Category: Chemistry

by Hebrew University of Jerusalem

Azobenzenes are incredibly versatile and have many potential uses, such as in making tiny machines and improving technology as well as making light controllable drugs. This molecule can switch between two different forms by light. However, the two forms are in equilibrium, which means that a mixture present that prevents optimal use for applications.

Being able to control them with visible light and enrich only one form opens up new possibilities for these applications, making them more efficient and accessible.

Azobenzenes have traditionally required ultraviolet light for photoisomerization. However, a new approach promises to change the game. Profs. Igor Schapiro from Hebrew University of Jerusalem, Rafal Klajn from the Weizmann Institute of Science and Institute of Science and Technology Austria, and Arri Priimagi from Tampere University along with a team of researchers, have introduced a novel concept termed “disequilibration by sensitization under confinement” or DESC.

This innovative approach offers for the first time the possibility of prompting a specific molecular transformation, specifically the conversion from an “E” to a “Z” state. They can be thought of as an “on” and “off” form in applications. This change can be triggered by visible light, including wavelengths in the red part of the visible spectrum.

The study, titled “Disequilibrating azobenzenes by visible-light sensitization under confinement,” was published in the journal, Science.

What makes azobenzene molecules particularly interesting is their ability to undergo changes in their shape in response to specific types of light, including ultraviolet and visible light. This phenomenon, known as photoisomerization, enables azobenzenes to transition between two distinct shapes or isomers, the “E” and “Z” isomers. This unique attribute holds immense significance, as it unlocks a diverse spectrum of applications spanning nanotechnology, data storage, drug delivery, materials science, and biological research.

In essence, azobenzenes serve as pivotal elements in numerous scientific and technological advancements.

“Through our computational studies and quantum chemical calculations, we’ve illuminated the path to an innovative approach, which not only advances the fundamental field of azobenzene but also paves the way for practical applications. These applications harness the power of visible light, including red wavelength of light,” said Prof. Igor Schapiro, Hebrew University of Jerusalem

Azobenzenes are pivotal components in a wide range of technologies, from molecular switches and actuators to data storage and drug delivery systems. Until now, their photoisomerization necessitated ultraviolet light, limiting their applicability. However, DESC represents a significant breakthrough, offering a supramolecular approach that enables controlled E-to-Z isomerization with harmless light.

This pioneering research opens up exciting new avenues for the utilization of azobenzenes across various fields. By broadening the range of light wavelengths that can induce isomerization, DESC promises to enhance the efficiency and applicability of azobenzene-based technologies.

More information: Julius Gemen et al, Disequilibrating azobenzenes by visible-light sensitization under confinement, Science (2023). DOI: 10.1126/science.adh9059. www.science.org/doi/10.1126/science.adh9059

Journal information: Science 

Provided by Hebrew University of Jerusalem 

by Science China Press

Understanding how voltage drives nanoscale electrocatalysts to initiate reactions is a fundamental scientific question. This is especially challenging when dealing with non-metallic electrocatalysts due to their low inherent carrier concentration, which leads to poor conductivity. When voltage is applied at the non-metal/solution interface, the situation becomes more complex than in the case of metal/solution interfaces.

One notable complexity is the significant potential drop within the non-metal, causing the surface potential to often deviate from the back potential. Analyzing the driving force for chemical reactions by applying classical metal models to non-metals can result in substantial inaccuracies.

Up until now, distinguishing the potential distribution between the nonmetallic catalyst and the EDL still relies on complex theoretical calculations. The actual potential drop across the semiconductor-electrolyte interface remains unknown, due to the lacks of in in-situ techniques.

Moreover, conventional electrochemical characterization only provides the ensemble information for electrode materials, neglecting the spatial heterogeneity in the electronic structures of catalysts. Therefore, a spatially resolved in-situ characterization technique is highly needed.

In a new research article published in National Science Review, scientists at Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Xiamen University, University of Chinese Academy of Sciences, Imperial College London autonomously constructed an in-situ surface potential microscope and successfully measured the surface potential of the basal plane of 2H molybdenum disulfide under various voltages.

This achievement addresses the experimental challenge of directly measuring the potential distribution at the non-metal/solution interface. The research findings highlight a notable difference in how the surface potential of semiconductors changes with applied voltage compared to metals.

When applying voltage from positive to negative, semiconductors shift from maintaining a stable surface potential to displaying variations, gradually resembling the behavior of metals. Scientists further clarified the differences in potential drop values at various applied voltages between the semiconductor (ΔV_sem) and the double layer (ΔV_edl).

They vividly explained how, in a solution environment, the semiconductor’s Fermi level and band structure evolve, demonstrating a transformation of the semiconductor into a highly conductive semimetal.

To further investigate the role of voltage in electrocatalytic reactions, scientists employed atomic force-scanning electrochemical microscopy (AFM-SECM) to study electron transfer (ET) and hydrogen evolution reaction (HER) imaging on molybdenum disulfide. In ET imaging, the semiconductor’s basal plane exhibited strong electron transfer capability, comparable to that of the semimetal edge. However, HER imaging revealed catalytic inertness at the basal plane.

Nano-electrochemical imaging results indicated that voltage only affects the ET step. Due to the absence of hydrogen adsorption sites on the basal plane (i.e., chemical sites), voltage cannot drive the electrons on the basal plane to further participate in chemical reactions. This work paves the way for the rational design of efficient nonmetallic electrocatalysts based on the understanding of how voltage acts on nonmetallic catalysts at the nanoscale.

More information: Ziyuan Wang et al, Visualizing the role of applied voltage in non-metal electrocatalysts, National Science Review (2023). DOI: 10.1093/nsr/nwad166

Provided by Science China Press 

by University of Eastern Finland

Boosting virtual screening with machine learning allowed for a 10-fold time reduction in the processing of 1.56 billion drug-like molecules. Researchers from the University of Eastern Finland teamed up with industry and supercomputers to carry out one of the world’s largest virtual drug screens.

In their efforts to find novel drug molecules, researchers often rely on fast computer-aided screening of large compound libraries to identify agents that can block a drug target. Such a target can, for instance, be an enzyme that enables a bacterium to withstand antibiotics or a virus to infect its host. The size of these collections of small organic molecules has seen a massive surge over the past years.

With libraries growing faster than the speed of the computers needed to process them, the screening of a modern billion-scale compound library against only a single drug target can take several months or years—even when using state-of-the-art supercomputers. Therefore, quite evidently, faster approaches are desperately needed.

In a study published in the Journal of Chemical Information and Modeling, Dr. Ina Pöhner and colleagues from the University of Eastern Finland’s School of Pharmacy teamed up with the host organization of Finland’s powerful supercomputers, CSC—IT Center for Science Ltd—and industrial collaborators from Orion Pharma to study the prospect of machine learning in the speed-up of giga-scale virtual screens.

Before applying artificial intelligence to accelerate the screening, the researchers first established a baseline: In a virtual screening campaign of unprecedented size, 1.56 billion drug-like molecules were evaluated against two pharmacologically relevant targets over almost six months with the help of the supercomputers Mahti and Puhti, and molecular docking. Docking is a computational technique that fits the small molecules into a binding region of the target and computes a “docking score” to express how well they fit. This way, docking scores were first determined for all 1.56 billion molecules.

Next, the results were compared to a machine learning-boosted screen using HASTEN, a tool developed by Dr. Tuomo Kalliokoski from Orion Pharma, a co-author of the study.

“HASTEN uses machine learning to learn the properties of molecules and how those properties affect how well the compounds score. When presented with enough examples drawn from conventional docking, the machine learning model can predict docking scores for other compounds in the library much faster than the brute-force docking approach,” Kalliokoski explains.

Indeed, with only 1% of the whole library docked and used as training data, the tool correctly identified 90% of the best-scoring compounds within less than 10 days.

The study represented the first rigorous comparison of a machine learning-boosted docking tool with a conventional docking baseline on the giga-scale. “We found the machine learning-boosted tool to reliably and repeatedly reproduce the majority of the top-scoring compounds identified by conventional docking in a significantly shortened time frame,” Pöhner says.

“This project is an excellent example of collaboration between academia and industry, and how CSC can offer one of the best computational resources in the world. By combining our ideas, resources and technology, it was possible to reach our ambitious goals,” said Professor Antti Poso, who leads the computational drug discovery group within the University of Eastern Finland’s DrugTech Research Community.

Studies on a comparable scale remain elusive in most settings. Thus, the authors released large datasets generated as part of the study into the public domain. Their ready-to-use screening library for docking enables others to speed up their respective screening efforts, with 1.56 billion compound-docking results for two targets that can be used as benchmarking data.

This data will encourage the future development of tools to save time and resources and will ultimately advance the field of computational drug discovery.

More information: Toni Sivula et al, Machine Learning-Boosted Docking Enables the Efficient Structure-Based Virtual Screening of Giga-Scale Enumerated Chemical Libraries, Journal of Chemical Information and Modeling (2023). DOI: 10.1021/acs.jcim.3c01239

Journal information: Journal of Chemical Information and Modeling 

Provided by University of Eastern Finland 

by Addison Dehaven, South Dakota State University

Next to water, coffee is the most popular beverage on Earth and is the world’s second most traded good, trailing only oil. It is estimated that humans drink more than 2 billion cups of coffee per day with over 60% of Americans having a cup each day. As a result, over 8 million tons of spent coffee grounds are disposed of on an annual basis.

What if, instead of ending up in a landfill, those coffee grounds could be used as a sustainable, climate-friendly packaging material?

While this may seem like wishful thinking, a new study from Srinivas Janaswamy, associate professor in South Dakota State University’s Department of Dairy and Food Science, has revealed how spent coffee grounds can be made into biodegradable films—material that could one day replace plastics.

The study, titled “Biodegradable, UV-blocking, and antioxidant films from lignocellulosic fibers of spent coffee grounds,” was published in the International Journal of Biological Macromolecules.

Alternatives to plastic

Plastics are strong, flexible and relatively inexpensive to produce, making them a near “perfect” material for packaging. Plastics, however, pose a serious environmental problem. While recyclable, most plastics end up as litter or in landfills, where they take 700 years to biodegrade. In the oceans, miles of plastic garbage patches—most notably, the Great Pacific Garbage Patch, which is currently the size of Texas and growing—float aimlessly, underlining the growing environmental crisis that an over-reliance on plastic has created.

Of growing concern are microplastics, a relatively new scientific discovery in which microscopic pieces of plastics are finding their way into the food and water that humans consume. Little to no research on the long-term health effects of microplastics on humans has been conducted thus far.

A safe, sustainable and climate-friendly plastic alternative is needed.

“Plastics constitute a wide range of materials designed to meet many daily needs,” Janaswamy said. “Replacing all existing plastics is far from possible at this stage. However, substituting low-cost daily commodity-used conventional plastics, which occupy the most considerable fraction of the environmental contaminants, is feasible and can be achieved.”

Why coffee grounds?

Over the past few years, Janaswamy has focused his research efforts on creating biodegradable alternatives to plastic, often from agricultural byproducts. Previously, Janaswamy has prepared films from the cellulose-rich peels of avocados and corn stover.

“This project continues my ongoing efforts to prepare films that could replace plastics,” Janaswamy said.

Spent coffee grounds were chosen as the source material for a few different reasons. First, spent coffee grounds are widely available with millions of tons produced annually. While most end up in landfills, some are used for other things, like gardening. While this may seem like an environmentally conscious move, as Janaswamy points out, it actually can cause environmental problems.

“Generally, we discard the coffee ground grounds after we make our coffee,” Janaswamy said. “Some of us use them for compositing, gardening and other things. Ironically, such a process demands high amounts of oxygen and releases a good amount of methane, which contributes to global warming.”

Second, as emerging economies begin adding chain coffee shops—like Starbucks—the amount of spent coffee grounds will only increase. Using this otherwise unused resource for biodegradable films is a sustainable and economical solution to the plastic crisis.

Finally, spent coffee grounds contain lignocellulosic fibers, the material needed to make the films.

Coffee into film

To prepare the films, the research team first extracted lignocellulosic fibers from the spent coffee grounds. A green chemical modification process was then deployed to make the film more suitable for packaging.

The resulting films were able to biodegrade within 45 days in the soil while also having high tensile strength. Further, the films also had some unique properties of which researchers took note.

“Interestingly, these films could block significant amounts of UV radiation and display antioxidant properties,” Janaswamy explained. “I sincerely believe this research outcome opens up new applications for spent coffee grounds.”

While this should still be considered “stage one” of turning spent coffee grounds into films, the results from this study showed significant promise.

“The potential for plastic-replacing films from the widely discarded but plentiful and sustainable spent coffee grounds remain unscathed and exciting toward value creation,” Janaswamy said.

Sajal Bhattarai, an SDSU graduate and a doctoral candidate at Purdue University, collaborated with Janaswamy on this research.

More information: Sajal Bhattarai et al, Biodegradable, UV-blocking, and antioxidant films from lignocellulosic fibers of spent coffee grounds, International Journal of Biological Macromolecules (2023). DOI: 10.1016/j.ijbiomac.2023.126798

Provided by South Dakota State University 

by José Tadeu Arantes, FAPESP

Researchers at São Paulo State University (UNESP) in Brazil have developed a strategy for removing glyphosate, one of the world’s most frequently used herbicides, from water. Inspired by the concept of the circular economy, the technique is based on sugarcane bagasse, a waste material produced by sugar and ethanol plants.

“Isolated and chemically functionalized sugarcane bagasse fibers can be used as adsorbent material. Glyphosate adheres to its surface and is removed as a water contaminant by filtration, decantation or centrifugation,” Maria Vitória Guimarães Leal, told Agência FAPESP.

She is the first author of an article on the research published in the journal Pure and Applied Chemistry. Adsorption is a process whereby molecules dispersed in a liquid or gaseous medium adhere to a solid insoluble surface, which is typically porous.

Owing to its low cost and high potential to raise crop yields, glyphosate is widely used to control the growth of unwanted plants, such as weeds, invasive species and agricultural pests, but scientific studies have shown that it can be a human health hazard and in particular may pose a cancer risk.

Application of glyphosate-containing products is restricted or banned in Austria, Bulgaria, Colombia, Costa Rica, Denmark, El Salvador, Germany and Greece, among other countries. In Brazil, however, annual use of such products averages 173,150.75 metric tons. Part of them is borne away by rain into rivers, wells and other aquatic environments.

Scientists at UNESP’s School of Sciences and Technology (FCT) in Presidente Prudente found a way to remove glyphosate products from water in research led by postdoctoral fellow Guilherme Dognani and Aldo Eloizo Job, a professor at FCT-UNESP.

How it works

Dognani explained the procedure. “The bagasse is shredded and the cellulose isolated by separating it from the hemicellulose and lignin. The cellulose fibers are then functionalized by adding quaternary ammonia groups to their surface so that the material is positively charged. The resulting cationic cellulose microfibers bind easily to glyphosate,” he said.

Leal added that there are certain favorable conditions, such as pH variation, which was the focus of the study. “When pH is varied, both the adsorbent material and the glyphosate display different molecular configurations. The most efficient level for interaction between them, inducing the most adsorption and hence optimal removal, is pH 14,” he said.

To evaluate adsorption capacity, the researchers prepared fractions of a glyphosate solution with pH 2, 6, 10 and 14, measured using a pH meter. They then added to each fraction identical amounts of functionalized cellulose microfiber.

The flasks with the solution contaminated by glyphosate plus cellulose were agitated for 24 hours. In accordance with the procedure described in the literature, they were then heated in a water bath until the reaction occurred, cooled to room temperature and analyzed by visible light spectrophotometry. Removal efficiency was calculated as a ratio of initial to final glyphosate levels in each sample, and adsorption capacity was calculated as a function of pH.

More information: Maria Vitória Guimarães Leal et al, pH dependence of glyphosate adsorption from aqueous solution using a cationic cellulose microfibers (cCMF) biosorbent, Pure and Applied Chemistry (2023). DOI: 10.1515/pac-2022-1205

Provided by FAPESP 

by Ecole Polytechnique Federale de Lausanne

Metal-organic frameworks (MOFs) are a class of materials that contain nano-sized pores. These pores give MOFs record-breaking internal surface areas, which make them extremely versatile for a number of applications: separating petrochemicals and gases, mimicking DNA, producing hydrogen, and removing heavy metals, fluoride anions, and even gold from water are just a few examples.

In the gas-separation domain, MOFs are particularly interesting for separating hydrogen from nitrogen, which is crucial for clean energy production, fuel cell efficiency, ammonia synthesis, and various industrial processes. Hydrogen-nitrogen separation also has a number of environmental benefits, making it integral to advancing sustainable technologies and industrial practices.

Now, a team of researchers led by Professor Kumar Varoon Agrawal at EPFL’s School of Basic Sciences have developed MOF film with smallest possible thickness that can perform record levels of hydrogen-nitrogen separation. The researchers worked with a type of MOFs known as zeolitic imidazolate frameworks (ZIFs), which have garnered considerable attention for their potential in molecular separations, sensing, and other applications.

Their research is published in Nature Materials.

To make the films, the researchers used an innovative crystallization method that capitalizes on the precise alignment of ultra-dilute precursor mixtures with the underlying crystalline substrate. By carefully controlling precursor concentrations and interactions with the substrate, the team were able to suppress out-of-plane growth—a common problem in making thin films.

The approach paid off: Within a matter of minutes, and at room temperature, the scientists were able to fabricate macroscopically uniform two-dimensional (2D) ZIF films with unprecedented thickness: just one structural unit, measuring only two nanometers. The scientists also showed that the process is scalable preparing films with area of hundreds of square centimeters. The breakthrough overcomes conventional methods, which have limited ZIF film thickness to 50 nanometers, making widespread use difficult.

The ZIF film has a unique configuration: a nanometer-thick film with a uniform array of hydrogen-sieving six-membered zinc-imidazolate coordination ring. Kumar Agrawal explains, “This allows for an exceptional combination of hydrogen flux and selectivity, holding immense potential for highly efficient gas-separation applications.”

More information: Unit-cell-thick zeolitic imidazolate framework films for membrane application, Nature Materials (2023). DOI: 10.1038/s41563-023-01669-z , www.nature.com/articles/s41563-023-01669-z

Journal information: Nature Materials 

Provided by Ecole Polytechnique Federale de Lausanne 

by University of Amsterdam

What chemicals are we exposed to on a daily basis? That is the central question of “non-targeted analysis” or NTA, an emerging field of analytical science that aims to identify all chemicals around us. A daunting task, because how can you be sure to detect everything if you don’t know exactly what you’re looking for?

In a paper published in Environmental Science and Technology, researchers at the Universities of Amsterdam (UvA, the Netherlands) and Queensland (UQ, Australia) have assessed this problem. In a meta-analysis of NTA results published over the past six years, they estimate that less than 2% of all chemicals have been identified.

According to Viktoriia Turkina who performed the research as a Ph.D. student with Dr. Saer Samanipour at the UvA’s Van ‘t Hoff Institute for Molecular Sciences, this limitation underscores the urgent need for a more proactive approach to chemical monitoring and management. “We need to incorporate more data-driven strategies into our studies to be able to effectively protect the human and environmental health,” she says.

Samanipour explains that current monitoring of chemicals is rather limited since it’s expensive, time consuming, and requires specialized experts. “As an example, in the Netherlands we have one of the most sophisticated monitoring programs for chemicals known to be of concern to human health. Yet we target less than 1,000 chemicals. There are far more chemicals out there that we don’t know about.”

A vast chemical space

To deal with those chemicals, some 15 to 20 years ago the concept of non-targeted analysis was introduced to look at possible exposure in an unbiased manner. The idea is to take a sample from the environment (air, water, soil, sewer sludge) or the human body (hair, blood, etc.) and analyze it using well-established techniques such as chromatography coupled with high resolution mass spectroscopy.

The challenge then is to trace the obtained signal back to the structures of chemicals that may be present in the sample. This will include already known chemicals, but also chemicals of which the potential presence in the environment is yet unknown.

In theory, this “chemical space” includes as many as 10⁶⁰ compounds, an incomprehensible number that exceeds the number of stars in the universe by far. On the other hand, the number of organic and inorganic substances published in the scientific literature and public databases is estimated at around 180 million.

To make their research more manageable, Turkina, Samanipour and co-workers focused on a subset of 60,000 well-described compounds from the NORMAN database. Turkina says, “This served as the reference to establish what is covered in NTA studies, and more importantly, to develop an idea about what is being overlooked.”

The vast ‘exposome’ of chemicals that humans are exposed to on a daily basis is a sign of our times, according to Samanipour.

“These days we are soaking in a giant ocean of chemicals. The chemical industry is part of that, but also nature is running all a whole bunch of reactions that result in exposure. And we expose ourselves to chemicals by the stuff we use—think for instance of the problem of microplastics. To solve all this we have to be able to go beyond pointing fingers. With our research, we hope to contribute to finding a solution together. Because we all are in the same boat.”

Much room for improvement

The meta analysis, which included 57 NTA papers, revealed that only around 2% of the estimated chemical space was covered. This can indicate that the actual exposure to chemicals is indeed quite low, however, it can also point to shortcomings in the applied analyses. According to Turkina and Samanipour, the latter is indeed the case. They focused on NTA studies applying liquid chromatography coupled with high resolution mass spectrometry (LC-HRMS) -one of the most comprehensive methods for the analysis of complex environmental and biological samples.

It turned out that there was much room for improvement. For instance in sample preparation, they observed a bias towards specific compounds rather than capturing a more diverse set of chemicals. They also observed poor selection and inconsistent reporting of LC-HRMS parameters and data acquisition methods.

“In general,” Samanipour says, “the chemical analysis community is to a great extent driven by the available technology that vendors have developed for specific analysis purposes. Thus the instrumental set-up and data processing methods are rather limited when it comes to non-targeted analysis.”

To Samanipour, the NTA approach is definitely worth pursuing. “But we need to develop it further and push it forward. Together with vendors we can develop new powerful and more versatile analytical technologies, as well as effective data analysis protocols.”

He also advocates a data-driven approach were the theoretical chemical space is “back calculated” towards a subset of chemicals that are highly likely to be present in our environment. “Basically we have to better understand what is the true chemical space of exposure. And once those boundaries are defined, then it becomes a lot easier to assess that number of 2% we have determined.”

More information: Tobias Hulleman et al, Critical Assessment of the Chemical Space Covered by LC–HRMS Non-Targeted Analysis, Environmental Science & Technology (2023). DOI: 10.1021/acs.est.3c03606

Journal information: Environmental Science and Technology  , Environmental Science & Technology 

Provided by University of Amsterdam 

by Kumamoto University

Researchers from Japan have unlocked the potential of tannic acid and ultra-high molecular weight polyethylene oxide by using them to synthesize strong and smart supramolecular gels in a zero-waste process. These gels exhibit remarkable characteristics, such as high elongation, strong adhesion, resistance to swelling, shape memory, self-healing property, and biocompatibility.

Going forward, these innovative, zero-waste gels can have promising applications as advanced medical materials, promoting a sustainable approach to material science.

Recent advances in chemistry have allowed for the cost-effective synthesis of supramolecular materials with advanced properties. Due to their unique properties, such as toughness, elasticity, self-healing, biodegradability, and shape memory, these materials find diverse applications as advanced materials in various fields. However, their fabrication often involves time-consuming and complex processes, organic solvents, and waste production, resulting in low yields and high synthesis costs.

One promising option is to use tannic acid (TA), a biodegradable polyphenol that can form unique supermolecules by bonding strongly with other molecules. It is a safe, affordable, and environmentally sustainable material with multiple applications, such as those in the pharmaceutical industry.

In recent years, TA has been used for the synthesis of supramolecular gels using many types of polymers, including macromolecules like polyethylene oxide (PEO). However, while such studies have utilized relatively low-molecular-weight PEO for creating TA gels, ultra-high-molecular-weight (UHMW) PEO has been less commonly used.

Inspired by these studies and the ability of TA to form a viscous glue-like liquid on mixing it in water with PEG, a research team led by Associate Professor Taishi Higashi and graduate student Yuika Goto, from the Graduate School of Pharmaceutical Sciences, Kumamoto University, decided to develop hydrogels containing TA and PEO.

Their experiments have revealed that when TA and UHMW PEO are mixed together in water, a highly stretchable gel, named “TaPeO gel,” is formed via a zero-waste process. This study was made available online on in the journalResults in Materials in September 2023.

“We started by dissolving TA in water, and then PEO solutions with different molecular weights were mixed with TA at specific ratios to create TA/PEO gels. Following this, we used UHMW PEO with a molecular weight of 500 kDa to create TaPeO Gels. They were obtained by mixing TA and PEO solutions at a ratio of 1:2 (v/v) and compressing the precipitated gel,” says Associate Professor Higashi.

Named TaPeO Gel after the TA family, the mechanical properties of this gel were impressive, stretching remarkably and demonstrating a maximum elongation of up to 1,000% or more. It demonstrated excellent adhesion ability, as observed when the cut surfaces were touched, resulting in the reattachment of TaPeO Gel.

The maximum tensile strength and elongation of the reattached gel were comparable to the original gel after adhesion. Additionally, it had a water content of approximately 20% and low swelling ratios, ranging from 105% to 107%. It is interesting to note that the mechanical properties of TaPeO Gels varied with PEO molecular weight, with longer PEO chains leading to higher maximum tensile strengths.

The team further prepared dry TaPeO Gel by drying the wet gel at 40°C for eight days. They observed that upon drying, TaPeO Gel transformed into a transparent, lightweight, plastic-like rigid material with self-healing properties. They were also found to possess shape memory ability, observed by the gel’s ability to return to its original shape upon immersion in hot water after deformation.

The mechanical properties of dry TaPeO Gel were influenced by PEO molecular weight, with higher molecular weights leading to higher three-point bending flexural strengths. After immersion in water, the reswollen dry TaPeO Gel exhibited mechanical properties similar to those of the wet TaPeO Gel, indicating reversibility of gel properties.

To evaluate their biocompatibility, human cervical cancer cells were exposed to the TaPeO Gel. These cells showed almost 100% viability, indicating low cytotoxicity and good biocompatibility of the synthesized gel.

Moreover, during the preparation of the gel, the team encountered an excess liquid byproduct. Instead of discarding it, they opted to dry the supernatant of the TA/PEO mixture. The resulting TaPeO films, although initially brittle, exhibited excessive elongation (over 1,500%) after reabsorbing moisture, which was beyond the measurement scope of the testing machine used in this study.

The thickness of these films decreased with increasing PEO molecular weight, as higher molecular weight PEO led to more efficient entanglement with TA and lower concentrations in the supernatant. Associate Professor Higashi says, “These findings suggest that supramolecular films with high elongation can be prepared from the supernatant of TA/PEO mixtures, potentially offering zero-waste production of gels and films.”

This study provides valuable insights for the development of innovative supramolecular functional materials based on TA and UHMW PEO. These materials could hold great promise for various eco-friendly applications, on account of their exceptional properties.

Moreover, the zero-waste production process aligns well with the objective of environmental sustainability, making these materials highly desirable in the future.

More information: Yuika Goto et al, Zero-waste preparation of supramolecular hydrogels and films comprising tannic acid and ultra-high-molecular-weight polyethylene oxide, Results in Materials (2023). DOI: 10.1016/j.rinma.2023.100425

Provided by Kumamoto University 

by Chantrell Frazier, Kenneth G. Furton and Vidia A. Gokool, The Conversation

From the aroma of fresh-cut grass to the smell of a loved one, you encounter scents in every part of your life. Not only are you constantly surrounded by odor, you’re also producing it. And it is so distinctive that it can be used to tell you apart from everyone around you.

Your scent is a complex product influenced by many factors, including your genetics. Researchers believe that a particular group of genes, the major histocompatibility complex, play a large role in scent production. These genes are involved in the body’s immune response and are believed to influence body odor by encoding the production of specific proteins and chemicals.

But your scent isn’t fixed once your body produces it. As sweat, oils and other secretions make it to the surface of your skin, microbes break down and transform these compounds, changing and adding to the odors that make up your scent. This scent medley emanates from your body and settles into the environments around you. And it can be used to track, locate or identify a particular person, as well as distinguish between healthy and unhealthy people.

We are researchers who specialize in studying human scent through the detection and characterization of gaseous chemicals called volatile organic compounds. These gases can relay an abundance of information for both forensic researchers and health care providers.

Science of body odor

When you are near another person, you can feel their body heat without touching them. You may even be able to smell them without getting very close. The natural warmth of the human body creates a temperature differential with the air around it. You warm up the air nearest to you, while air that’s farther away remains cool, creating warm currents of air that surround your body.

Researchers believe that this plume of air helps disperse your scent by pushing the millions of skin cells you shed over the course of a day off your body and into the environment. These skin cells act as boats or rafts carrying glandular secretions and your resident microbes—a combination of ingredients that emit your scent—and depositing them in your surroundings.

Your scent is composed of the volatile organic compounds present in the gases emitted from your skin. These gases are the combination of sweat, oils and trace elements exuded from the glands in your skin. The primary components of your odor depend on internal factors such as your race, ethnicity, biological sex and other traits. Secondary components waver based on factors like stress, diet and illness. And tertiary components from external sources like perfumes and soaps build on top of your distinguishable odor profile.

Identity of scent

With so many factors influencing the scent of any given person, your body odor can be used as an identifying feature. Scent detection canines searching for a suspect can look past all the other odors they encounter to follow a scent trail left behind by the person they are pursuing. This practice relies on the assumption that each person’s scent is distinct enough that it can be distinguished from other people’s.

Researchers have been studying the discriminating potential of human scent for over three decades. A 1988 experiment demonstrated that a dog could distinguish identical twins living apart and exposed to different environmental conditions by their scent alone. This is a feat that could not be accomplished using DNA evidence, as identical twins share the same genetic code.

The field of human scent analysis has expanded over the years to further study the composition of human scent and how it can be used as a form of forensic evidence. Researchers have seen differences in human odor composition that can be classified based on sex, gender, race and ethnicity. Our research team’s 2017 study of 105 participants found that specific combinations of 15 volatile organic compounds collected from people’s hands could distinguish between race and ethnicity with an accuracy of 72% for whites, 82% for East Asians and 67% for Hispanics. Based on a combination of 13 compounds, participants could be distinguished as male or female with an overall 80% accuracy.

Researchers are also producing models to predict the characteristics of a person based on their scent. From a sample pool of 30 women and 30 men, our team built a machine learning model that could predict a person’s biological sex with 96% accuracy based on hand odor.

Scent of health

Odor research continues to provide insights into illnesses. Well-known examples of using scent in medical assessments include seizure and diabetic alert canines. These dogs can give their handlers time to prepare for an impending seizure or notify them when they need to adjust their blood glucose levels.

While these canines often work with a single patient known to have a condition that requires close monitoring, medical detection dogs can also indicate whether someone is ill. For example, researchers have shown that dogs can be trained to detect cancer in people. Canines have also been trained to detect COVID-19 infections at a 90% accuracy rate.

Similarly, our research team found that a laboratory analysis of hand odor samples could discriminate between people who are COVID-19 positive or negative with 75% accuracy.

Forensics of scent

Human scent offers a noninvasive method to collect samples. While direct contact with a surface like touching a doorknob or wearing a sweater provides a clear route for your scent to transfer to that surface, simply standing still will also transfer your odor into the surrounding area.

Although human scent has the potential to be a critical form of forensic evidence, it is still a developing field. Imagine a law enforcement officer collecting a scent sample from a crime scene in hopes that it may match with a suspect.

Further research into human scent analysis can help fill the gaps in our understanding of the individuality of human scent and how to apply this information in forensic and biomedical labs.

Provided by The Conversation 

This article is republished from The Conversation under a Creative Commons license. Read the original article.

by Tokyo University of Science

Water is one of the most abundant substances on Earth and partakes in countless biological, chemical, and ecological processes. Thus, understanding its behavior and properties is essential in a wide variety of scientific and applied fields. To do so, researchers have developed various water models to reproduce the behavior of bulk water in molecular simulations.

While these simulations can provide valuable insights into the specific properties of water, selecting an appropriate model for the system under study is crucial. Today, two water models have become very popular among biomolecular researchers: the 4-point Optimal Point Charge (OPC) and 3-point OPC (OPC3) models.

These models are known for their ability to reproduce several properties of water with high accuracy, including density, heat of vaporization, and dielectric constant. However, there is limited information on whether OPC and OPC3 water models can accurately predict the shear viscosity of water.

The viscosity of water greatly affects how water molecules interact with other substances and surfaces, dictating critical phenomena such as diffusion and absorption. This affects the texture and taste of foods and beverages, as well as how oils and liquids interact with food during cooking.

More importantly, the viscosity of water needs to be considered when designing and manufacturing pharmaceutical products, as well as many types of lubricants and polymeric materials. In addition, it influences how water and water-based solutions flow through small tubes, such as those in our circulatory system and in microfluidic devices.

Recently, Associate Professor Tadashi Ando from Tokyo University of Science conducted a study to test the performance of the OPC and OPC3 models, by evaluating their shear viscosities and comparing the values to the experimental calculations. These findings were published in The Journal of Chemical Physics.

First, Dr. Ando set up molecular dynamics simulations of up to 2,000 water molecules using popular water models, including OPC, OPC3, and variants of the Transferable Intermolecular Potential 3-point (TIP3P) and 4-point (TIP4P) models. Next, he used an approach known as the Green-Kubo formalism—a commonly used method from statistical mechanics to study viscosity and heat conduction in various materials— to calculate the viscosity of the models.

The calculated viscosities for both OPC and OPC3 water models were very close to each other for temperatures ranging from 273 K to 373 K. Notably, for temperatures above 310 K, the viscosity predicted by these models was very close to that predicted by previous experimental findings. However, this was not the case at lower temperatures.

Dr. Ando explains, “Compared to other water models, the performance of the OPC and OPC3 models in terms of predicting the shear viscosity was lower than that of TIP4P and TIP3P variants, but only for temperatures below 293 K.” Notably, at 273 K and 293 K, the shear viscosities of the two models were around 10% and 20% lower, respectively, as compared to those derived experimentally.

In addition to viscosity, Dr. Ando also assessed the performance of the OPC and OPC3 models for predicting other important water properties, such as surface tension and self-diffusion. The performance of OPC and OPC3 for these properties was remarkably accurate. “Based on the results of this study, along with those from previous reports, we can conclude that the OPC and OPC3 are among the best nonpolarizable water models at present, accounting for the various static and dynamic properties of water,” highlights Dr. Ando.

More information: Tadashi Ando, Shear viscosity of OPC and OPC3 water models, The Journal of Chemical Physics (2023). DOI: 10.1063/5.0161476

Journal information: Journal of Chemical Physics 

Provided by Tokyo University of Science