You Are Not A Cat, But A Cat Could Someday Help Treat Your Chronic Kidney Disease (Medicine)

Veterinary regenerative medicine can unlock doors to human disease

The Wake Forest Institute for Regenerative Medicine is investigating how cats with chronic kidney disease could someday help inform treatment for humans.

In humans, treatment for chronic kidney disease — a condition in which the kidneys are damaged and cannot filter blood as well as they should — focuses on slowing the progression of the organ damage. The condition can progress to end-stage kidney failure, which is fatal without dialysis or a kidney transplant. An estimated 37 million people in the US suffer from chronic kidney disease, according to the Centers for Disease Control.

The American Veterinary Medical Association estimates there are about 58 million cats in the United States. Chronic kidney disease affects 30-50% of cats age 15 years or older. The fibrosis or scarring that occurs as a result of the disease is a common final pathway for kidney disease in both animals and people. For cats, end-stage kidney disease has no effective cure.

In a new study published online by Frontiers in Veterinary Science in the Veterinary Regenerative Medicine platform, the WFIRM research team set out to test the effects of a cell-derived molecular therapy to treat kidney fibrosis in cats. Regenerative therapies using stem cells and vascular fractions have been tested, but the collection of cells or cell fractions is expensive, time consuming, and requires advanced cell processing capabilities not available in most veterinary general practices.

Alternatively, “The use of cell-based molecules to treat kidney fibrosis may be a promising approach,” said lead author Julie Bennington, DVM, a WFIRM research fellow and PhD candidate. “Current treatments include pharmaceutical therapies and dietary management to slow disease progression and increase longevity, and alternatives are needed.”

In this study, authors used a cell-signaling chemokine — CXCL12 — that is produced by cells and stimulates tissue regeneration. Recombinant human CXCL12 is commercially available, inexpensive, and has been shown to reduce fibrosis in rodent models of chronic kidney disease.

The goal of this study was to test the safety, feasibility, and efficacy of ultrasound-guided intra-renal CXCL12 injection in cats with chronic kidney fibrosis, first in a preclinical cat model, and, then in a pilot study in cats that may have early kidney disease.

“Results of these studies together show that intra-renal injection of CXCL12 may be a potential new therapy to treat early kidney disease in cats with a capability for widespread use,” said co-author Koudy Williams, DVM, also of WFIRM. “Further clinical evaluations are needed.”

Piedmont Animal Health, the company that funded the research, is preparing to set up a clinical pilot study in the US, and Bennington will serve as a consultant.

WFIRM Director Anthony Atala, MD, said this research is a good example of “how a condition like chronic kidney disease, common to both dogs and cats, can be studied and potentially applied to the disease in humans.”

Additional co-authors include: Shannon Lankford, Renata Magalhaes, Douglas Shankle, all of WFIRM; Jason Fanning of Wake Forest University; Gopal Badlani, MD, of Wake Forest Baptist Health Urology; and Cucu Kartini, Irma Suparto, Winda Kusumawardhani, M A. Putra, and Silmi Mariya, all of Indonesia.

Featured image: Intraoperative images during I/R injury surgery with vascular clamps occluding left renal artery and left renal vein and purple discoloration of the kidney. Clamps remained in place for 65 min and then were released restoring renal blood flow that was confirmed using a Doppler probe to detect renal artery pulsation. © Bennington et al.


Reference: Julie Bennington, Shannon Lankford et al., “Chemokine Therapy in Cats With Experimental Renal Fibrosis and in a Kidney Disease Pilot Study”, Front. Vet. Sci., 04 March 2021 | https://doi.org/10.3389/fvets.2021.646087


Provided by Wake Forest Baptist Medical Center

Astronomers Detect A Black Hole On The Move (Astronomy)

Scientists have long theorized that supermassive black holes can wander through space—but catching them in the act has proven difficult.

Now, researchers at the Center for Astrophysics | Harvard & Smithsonian have identified the clearest case to date of a supermassive black hole in motion. Their results are published today in The Astrophysical Journal.

“We don’t expect the majority of supermassive black holes to be moving; they’re usually content to just sit around,” says Dominic Pesce, an astronomer at the Center for Astrophysics who led the study. “They’re just so heavy that it’s tough to get them going. Consider how much more difficult it is to kick a bowling ball into motion than it is to kick a soccer ball — realizing that in this case, the ‘bowling ball’ is several million times the mass of our Sun. That’s going to require a pretty mighty kick.”

Pesce and his collaborators have been working to observe this rare occurrence for the last five years by comparing the velocities of supermassive black holes and galaxies.

“We asked: Are the velocities of the black holes the same as the velocities of the galaxies they reside in?” he explains. “We expect them to have the same velocity. If they don’t, that implies the black hole has been disturbed.”

For their search, the team initially surveyed 10 distant galaxies and the supermassive black holes at their cores. They specifically studied black holes that contained water within their accretion disks — the spiral structures that spin inward towards the black hole.

As the water orbits around the black hole, it produces a laser-like beam of radio light known as a maser. When studied with a combined network of radio antennas using a technique known as very long baseline interferometry (VLBI), masers can help measure a black hole’s velocity very precisely, Pesce says.

The technique helped the team determine that nine of the 10 supermassive black holes were at rest—but one stood out and seemed to be in motion.

Located 230 million light-years away from Earth, the black hole sits at the center of a galaxy named J0437+2456. Its mass is about three million times that of our Sun.

Using follow-up observations with the Arecibo and Gemini Observatories, the team has now confirmed their initial findings. The supermassive black hole is moving with a speed of about 110,000 miles per hour inside the galaxy J0437+2456.

But what’s causing the motion is not known. The team suspects there are two possibilities.

“We may be observing the aftermath of two supermassive black holes merging,” says Jim Condon, a radio astronomer at the National Radio Astronomy Observatory who was involved in the study. “The result of such a merger can cause the newborn black hole to recoil, and we may be watching it in the act of recoiling or as it settles down again.”

But there’s another, perhaps even more exciting possibility: the black hole may be part of a binary system.

“Despite every expectation that they really ought to be out there in some abundance, scientists have had a hard time identifying clear examples of binary supermassive black holes,” Pesce says. “What we could be seeing in the galaxy J0437+2456 is one of the black holes in such a pair, with the other remaining hidden to our radio observations because of its lack of maser emission.”

Further observations, however, will ultimately be needed to pin down the true cause of this supermassive black hole’s unusual motion.

Co-authors of the new study are Anil Seth of the University of Utah; Jenny Greene of Princeton University; Jim Braatz, Jim Condon, and Brian Kent of the National Radio Astronomy Observatory; and Davor Krajnović of the Leibniz Institute for Astrophysics in Potsdam, Germany.

Featured image: Galaxy J0437+2456 is thought to be home to a supermassive, moving black hole. © Sloan Digital Sky Survey (SDSS).


Reference: Dominic W. Pesce, Anil C. Seth, Jenny E. Greene, James A. Braatz, James J. Condon, Brian R. Kent, and Davor Krajnović, “A Restless Supermassive Black Hole in the Galaxy J0437+2456”, The Astrophysical Journal, Volume 909, Number 2, 2021. https://iopscience.iop.org/article/10.3847/1538-4357/abde3d


Provided by Center for Astrophysics Harvard and Smithsonian


About the Center for Astrophysics | Harvard & Smithsonian

The Center for Astrophysics | Harvard & Smithsonian is a collaboration between Harvard and the Smithsonian designed to ask—and ultimately answer—humanity’s greatest unresolved questions about the nature of the universe. The Center for Astrophysics is headquartered in Cambridge, MA, with research facilities across the U.S. and around the world.

Release of Serotonin From Mast Cells Contribute To Airway Hyperresposivness in Asthma (Medicine)

In asthma, the airways become hyperresponsive. Researchers from Uppsala University have found a new mechanism that contributes to, and explains, airway hyperresponsiveness. The results are published in the scientific journal Allergy.

Some 10 per cent of Sweden’s population suffer from asthma. In asthmatics, the airways are hyperresponsive (overreactive) to various types of stimuli, such as cold air, physical exertion and chemicals. The airways become constricted, making breathing difficult.

To diagnose asthma, a “methacholine test” is commonly used to determine whether a person is showing signs of airway hyperresponsiveness. Methacholine binds to what are known as muscarinic receptors in the smooth muscle cells lining the inside of the trachea. These muscle cells then begin to contract, causing constriction of the trachea.

In the new study, the scientists show that the airway hyperresponsiveness induced by methacholine is due partly to the body’s mast cells. The research was conducted using a mouse model of asthma, where the mice were made allergic to house dust mites.

Mast cells, which are immune cells of a specific type belonging to the innate immune system, are found mainly in tissues that are in contact with the external environment, such as the airways and the skin. Because of their location and the fact that they have numerous different receptors capable of recognising parts of foreign or pathogenic substances, they react quickly and become activated. In their cytoplasm, mast cells have storage capsules, known as granules, in which some substances are stored in their active form. When the mast cell is activated, these substances can be rapidly released and provoke a physiological reaction. This plays a major part in the body’s defence against pathogens, but in asthma and other diseases where the body starts reacting against harmless substances in the environment, it becomes a problem.

In their study, the researchers were able to demonstrate that the mast cells contribute to airway hyperresponsiveness by having a receptor that recognises methacholine: muscarinic receptor-3 (M3). When methacholine binds M3, the mast cells release serotonin. This then acts on nerve cells, which in turn control the airways. Thereafter, the airways produce acetylcholine, which also acts on M3 in smooth muscle cells and makes the trachea contract even more. A vicious cycle is under way.

The scientists’ discovery also means that drugs like tiotropium, which were previously thought to work solely by blocking M3 in smooth muscle, are probably also efficacious because they prevent activation through M3 in mast cells. Accordingly, the ability of mast cells to rapidly release serotonin in response to various stimuli, thereby contributing to airway hyperresponsiveness, has been underestimated.


Reference: Mendez-Enriquez E, Alvarado-Vazquez PA, Abma W, Simonson OE, Rodin S, Feyerabend TB, Rodewald HR, Malinovschi A, Janson C, Adner M and Hallgren J. Mast cell-derived serotonin enhances methacholine-induced airway hyperresponsiveness in house dust mite-induced experimental asthma. Allergy. 2021 doi: 10.1111/all.14748


Provided by Uppsala University

Poor Survival After Heart Attack Linked to Excess Levels of Signaling Protein in Heart (Medicine)

New study by scientists at Lewis Katz School of Medicine at Temple University published online in the journal Cardiovascular Research

About 6.2 million Americans suffer from heart failure, an incurable disease with a staggering mortality rate – some 40 percent of patients die within five years of diagnosis. Heart failure is one form of heart disease, for which new therapies are desperately needed.

Now, in new work, scientists at the Lewis Katz School of Medicine (LKSOM) at Temple University identify a path to a promising novel therapeutic strategy, taking aim at a molecule in the heart known as G protein-coupled receptor kinase 5 (GRK5). In a study published online in the journal Cardiovascular Research, the scientists show in mice that reducing GRK5 levels can significantly improve survival following heart attack.

“Previous studies had found that GRK5 is elevated in patients with heart failure,” explained Claudio de Lucia, MD, PhD, an associate scientist in the Center for Translational Medicine at LKSOM and lead author on the new study. “Our new research, in mice that experienced myocardial infarction (heart attack), shows that GRK5 overexpression is associated with physiological changes in the heart that decrease cardiac function.”

Too much GRK5 in the heart was further linked to increased recruitment of immune cells into damaged heart tissue and harmful inflammation. The combination of these factors – reduced heart function and an influx of immune cells and inflammation – ultimately contributed to increased mortality in mice after heart attack.

Dr. de Lucia and colleagues, working with Walter J. Koch, PhD, W.W. Smith Endowed Chair in Cardiovascular Medicine, Professor and Chair of the Department of Pharmacology, Director of the Center for Translational Medicine at LKSOM, and senior investigator on the new study, examined GRK5 levels in the heart eight weeks after mice experienced heart attack. By that time, animals had developed a condition known as post-ischemic heart failure, in which heart function declines over time owing to reduced blood supply. Tissue damage that impairs circulation in the heart ultimately starves heart cells of the oxygen and nutrients they need to keep the heart working.

After establishing a link between increased GRK5 expression, decreased heart function, and decreased survival in the weeks following heart attack, the researchers explored the effect of manipulating GRK5 to lower its levels in the heart. To do this, they developed a GRK5 knockout mouse model, in which GRK5 expression was eliminated specifically from heart cells.

“After heart attack, our GRK5 knockout mice had much better heart function and better survival curves compared to wild-type mice with normal GRK5,” Dr. de Lucia explained. “This raises the possibility that GRK5 inhibition may be a viable therapeutic strategy in human patients, as well.”

The team’s future work will focus on GRK5 inhibitors and understanding their effects in animals with heart disease.

“Highly selective drugs that block GRK5 are already available,” Dr. de Lucia said. “Our next step is to test these agents in animal models of heart failure in order to determine their effect on cardiac function and survival.”

Dr. Koch added, “Targeting abnormal levels and activity of GRK5 would represent a totally new drug class [for heart failure] that we hope will add important and innovative value to our fight against heart disease.”

Other researchers who contributed to the study include Laurel A. Grisanti, Department of Biomedical Sciences, College of Veterinary Medicine, University of Missouri; Giulia Borghetti and Steven R. Houser, Cardiovascular Research Center, Lewis Katz School of Medicine at Temple University; Michela Piedepalumbo, Jessica Ibetti, Anna Maria Lucchese, Eric W. Barr, Rajika Roy, Ama Dedo Okyere, Haley Christine Murphy, Erhe Gao, and Douglas G. Tilley, Center for Translational Medicine, Lewis Katz School of Medicine at Temple University; Giuseppe Rengo, Department of Translational Medical Sciences, Division of Geriatrics, Federico II University, Naples, Italy.

The research was supported in part by grants from the National Institutes of Health and the American Heart Association.

Reference: Claudio de Lucia, Laurel A Grisanti, Giulia Borghetti, Michela Piedepalumbo, Jessica Ibetti, Anna Maria Lucchese, Eric W Barr, Rajika Roy, Ama Dedo Okyere, Haley Christine Murphy, Erhe Gao, Giuseppe Rengo, Steven R Houser, Douglas G Tilley, Walter J Koch, G protein-coupled receptor kinase 5 (GRK5) contributes to impaired cardiac function and immune cell recruitment in post-ischemic heart failure, Cardiovascular Research, 2021;, cvab044, https://doi.org/10.1093/cvr/cvab044


Provided by Temple University Health System

Are There Differences in the Brains of Autistic Men and Women? (Neuroscience)

Large-scale brain imaging study suggest that atypical connectivity between brain hemispheres in autism reflects a combination of biological sex-dependent (i.e., specific to male or females) and independent (i.e., common across sexes) effects

Around three times as many males are diagnosed with autism than females. This suggests that biological sex factors may play a role in the development and presentation of autism.

Studies on the neurobiology (brain biology) of males and females with autism have begun to examine brain networks but results have been mixed. This is largely due to the limited availability of data from autistic females.

In response, researchers from Child Mind Institute and colleagues involved in the AIMS2TRIALS, have combined thousands of MRI data openly available for scientific discovery in the Autism Brain Imaging Exchange (ABIDE) repository to explore brain network differences between autistic and neurotypical control males and females. They used the ABIDE sample for discovery of new information and two additional large samples to see if those findings could be repeated (i.e., replicated). These included one sample derived from the Gender Explorations of Neurogenetics and Development to Advance Autism Research made available through the National Database for Autism Research and another one shared by the collaborators of the AIMS2TRIALS.

Across these three samples, the researchers found that both neurotypical males and autistic people showed reduced resting-state brain function in the so-called ‘default network’, a network that is active when we engage in social cognition or thoughts about ourselves. Additionally, in the discovery sample and in one of the largest of the two replication samples, it was shown that connections between hemispheres (the two halves of the brain) in the visual cortex are reduced in autistic females, while autistic males are not different from males who are not autistic. The results suggest that many autistic people may have different interactions between the two hemispheres of their brain when compared to non-autistic people. This reflects a combination of effects, including some that appear to be unrelated to sex, and some in which there is an interaction between sex and autism diagnosis. Each of these effects appears specific to a different system in the brain.

This study highlights the importance of data sharing and collaboration for implementing discovery science and addressing critical challenges related to reproducibility of findings – which affect all of fields of science. The researchers suggest that there remains an urgent need for more research with similarly large groups of participants, as only then do studies have enough statistical power to reliably account for sources of variability and therefore generate robust conclusions. Until now, limited replication of imaging findings has hampered brain imaging research in autism. The open sharing policies of the Autism Brain Imaging Data Exchange and the NIMH Data Archive, through which the Gender Explorations of Neurogenetics Development to Advance Autism Research was made available, are particularly promising for accelerating the pace of advancement.


Reference: Floris, D.L., Filho, J.O.A., Lai, MC. et al. Towards robust and replicable sex differences in the intrinsic brain function of autism. Molecular Autism 12, 19 (2021). https://doi.org/10.1186/s13229-021-00415-z


Provided by Child Mind Institute

New Clinical Method Could Lower Risk of Recurring Heart Attacks (Medicine)

Researchers at Lund University in Sweden can now show that a new examination method identifies high-risk plaques in the blood vessels surrounding the heart, that cannot be seen solely with traditional angiograms. This type of plaque, rich in fat, could potentially cause recurring heart attacks in patients with heart disease. The study is published in the The Lancet.

”We have been working on this study for ten years. This creates a unique opportunity to treat plaques before they cause a heart attack”, says David Erlinge, professor of cardiology at Lund University and Consultant in Interventional Cardiology at Skåne University Hospital, who together with researchers in New York led the study.

The results show that over fourteen percent of the treated patients had some form of heart disease recurrence within four years. In eight percent of the cases, the cause was high-risk plaque that was not detected in a previous angiogram.

Several autopsy studies have previously shown that vulnerable plaques are the underlying cause of most coronary heart disease. When a plaque ruptures and forms one or more clots, they cause the majority of heart attacks and infarction-related sudden death.

“This a major step forward for cardiology,” said co-author James Muller, MD, of the Division of Cardiovascular Medicine at Brigham and Women’s Hospital in Boston, Mass. “This study has demonstrated a superior way to quantify risk at the plaque level and to identify patients who are at increased risk of experiencing adverse cardiac events.”

The new method, known as NIRS (Near-Infrared Spectroscopy) and IVUS (Intravascular Ultrasound), uses infrared light and ultrasound. The examination of the patient is typically performed with a catheter brought to the heart area via the wrist, and done in connection with an angiogram. The high-fat plaques can then be seen in yellow on a color-coded map.

”An angiogram only reveals a shadow of the vessel walls, not what is in the wall. With the new NIRS-IVUS method, we can see vulnerable plaque there as well”, says David Erlinge.

The study included 898 patients from 16 hospitals in Sweden, Denmark and Norway. All had suffered a heart attack and were treated with balloon dilation and stents in the coronary arteries. 14.4 percent of the patients in the study experienced new issues within four years of the heart attack. In 8 percent of the patients, the direct cause was untreated plaque. A total of 3,629 untreated plaques were found, which is an average of about four per treated patient.

”The study shows that most of the subsequent cardiac events were caused by plaque not revealed in previous examinations using angiograms and physiological pressure measurements, which are the methods used clinically today”, says David Erlinge.

The next big question is how to treat these plaques. The researchers included a small treatment study that showed that stenting of dangerous plaques opened up the vessel and halved the number of cardiac events. This needs to be confirmed by larger studies, however.

Publication:

Link to the article in The Lancet:

Identification of vulnerable plaques and patients by intracoronary near-infrared spectroscopy and ultrasound (PROSPECT II): a prospective natural history study

Financing:

The study was financed by: Abbott Vascular, Infraredx, and The Medicines Company. For more details please see “Declaration of interests” in the study.

Featured image: Illustration of Heart, arteries © Photo: Mostphotos


Provided by Lund University

Remote Con­trol For Quan­tum Emitters (Quantum)

Quantum technologies are enabled by precise control of the state and interactions of individual quantum objects. Innsbruck physicists have now proposed a way to remotely control the state of individual quantum emitters. The underlying idea, developed by a research group led by Oriol Romero-Isart, is based on chirped light pulses.

In order to exploit the properties of quantum physics technologically, quantum objects and their interaction must be precisely controlled. In many cases, this is done using light. Researchers at the University of Innsbruck and the Institute of Quantum Optics and Quantum Information (IQOQI) of the Austrian Academy of Sciences have now developed a method to individually address quantum emitters using tailored light pulses. “Not only is it important to individually control and read the state of the emitters,” says Oriol Romero-Isart, “but also to do so while leaving the system as undisturbed as possible.” Together with Juan José García-Ripoll (IQOQI visiting fellow) from the Instituto de Física Fundamental in Madrid, Romero-Isart’s research group has now investigated how specifically engineered pulses can be used to focus light on a single quantum emitter.

Self-compressing light pulse

“Our proposal is based on chirped light pulses,” explains Silvia Casulleras, first author of the research paper. “The frequency of these light pulses is time-dependent.” So, similar to the chirping of birds, the frequency of the signal changes over time. In structures with certain electromagnetic properties – such as waveguides – the frequencies propagate at different speeds. “If you set the initial conditions of the light pulse correctly, the pulse compresses itself at a certain distance,” explains Patrick Maurer from the Innsbruck team. “Another important part of our work was to show that the pulse enables the control of individual quantum emitters.” This approach can be used as a kind of remote control to address, for example, individual superconducting quantum bits in a waveguide or atoms near a photonic crystal.

Wide range of applications

In their work, now published in Physical Review Letters, the scientists show that this method works not only with light or electromagnetic pulses, but also with other waves such as lattice oscillations (phonons) or magnetic excitations (magnons). The research group led by the Innsbruck experimental physicist Gerhard Kirchmair, wants to implement the concept for superconducting qubits in the laboratory in close collaboration with the team of theorists.

The research was financially supported by the European Union.
Links


Provided by University of Innsbruck

New Insulation Takes Heat Off Environment (Material Science)

Wool fibre + industrial waste = green solution

Waste cooking oil, sulfur and wool offcuts have been put to good use by green chemists at Flinders University to produce a sustainable new kind of housing insulation material.

The latest environmentally friendly building product from experts at the Flinders Chalker Lab and colleagues at Deakin and Liverpool University, has been described in a new paper published in Chemistry Europe ahead of Global Recycling Day (18 March 2021)

The insulating composite was made from the sustainable building blocks of wool fires, sulfur, and canola oil to produce a promising new model for next-generation insulation – not only capitalising on wool’s natural low flammability but also to make significant energy savings for property owners and tenants.

The new composite is one of several exciting new composites and polysulfide polymers made from waste products that are now being commercialised, says lead author Associate Professor Justin Chalker, the New Innovators winner in the 2020 Prime Minister’s Prizes for Science.

“The aim of this new study was to evaluate a composite made from sulfur, canola oil, and wool as thermal insulation. The material is prepared by hot pressing raw wool with a polymer made from sulfur and canola oil,” Associate Professor Chalker says.

“The promising mechanical and insulation properties of this composite bodes well for further exploration in energy saving insulation in our built environment.”

ChemSusChem diagram in the new paper © Flinders University

The new study adds to a suite of other composites, such as a new type of building block and a renewable rubber material created in the Chalker Lab.

The long-term biodegradation of these materials in a safe and responsible way at the end of their life is also a target of the research.

The last decade has been described as the hottest on record, and reusing waste is one way to extend the life of billions of tonnes of natural resources consumed every year.

Global company Clean Earth Technologies is commercialising the polymers for a range of applications – from removing mercury contamination from soil and retrieving oil after a large-scale spill, to a polymer to release fertiliser more slowly to reduce run-off, and facilitating a safer method of leaching and extracting gold.

In line with the UN’s Sustainable Development Goals 2030, Global Recycling Day recognises individuals, governments and organisations taking direct action to support the global green agenda.

Recycling is a key part of the circular economy, helping to protect our natural resources. Each year the ‘Seventh Resource’ (recyclables) saves over 700 million tonnes in CO2 emissions and this is projected to increase to 1 billion tonnes by 2030.

Funding for this research came from the Australian Research Council and the Royal Society with support from Flinders University Microscopy and Microanalysis Centre and SA node of the Australian National Fabrication Facility under the National Collaborative Research Infrastructure Strategy to provide nano and microfabrication facilities for Australia’s researchers.

The paper ‘Insulating composites made from sulfur, canola oil, and wool’ (2021) by IB Najmah, NA Lundquist, MK Stanfield, F Stojcevski, JA Campbell, LJ Esdaile, CT Gibson, DA Lewis, LC Henderson, T Hasell and JM Chalker has been published by the Wiley journal ChemSusChem (Chemistry-Sustainability-Energy-Materials) European Chemical Societies Publishing DOI: 10.1002/cssc.202100187

Featured image: Organic chemist Associate Professor Justin Chalker, Flinders University, Australia © Flinders University


Provided by Flinders University

New Perovskite LED Emits A Circularly Polarized Glow (Physics)

Light-emitting diodes (LEDs) have revolutionized the displays industry. LEDs use electric current to produce visible light without the excess heat found in traditional light bulbs, a glow called electroluminescence. This breakthrough led to the eye-popping, high-definition viewing experience we’ve come to expect from our screens. Now, a group of physicists and chemists have developed a new type of LED that utilizes spintronics without needing a magnetic field, magnetic materials or cryogenic temperatures; a “quantum leap” that could take displays to the next level.

“The companies that make LEDs or TV and computer displays don’t want to deal with magnetic fields and magnetic materials. It’s heavy and expensive to do it,” said Valy Vardeny, distinguished professor of physics and astronomy at the University of Utah. “Here, chiral molecules are self-assembled into standing arrays, like soldiers, that actively spin polarize the injected electrons, which subsequently lead to circularly polarized light emission. With no magnetic field, expensive ferromagnets and with no need for extremely low temperatures. Those are no-nos for the industry.”

Most opto-electronic devices, such as LEDs, only control charge and light and not the spin of the electrons. The electrons possess tiny magnetic fields that, like the Earth, have magnetic poles on opposite sides. Its spin may be viewed as the orientation of the poles and can be assigned binary information—an “up” spin is a “1,” a “down” is a “0.” In contrast, conventional electronics only transmit information through bursts of electrons along a conductive wire to convey messages in “1s” and “0s.” Spintronic devices, however, could utilize both methods, promising to process exponentially more information than traditional electronics.

From bottom to top. The first layer is a semitransparent anode, such as ITO, that injects unpolarized “holes,” a quantum feature of electrons, with a certain spin. The second layer is the two-dimensional chiral hybrid perovskite that is an active spin filter, allowing only holes with specific spin to pass by, depending on the helicity of the chiral molecules. The third layer is the emitter film, composed of a non-chiral inorganic perovskite such as CsPbBr3. The fourth and fifth layers are the cathode that injects spin up and spin down electrons. Only the spin down electrons recombine with the spin up injected holes to produce circularly polarized light with helicity that depends on the chiral molecules helicity in the two-dimensional organic-inorganic layer. © PHOTO CREDIT: Adapted from: Kim, Y.H. et. al., Science (2021)

One barrier to commercial spintronics is setting the electron spin. Presently, one needs to produce a magnetic field to orient the electron spin direction. Researchers from the University of Utah and the National Renewable Energy Laboratory (NREL) developed technology that acts as an active spin filter made of two layers of material called chiral two-dimension metal-halide perovskites. The first layer blocks electrons having spin in the wrong direction, a layer that the authors call a chiral-induced spin filter. Then when the remaining electrons pass through the second light-emitting perovskite layer, they cause the layer to produce photons that move in unison along a spiral path, rather than a conventional wave pattern, to produce circular polarized electroluminescence.

The study was published in the journal Science on March 12, 2021.

Left-handed, right-handed molecules

The scientists exploited a property called chirality that describes a particular type of geometry. Human hands are a classic example; the right and left hands are arranged as mirrors of one another, but they will never perfectly align, no matter the orientation. Some compounds, such as DNA, sugar and chiral metal-halide perovskites, have their atoms arranged in a chiral symmetry. A “left-handed” oriented chiral system may allow transport of electrons with “up” spins but block electrons with “down” spins, and vice versa.

A schematic of circularly polarized light. Photons that move in unison along a spiral path, rather than a conventional wave pattern, produce circular polarized light. The light-emitting perovskite layer of the spin-LED device produces either left-handed or right-handed polarized light, depending the spin of the electrons that made it past the perovskite filter. PHOTO CREDIT: Dave3457 via Wikicommons

“If you try to transport electrons through these compounds, then the electron spin becomes aligned with the chirality of the material,” Vardeny said. Other spin filters do exist, but they either require some kind of magnetic field, or they can only manipulate electrons in a small area. “The beauty of the perovskite material that we used is that it’s two-dimensional—you can prepare many planes of 1 cm2 area that contain one million of a billion (1015) standing molecules with the same chirality.”

Metal-halide perovskite semiconductors are mostly used for solar cells these days, as they are highly efficient at converting sunlight to electricity. Since a solar cell is one of the most demanding applications of any semiconductor, scientists are discovering other uses exist as well, including spin-LEDs.

“We are exploring the fundamental properties of metal-halide perovskites, which has allowed us to discover new applications beyond photovoltaics,” said Joseph Luther, a co-author of the new paper and NREL scientist. “Because metal-halide perovskites, and other related metal halide organic hybrids, are some of the most fascinating semiconductors, they exhibit a host of novel phenomena that can be utilized in transforming energy.”

Although metal-halide perovskites are the first to prove the chiral-hybrid devices are feasible, they are not the only candidates for spin-LEDs. The general formula for the active spin filter is one layer of an organic, chiral material, another layer of an inorganic metal halide, such as lead iodine, another organic layer, inorganic layer and so on.

“That’s beautiful. I’d love that someone will come out with another 2-D organic/inorganic layer material that may do a similar thing. At this stage, it’s very general. I’m sure that with time, someone will find a different two-dimensional chiral material that will be even more efficient,” Vardeny said.

The concept proves that using these two dimensional chiral-hybrid systems gain control over spin without magnets and has “broad implications for applications such as quantum-based optical computing, bioencoding and tomography,” according to Matthew Beard, a senior research fellow and director of Center for Hybrid Organic Inorganic Semiconductors for Energy.

Vardeny and Xin Pan from the Department of Physics & Astronomy at the University of Utah co-authored the study. The other co-authors from NREL are Beard, Young-Hoon Kim, Yaxin Zhai, Haipeng Lu, Chuanxiao Xiao, E. Ashley Gaulding, Steven Harvey and Joseph Berry. All are part of CHOISE collaboration, an Energy Frontier Research Center (EFRC) funded by the Office of Science within DOE.

Funding for the research came from CHOISE.


Reference: Young-Hoon Kim, Yaxin Zhai, Haipeng Lu, Xin Pan, Chuanxiao Xiao, E. Ashley Gaulding, Steven P. Harvey, Joseph J. Berry, Zeev Valy Vardeny, Joseph M. Luther, Matthew C. Beard, “Chiral-induced spin selectivity enables a room-temperature spin light-emitting diode”, Science 12 Mar 2021: Vol. 371, Issue 6534, pp. 1129-1133 DOI: 10.1126/science.abf5291


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