Magnetic Nanoparticles ease Removal of ‘microcontaminants’ from Wastewater


efficientremMany wastewater treatment plants do not completely remove chemical substances from wastewater. Credit: Symbol image: Shutterstock

Microcontaminants place a considerable burden on our water courses, but removing them from wastewater requires considerable technical resources. Now, ETH researchers have developed an approach that allows the efficient removal of these problematic substances.

In our , we all use a multitude of chemical substances, including cosmetics, medications, contraceptive pills, plant fertilisers and detergents—all of which help to make our lives easier. However, the use of such products has an adverse effect on the environment, because many of them cannot be fully removed from wastewater at today’s treatment plants. As , they ultimately end up in the environment, where they place a burden on fauna and flora in our water courses.

As part of a revision of the Waters Protection Act, parliament therefore decided in 2014 to fit an additional purification stage to selected water treatment plants by 2040 with a view to removing microcontaminants. Although the funding for this has in principle been secured, the project presents a challenge for plant operators because it is only possible to remove the critical substances using complex procedures, which are typically based on ozone, activated carbon or light.

Nanoparticles aid degradation

Now, researchers at ETH Zurich’s Institute of Robotics and Intelligent Systems have developed an elegant approach that could allow these substances to be removed more easily. Using multiferroic , they have succeeded in inducing the decomposition of chemical residues in contaminated water. Here, the nanoparticles are not directly involved in the chemical reaction but rather act as a catalyst, speeding up the conversion of the substances into harmless compounds.

“Nanoparticles such as these are already used as a catalyst in  in numerous areas of industry,” explains Salvador Pané, who has played a key role in advancing this research in his capacity as Senior Scientist. “Now, we’ve managed to show that they can also be useful for wastewater purification.”

Efficient removal of problem substances
Based on the example of various organic pigments, such as those used in the textile industry, the researchers are able to demonstrate the effectiveness of their approach. Picture left before treatment, right after treatment. Credit: ETH Zurich / Fajer Mushtaq

An 80 percent reduction

For their experiments, the researchers used aqueous solutions containing trace quantities of five common medications. The experiments confirmed that the nanoparticles can reduce the concentration of these substances in water by at least 80 percent. Fajer Mushtaq, a doctoral student in the group, underlines the importance of these results: “These  also included two compounds that can’t be removed using the conventional ozone-based method.”

“Remarkably, we’re able to precisely tune the catalytic output of the nanoparticles using magnetic fields,” explains Xiangzhong Chen, a postdoc who also participated in the project. The particles have a cobalt ferrite core surrounded by a bismuth ferrite shell. If an external alternating magnetic field is applied, some regions of the particle surface adopt positive electric charges, while others become negatively charged. These charges lead to the formation of reactive oxygen species in water, which break down the organic pollutants into harmless compounds. The magnetic nanoparticles can then be easily removed from water using , says Chen.

Positive responses from industry

The researchers believe that the new approach is a promising one, citing its easier technical implementation than that of ozone-based , for example. “The wastewater industry is very interested in our findings,” says Pané.

However, it will be some time before the method can be applied in practice, as it has been investigated only in the laboratory so far. At any rate, Mushtaq says that approval has already been given for a BRIDGE project jointly funded by the Swiss National Science Foundation and Innosuisse with a view to support the method’s transfer into practical applications. In addition, plans are already in place to establish a spin-off company, in which the researchers intend to develop their idea to market maturity.


Explore further

Chemists suggest a new method to synthesise titanium nanoparticles for water purification


More information: Fajer Mushtaq et al. Magnetoelectrically Driven Catalytic Degradation of Organics, Advanced Materials (2019). DOI: 10.1002/adma.201901378

Journal information: Advanced Materials
Provided by ETH Zurich
Advertisements

Platinum Nanoparticles Offer ‘Selective Treatment’ of Liver Cancer Cells


1-platinumnano
Non-oxidised platinum nanoparticles have virtually no toxic effect on normal cells (bottom left). Once inside liver cancer cells (top right), the platinum is oxidised, releasing its toxic effect. Credit: ETH Zurich / Helma Wennemers

Researchers at ETH Zurich recently demonstrated that platinum nanoparticles can be used to kill liver cancer cells with greater selectivity than existing cancer drugs.

In recent years, the number of targeted  has continued to rise. However, conventional chemotherapeutic agents still play an important role in cancer treatment. These include -based  that attack and kill . But these agents also damage healthy tissue and cause severe side effects. Researchers at ETH Zurich have now identified an approach that allows for a more selective cancer treatment with drugs of this kind.

Platinum can be cytotoxic when oxidised to platinum(II) and occurs in this form in conventional platinum-based chemotherapeutics. Non-oxidised platinum(0), however, is far less toxic to cells. Based on this knowledge, a team led by Helma Wennemers, Professor at the Laboratory of Organic Chemistry, and Michal Shoshan, a postdoc in her group, looked for a way to introduce platinum(0) into the , and only then for it to be oxidised to platinum(II). To this end, they used non-oxidised platinum nanoparticles, which first had to be stabilized with a peptide. They screened a library containing thousands of peptides to identify a peptide suitable for producing platinum nanoparticles (2.5 nanometres in diameter) that are stable for years.

Oxidised inside the cell

Tests with cancer cell cultures revealed that the platinum(0) nanoparticles penetrate into cells. Once inside the specific environment of liver cancer cells, they become oxidised, triggering the cytotoxic effect of platinum(II).

Studies with ten different types of human cells also showed that the toxicity of the peptide-coated nanoparticles was highly selective to liver cancer cells. They have the same toxic effect as Sorafenib, the most common drug used to treat primary liver tumours today. However, the nanoparticles are more selective than Sorafenib and significantly more so than the well-known chemotherapeutic Cisplatin. It is therefore conceivable that the nanoparticles will have fewer side effects than conventional medication.

Joining forces with ETH Professor Detlef Günther and his research group, Wennemers and her team were able to determine the platinum content inside the cells and their nuclei using special mass spectrometry. They concluded that the platinum content in the nuclei of liver cancer cells was significantly higher than, for instance, in colorectal cancer . The authors believe that the platinum(II) ions – produced by oxidation of the  in the  – enter the nucleus, and there release their toxicity.

“We are still a very long and uncertain way away from a new drug, but the research introduced a new approach to improve the selectivity of drugs for certain types of  – by using a selective activation process specific to a given cell type,” Wennemers says. Future research will expand the chemical properties of the nanoparticles to allow for greater control over their biological effects.

 Explore further: Gold Nanoparticles Delivery Platinum Warheads to Tumors

More information: Michal S. Shoshan et al. Peptide-Coated Platinum Nanoparticles with Selective Toxicity against Liver Cancer Cells, Angewandte Chemie International Edition (2018). DOI: 10.1002/anie.201813149

Read more at: https://phys.org/news/2019-02-platinum-nanoparticles-treatment-liver-cancer.html#jCp

Super-stable antinomy carbon composite anodes to boost potassium-ion battery storage performance


id51930_1

Potassium-ion batteries (PIBs) have been considered as promising alternatives to lithium-ion batteries due to the rich natural abundance of potassium (K) and similar redox potential with Li+/Li.

However, due to the large K ion radius and slow reaction dynamics, the previously reported PIB anode materials (carbon-based materials, alloy-based anodes such as tin and antimony, metal oxides, etc.) suffer from a low capacity and fast capacity decay.
In order to achieve a high capacity and excellent cycle stability for K storage process, rational design of the electrode materials and proper selection of the electrolytes should be considered simultaneously.
Recently, two research teams led by Prof. Chunsheng Wang and Prof. Michael R. Zachariah from the University of Maryland, College Park, have designed and fabricated a novel antimony (Sb) carbon composite PIB anode via a facile and scalable electrospray-assisted strategy and found that this anode delivered super high specific capacities as well as cycling stability in a highly concentrated electrolyte (4M KTFSI/EC+DEC).
This work has been published in Energy and Environmental Science (“Super Stable Antimony-carbon composite anodes for potassium-ion batteries”).

 

id51930_1
Figure 1. Schematic illustration of electrospray-assisted strategy for fabricating antimony @carbon sphere network electrode materials. (© Royal Society of Chemistry)
We have successfully fabricated a novel antimony carbon composite with small Sb nanoparticles uniformly confined in the carbon sphere network (Sb@CSN) via a facile and scalable electrospray-assisted strategy.
Such a unique nanostructure can effectively mitigate the deleteriously mechanical damage from large volume changes and provide a highly conductive framework for fast electron transport during alloy/de-alloy cycling process.
Alongside the novel structural design of the anode material, formation of a robust solid-electrolyte-interphase (SEI) on the anode is crucially important to achieve its long-term cycling stability.
The formation of a robust SEI on the anode material is determined by both the surface chemistries of active electrode materials as well as electrolyte compositions such as salt anion types and concentrations.
Therefore, designing a proper electrolyte is extremely important for the anode to achieve a high cycling stability.
In our study, we have for the first time developed a stable and safe electrolyte of highly concentrated 4M KTFSI/EC+DEC for PIBs to promote the formation of a stable and robust KF-rich SEI layer on an Sb@CSN anode, which guarantees stable electrochemical alloy/de-alloy reaction dynamics during long-time cycling process.
Cycling performance of antimony carbon sphere network electrode materials
Figure 2. Cycling performance of antimony carbon sphere network electrode materials at 200mA/g current density in the highly concentrated electrolyte (4M KTFSI/EC+DEC). (© Royal Society of Chemistry)
In the optimized 4M KTFSI/EC+DEC electrolyte, the Sb@CSN composite delivers excellent reversible capacity of 551 mAh/g at 100 mA/g over 100 cycles with a capacity decay of 0.06% per cycle from the 10st to 100th cycling and 504 mAh/g even at 200 mA/g after 220 cycling. This demonstrates the best electrochemical performances with the highest capacity and longest cycle life when compared with all K-ion batteries anodes reported to date.
The electrochemical reaction mechanism was further revealed by density functional theory (DTF) calculation to support such excellent Potassium-storage properties.
Capacity comparison of Sb@CSN anode with previous reported anodes in potassium ion batteries
Figure 3. Capacity comparison of Sb@CSN anode with previous reported anodes in potassium ion batteries. (© Royal Society of Chemistry)
In conclusion, these outstanding performances should be attributed to the novel nanostructure of Sb nanoparticles uniformly encapsulated into conductive carbon network and the formation of a more stable and robust KF-rich SEI layer on Sb@CSN in the optimized 4M KTFSI electrolyte.
These encouraging results will significantly promote the deep understanding of the fundamental electrochemistry in Potassium-ion batteries as well as rational development of efficient electrolyte systems for next generation high-performance Potassium-ion batteries.
Yong Yang, Research Associate, Prof. Zachariah Research Group, Department of Chemical and Environmental Engineering, University of California, Riverside

U of Manchester – Nobel-prize Winning Chemistry for Clean Energy Breakthrough used to Reduce the cost of Fuel Cells used in Renewable Energy Vehicles – Reduce harmful emissions from ICE’s


nobelenergynanoparticlesCredit: CC0 Public Domain

Scientists have used a Nobel-prize winning chemistry technique on a mixture of metals to potentially reduce the cost of fuel cells used in electric cars and reduce harmful emissions from conventional vehicles.

The researchers have translated a biological , which won the 2017 Nobel Chemistry Prize, to reveal atomic scale chemistry in metal . These materials are one of the most effective catalysts for energy converting systems such as fuel cells. It is the first time this technique has been for this kind of research.

The particles have a complex star-shaped geometry and this new work shows that the edges and corners can have different chemistries which can now be tuned to reduce the cost of batteries and catalytic convertors.

The 2017 Nobel Prize in Chemistry was awarded to Joachim Frank, Richard Henderson and Jacques Dubochet for their role in pioneering the technique of single particle reconstruction. This electron microscopy technique has revealed the structures of a huge number of viruses and proteins but is not usually used for metals.

Now, a team at the University of Manchester, in collaboration with researchers at the University of Oxford and Macquarie University, have built upon the Nobel Prize winning technique to produce three dimensional elemental maps of metallic nanoparticles consisting of just a few thousand atoms.

Published in the journal Nano Letters, their research demonstrates that it is possible to map different elements at the nanometre scale in three dimensions, circumventing damage to the particles being studied.

Metal nanoparticles are the primary component in many catalysts, such as those used to convert toxic gases in car exhausts. Their effectiveness is highly dependent on their structure and chemistry, but because of their incredibly small structure,  are required in order to provide image them. However, most imaging is limited to 2-D projections.

“We have been investigating the use of tomography in the electron microscope to map elemental distributions in three dimensions for some time,” said Professor Sarah Haigh, from the School of Materials, University of Manchester. “We usually rotate the particle and take images from all directions, like a CT scan in a hospital, but these particles were damaging too quickly to enable a 3-D image to be built up. Biologists use a different approach for 3-D imaging and we decided to explore whether this could be used together with spectroscopic techniques to map the different elements inside the nanoparticles.”

“Like ‘single particle reconstruction’ the technique works by imaging many particles and assuming that they are all identical in structure, but arranged at different orientations relative to the electron beam. The images are then fed in to a computer algorithm which outputs a three dimensional reconstruction.”

In the present study the new 3-D chemical imaging method has been used to investigate platinum-nickel (Pt-Ni) metal nanoparticles.

Lead author, Yi-Chi Wang, also from the School of Materials, added: “Platinum based nanoparticles are one of the most effective and widely used catalytic materials in applications such as fuel cells and batteries. Our new insights about the 3-D local chemical distribution could help researchers to design better catalysts that are low-cost and high-efficiency.”

“We are aiming to automate our 3-D chemical reconstruction workflow in the future”, added author Dr. Thomas Slater.”We hope it can provide a fast and reliable method of imaging nanoparticle populations which is urgently needed to speed up optimisation of nanoparticle synthesis for wide ranging applications including biomedical sensing, light emitting diodes, and solar cells.”

 Explore further: Video: The 2017 Nobel Prize in Chemistry: Cryo-electron microscopy explained

More information: Yi-Chi Wang et al. Imaging Three-Dimensional Elemental Inhomogeneity in Pt–Ni Nanoparticles Using Spectroscopic Single Particle Reconstruction, Nano Letters (2019). DOI: 10.1021/acs.nanolett.8b03768

 

Brookhaven National Laboratory – Searching for More Cost Efficient Catalysts for Hydrogen Fuel Cells – Illuminating Nanoparticle Growth With X-Rays


brookhaven fuel cell research 189306_web
Brookhaven Lab scientists Mingyuan Ge, Iradwikanari Waluyo, and Adrian Hunt are pictured left to right at the IOS beamline, where they studied the growth pathway of an efficient catalyst for hydrogen fuel cells. Credit: Brookhaven National Laboratory

Hydrogen fuel cells are a promising technology for producing clean and renewable energy, but the cost and activity of their cathode materials is a major challenge for commercialization. Many fuel cells require expensive platinum-based catalysts–substances that initiate and speed up chemical reactions–to help convert renewable fuels into electrical energy. To make hydrogen fuel cells commercially viable, scientists are searching for more affordable catalysts that provide the same efficiency as pure platinum.

“Like a battery, hydrogen fuel cells convert stored chemical energy into electricity. The difference is that you’re using a replenishable fuel so, in principle, that ‘battery’ would last forever,” said Adrian Hunt, a scientist at the National Synchrotron Light Source II(NSLS-II), a U.S. Department of Energy (DOE) Office of Science User Facility at DOE’s Brookhaven National Laboratory. “Finding a cheap and effective catalyst for hydrogen fuel cells is basically the holy grail for making this technology more feasible.”

Taking part in this worldwide search for fuel cell cathode materials, researchers at the University of Akron developed a new method of synthesizing catalysts from a combination of metals–platinum and nickel–that form octahedral (eight-sided) shaped nanoparticles. While scientists have identified this catalyst as one of the most efficient replacements for pure platinum, they have not fully understood why it grows in an octahedral shape. To better understand the growth process, the researchers at the University of Akron collaborated with multiple institutions, including Brookhaven and its NSLS-II.

brookhaven fc 6-scientistsbo

Schematic diagram of the oxygen reduction reaction (reduction of O2 into H2O) on the Pt(110) surface of the PtPb/Pt nanoplates, with purple representing Pt atoms and orange representing Pb atoms. Credit: Brookhaven National Laboratory

“Understanding how the faceted catalyst is formed plays a key role in establishing its structure-property correlation and designing a better catalyst,” said Zhenmeng Peng, principal investigator of the catalysis lab at the University of Akron. “The growth process case for the platinum-nickel system is quite sophisticated, so we collaborated with several experienced groups to address the challenges. The cutting-edge techniques at Brookhaven National Lab were of great help to study this research topic.”

Using the ultrabright x-rays at NSLS-II and the advanced capabilities of NSLS-II’s In situ and Operando Soft X-ray Spectroscopy (IOS) beamline, the researchers revealed the chemical characterization of the catalyst’s growth pathway in real time. Their findings are published in Nature Communications.

“We used a research technique called ambient-pressure x-ray photoelectron spectroscopy (AP-XPS) to study the surface composition and chemical state of the metals in the nanoparticles during the growth reaction,” said Iradwikanari Waluyo, lead scientist at IOS and a co-corresponding author of the research paper. “In this technique, we direct x-rays at a sample, which causes electrons to be released. By analyzing the energy of these electrons, we are able to distinguish the chemical elements in the sample, as well as their chemical and oxidation states.”

Hunt, who is also an author on the paper, added, “It is similar to the way sunlight interacts with our clothing. Sunlight is roughly yellow, but once it hits a person’s shirt, you can tell whether the shirt is blue, red, or green.”

Rather than colors, the scientists were identifying chemical information on the surface of the catalyst and comparing it to its interior. They discovered that, during the growth reaction, metallic platinum forms first and becomes the core of the nanoparticles. Then, when the reaction reaches a slightly higher temperature, platinum helps form metallic nickel, which later segregates to the surface of the nanoparticle. In the final stages of growth, the surface becomes roughly an equal mixture of the two metals. This interesting synergistic effect between platinum and nickel plays a significant role in the development of the nanoparticle’s octahedral shape, as well as its reactivity.

“The nice thing about these findings is that nickel is a cheap material, whereas platinum is expensive,” Hunt said. “So, if the nickel on the surface of the nanoparticle is catalyzing the reaction, and these nanoparticles are still more active than platinum by itself, then hopefully, with more research, we can figure out the minimum amount of platinum to add and still get the high activity, creating a more cost-effective catalyst.”

The findings depended on the advanced capabilities of IOS, where the researchers were able to run the experiments at gas pressures higher than what is usually possible in conventional XPS experiments.

“At IOS, we were able to follow changes in the composition and chemical state of the nanoparticles in real time during the real growth conditions,” said Waluyo.

Additional x-ray and electron imaging studies completed at the Advanced Photon Source (APS) at DOE’s Argonne National Laboratory–another DOE Office of Science User Facility–and University of California-Irvine, respectively, complemented the work at NSLS-II.

“This fundamental work highlights the significant role of segregated nickel in forming the octahedral-shaped catalyst. We have achieved more insight into shape control of catalyst nanoparticles,” Peng said. “Our next step is to study catalytic properties of the faceted nanoparticles to understand the structure-property correlation.”

MIT – Nanoparticles Deliver Potential Arthritis Treatment and could Prevent Cartilage Breakdown – Potential to Heal Tissue Damaged by Osteoarthritis


MIT-Cartilage-Drug-Delivery-01_0

Six days after treatment with IGF-1 carried by dendrimer nanoparticles (blue), the particles have penetrated through the cartilage of the knee joint. Image: Brett Geiger and Jeff Wyckof

Courtesy of MIT News

Injectable material made of nanoscale particles can deliver arthritis drugs throughout cartilage.

Osteoarthritis, a disease that causes severe joint pain, affects more than 20 million people in the United States. Some drug treatments can help alleviate the pain, but there are no treatments that can reverse or slow the cartilage breakdown associated with the disease.

In an advance that could improve the treatment options available for osteoarthritis, MIT engineers have designed a new material that can administer drugs directly to the cartilage. The material can penetrate deep into the cartilage, delivering drugs that could potentially heal damaged tissue.

“This is a way to get directly to the cells that are experiencing the damage, and introduce different kinds of therapeutics that might change their behavior,” says Paula Hammond, head of MIT’s Department of Chemical Engineering, a member of MIT’s Koch Institute for Integrative Cancer Research, and the senior author of the study.

In a study in rats, the researchers showed that delivering an experimental drug called insulin-like growth factor 1 (IGF-1) with this new material prevented cartilage breakdown much more effectively than injecting the drug into the joint on its own.

Brett Geiger, an MIT graduate student, is the lead author of the paper, which appears in the Nov. 28 issue of Science Translational Medicine. Other authors are Sheryl Wang, an MIT graduate student, Robert Padera, an associate professor of pathology at Brigham and Women’s Hospital, and Alan Grodzinsky, an MIT professor of biological engineering.

Better delivery

Osteoarthritis is a progressive disease that can be caused by a traumatic injury such as tearing a ligament; it can also result from gradual wearing down of cartilage as people age. A smooth connective tissue that protects the joints, cartilage is produced by cells called chondrocytes but is not easily replaced once it is damaged.

Previous studies have shown that IGF-1 can help regenerate cartilage in animals. However, many osteoarthritis drugs that showed promise in animal studies have not performed well in clinical trials.

The MIT team suspected that this was because the drugs were cleared from the joint before they could reach the deep layer of chondrocytes that they were intended to target. To overcome that, they set out to design a material that could penetrate all the way through the cartilage.

The sphere-shaped molecule they came up with contains many branched structures called dendrimers that branch from a central core. The molecule has a positive charge at the tip of each of its branches, which helps it bind to the negatively charged cartilage. Some of those charges can be replaced with a short flexible, water-loving polymer, known as PEG, that can swing around on the surface and partially cover the positive charge. Molecules of IGF-1 are also attached to the surface.

When these particles are injected into a joint, they coat the surface of the cartilage and then begin diffusing through it. This is easier for them to do than it is for free IGF-1 because the spheres’ positive charges allow them to bind to cartilage and prevent them from being washed away. The charged molecules do not adhere permanently, however. Thanks to the flexible PEG chains on the surface that cover and uncover charge as they move, the molecules can briefly detach from cartilage, enabling them to move deeper into the tissue.

“We found an optimal charge range so that the material can both bind the tissue and unbind for further diffusion, and not be so strong that it just gets stuck at the surface,” Geiger says.

Once the particles reach the chondrocytes, the IGF-1 molecules bind to receptors on the cell surfaces and stimulate the cells to start producing proteoglycans, the building blocks of cartilage and other connective tissues. The IGF-1 also promotes cell growth and prevents cell death.

Joint repair

When the researchers injected the particles into the knee joints of rats, they found that the material had a half-life of about four days, which is 10 times longer than IGF-1 injected on its own. The drug concentration in the joints remained high enough to have a therapeutic effect for about 30 days. If this holds true for humans, patients could benefit greatly from joint injections — which can only be given monthly or biweekly — the researchers say.

In the animal studies, the researchers found that cartilage in injured joints treated with the nanoparticle-drug combination was far less damaged than cartilage in untreated joints or joints treated with IGF-1 alone. The joints also showed reductions in joint inflammation and bone spur formation.

“This is an important proof-of-concept that builds on the recent advances in the identification of anabolic growth factors with clinical promise (such as IGF-1), with promising disease-modifying results in a clinically relevant model. Delivery of growth factors using nanoparticles in a manner that sustains and improves treatments for osteoarthritis is a significant step for nanomedicines,” says Kannan Rangaramanujam, a professor of ophthalmology and co-director of the Center for Nanomedicine at Johns Hopkins School of Medicine, who was not involved in the research.

Cartilage in rat joints is about 100 microns thick, but the researchers also showed that their particles could penetrate chunks of cartilage up to 1 millimeter — the thickness of cartilage in a human joint.

“That is a very hard thing to do. Drugs typically will get cleared before they are able to move through much of the cartilage,” Geiger says. “When you start to think about translating this technology from studies in rats to larger animals and someday humans, the ability of this technology to succeed depends on its ability to work in thicker cartilage.”

The researchers began developing this material as a way to treat osteoarthritis that arises after traumatic injury, but they believe it could also be adapted to treat age-related osteoarthritis. They now plan to explore the possibility of delivering different types of drugs, such as other growth factors, drugs that block inflammatory cytokines, and nucleic acids such as DNA and RNA.

The research was funded by the Department of Defense Congressionally Funded Medical Research Program and a National Science Foundation fellowship.

North Western U: Study Provides insight into how Nanoparticles interact with Biological Systems


7-studyprovide.jpg
Computer simulation of a lipid corona around a 5-nanometer nanoparticle showing ammonium-phosphate ion pairing. Credit: Northwestern University

Personal electronic devices—smartphones, computers, TVs, tablets, screens of all kinds—are a significant and growing source of the world’s electronic waste. Many of these products use nanomaterials, but little is known about how these modern materials and their tiny particles interact with the environment and living things.

Now a research team of Northwestern University chemists and colleagues from the national Center for Sustainable Nanotechnology has discovered that when certain coated  interact with living organisms it results in new properties that cause the nanoparticles to become sticky. Fragmented  coronas form on the particles, causing them to stick together and grow into long kelp-like strands. Nanoparticles with 5-nanometer diameters form long structures that are microns in size in solution. The impact on cells is not known.

“Why not make a particle that is benign from the beginning?” said Franz M. Geiger, professor of chemistry in Northwestern’s Weinberg College of Arts and Sciences. He led the Northwestern portion of the research.

“This study provides insight into the molecular mechanisms by which nanoparticles interact with biological systems,” Geiger said. “This may help us understand and predict why some /ligand coating combinations are detrimental to cellular organisms while others are not. We can use this to engineer nanoparticles that are benign by design.”

Using experiments and computer simulations, the research team studied polycation-wrapped gold nanoparticles and their interactions with a variety of bilayer membrane models, including bacteria. The researchers found that a nearly circular layer of lipids forms spontaneously around the particles. These “fragmented lipid coronas” have never been seen before.

The study points to solving problems with chemistry. Scientists can use the findings to design a better ligand coating for nanoparticles that avoids the ammonium-phosphate interaction, which causes the aggregation. (Ligands are used in nanomaterials for layering.)

The results will be published Oct. 18 in the journal Chem.

Geiger is the study’s corresponding author. Other authors include scientists from the Center for Sustainable Nanotechnology’s other institutional partners. Based at the University of Wisconsin-Madison, the center studies engineered nanomaterials and their interaction with the environment, including biological systems—both the negative and positive aspects.

“The nanoparticles pick up parts of the lipid cellular membrane like a snowball rolling in a snowfield, and they become sticky,” Geiger said. “This unintended effect happens because of the presence of the nanoparticle. It can bring lipids to places in cells where lipids are not meant to be.”

The experiments were conducted in idealized laboratory settings that nevertheless are relevant to environments found during the late summer in a landfill—at 21-22 degrees Celsius and a couple feet below ground, where soil and groundwater mix and the food chain begins.

By pairing spectroscopic and imaging experiments with atomistic and coarse-grain simulations, the researchers identified that ion pairing between the lipid head groups of biological membranes and the polycations’ ammonium groups in the nanoparticle wrapping leads to the formation of fragmented lipid coronas. These coronas engender new properties, including composition and stickiness, to the particles with diameters below 10 nanometers.

The study’s insights help predict the impact that the increasingly widespread use of engineered nanomaterials has on the nanoparticles’ fate once they enter the food chain, which many of them may eventually do.

“New technologies and mass consumer products are emerging that feature nanomaterials as critical operational components,” Geiger said. “We can upend the existing paradigm in nanomaterial production towards one in which companies design nanomaterials to be sustainable from the beginning, as opposed to risking expensive product recalls—or worse—down the road.”

 Explore further: Water matters to metal nanoparticles

More information: “Lipid Corona Formation from Nanoparticle Interactions with Bilayers,” Chem (2018). DOI: 10.1016/j.chempr.2018.09.018

 

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

Dengue fever vaccine delivered with nanotechnology targets all four virus serotypes – University of North Carolina Research


denguefeverCredit: CC0 Public Domain

The latest in a series of studies led by the Aravinda de Silva Lab at the UNC School of Medicine shows continued promise in a dengue virus vaccine delivered using nanoparticle technology.

 

Each year, an estimated 25,000 people die from dengue infections and millions more are infected. Scientists have been trying to create a  for many years, but creating an effective  is challenging due to the four different serotypes of the virus. For a person to be fully protected against dengue, they need to be vaccinated against all four serotypes at once – something current vaccines do not achieve. In their paper published in PLOS Neglected Tropical Diseases, Aravinda de Silva, Ph.D., professor of microbiology and immunology, and UNC research associate Stefan Metz, Ph.D., detail how their nanoparticle delivery platform is producing a more balanced immune  versus other vaccine delivery platforms.

To deliver the vaccine, the de Silva lab is using a nanoparticle platform produced with PRINT (Particle Replication in Non-wetting Templates) technology, which was developed by Joseph DeSimone, Ph.D., the Chancellor’s Eminent Professor of Chemistry at UNC-Chapel Hill, with an appointment in the department of pharmacology. Rather than using a killed or attenuated virus to develop a vaccine for , researchers are focusing on expressing the E protein and attaching it to  to induce good immune responses. In previous studies of monovalent vaccines, they have shown that the platform can induce protective immune response in individual serotypes. Their latest study of a tetravalent vaccine shows the response in all four serotypes at the same time.

“We are also seeing a more balanced immune response for each of the serotypes, which means the quality of neutralizing antibodies created is leading to a better overall protective reaction for the patient,” said Metz, the paper’s lead author.

The de Silva lab performed the experiments on their Dengue vaccine in close collaboration with co-author Shaomin Tian, Ph.D., research assistant professor in the department of microbiology and immunology. The proteins used in the experiments were produced by the UNC Protein Expression and Purification (PEP) core.

The de Silva lab’s next steps include optimizing the technique they use to attach the E protein to the nanoparticle. This work will be extremely important when trying to create a vaccine that induces consistently strong protective immune responses.

 Explore further: Nanoparticle vaccinates mice against dengue fever

More information: Stefan W. Metz et al. Nanoparticle delivery of a tetravalent E protein subunit vaccine induces balanced, type-specific neutralizing antibodies to each dengue virus serotype, PLOS Neglected Tropical Diseases (2018). DOI: 10.1371/journal.pntd.0006793

Rice University: NEWT (Nano Enabled Water Treatment) Reusable water-treatment particles effectively eliminate BPA


Rice U reusablewate water
Rice University researchers have enhanced micron-sized titanium dioxide particles to trap and destroy BPA, a water contaminant with health implications. Cyclodextrin molecules on the surface trap BPA, which is then degraded by reactive …more

Rice University scientists have developed something akin to the Venus’ flytrap of particles for water remediation.

The research is detailed in the American Chemical Society journal Environmental Science & Technology.

BPA is commonly used to coat the insides of food cans, bottle tops and  supply lines, and was once a component of baby bottles. While BPA that seeps into food and drink is considered safe in low doses, prolonged exposure is suspected of affecting the health of children and contributing to high blood pressure.

The good news is that reactive oxygen species (ROS) – in this case, hydroxyl radicals – are bad news for BPA. Inexpensive titanium dioxide releases ROS when triggered by ultraviolet light. But because oxi-dating molecules fade quickly, BPA has to be close enough to attack.

That’s where the trap comes in.

Close up, the spheres reveal themselves as flower-like collections of titanium dioxide petals. The supple petals provide plenty of surface area for the Rice researchers to anchor cyclodextrin molecules.

Reusable water-treatment particles effectively eliminate BPA
“Petals” of a titanium dioxide sphere enhanced with cyclodextrin as seen under a scanning electron microscope. When triggered by ultraviolet light, the spheres created at Rice University are effective at removing bisphenol A contaminants from water. Credit: Alvarez Lab

Cyclodextrin is a benign sugar-based molecule often used in food and drugs. It has a two-faced structure, with a hydrophobic (water-avoiding) cavity and a hydrophilic (water-attracting) outer surface. BPA is also hydrophobic and naturally attracted to the cavity. Once trapped, ROS produced by the spheres degrades BPA into harmless chemicals.

In the lab, the researchers determined that 200 milligrams of the spheres per liter of contaminated water degraded 90 percent of BPA in an hour, a process that would take more than twice as long with unenhanced titanium dioxide.

0629_NEWT-log-lg-310x310The work fits into technologies developed by the Rice-based and National Science Foundation-supported Center for Nanotechnology-Enabled Water Treatment because the spheres self-assemble from titanium dioxide nanosheets.

“Most of the processes reported in the literature involve nanoparticles,” said Rice graduate student and lead author Danning Zhang. “The size of the particles is less than 100 nanometers. Because of their very small size, they’re very difficult to recover from suspension in water.”

The Rice particles are much larger. Where a 100-nanometer particle is 1,000 times smaller than a human hair, the enhanced  is between 3 and 5 microns, only about 20 times smaller than the same hair. “That means we can use low-pressure microfiltration with a membrane to get these particles back for reuse,” Zhang said. “It saves a lot of energy.”
Reusable water-treatment particles effectively eliminate BPA
Rice graduate student Danning Zhang, who led the development of a particle that attracts and degrades contaminants in water, checks a sample in a Rice environmental lab. Credit: Jeff Fitlow

Because ROS also wears down cyclodextrin, the spheres begin to lose their trapping ability after about 400 hours of continued ultraviolet exposure, Zhang said. But once recovered, they can be easily recharged.

“This new material helps overcome two significant technological barriers for photocatalytic water treatment,” Alvarez said. “First, it enhances treatment efficiency by minimizing scavenging of ROS by non-target constituents in water. Here, the ROS are mainly used to destroy BPA.

“Second, it enables low-cost separation and reuse of the catalyst, contributing to lower treatment cost,” he said. “This is an example of how advanced materials can help convert academic hypes into feasible processes that enhance water security.”

 Explore further: Mat baits, hooks and destroys pollutants in water

More information: Danning Zhang et al. Easily-recoverable, micron-sized TiO2 hierarchical spheres decorated with cyclodextrin for enhanced photocatalytic degradation of organic micropollutants, Environmental Science & Technology (2018). DOI: 10.1021/acs.est.8b04301