Colorful solution to a chemical industry bottleneck – KAUST Researchers Develop an “hourglass shape” Graphene-Oxide Membrane to rapidly separate chemical mixtures – Application Pharmaceuticals (other chemical mixtures)


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A graphene-oxide membrane design inspired by nature swiftly separates solvent molecules.

The nanoscale water channels that nature has evolved to rapidly shuttle water molecules into and out of cells could inspire new materials to clean up chemical and pharmaceutical production. KAUST researchers have tailored the structure of graphene-oxide layers to mimic the hourglass shape of these biological channels, creating ultrathin membranes to rapidly separate chemical mixtures.

“In making pharmaceuticals and other chemicals, separating mixtures of organic molecules is an essential and tedious task,” says Shaofei Wang, postdoctoral researcher in Suzana Nuñes lab at KAUST. One option to make these chemical separations faster and more efficient is through selectively permeable membranes, which feature tailored nanoscale channels that separate molecules by size.

But these membranes typically suffer from a compromise known as the permeance-rejection tradeoff. This means narrow channels may effectively separate the different-sized molecules, but they also have an unacceptably low flow of solvent through the membrane, and vice versa—they flow fast enough, but perform poorly at separation.

Nuñes, Wang and the team have taken inspiration from nature to overcome this limitation. Aquaporins have an hourglass-shaped channel: wide at each end and narrow at the hydrophobic middle section. This structure combines high solvent permeance with high selectivity. Improving on nature, the team has created channels that widen and narrow in a synthetic membrane.

The membrane is made from flakes of a two-dimensional carbon nanomaterial called graphene oxide. The flakes are combined into sheets several layers thick with graphene oxide. Organic solvent molecules are small enough to pass through the narrow channels between the flakes to cross the membrane, but organic molecules dissolved in the solvent are too large to take the same path. The molecules can therefore be separated from the solvent.

To boost solvent flow without compromising selectivity, the team introduced spacers between the graphene-oxide layers to widen sections of the channel, mimicking the aquaporin structure. The spacers were formed by adding a silicon-based molecule into the channels that, when treated with sodium hydroxide, reacted in situ to form silicon-dioxide nanoparticles. “The hydrophilic nanoparticles locally widen the interlayer channels to enhance the solvent permeance,” Wang explains.

When the team tested the membrane’s performance with solutions of organic dyes, they found that it rejected at least 90 percent of dye molecules above a threshold size of 1.5 nanometers. Incorporating the nanoparticles enhanced solvent permeance 10-fold, without impairing selectivity. The team also found there was enhanced membrane strength and longevity when chemical cross-links formed between the graphene-oxide sheets and the nanoparticles.

“The next step will be to formulate the nanoparticle graphene-oxide material into hollow-fiber membranes suitable for industrial applications,” Nuñes says.

References

Wang, S., Mahalingam, D., Sutisna, B. & Nunes, S.P. 2D-dual-spacing channel membranes for high performance organic solvent nanofiltration. Journal of Materials Chemistry Aadvance online publication, 10 January 2019.| article

 

BIG Discoveries from Tiny Particles – from Photonics to Pharmaceuticals, materials made with Polymer Nanoparticles hold promise for products of the future – U of Delaware


Big discovery nanoparticles 181008101017_1_540x360
In this illustration, arrows indicate the vibrational activity of particles studied by UD researchers, while the graph shows the frequencies of this vibration.
Credit: Illustration courtesy of Hojin Kim
Summary:
Understanding the mechanical properties of nanoparticles are essential to realizing their promise in being used to create exciting new products. This new research has taken a significant step toward gaining the knowledge that can lead to better performance with products using polymer nanoparticles.

From photonics to pharmaceuticals, materials made with polymer nanoparticles hold promise for products of the future. However, there are still gaps in understanding the properties of these tiny plastic-like particles.

Now, Hojin Kim, a graduate student in chemical and biomolecular engineering at the University of Delaware, together with a team of collaborating scientists at the Max Planck Institute for Polymer Research in Germany, Princeton University and the University of Trento, has uncovered new insights about polymer nanoparticles. The team’s findings, including properties such as surface mobility, glass transition temperature and elastic modulus, were published in Nature Communications.

Under the direction of MPI Prof. George Fytas, the team used Brillouin light spectroscopy, a technique that spelunks the molecular properties of microscopic nanoparticles by examining how they vibrate.

“We analyzed the vibration between each nanoparticle to understand how their mechanical properties change at different temperatures,” Kim said. “We asked, ‘What does a vibration at different temperatures indicate? What does it physically mean?’ ”

The characteristics of polymer nanoparticles differ from those of larger particles of the same material. “Their nanostructure and small size provide different mechanical properties,” Kim said. “It’s really important to understand the thermal behavior of nanoparticles in order to improve the performance of a material.”

Take polystyrene, a material commonly used in nanotechnology. Larger particles of this material are used in plastic bottles, cups and packaging materials.

“Polymer nanoparticles can be more flexible or weaker at the glass transition temperature at which they soften from a stiff texture to a soft one, and it decreases as particle size decreases,” Kim said. That’s partly because polymer mobility at small particle surface can be activated easily. It’s important to know when and why this transition occurs, since some products, such as filter membranes, need to stay strong when exposed to a variety of conditions.

For example, a disposable plastic cup made with the polymer polystyrene might hold up in boiling water — but that cup doesn’t have nanoparticles. The research team found that polystyrene nanoparticles start to experience the thermal transition at 343 Kelvin (158 degrees F), known as the softening temperature, below a glass transition temperature of 372 K (210 F) of the nanoparticles, just short of the temperature of boiling water. When heated to this point, the nanoparticles don’t vibrate — they stand completely still.

This hadn’t been seen before, and the team found evidence to suggest that this temperature may activate a highly mobile surface layer in the nanoparticle, Kim said. As particles heated up between their softening temperature and glass transition temperature, the particles interacted with each other more and more. Other research groups have previously suspected that glass transition temperature drops with decreases in particle size decreases because of differences in particle mobility, but they could not observe it directly.

“Using different method and instruments, we analyzed our data at different temperatures and actually verified there is something on the polymer nanoparticle surface that is more mobile compared to its core,” he said.

By studying interactions between the nanoparticles, the team also uncovered their elastic modulus, or stiffness.

Next up, Kim plans to use this information to build a nanoparticle film that can govern the propagation of sound waves.

Eric Furst, professor and chair of the Department of Chemical and Biomolecular Engineering at UD, is also a corresponding author on the paper.

“Hojin took the lead on this project and achieved results beyond what I could have predicted,” said Furst. “He exemplifies excellence in doctoral engineering research at Delaware, and I can’t wait to see what he does next.”

Story Source:

Materials provided by University of DelawareNote: Content may be edited for style and length.


Journal Reference:

  1. Hojin Kim, Yu Cang, Eunsoo Kang, Bartlomiej Graczykowski, Maria Secchi, Maurizio Montagna, Rodney D. Priestley, Eric M. Furst, George Fytas. Direct observation of polymer surface mobility via nanoparticle vibrationsNature Communications, 2018; 9 (1) DOI: 10.1038/s41467-018-04854-w

Quantum Dots (LE) Create Carbon-Bonds as effectively as the rare-metal catalysts = Low Cost Synthesis of Pharmaceuticals, Fine and Argo-Chemicals


lightemittinA quantum dot has the chemical and photo stability of minerals, but has a layer of organic molecules on the outside that “allows it to be manipulated just as you would manipulate small molecules in solution. You can spray them, you can coat …more

At one time you could wander through the labs of pharmaceutical companies and hardly ever see light being used to mediate chemical reactions. Now “photoredox catalysis” has become an essential way to synthesize novel organic compounds.

This type of chemistry may soon be used even more widely—and less expensively— thanks to University of Rochester researchers.

In a paper published recently in the Journal of the American Chemical Society, the labs of Todd Krauss and Daniel Weix demonstrate for the first time how light emitting can be used as photoredox catalysts to create .

Moreover, the researchers— including Jill Caputo ’16 (PhD) and Norman Zhao ’17 from Weix’s lab and Leah Frenette ’14 (MS) and Kelly Sowers ’16 (PhD) from Krauss’s group—showed that quantum dots create these bonds just as effectively as the rare-metal catalysts now used in photoredox chemistry, such as ruthenium and iridium.Efficient-and-Limiting-Reactions-in-Aqueous_14_jacs_Palomares_Llobet

“The potential impact could be great,” says Weix, an associate professor in the Department of Chemistry. Carbon-carbon bonds are the basic building blocks for numerous molecular forms, many of them essential to biological functions.

The quantum dots have potential applications in the synthesis of pharmaceuticals, fine chemicals, and agro-chemicals. “These are markets where people are most actively searching for chemical compounds with new properties,” Weix says.

Quantum dots are tiny semiconductor crystals. Containing some thousands of atoms, they “live in a world between bulk minerals—like a chunk of rock, with billions upon billions of atoms—and a single molecule with only 10 or 20 atoms,” says Krauss, a professor of chemistry and chair of the department. But, he adds, “quantum dots have properties of both the molecular and the macroscopic world.”

For example, a quantum dot has the chemical and photo stability of minerals, but has a layer of organic molecules on the outside that “allows it to be manipulated just as you would manipulate small molecules in solution. You can spray them, you can coat them on surfaces, you can mix them, and do all different chemistries with them,” Krauss says.

Until now, most chemists have studied quantum dots for their basic properties, with applications primarily limited to displays such as televisions. This particular discovery originated in prior work at Rochester that demonstrated quantum dots could be excellent catalysts for creating hydrogen-hydrogen bonds for solar fuel applications.

NPs Applications 353d9d7

For this study, Krauss and Weix tested the effectiveness of cadmium/selenium (CdSe) quantum dots in creating carbon-carbon bonds by using five well-known photoredox reactions. They found that a single-sized, easily made CdSe quantum dot could replace several different catalysts now used, with equal or greater efficiency.

“The chemistry ranged from more simple reactions, where the quantum dot served as the sole redox mediator [sole agent transferring an electron], to reactions involving one or more cocatalysts, with a lot of reagents in the flask,” Weix says. “There was a concern in the beginning whether the dots would survive in this chemical stew, but they did.”

Weix cautions that paper represents only a “first step towards showing you could use to replace other catalysts.” The dots may need to be further refined to be suitable for industrial applications.

But he’s excited about their potential, and momentum appears to be building. He notes that concurrent with their work, colleagues at Northwestern made important strides toward improving quantum dot catalysts. Weix further pointed to related photochemical work with nanocrystaline titanium dioxide (TiO2) from researchers at the University of Ottawa and the University of Wisconsin.

“We, and others, have so far looked at how quantum dots would perform in reactions that were reasonably well studied, because this is a new and we wanted to compare it to what came before,” Weix says. “The next step is to look at what these things do that nothing else can do. That’s the promise of the future.”

Explore further: Finding needles in chemical haystacks

More information: Jill A. Caputo et al. General and Efficient C–C Bond Forming Photoredox Catalysis with Semiconductor Quantum Dots, Journal of the American Chemical Society (2017). DOI: 10.1021/jacs.6b13379

 

MIT: Advanced thin-film technique could deliver long-lasting medication: 1 in 4 Seniors could benefit


Paula Hammond MIT 1-implantable-film-MITMIT professor Paula Hammond (right) and Bryan Hsu PhD’ 14 have developed a nanoscale film that can be used to deliver medication, either directly through injections, or by coating implantable medical devices. Photo: Dominick Reuter

Nanoscale, biodegradable drug-delivery method could provide a year or more of steady doses.

About one in four older adults suffers from chronic pain. Many of those people take medication, usually as pills. But this is not an ideal way of treating pain: Patients must take medicine frequently, and can suffer side effects, since the contents of pills spread through the bloodstream to the whole body.

Now researchers at MIT have refined a technique that could enable pain medication and other drugs to be released directly to specific parts of the body — and in steady doses over a period of up to 14 months.  The method uses biodegradable, nanoscale “thin films” laden with drug molecules that are absorbed into the body in an incremental process.

“It’s been hard to develop something that releases [medication] for more than a couple of months,” says Paula Hammond, the David H. Koch Professor in Engineering at MIT, and a co-author of a new paper on the advance. “Now we’re looking at a way of creating an extremely thin film or coating that’s very dense with a drug, and yet releases at a constant rate for very long time periods.”

In the paper, published today in the Proceedings of the National Academy of Sciences, the researchers describe the method used in the new drug-delivery system, which significantly exceeds the release duration achieved by most commercial controlled-release biodegradable films.

“You can potentially implant it and release the drug for more than a year without having to go in and do anything about it,” says Bryan Hsu PhD ’14, who helped develop the project as a doctoral student in Hammond’s lab. “You don’t have to go recover it. Normally to get long-term drug release, you need a reservoir or device, something that can hold back the drug. And it’s typically nondegradable. It will release slowly, but it will either sit there and you have this foreign object retained in the body, or you have to go recover it.”

Layer by layer

The paper was co-authored by Hsu, Myoung-Hwan Park of Shamyook University in South Korea, Samantha Hagerman ’14, and Hammond, whose lab is in the Koch Institute for Integrative Cancer Research at MIT.

The research project tackles a difficult problem in localized drug delivery: Any biodegradable mechanism intended to release a drug over a long time period must be sturdy enough to limit hydrolysis, a process by which the body’s water breaks down the bonds in a drug molecule. If too much hydrolysis occurs too quickly, the drug will not remain intact for long periods in the body. Yet the drug-release mechanism needs to be designed such that a drug molecule does, in fact, decompose in steady increments.

To address this, the researchers developed what they call a “layer-by-layer” technique, in which drug molecules are effectively attached to layers of thin-film coating. In this specific case, the researchers used diclofenac, a nonsteroidal anti-inflammatory drug that is often prescribed for osteoarthritis and other pain or inflammatory conditions. They then bound it to thin layers of poly-L-glutamatic acid, which consists of an amino acid the body reabsorbs, and two other organic compounds. The film can be applied onto degradable nanoparticles for injection into local sites or used to coat permanent devices, such as orthopedic implants.

In tests, the research team found that the diclofenac was steadily released over 14 months. Because the effectiveness of pain medication is subjective, they evaluated the efficacy of the method by seeing how well the diclofenac blocked the activity of cyclooxygenase (COX), an enzyme central to inflammation in the body.

“We found that it remains active after being released,” Hsu says, meaning that the new method does not damage the efficacy of the drug. Or, as the paper notes, the layer-by-layer method produced “substantial COX inhibition at a similar level” to pills.

The method also allows the researchers to adjust the quantity of the drug being delivered, essentially by adding more layers of the ultrathin coating.

A viable strategy for many drugs

Hammond and Hsu note that the technique could be used for other kinds of medication; an illness such as tuberculosis, for instance, requires at least six months of drug therapy.

“It’s not only viable for diclofenac,” Hsu says. “This strategy can be applied to a number of drugs.”

Indeed, other researchers who have looked at the paper say the potential medical versatility of the thin-film technique is of considerable interest.

“I find it really intriguing because it’s broadly applicable to a lot of systems,” says Kathryn Uhrich, a professor in the Department of Chemistry and Chemical Biology at Rutgers University, adding that the research is “really a nice piece of work.”

To be sure, in each case, researchers will have to figure out how best to bind the drug molecule in question to a biodegradable thin-film coating. The next steps for the researchers include studies to optimize these properties in different bodily environments and more tests, perhaps with medications for both chronic pain and inflammation.

A major motivation for the work, Hammond notes, is “the whole idea that we might be able to design something using these kinds of approaches that could create an [easier] lifestyle” for people with chronic pain and inflammation.

Hsu and Hammond were involved in all aspects of the project and wrote the paper, while Hagerman and Park helped perform the research, and Park helped analyze the data.

The research described in the paper was supported by funding from the U.S. Army and the U.S. Air Force.