The American Chemical Society is offering a new service in hopes of making science more accessible to the public. Each week they issue a short collection of science articles, written in an interesting and engaging style, that you might use with your students to help them make connections between the curriculum and their own lives. The service is called Discoveries!, and it is free. At this point, the articles are not available on a website, but are emailed to ACS members. I am posting examples of the articles below with permission.
I am always on the lookout for science articles that I can share with my own students. I appreciate that these are written at a level any of my students can handle. Even better, if my students want to investigate further, they can access the original full text version.
MARCH 2018
With a TENG, solar cells could work come rain or shine
ACS Nano
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Despite the numerous advances in solar cells, one thing remains constant: cloudy, rainy conditions put a damper on the amount of electricity created. Now researchers reporting in the journal ACS Nano have developed hybrid solar cells that can generate power from raindrops.
In areas where it frequently rains, solar cells might not seem like the best choice for energy production. The sky becomes cloudy, preventing the sun's rays from reaching the cell. Researchers have been developing devices that can generate energy in rainy conditions. Previous studies add a pseudocapacitor or triboelectric nanogenerator (TENG) to an existing solar cell, creating a device that can make energy from the motion of raindrops. But these devices are usually complicated to manufacture and are bulky. So Zhen Wen, Xuhui Sun, Baoquan Sun and colleagues wanted to develop a better hybrid energy harvesting system.
The researchers imprinted two polymers, PDMS and PEDOT:PSS, with grooves by placing them onto commercially available DVDs. PDMS is polydimethylsiloxane and PEDOT:PSS is poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate). Adding texture to the PDMS increased the TENG performance of this material when water drops touched it and then fell off it. The textured PEDOT:PSS layer acted as a mutual electrode for both the TENG and the solar cell. It was placed between the two devices and conducted energy from the TENG to the cell. Because the polymers are transparent, the solar cell could still generate energy from sunlight, as well as from falling raindrops. The team notes this simple design demonstrates a new concept in energy harvesting during various weather conditions.
The authors acknowledge funding from the National Key Research and Development Program of China, the National Natural Science Foundation of China, the Priority Academic Program Development of Jiangsu Higher Education Institutions, the 111 Projects and the Collaborative Innovation Center of Suzhou Nano Science and Technology.
"Integrating Silicon Solar Cell with Triboelectric Nanogenerator via a Mutual Electrode for Harvesting Energy from Sunlight and Raindrops"
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Note: ACS does not conduct research, but publishes and publicizes peer-reviewed scientific studies.
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More realistic and accurate organs-on-chips ACS Biomaterials Science
In a step toward better diagnosis and treatment of digestive conditions, such as inflammatory bowel disease, scientists report in ACS Biomaterials & Engineering that they have developed a first-of-its-kind collagen-based membrane for use in microchips. The membrane is more natural than others that are available, and it could allow organs-on-chips to more accurately replicate how healthy intestinal cells become diseased and how they react to drug treatments.
Traditionally, scientists have cultured cells on laboratory dishes and have used animal models to study disease and its potential treatments. But neither of these approaches fully mimic what occurs in the human body. Recently, researchers developed a way to grow living cells in microfluidic chips. Commonly called an organ-on-a-chip, each device is typically composed of a pair of flexible, translucent polymers or plastics that surround a porous membrane. Human cells extracted from an organ can be grown on the polymer or on the membrane. However, because the membrane itself is often made of plastic, it can disrupt cell interactions and skew the results. So, Abhinav Bhushan and colleagues at Illinois Institute of Technology sought to create a more natural membrane that would encourage the normal growth and development of human cells.
The researchers produced three types of microfluidic devices. One had no membrane, and the second had a plastic-derived membrane. For the third device, the research team used collagen to form the membrane. Collagen is one of the most common proteins in the body, and it helps form connective tissues. Then, they placed human colon cells in each device. After 5 days, microscopic evaluation revealed that colon cells on the collagen membrane were far more viable compared to those grown in the other devices. In addition, the cells grown on the collagen membrane were more differentiated. They also appeared to be integrating with the collagen fibers to remodel the microenvironment. The researchers concluded that using collagen-based membranes in organ-on-a-chip devices enhance the growth, viability and barrier function of human colon cells and that the method likely could be extended to cells from other organs.
The authors acknowledge funding from the Nayar Prize II and student scholarships from the " Armour College of Engineering.
> "A Novel Microfluidic Colon With An Extracellular Matrix Membrane"
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Note: ACS does not conduct research, but publishes and publicizes peer-reviewed scientific studies
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How cats and dogs are consuming and processing parabens
Environmental Science & Technology
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Many households can claim at least one four-legged friend as part of the family. But pets that primarily stay indoors can have increased rates of diseases, such as diabetes, kidney diseases and hypothyroidism compared with those that stay exclusively outside. Some scientists propose that chemical substances in the home could contribute to these illnesses. One group has examined how pets could be exposed to parabens, as reported in ACS' journal Environmental Science and Technology.
Parabens are preservatives commonly found in cosmetic and pharmaceutical products, and their use in human food products and dog and cat food is regulated by the U.S. Food and Drug Administration. The substances also have been shown to be endocrine-disrupting compounds (EDCs). Research has shown EDCs potentially interfere with hormones and have harmful effects on developmental, reproductive and neurological systems. Previous studies have examined the presence of other EDCs, such as heavy metals and bisphenol A, in pet food, but very little is known about parabens in this context. So, Kurunthachalam Kannan and colleagues wanted to examine the exposure of dogs and cats to parabens in commercially available pet food and analyze the substances in the animals' urine.
The team examined 58 variations of dog and cat food, as well as 60 urine samples from animals. The paraben called methyl paraben and the metabolite called 4-hydroxybenzoic acid (4-HB) were the most abundant chemicals detected in pet food and urine. The researchers found that dry food contained higher levels of parabens and their metabolites than wet food. In addition, the researchers report, cat food had higher paraben concentrations than dog food. After the urine analysis, the group calculated the cumulative exposure intake for the dogs and cats. By comparing the calculations, the team concluded that dogs are exposed to other sources of parabens, besides food, whereas cats' exposure is mainly from their diet. The group also notes that to their knowledge, this is the first time the occurrence of these substances has been reported in pet food and urine in the U.S.
ARTICLE #3 FOR IMMEDIATE RELEASE
"Parabens and Their Metabolites in Pet Food and Urine from New York State, United States"
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Note: ACS does not conduct research, but publishes and publicizes peer-reviewed scientific studies.
Mind-controlling molecules from wasp venom could someday help Parkinson's patients
Biochemistry
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Scientists have long studied venoms, such as that of the wasp, seeking out novel and potent molecules to treat disease, among other applications. In the case of the enigmatic wasp Ampulex compressa, it uses its venom in a two-pronged approach against the cockroach, with an initial sting to the thorax to paralyze the front legs and a subsequent sting directly to the brain. This second sting causes the roach first to vigorously groom itself, then to fall into a state of lethargy, allowing the wasp to do whatever it wants. This immobile state resembles symptoms of Parkinson's disease, and both may be related to dysfunction in the dopamine pathway. In this study, Michael E. Adams and colleagues wanted to identify the ingredients in wasp venom that dictate this behavior.
The researchers milked wasps for their venom and then analyzed the components using liquid chromatography and mass spectrometry. They identified a new family of alpha-helical peptides and named them ampulexins. To test their function, the team injected the most abundant venom peptide into cockroaches. Afterward, the bugs needed, on average, a 13-volt electric shock to the foot to get them moving, while an average of 9 volts sufficed prior to the injection, suggesting the peptides help the wasp immobilize its prey. Future work will focus on identifying cellular targets of ampulexins, and potentially generating a useful animal model for the study of Parkinson's disease treatments.
The authors acknowledge funding from the United States-Israel Binational Science Foundation, the University of California, Riverside Office of Research and Economic Development and the University of California Agricultural Experiment Station.
"Ampulexins: A New Family of Peptides in Venom of the Emerald Jewel Wasp, Ampulex compressa"
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Note: ACS does not conduct research, but publishes and publicizes peer-reviewed scientific studies.
MARCH 2017
Corralling stink bugs could lead to better wine
Journal of Agricultural and Food Chemistry
To wine makers, stink bugs are more than a nuisance. These tiny pests can hitch rides on grapes going through the wine making process, releasing stress compounds that can foul the smell and taste of the finished product. Now, in a study published in the Journal of Agricultural and Food Chemistry, scientists report the threshold of stink bugs per grape cluster that will impact the integrity of the wine.
In vineyards, brown marmorated stink bugs feed on grapes, reducing their yield and quality. And because they are small and blend in, the insects hitchhike on the grapes and wind up in the winery, giving off stress compounds that sometimes affecting the quality of the wine and juice. Pesticides used in the vineyard are not completely effective, so attention is being focused on ways to reduce the presence of the insects in wineries post-harvest. To find out exactly how grape processing impacts the release of stink bug stress compounds and how this affects wine, Elizabeth Tomasino and colleagues took a closer look.
The researchers placed varying numbers of live or dead stink bugs on grapes and measured the release of insect stress compounds as wine was produced from the fruits. The found that pressing was a key step in the release of two of the most common stress compounds — tridecane, which is odorless, and (E)-2-decenal, which produces an undesirable musty-like, coriander or cilantro aroma. Interestingly, white wine was contaminated less often than red. The researchers suggest that this is because these two wines are pressed at different points in the winemaking process. The team concludes that if winemakers could limit stink bugs to no more than three per grape cluster, the levels of tridecane and (E)-2-decenal in wine would be below the consumer rejection threshold.
The authors acknowledge funding from the National Institute of Food and Agriculture, U.S. Department of Agriculture and the U.S. Department of Agriculture, Northwest Center for Small Fruits Research.
Expanding point-of-care disease diagnostics with ultrasound (video)
ACS Nano
Fast, accurate and inexpensive medical tests in a doctor's office are only possible for some conditions. To create new in-office diagnostics for additional diseases, researchers report in the journal ACS Nano a new technique that uses ultrasound to concentrate fluorescently labeled disease biomarkers otherwise impossible to detect with current equipment in an office setting. The markers' signal could someday be analyzed via a smartphone app.
Ultrasound is a safe, noninvasive, inexpensive and portable technique best known for monitoring pregnancies. But these high-frequency acoustic waves can also be used to gently handle blood components, cells and protein crystals at the microscopic level. With an eye toward point-of-care diagnostic applications, Ton Huang, Zhangming Mao and colleagues wanted to harness these sound waves to help detect even smaller particles and biomarkers for diseases such as cancer that often require special laboratory equipment to detect.
The researchers developed an acoustofluidic chip that, though vibrations, can form a streaming vortex inside a tiny glass capillary tube using a minimal amount of energy. Testing showed that the vortex could force nanoparticles ranging in diameter from 80 to 500 nanometers to swirl into the center of the capillary. The nanoparticles captured biomarkers labeled with a fluorscent tag, concentrating them in the capillary to boost their signal. This increased brightness could make the signal readable with a smartphone camera.
The authors acknowledge funding from the National Institutes of Health and the National Science Foundation.
Watch the Headline Science video here explaining the diagnostic technique.
Using E. coli to detect hormone disruptors in the environment
ACS Central Science
Endocrine disrupting chemicals (EDCs) have been implicated in the development of obesity, diabetes and cancer and are found in a wide array of products including pesticides, plastics and pharmaceuticals. EDCs are potentially harmful, even at low concentrations, equal in some cases to mere milligrams dissolved in in a swimming pool full of water. Now researchers report in ACS Central Science that they can quickly detect environmentally relevant concentrations of EDCs using engineered E. coli bacteria.
Detecting EDCs can be tough because the classification is based on their activity — disrupting hormone function — instead of their structures. Thus the term encompasses a broad spectrum of chemicals and often, health risks arise from aggregate exposure to several different species. Because many EDCs act on the same hormone receptors on a cell's surface, researchers have been developing tests that detect the compounds based on their ability to interfere with hormones. But these methods currently take days to produce a result or involve many complicated and expensive steps. Here, Matthew Francis and colleagues overcame these challenges by using E. coli in their device.
Non-toxic, dead E. coli cells display an estrogen receptor on the surface of the researchers' portable sensor. A protein on the sensor surface recognizes the EDC-E. coli complex, producing an electronic read-out in minutes. The inexpensive device can determine the concentration of many known EDCs individually and overall concentrations as mixtures. They tested the detection in water and in complex solutions like baby formula. It also can detect EDCs released into liquid from a plastic baby bottle following microwave heating. The team notes that their test is suitable for use in the field and can be modified to test for other types of chemicals that act on human receptors.
The authors acknowledge funding from the HoundLabs, the National Science Foundation and the Beckman Foundation.
Watching water freeze (video)
ACS Omega
Every winter, snow and ice dusts mountains and makes roads slick in cold climates. This phenomenon is ages old, but a detailed explanation for how ice crystals form has eluded us. In a study appearing in the journal ACS Omega, scientists now report a method to visualize ice in three dimensions as it grows. This knowledge could have a range of potential uses in materials science, geophysics, biology and food engineering.
What scientists know for sure is that ice shape and size depend on a number of factors, such as pH, the speed at which the temperature drops and the composition of additives. They have tried controlling ice shape by adding a variety of compounds, including sugar, ethanol and naturally occurring anti-freeze proteins from fishes, plants and insects. But to gain a deeper understanding of how ice forms — and potentially to have better control over the process — scientists have been working on new ways to watch crystals grow in real time. Several methods have been attempted, but none have provided reliable 3-D visualizations. A team of scientists from the Ceramics Synthesis and Functionalization Lab in France took a different approach.
The researchers demonstrated that confocal laser scanning microscopy and image analysis can rapidly capture a series of pictures showing the ice crystals growing. The images can then be used to measure how fast the crystals expand and lengthen. The approach has promise for further studying ice growth under varying conditions and with the addition of polymers, proteins or other compounds, the researchers say.
The authors acknowledge funding from the European Research Council.
Watch ice crystals form in this video.