several aspects of these meat products and their refrigeration units:

* Discoloration: The researchers brought in trained color panelists to score meat color changes over time while displayed under both lighting types.

* Rancidity: The researchers measured the rancidity of the meat products stored under both types of light. Light affects the oxidation of fat in meat, which can cause rancidity and a change in taste.

* Operating efficiency: The researchers studied operating efficiency of the two types of lights by measuring how many times a refrigeration unit had to cycle to keep the meat cool and how many running hours that cycle lasted.

The researchers found that LED lights scored positively in nearly all areas. Most significantly, LED lights helped reduce operating costs and prolonged the shelf life for most of the meat products.

"Most meat products displayed under LED lighting had colder internal product temperatures, which helps extend product shelf life," Steele said. "Beef loin steaks and inside round steaks that were stored under LED lights can have up to one day longer shelf life."

Among operational costs, LED lights had fewer cycles per running hour, meaning they were a more efficient and cost-saving light source than fluorescent lights.

Steele will give a research presentation titled " of five meat products displayed under light emitting diode or fluorescent lighting" at the Capitol Graduate Research Summit in Topeka in February.

Provided by Kansas State University (news : web)

Iridescence and superhydrophobicity combined on one surface

The researchers, Jian-Nan Wang and coauthors from Jilin University in Changchun, China, achieved these properties by creating a microscopic texture on the graphene oxide’s surface. By shining two laser beams on the surface, they created an interference pattern that burned tiny grooves into the material. The surface immediately took on an iridescent appearance, shimmering like a butterfly’s wing. The scientists explained that the tiny grooves, which form highly ordered periodic structures, act as diffraction gratings that split white light into its various colored wavelengths.

The researchers discovered that the surface effects also caused the graphene oxide to exhibit highly adhesive superhydrophobicity. When they poured water on the surface, the water merged into nearly spherical droplets. Although the droplets are barely in contact with the graphene oxide, they adhere to the surface, not detaching even when the surface is held upside down. The researchers attributed this phenomenon to the surface’s microscopic unevenness and a decrease in surface energy caused during laser irradiation, which removes some hydrophilic oxygen groups.

The researchers predict that the combination of these two properties on one surface could have applications in microfluidic devices, where a superhydrophobic surface is useful for transporting small amounts of liquid in a controlled way. oxide might also be used as a biocompatible surface for growing cells, which requires controlled wetting.

The might be used for color-coding different states in microfluidic devices, as well as decorating for aesthetic purposes. Also, by altering the optical properties of graphene-based devices, it may open doors to new optical or electronic devices.

More information: Jian-Nan Wang, et al. “Biomimetic Graphene Surfaces with Superhydrophobicity and Iridescence.” Chemistry - An Asian Journal. DOI: 10.1002/asia.201100882
via: Chemistry World

? 2011

Novel contact lenses provide extended pain relief to laser eye surgery patients

Anuj Chauhan and colleagues explain that more than 1 million laser eye correction procedures are performed each year in the U.S. The surgery enables most to see clearly without eye glasses or . The procedure known as LASIK is the most common type of laser , but complications can develop if the patient undergoes trauma or is hit very hard at any time after the procedure. Photorefractive keratectomy (PRK) doesn't have this complication, and that's why it is preferred for athletes and those in the military. A downside to PRK, however, is a longer period of pain after surgery. To ease their pain, PRK patients place drops of several medications, including anesthetics, into their eyes every few hours, which can interfere with daily life and increase the risk of drug overdose. PRK patients receive a special "bandage contact lens" after surgery to help the outer layer of the eye heal.

The researchers tested whether anesthetics loaded onto this type of lens could release the drugs over time automatically. They found that adding vitamin E to the lenses extended the time of release of three commonly used anesthetics from just under two hours to up to an entire day — or a few days in some instances. The vitamin E acts as a barrier, keeping the anesthetics on the eye, right where they are needed. The researchers say that, in the future, these lenses could serve as bandage contact lenses after PRK surgery while also delivering necessary pain medications.

More information: Transport of Topical Anesthetics in Vitamin E Loaded Silicone Hydrogel Contact Lenses, Langmuir, 2012, 28 (2), pp 1478–1487. DOI: 10.1021/la203606z

Transport of surface active anesthetic drugs through silicone hydrogel contact lenses containing nanosized vitamin E aggregates is explored for achieving extended anesthetics delivery. Commercial silicone hydrogel contact lenses release most ophthalmic drugs including local anesthetics for only a few hours, which is not adequate. Here we focus on creating dispersion of highly hydrophobic vitamin E aggregates in the lenses as barriers for drug diffusion for increasing the release durations. This approach has been shown previously to be successful in extending the release durations for some common hydrophilic ophthalmic drugs. The topical anesthetic drugs considered here (lidocaine, bupivacaine, and tetracaine) are hydrophilic at physiologic pH due to the charge, and so these cannot partition into the vitamin E barriers. However, these surface active drug molecules adsorb on the surface of the vitamin E barriers and diffuse along the surface, leading to only a small decrease in the effective diffusivity compared to non-surface-active hydrophilic drugs. The drug adsorption can be described by the Langmuir isotherm, and measurements of surface coverage of the drugs on the vitamin E provide an estimate of the available surface area of vitamin E, which can then be utilized to estimate the size of the aggregates. A diffusion controlled transport model that includes surface diffusion along the vitamin E aggregates and diffusion in the gel fit the transport data well. In conclusion, the vitamin E loaded silicone contact lens can provide continuous anesthetics release for about 1–7 days, depending on the method of drug loading in the lenses, and thus could be very useful for postoperative pain control after corneal surgery such as the photorefractive keratectomy (PRK) procedure for vision correction.

Provided by American Chemical Society (news : web)

Bubble-propelled microrockets could operate in the human stomach

The researchers, Wei Gao, Aysegul Uygun, and Joseph Wang from the University of California, San Diego, have published their study on the hydrogen-bubble-propelled microrockets in a recent issue of the Journal of the American Chemical Society.

“This is the first reported example of chemically-powered microrockets that can be self-propelled without an external fuel (such as the common ),” Wang told “Such acid-powered microrockets could greatly expand the scope of applications of nano-/microscale motors toward new extreme environments (e.g., the human stomach or silicon wet-etching baths) and could thus lead to diverse new biomedical or industrial applications ranging from targeted drug delivery or nanoimaging to the monitoring of industrial processes.”

The microrockets are in the shape of tiny tubes, measuring about 10 micrometers long with diameters varying from 2 to 5 micrometers. The researchers fabricated the tubes out of the common polymer polyaniline (PANI) in templates, and then electrodeposited a thin layer of zinc on the inner surface. When the microrockets are immersed in any highly acidic solution, the zinc loses electrons and – due to having a more negative redox potential than hydrogen – promotes the production of hydrogen bubbles. The researchers experimented with using other metals, such as iron and lead, but they did not produce as many bubbles as zinc.

Tests showed that the microrockets’ speed increases as the pH of the solution decreases. The fastest speed of 1,050 micrometers per second (equivalent to about 100 body lengths per second) was achieved by a 5-micrometer-diameter microrocket at a pH of -0.2. The speed decreased to about 10 micrometers per second at a pH of 1.3. Although the microckets have a limited pH range, the researchers noted that they could be useful in the stomach, which has a pH range of 0.8-2.0, as well as in some types of human serum.

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Slow-motion video of a microrocket self-propelled at a speed of about 500 micrometers per second. Video credit: Wei Gao, et al. ?2012 American Chemical Society

Tests also showed that the lifetime of the microrockets can vary from 10 seconds to 2 minutes, depending on the rate of zinc dissolution. The more zinc the rocket has, and the higher the pH of the solution, the longer the microrocket’s lifetime.

While the microrockets can move autonomously in this way, the researchers also showed that it’s possible to control their direction and even to make them pick up and release cargo. The scientists did this by depositing a magnetic layer on the microcket’s outer surface, and then magnetically guiding the device in the preferred direction. They showed that a microcket could magnetically capture a polystyrene cargo, transport it on a predetermined path, and then release it by rapidly changing the magnetic field direction.

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Magnetically guided movement of a microrocket at a speed of about 100 micrometers per second. Video credit: Wei Gao, et al. ?2012 American Chemical Society

The scientists predict that this capability could prove especially useful for a variety of biomedical applications as well as monitoring industrial processes such as semiconductor processing. In addition, because the microrocket’s speed is directly related to the solution’s pH, the devices could be used for sensitive pH sensing, such as detecting changes in stomach acidity. With its biggest advantage of being fueled by its acidic environment, without the need for additional fuel, the microrockets could further expand the scope of applications in many directions.

“With further improvements and optimization, we hope to improve and expand the working environments to milder conditions and extend the lifetime of such microrockets to longer periods,” Wang said. “We are also exploring new materials to broaden the scope of our microengines towards new environments.”

More information: Wei Gao, et al. “Hydrogen-Bubble-Propelled Zinc-Based Microrockets in Strongly Acidic Media.” Journal of the American Chemical Society. DOI: 10.1021/ja210874s

Copyright 2012
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