Skoltech Researchers Unveil Complex Defect Structure Of Li-ion Cathode Material (Material Science)

Skoltech scientists have studied the hydroxyl defects in LiFePO4, a widely used cathode material in commercial lithium-ion batteries, contributing to the overall understanding of the chemistry of this material. This work will help improve the LiFePOmanufacturing process to avoid formation of adverse intrinsic structural defects which deteriorate its performance. The paper was published in the journal Inorganic Chemistry.

Lithium iron phosphate, LiFePO4, is a safe, stable and affordable cathode material for Li-ion batteries that has been very well optimized for practical applications despite its low conductivity and medium energy density. Yet scientists continue to study the various properties of this material, and in particular the impact of its defects on electrochemical performance.

“It is well known that LiFePO4 materials usually have a considerable amount of Li/Fe antisite defects. This is a type of point defect when Li and Fe atoms exchange their positions in the crystal lattice. However, before us, nobody had assumed that the PO4 part can be also defect-active in this material. We discovered that in some cases the PO4 anion can be substituted by four or five OH groups, which has a negative effect on electrochemical performance of LiFePO4-based batteries. Such defects are called OH defects or more specifically hydrogarnet-type hydroxyl defects,” Dmitry Aksyonov, Skoltech Senior Research Scientist and the first author of the paper, explains.

Aksyonov, Assistant Professor Stanislav Fedotov, and Professor Artem Abakumov (CEST) with their colleagues used a joint computational and experimental approach combining density functional theory and neutron diffraction to study the hydroxyl (OH) defects in LiFePO4. They were also able to confirm their results experimentally in a LiFePO4 sample.

“The hydrogarnet OH defects are well known in geology, but not so much in materials science. The presence of OH defects in LiFePO4 could have been envisaged much earlier by drawing parallels with its structural analogues in the olivine mineral group. Therefore, the biggest takeaway from our work is probably that researchers should seek knowledge not only in their home field but in other fields as well,” Aksyonov says.

Since OH defects are not trivial to detect, commercially produced LiFePO4 materials may have them as well, he notes, and it is important to have these deteriorating effects under control.

“The simplest practical outcome of this research would be to put efforts in modifying the synthesis procedure so as to fully eliminate this type of defects from the LiFePO4 materials. However, our experience tells that fighting defects makes much less sense than turning them in our favor. So, the story has all chances to be continued,” Stanislav Fedotov adds.


Provided by Skoltech

Novel Antibody Drug Wakes Up the Body’s Defense System in Advanced-stage Cancer (Medicine)

Researchers at the University of Turku, Finland, showed that the antibody treatment reactivates the immune defense in patients with advanced-stage cancer. The treatment alters the function of the body’s phagocytes and facilitates extensive activation of the immune system.

The immune defense is the body’s own defense system equipped to combat cancer. However, cancer learns to hide from immune attacks and harnesses this system to promote its own growth. Therefore, it would be beneficial to be able to return the immune defense back to restricting the advancement of cancer.

Macrophages, a type of white blood cell, are central in the fight against cancer. Cancer educates macrophages to subdue the defense system and renders many treatments targeting the immune system ineffective.

Academy Research Fellow Maija Hollmén’s research group has searched for means of altering the activity of macrophages in order to direct the immune defense to attack cancer. The antibody bexmarilimab, developed based on this research and in collaboration with Faron Pharmaceuticals, is currently undergoing clinical trials in patients. Hollmén’s group has studied the changes occurring in the defense systems of patients with cancer following antibody treatment.

– In the majority of patients, the antibody treatment activated killer T cells, which are the body’s strike force against cancer. Additionally, the antibody treatment successfully lowered the suppressive potential of macrophage precursors travelling in the blood circulation. The patients also showed increases in certain mediators of inflammation and types of white blood cell in the blood, describes Hollmén.

– The activation of the killer T cells is a very promising demonstration of the antibody’s capability to boost the defense system against cancer. The treated patients had very advanced and poorly treatable cancers, which highlights the significance of the results, says Doctoral Candidate Jenna Rannikko.

Bexmarilimab May Benefit Patients for Whom Current Treatment Options Are Ineffective

The research also yielded new information on the mode of action of bexmarilimab. The antibody binds the molecule Clever-1 present on macrophages and alters its function.

Clever-1 transports material needless to the body inside macrophages to be degraded. Objects disposed in this manner are swept under the rug, in a manner of speaking. This kind of concealment is beneficial for the body’s natural balance and helps to avoid stirring the immune defense unnecessarily. 

– However, cells originating from cancer should be detected. When the antibody is used to block Clever-1 from performing its cleaning job, it facilitates the activation of cells of the immune defense. This in part leads to the waking up of the T cells in patients, describes Doctoral Candidate Miro Viitala.

There is demand for treatments that boost the activity of the immune defense since the current options on the market only help some patients.

– Bexmarilimab’s mode of action is different from the drug treatments against cancer currently on the market. Therefore, it can be beneficial for patients for whom current treatment options are ineffective, concludes Postdoctoral Researcher Reetta Virtakoivu.

Maija Hollmén’s research group is part of the InFLAMES Flagship which is a joint initiative of University of Turku and Åbo Akademi University. The goal of the Flagship is to integrate immunological and immunology-related research activities to develop and exploit new diagnostic and therapeutic tools.

The research article has been published in the esteemed Clinical Cancer Research publication series.

RESEARCH ARTICLE

Systemic blockade of Clever-1 elicits lymphocyte activation alongside checkpoin…


Provided by University of Turku

Electrochemical Cell Harvests Lithium From Seawater (Chemistry)

The system offers an economical way to source essential battery material.

Lithium is a vital element in the batteries that power electric vehicles, but soaring lithium demand is expected to exhaust land-based reserves by 2080. KAUST researchers have now developed an economically viable system that can extract high-purity lithium from seawater.

The oceans contain about 5,000 times more lithium than the land but at extremely low concentrations of about 0.2 parts per million (ppm). Larger ions, including sodium, magnesium and potassium, are all present in seawater at much higher concentrations; however, previous research efforts to tease lithium from this mixture have yielded little.

The KAUST team solved this problem with an electrochemical cell containing a ceramic membrane made from lithium lanthanum titanium oxide (LLTO). Its crystal structure contains holes just wide enough to let lithium ions pass through while blocking larger metal ions. “LLTO membranes have never been used to extract and concentrate lithium ions before,” says postdoc Zhen Li, who developed the cell.

The electrochemical cell designed by the KAUST team separates lithium ions from seawater while also producing valuable hydrogen and chlorine gas.
The electrochemical cell designed by the KAUST team separates lithium ions from seawater while also producing valuable hydrogen and chlorine gas. © Li et al. (2021). Published by The Royal Society of Chemistry

The cell contains three compartments. Seawater flows into a central feed chamber, where positive lithium ions pass through the LLTO membrane into a side compartment that contains a buffer solution and a copper cathode coated with platinum and ruthenium. Meanwhile, negative ions exit the feed chamber through a standard anion exchange membrane, passing into a third compartment containing a sodium chloride solution and a platinum-ruthenium anode.

The researchers tested the system using seawater from the Red Sea. At a voltage of 3.25V, the cell generates hydrogen gas at the cathode and chlorine gas at the anode. This drives the transport of lithium through the LLTO membrane, where it accumulates in the side-chamber. This lithium-enriched water then becomes the feedstock for four more cycles of processing, eventually reaching a concentration of more than 9,000 ppm. Adjusting the pH of this solution delivers solid lithium phosphate that contains mere traces of other metal ions — pure enough to meet battery manufacturers’ requirements.

The researchers estimate that the cell would need only US$5 of electricity to extract 1 kilogram of lithium from seawater. The value of hydrogen and chlorine produced by the cell would more than offset this cost, and residual seawater could also be used in desalination plants to provide freshwater.

“We will continue optimizing the membrane structure and cell design to improve the process efficiency,” says group leader Zhiping Lai. His team also hopes to collaborate with the glass industry to produce the LLTO membrane at large scale and affordable cost.

Featured image: KAUST researchers have developed a method to extract lithium, a vital element in autonomous vehicle batteries, from seawater in a more economically viable way. © 2021 Morgan Bennett Smith


Reference

  1. . Li, Z., Li, C., Liu, X., Cao, L., Li, P., Wei, R., Li, X., Guo, D., Huang, K-W. & Lai, Z. Continuous electrical pumping membrane process for seawater lithium mining. Energy and Environmental Science  14, 3152-3159 (2021).| article

Provided by KAUST

Quantum Computing With Holes (Physics)

Scientists found a new and promising qubit at a place where there is nothing

Quantum computers with their promises of creating new materials and solving intractable mathematical problems are a dream of many physicists. Now, they are slowly approaching viable realizations in many laboratories all over the world. But there are still enormous challenges to master. A central one is the construction of stable quantum bits – the fundamental unit of quantum computation called qubit for short – that can be networked together.

In a study published in Nature Materials and led by Daniel Jirovec from the Katsaros group at IST Austria in close collaboration with researchers from the L-NESS Inter-university Centre in Como, Italy, scientists now have created a new and promising candidate system for reliable qubits.

Spinning Absence

The researchers created the qubit using the spin of so-called holes. Each hole is just the absence of an electron in a solid material. Amazingly, a missing negatively charged particle can physically be treated as if it were a positively charged particle. It can even move around in the solid when a neighboring electron fills the hole. Thus, effectively the hole described as positively charged particle is moving forward.

These holes even carry the quantum-mechanical property of spin and can interact if they come close to each other. “Our colleagues at L-NESS layered several different mixtures of silicon and germanium just a few nanometers thick on top of each other. That allows us to confine the holes to the germanium-rich layer in the middle,” Jirovec explains. “On top, we added tiny electrical wires – so-called gates – to control the movement of holes by applying voltage to them. The electrically positively charged holes react to the voltage and can be extremely precisely moved around within their layer.”

Daniel Jirovec, Institute of Science and Technology Austria© Daniel Jirovec

Using this nano-scale control, the scientists moved two holes close to each other to create a qubit out of their interacting spins. But to make this work, they needed to apply a magnetic field to the whole setup. Here, their innovative approach comes into play.

Linking Qubits

In their setup, Jirovec and his colleagues cannot only move holes around but also alter their properties. By engineering different hole properties, they created the qubit out of the two interacting hole spins using less than ten millitesla of magnetic field strength. This is a weak magnetic field compared to other similar qubit setups, which employ at least ten times stronger fields.

But why is that relevant? “By using our layered germanium setup we can reduce the required magnetic field strength and therefore allow the combination of our qubit with superconductors, usually inhibited by strong magnetic fields,” Jirovec says. Superconductors – materials without any electrical resistance – support the linking of several qubits due to their quantum-mechanical nature. This could enable scientists to build new kinds of quantum computers combining semiconductors and superconductors.

In addition to the new technical possibilities, these hole spin qubits look promising because of their processing speed. With up to one hundred million operations per second as well as their long lifetime of up to 150 microseconds they seem particularly viable for quantum computing. Usually, there is a tradeoff between these properties, but this new design brings both advantages together.

Featured image: The two holes are confined to the germanium-rich layer just a few nanometers thick. On top, the electrical gates are formed by individual wires with voltages applied. The positively charged holes feel the push and pull from the wires and can therefore be moved around within their layer. © Daniel Jirovec


Reference: Jirovec, D., Hofmann, A., Ballabio, A. et al. A singlet-triplet hole spin qubit in planar Ge. Nat. Mater. (2021). https://doi.org/10.1038/s41563-021-01022-2


Provided by IST Austria

3D Printed Micro-optics For Quantum Technology (Physics)

Quantum computing and quantum communication are believed to be the future of information technology. In order to achieve the challenging and long-standing goal to make secure, wide-spread quantum communication networks a reality, high-brightness single-photon sources are indispensable. Single-photon emission from semiconductor quantum dots (QDs) has been shown to be a pure and efficient non-classical light source with a high degree of indistinguishability. However, the total internal reflection (TIR) as a result of the high semiconductor-to-air refractive index contrast severely limits the single-photon extraction efficiency. Another crucial step in the development of practical quantum networks is the implementation of quantum repeater protocols, which enable long-distance quantum communication via optical fibre channels. These protocols rely on the use of highly indistinguishable, entangled photons, which require the use of single-mode fibres. Thus, an efficient on-chip single-mode fibre-coupled quantum light source is a key element in the realisation of a QD-based real-world quantum communication network.

In a new paper published in Light Science & Application, a team of scientists, led by, Professor Harald Giessen and Professor Peter Michler from the 4th Physics Institute and the Institut für Halbleiteroptik und Funktionelle Grenzflächen, University of Stuttgart, Germany, and co-workers have worked on enhancing the extraction efficiency of semiconductor QDs by optimising micrometre-sized solid-immersion lens (SIL) designs. Two state-of-the-art technologies, i.e., low-temperature deterministic lithography and femtosecond 3D direct laser writing, are used in combination to deterministically fabricate micro-lenses on pre-selected QDs. Because of the high flexibility of 3D direct laser writing, various SIL designs, including hemispherical SILs (h-SILs), Weierstrass SILs (W-SILs), and total internal reflection SILs (TIR-SILs), can be produced and compared with respect to single-photon extraction enhancement. The experimentally obtained values are compared with analytical calculations, and the role of misalignment between SIL and QD as an error source is discussed in detail.

Furthermore, they highlight the implementation of an integrated single-mode fibre-coupled single-photon source based on 3D printed micro-optics. A 3D printed fibre chuck is used to precisely position an optical single-mode fibre onto a QD with a micro-lens printed on top. This fibre is equipped with another specifically designed 3D printed in-coupling lens to efficiently guide light from the TIR-SIL into the fibre core.

The main results presented in this paper are two-fold:

  1. A reproducible method to enhance the collection efficiency of single QDs based on 3D printed micro-lenses is presented. For all lens geometries, an increase in the collection efficiency was confirmed. The simplest geometry, namely h-SIL, resulted in an intensity enhancement of approximately 2.1. A further increase of up to approximately 3.9 in collection efficiency is promised by the hyperhemispherical Weierstrass geometry. The highest values were achieved for the total internal reflection geometries which reliably provide a PL intensity ratio between 6 and 10.
  2. A standalone a fibre-coupled standalone quantum dot device was realised. The validation of the approach for fibre in-coupling, that is the use of a QD provided with a TIR-SIL and a fibre with an additional focusing lens, was performed, employing a setup capable of precisely aligning the fibre with respect to the emitter. A value of up to 26±5% was shown, opening the route to a stable stand-alone, fibre-coupled device.

In the future, this technology can be combined with a QD single-photon source based on circular Bragg gratings, NV centres, defects, and a variety of other quantum emitters. In addition, a highly efficient combination with single quantum detectors should be feasible.

Featured image: a, μ-PL spectra of the same QD underneath a Weierstrass SIL (left) and a TIR-SIL (right) and without a lens. Emission characteristics were identified prior to the intensity enhancement evaluation via power-dependent measurements. The insets depict an SEM angular view picture (45° tilt) of the printed lenses. b, (left) Schematic of the fiber chuck design. A TIR-SIL with an NA of 0.001 is printed deterministically aligned on the QD position. After the characterization of the printed lens, the big tube-like chuck is fabricated, being aligned on this lens. On the fiber tip, another lens is printed for coupling the modified emission into the fiber core. The modified fiber is then inserted into the chuck. Epoxy is used to fix the fiber position. Excitation and collection of the QD are carried out via the same fiber. (right) Microscope picture of a fiber inside a fiber chuck. The fiber is stopped via the step indicated by the dashed white lines and is ready for being fixed with epoxy glue. c, Unfiltered PL signal of the standalone QD device (left) and spectrum filtered with a band-pass filter that is designed for 885?nm?±?12.5?nm (right). Tilting the filter shifts the wavelength window down to lower wavelengths. © by Marc Sartison, Ksenia Weber, Simon Thiele, Lucas Bremer, Sarah Fischbach, Thomas Herzog, Sascha Kolatschek, Michael Jetter, Stephan Reitzenstein, Alois Herkommer, Peter Michler, Simone Luca Portalupi, and Harald Giessen


Reference: “3D printed micro-optics for quantum technology: Optimised coupling of single quantum dot emission into a single-mode fibre”, Light: Advanced Manufacturing , Article number: 6 (2021). doi: https://doi.org/10.37188/lam.2021.006


Provided by CIOMP

How Quantum Dots Can “Talk” to Each Other (Physics)

A group at HZB has worked out theoretically how the communication between two quantum dots can be influenced with light.  The team led by Annika Bande also shows ways to control the transfer of information or energy from one quantum dot to another. To this end, the researchers calculated the electronic structure of two nanocrystals, which act as quantum dots. With the results, the movement of electrons in quantum dots can be simulated in real time.

So-called quantum dots are a new class of materials with many applications. Quantum dots are realized by tiny semiconductor crystals with dimensions in the nanometre range. The optical and electrical properties can be controlled through the size of these crystals. As QLEDs, they are already on the market in the latest generations of TV flat screens, where they ensure particularly brilliant and high-resolution colour reproduction. However, quantum dots are not only used as “dyes”, they are also used in solar cells or as semiconductor devices, right up to computational building blocks, the qubits, of a quantum computer.

Now, a team led by Dr. Annika Bande at HZB has extended the understanding of the interaction between several quantum dots with an atomistic view in a theoretical publication. 

Annika Bande heads the “Theory of Electron Dynamics and Spectroscopy” group at HZB and is particularly interested in the origins of quantum physical phenomena. Although quantum dots are extremely tiny nanocrystals, they consist of thousands of atoms with, in turn, multiples of electrons. Even with supercomputers, the electronic structure of such a semiconductor crystal could hardly be calculated, emphasises the theoretical chemist, who recently completed her habilitation at Freie Universität. “But we are developing methods that describe the problem approximately,” Bande explains. “In this case, we worked with scaled-down quantum dot versions of only about a hundred atoms, which nonetheless feature  the characteristic properties of real nanocrystals.”  

With this approach, after a year and a half of development and in collaboration with Prof. Jean Christophe Tremblay from the CNRS-Université de Lorraine in Metz, we succeeded in simulating the interaction of two quantum dots, each made of hundreds of atoms, which exchange energy with each other. Specifically, we have investigated how these two quantum dots can absorb, exchange and permanently store the energy controlled by light. A first light pulse is used for excitation, while the second light pulse induces the storage.

In total, we investigated three different pairs of quantum dots to capture the effect of size and geometry. We calculated the electronic structure with highest precision and simulated the electronic motion in real time at femtosecond resolution (10-15 s).

The results are also very useful for experimental research and development in many fields of application, for example for the development of qubits or to support photocatalysis, to produce green hydrogen gas by  sunlight. “We are constantly working on extending our models towards even more realistic descriptions of quantum dots,” says Bande, “e.g. to capture the influence of temperature and environment.”

Featured image: The illustration shows two quantum dots “communicating” with each other by exchanging light. © HZB


Reference: Pascal Krause,Jean Christophe Tremblay, and Annika Bande, “Atomistic Simulations of Laser-controlled Exciton Transfer and Stabilization in Symmetric Double Quantum Dots”, J. Phys. Chem. A (2021). DOI: 10.1021/acs.jpca.1c02501


Provided by HZB

Biomarker Predicts Bowel Cancer Recurrence (Biology)

A biomarker in the blood of patients with bowel cancer may provide valuable insight into the risk of cancer relapse after surgery and the effectiveness of chemotherapy.

Research published in PLOS found circulating tumour DNA (ctDNA) measured before and after surgery provided a reliable marker for predicting whether the cancer would recur following chemotherapy treatment.

The ctDNA also provided a real-time measure of the effectiveness of chemotherapy, highlighting the potential for this test to provide an early indication of the success of chemotherapy in eradicating microscopic cancer.

At a glance

  • By measuring levels of ctDNA present in the blood of bowel cancer patients after surgery, researchers were able to predict the likelihood of the cancer recurring.
  • Measuring the presence of ctDNA after chemotherapy provided a real time indication of whether the chemotherapy had cleared the cancer.
  • ctDNA could be used as a biomarker in the future to improve patient care and treatment

Prognostic impact of ctDNA

Led by Associate Professor Jeanne Tie, who is also a medical oncologist at the Peter MacCallum Cancer Centre and Western Health, the research followed a group of patients with metastatic bowel cancer who had secondary cancer in the liver that had been removed by surgery. The study builds on earlier research reported in 2018.

The ctDNA test looks for fragments of tumour DNA in a patient’s blood before and after the removal of a cancerous tumour.

The presence of ctDNA in the blood of patients after surgery provides evidence of remaining microscopic tumours, enabling researchers to predict the likelihood of the cancer reoccurring.

Associate Professor Tie said the study once again confirmed the prognostic impact of ctDNA.

“What we found is that if ctDNA is present after surgery, it predicts an almost 100 per cent recurrence rate for these patients,” she said.

“In contrast, for patients who were ctDNA-negative after surgery, the likelihood of the cancer reoccurring was far lower, about 25 per cent.”

Measuring chemotherapy in real time

Associate Professor Tie said ctDNA also provided an indication of the effectiveness of chemotherapy.

“This biomarker could also identify whether patients would respond to chemotherapy treatment,” she said.

“Until now, we had no way of measuring the effectiveness of chemotherapy in real time. The usual process is to do the surgery to remove the cancer metastases, give the patient chemotherapy, and then follow up with CT scans every six to 12 months, to see if the cancer recurs. And if the cancer does recur, you know the treatment hasn’t worked. By measuring the ctDNA in the blood, we could immediately see whether the chemotherapy had cleared the cancer and were therefore able to predict the likelihood of the cancer recurring.”

Associate Professor Tie said ctDNA biomarkers might allow clinicians to intervene earlier.

“Cancer that can be detected on a CT scan is unlikely to be curable by chemotherapy. But if we are able to detect microscopic disease, that we can’t pick up on a scan, we can intervene earlier and potentially still offer the patient a chance of cure.”

Promising sign for the future of cancer treatment

Associate Professor Tie said while ctDNA technology was already being used in the US, further research was needed before it could be rolled out in Australia.

“The test needs to be very sensitive to be able to pick up microscopic cancer cells. I am hopeful the new technology coming through will have enough sensitivity that we will be able to use this technique in the years ahead to improve patient care and treatment,” she said.

“With further development of this technology, this could also mean patients with a low recurrence risk could avoid unnecessary chemotherapy.”

This work was made possible with support from the National Institutes of Health, the Virginia and D.K Ludwig Fund for Cancer Research, the Victorian Cancer Agency Clinical Research Fellowship, the Victorian Government, the Sol Goldman Sequencing Facility at Johns Hopkins, and the John Templeton Foundation.

Featured image: Crypts and buds in the small intestine and colon. © Dr. Maree Faux, WEHI.


Reference: Tie J, Wang Y, Cohen J, Li L, Hong W, Christie M, et al. (2021) Circulating tumor DNA dynamics and recurrence risk in patients undergoing curative intent resection of colorectal cancer liver metastases: A prospective cohort study. PLoS Med 18(5): e1003620. doi:10.1371/journal.pmed.1003620


Provided by WEHI

Yale-NUS College Scientist Discovers How Leafbirds Make Complex Colour-producing Crystals (Physics)

These mind-bendingly complex crystals called the single gyroid, found in blue-winged leafbirds, have the potential to make fibre optics, solar cells and fuel cells more efficient

A recent study by a team of researchers led by Dr Vinod Kumar Saranathan from the Division of Science at Yale-NUS College has discovered a complex, three-dimensional crystal called the single gyroid within feathers of the blue-winged leafbird. Dr Saranathan and his team’s breakthrough came from their investigation of the feather colours of leafbirds, an enigmatic group of perching birds endemic to South and Southeast Asia (including Singapore), one species of which has evolved the unique crystals in its plumage.

By comparing the colour-producing nanostructures present in close relatives, the team reported that this species is able to directly synthesise single gyroid photonic crystals, which have highly desirable optical and electronic properties that make them ideal for use in photovoltaic cells to generate solar energy. Use of this crystal – a “crowning achievement” in material science engineering which thus far has been manufactured only with great difficulty – has the potential not only to improve photovoltaic cells, meaning they can be produced more easily and cheaply, but also for use in other industrial applications like catalysis in fuel cells and fibre optics.

Published in Proceedings of the National Academy of Sciences of the United States of America (PNAS), this study is particularly relevant as the search for renewable sources of energy and sustainable manufacturing has taken on a fresh urgency.

Dr Saranathan, who holds a concurrent appointment at the National University of Singapore’s Department of Biological Sciences, said, “Currently, we cannot industrially manufacture single gyroid photonic crystals to work in the visible light spectrum, via self-assembly, a process that spontaneously brings together nanoscale chemical ‘Lego-blocks’. Larger crystals can be manufactured and then heat-shrunk to work with visible light, but so far this can be done only on a small scale and is not defect-free. Thus, our discovery of the first directly self-assembled single gyroid crystals known to science, found in these leafbirds, we think is revolutionary. The way leafbirds manufacture these crystals is much more straightforward than how butterflies (some of which use the same structure in their wing scales) or material scientists are known to do so.”

“Our research provides a clear insight on the class of patchy particles like charged proteins that researchers can investigate in the future, to see if they can be coaxed into forming these crystals at visible light scales. Knowing how leafbirds manufacture these exotic structures can spur novel biomimetic eco-friendly self-assembly strategies for large-scale materials synthesis at these highly challenging optical length-scales, given the urgent ecological need for such materials.”

The research team includes Dr Suresh Narayanan and Dr Alec Sandy from the Argonne National Laboratory, Professor Eric R Dufresne from ETH Zurich, and Professor Richard O Prum from Yale University.

Featured image: Barb tips of male blue-winged leafbirds, showing the presence of colour-producing nanostructures. Image provided by Dr Vinod Kumar Saranathan.


Provided by Yale NUS College

Majority of Lupus Patients with COVID-19 Produce & Maintain Antibody Response (Medicine)

The underlying immune dysregulation in patients with systemic lupus erythematosus (SLE) and their frequent treatment with immunosuppressants have prompted concerns that such patients could be at greater risk for coronavirus disease (COVID-19). A large multidisciplinary study at NYU Langone Health, however, previously supported prior findings that neither lupus-specific factors nor immunosuppressant use appear to increase the risk of infection with the SARS-CoV-2 virus. Among patients who tested positive, a follow-up study has now found that most produced a significant and durable SARS-CoV-2 IgG response, suggesting that these SLE patients may be at least partially protected against reinfection.

Seroprevalence Rates May Suggest That SLE and Therapeutic Regimens Are Not Associated with Higher Risk for COVID-19

In July 2020, NYU Langone researchers published a large study concluding that for SLE patients with PCR-confirmed COVID-19, variables predicting hospitalization matched those of the general population. But given the absence of antibody testing at the time, the study couldn’t capture all potential COVID-19 infections, particularly those that might have been relatively asymptomatic. Led by Amit Saxena, MD, assistant professor of medicine, a follow-up study in The Lancet Rheumatology has used antibody testing to provide a more comprehensive assessment of COVID-19 prevalence among 329 lupus patients from 2 overlapping cohorts at NYU Langone who were recruited primarily as part of routine care.

Overall, the study found that 15.5 percent of the lupus patients had a reactive SARS-CoV-2 antibody test, compared with seroprevalence estimates of about 20 percent in New York City. Within their lupus cohort, Dr. Saxena and colleagues found that seropositive patients were more likely to be Hispanic, and theorized that Hispanic people may have increased exposure to COVID-19 due to systemic drivers impacting their living and working conditions. The researchers, however, found no association between immunosuppressant medications, hydroxychloroquine, or steroid use and COVID-19 seropositivity.

Durability of SARS-CoV-2 IgG Production in Most SLE Patients Points to Lower Risk of Reinfection and Higher Likelihood of Vaccine Protection

A second study arm assessed the extent to which SLE patients who tested positive for COVID-19 developed antibodies against the virus. For patients on lupus medications, especially those that lower immune responses, Dr. Saxena says, clinicians have been concerned that antibody production might be altered. “That also has some indirect associations with vaccinations going forward: Can patients on these medications mount a protective response to those vaccines?” he says.

Of the SLE patients with PCR-confirmed COVID-19, the study found that 83 percent subsequently developed an antibody response to SARS-CoV-2, despite 62 percent being on immunosuppressants. In a subset of patients for whom the initial date of COVID-19 diagnosis was known, 88 percent retained their antibody response 10 weeks later; by 40 weeks, 70 percent still retained positivity. “Probably the biggest take-home point of this study is that the immune response is functional and enough to react to the SARS-CoV-2 virus for the vast majority of our lupus patients, despite the use of immunosuppressants,” Dr. Saxena says.

The patients who were the sickest with COVID-19 sustained their positivity, he notes, while those who lost their positivity started out at the lowest titers. Antibody production is only one component of the body’s complex immune reaction, and Dr. Saxena says memory T cell responses could afford even longer-lasting immunity than antibody responses. “I think it’s safe to say that there’s likely some protection from reinfection in patients who develop these antibodies,” he says. How they may respond to vaccines is a harder question to answer. “But assuming that these patients can generate antibodies to the virus, then there’s no real reason to think they couldn’t create antibodies to antigenic stimulus from a vaccine also, although not all patients were reactive,” he says.

Researchers and clinicians remain concerned that 5 COVID-19–positive patients (17 pervent) did not meet the laboratory threshold for a positive antibody response to the virus, though the study found no clear patterns associated with that negative response. Other studies have found undetectable neutralizing antibodies in a small percentage of patients with milder COVID-19, though Dr. Saxena says several of the SLE patients with negative antibodies had titers just below the positive threshold, suggesting earlier reactivity. The question of whether those patients may have retained some immunity will require additional study of the broader immune response, and Dr. Saxena and colleagues are now testing patients’ immune responses two weeks after vaccination to determine the presence and extent of neutralizing antibodies.

Completing the ambitious study, he says, relied on extensive communication throughout the medical center and the ability to draw upon NYU Langone’s large lupus patient cohorts. “It was a huge team effort. It was really a system-wide endeavor to get this information out as quickly as possible during the height of the pandemic,” Dr. Saxena says. “It’s a large number of patients for a lupus study, and being able to mobilize quickly and accurately speaks to the strong infrastructure we have in place here.”

Featured image: NYU Langone researchers are investigating COVID-19 antibody responses in lupus patients. PHOTO: KTSDESIGN/SCIENCE PHOTO LIBRARY/GETTY


Reference: Amit Saxena, Allison Guttmann et al., “Evaluation of SARS-CoV-2 IgG antibody reactivity in patients with systemic lupus erythematosus: analysis of a multi-racial and multi-ethnic cohort”, Lancet, 2021. DOI: https://doi.org/10.1016/S2665-9913(21)00114-4


Provided by NYU Langone