Researchers led by David Pine, professor of chemical and biomolecular engineering at the NYU Tandon School of Engineering and professor of physics at NYU, have devised a new process for the reliable self-assembly of colloids in a diamond formation that could lead to cheap, scalable fabrication of such structures. The discovery, detailed in “Colloidal Diamond,” appearing in the September 24 issue of Nature, could open the door to highly efficient optical circuits leading to advances in optical computers and lasers, light filters that are more reliable and cheaper to produce than ever before, and much more.

Pine and his colleagues, including lead author Mingxin He, a postdoctoral researcher in the Department of Physics at NYU, and corresponding author Stefano Sacanna, associate professor of chemistry at NYU, have been studying colloids and the possible ways they can be structured for decades. These materials, made up of spheres hundreds of times smaller than the diameter of a human hair, can be arranged in different crystalline shapes depending on how the spheres are linked to one another. Each colloid attaches to another using strands of DNA glued to surfaces of the colloids that function as a kind of molecular Velcro. When colloids collide with each other in a liquid bath, the DNA snags and the colloids are linked. Depending on where the DNA is attached to the colloid, they can spontaneously create complex structures.

This process has been used to create strings of colloids and even colloids in a cubic formation. But these structures did not produce the Holy Grail of photonics — a band gap for visible light. Much as a semiconductor filters out electrons in a circuit, a band gap filters out certain wavelengths of light. Filtering light in this way can be reliably achieved by colloids if they are arranged in a diamond formation, a process deemed too difficult and expensive to perform at commercial scale.

“There’s been a great desire among engineers to make a diamond structure,” said Pine. “Most researchers had given up on it, to tell you the truth — we may be the only group in the world who is still working on this. So I think the publication of the paper will come as something of a surprise to the community.”

The investigators, including Etienne Ducrot, a former postdoc at NYU Tandon, now at the Centre de Recherche Paul Pascal — CNRS, Pessac, France; and Gi-Ra Yi of Sungkyunkwan University, Suwon, South Korea, discovered that they could use a steric interlock mechanism that would spontaneously produce the necessary staggered bonds to make this structure possible. When these pyramidal colloids approached each other, they linked in the necessary orientation to generate a diamond formation. Rather than going through the painstaking and expensive process of building these structures through the use of nanomachines, this mechanism allows the colloids to structure themselves without the need for outside interference. Furthermore, the diamond structures are stable, even when the liquid they form in is removed.

The discovery was made because He, a graduate student at NYU Tandon at the time, noticed an unusual feature of the colloids he was synthesizing in a pyramidal formation. He and his colleagues drew out all of the ways these structures could be linked. When they happened upon a particular interlinked structure, they realized they had hit upon the proper method. “After creating all these models, we saw immediately that we had created diamonds,” said He.

“Dr. Pine’s long-sought demonstration of the first self-assembled colloidal diamond lattices will unlock new research and development opportunities for important Department of Defense technologies which could benefit from 3D photonic crystals,” said Dr. Evan Runnerstrom, program manager, Army Research Office (ARO), an element of the U.S. Army Combat Capabilities Development Command’s Army Research Laboratory.

He explained that potential future advances include applications for high-efficiency lasers with reduced weight and energy demands for precision sensors and directed energy systems; and precise control of light for 3D integrated photonic circuits or optical signature management.

“I am thrilled with this result because it wonderfully illustrates a central goal of ARO’s Materials Design Program — to support high-risk, high-reward research that unlocks bottom-up routes to creating extraordinary materials that were previously impossible to make.”

The team, which also includes John Gales, a graduate student in physics at NYU, and Zhe Gong, a postdoc at the University of Pennsylvania, formerly a graduate student in chemistry at NYU, are now focused on seeing how these colloidal diamonds can be used in a practical setting. They are already creating materials using their new structures that can filter out optical wavelengths in order to prove their usefulness in future technologies.

This research was supported by the US Army Research Office under award number W911NF-17-1-0328. Additional funding was provided by the National Science Foundation under award number DMR-1610788.

While the maternal gut microbiota has been associated with abnormalities in the brain function and behavior of offspring — often in response to factors like infection, a high-fat diet or stress during pregnancy — scientists had not known until now whether it influenced brain development during critical prenatal periods and in the absence of such environmental challenges.

To test the impact the gut microbiata has on the metabolites and other biochemicals that circulate in maternal blood and nurture the rapidly developing fetal brain, the researchers raised mice that were treated with antibiotics to kill gut bacteria, as well as mice that were bred microbe-free in a laboratory.

“Depleting the maternal gut microbiota, using both methods, similarly disrupted fetal brain development,” said the study’s lead author, Helen Vuong, a postdoctoral scholar in laboratory of UCLA’s Elaine Hsiao.

Depleting the maternal gut microbiota altered which genes were turned on in the brains of developing offspring, including many genes involved in forming new axons within neurons, Vuong said. Axons are tiny fibers that link brain cells and enable them to communicate.

In particular, axons that connect the brain’s thalamus to its cortex were reduced in number and in length, the researchers found.

“These axons are particularly important for the ability to sense the environment,” Vuong said. “Consistent with this, offspring from mothers lacking a gut microbiota had impairments in particular sensory behaviors.”

The findings indicate that the maternal gut microbiota can promote healthy fetal brain development by regulating metabolites that enter the fetal brain itself, Vuong said.

“When we measured the types and levels of molecules in the maternal blood, fetal blood and fetal brain, we found that particular metabolites were commonly decreased or missing when the mother was lacking a gut microbiota during pregnancy,” she said.

The biologists then grew neurons in the presence of these key metabolites. They also introduced these metabolites into the microbiata-depleted pregnant mice.

“When we grew neurons in the presence of these metabolites, they developed longer axons and greater numbers of axons,” Vuong said. “And when we supplemented the pregnant mice with key metabolites that were decreased or missing when the microbiata was depleted, levels of those metabolites were restored in the fetal brain and the impairments in axon development and in offspring behavior were prevented.

“The gut microbiota has the incredible capability to regulate many biochemicals not only in the pregnant mother but also in the developing fetus and fetal brains,” Vuong said. “Our findings also pinpoint select metabolites that promote axon growth.”

The results suggest that interactions between the microbiota and nervous system begin prenatally through the influence of the maternal gut microbiota on the fetal brain, at least in mice.

The applicability of the findings to humans is still unclear, said the study’s senior author, Elaine Hsiao, a UCLA associate professor of integrative biology and physiology, and of microbiology, immunology and molecular genetics in the UCLA College.

“We don’t know whether and how the findings may apply to humans,” said Hsiao, who is also an associate professor of digestive diseases at the David Geffen School of Medicine at UCLA. “However, there are many neurodevelopmental disorders that are believed to be caused by both genetic and environmental risk factors experienced during pregnancy. Our study suggests that maternal gut microbiota during pregnancy should also be considered and further studied as a factor that could potentially influence not only the health of the mother but the health of the developing offspring as well.”

Hsiao, Vuong and colleagues reported in 2019 that serotonin and drugs that target serotonin, such as antidepressants, can have a major effect on the gut’s microbiota. In 2018, Hsiao and her team established a causal link between seizure susceptibility and gut microbiota and identified specific gut bacteria that play an essential role in the anti-seizure effects of the ketogenic diet.

Hearing aids are a major tool for individuals with hearing loss — especially age-related hearing loss, which currently affects approximately 226 million adults over the age of 65 worldwide (and is projected to affect 900 million by 2050). However, hearing aid adoption remains relatively low among adults: fewer than 3 percent of adults in low-and-middle-income countries (LMIC) use hearing aids, versus around 20 percent of adults in non-LMIC countries. Though various reasons contribute to this poor uptake, cost is a significant factor. While the price to manufacture hearing aids has decreased over time, the retail price for a pair of hearing aids ranges from $1,000 to $8,000 USD, with the average pair costing $4,700 in the US.

In this study, Sinha and colleagues used mass-produced open source electronics to engineer a durable, affordable, self-serviceable hearing aid that meets most of the targets set by the WHO for mild-to-moderate age-related hearing loss: “LoCHAid.” When mass-produced at 10,000 units including earphones, a coin-cell battery, and holder, LoCHAid costs $0.98 (this doesn’t include labor costs) and is designed to be marketed over-the-counter — or even as a DIY project. LoCHAid doesn’t require specialty parts, and repairs can be completed by a minimally skilled user with access to a soldering iron and solder. Though it’s not currently programmable, simulations show that the LoCHAid is well fitted to a range of age-related hearing loss profiles for men and women between the ages of 60-79 years.

Potential limitations include the device lifetime (currently 1.5 years), as well as its relatively large size, which may not appeal to all consumers. The authors are currently working on a smaller prototype, but this costs more money to produce and would likely require third-party assemblers.

Despite these limitations, LoCHAid shows great potential to benefit individuals impacted by age-related hearing loss, especially those consumers challenged by the affordability and accessibility of current hearing aids available on the market.

The authors add: “In this work, we describe the development and rigorous audiological testing a minimal, 3d-printed and ultra low-cost ($1 in parts) hearing aid. The vision of the device is to make hearing aid accessible and affordable for elderly individuals with age related hearing loss in low- and middle-income countries.”

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Rheumatoid arthritis is the most common type of autoimmune arthritis, caused when the immune system attacks healthy cells in the linings of joints. Over the last decade it has become clear that there are differences in RA patients with and without RA-associated autoantibodies detectable in their blood. In the new study, researchers followed 1,285 RA patients between 1993 and 2016 through the Leiden Early Arthritis Clinic cohort. Data on patients’ symptoms, treatments, autoantibody status, disability and mortality was collected annually.

In total, 823 patients had autoantibody-positive RA and 462 patients had autoantibody-negative RA. In both groups, disease activity decreased significantly over time. Sustained drug-free remission rates increased, as a new treat-to-target treatment strategy became common in 2006 to 2010, in patients with autoantibody-positive, but not autoantibody-negative, RA. Moreover, mortality and functional disability rates decreased with treat-to-target adjustments only in autoantibody-positive patients.

“The disconnection between improvement in disease activity and subsequent improvement in long-term outcomes in RA without autoantibodies suggests that the underlying pathogenesis of RA with and without autoantibodies is different,” the authors say. “We propose that it is time to formally divide RA into type 1, with autoantibodies, and type 2, without autoantibodies, in the hope that it leads to stratified treatment in autoantibody-positive and autoantibody-negative RA.”

Dr. Matthijssen notes “In the last decennia research in RA has largely focused on the autoantibody-positive subset. More research on autoantibody-negative RA is urgently needed to identify methods to also improve their long-term outcomes.”

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Previous research suggests that people from racial and ethnic minority backgrounds are at greater risk of severe or deadly cases of COVID-19. However, most studies of these disparities have only investigated patients who had already tested positive or who were hospitalized. Understanding disparities in who was tested and whether they tested positive could help inform efforts to reduce the burden of COVID-19 in minority communities.

To improve understanding of testing disparities, Rentsch and colleagues investigated statistical associations between 5.8 million VA patients’ race/ethnicity and their detailed medical records (the VA comprises more than 1,200 points-of-care nationally including hospitals, medical centers, and community outpatient clinics, with around nine million individuals accessing VA care each year), including COVID-19 testing records from February 8 through July 22, 2020. 91% of participants were male; 7% were of Hispanic ethnicity, 19% were Black and 74% were White.

Over 250,000 of the patients studied received a COVID-19 test during the study period, 16,317 tested positive, and 1,057 died within 30 days of testing. Black and Hispanic patients were more likely to receive a test and were more likely to test positive than White patients, even when accounting for other demographics underlying medical conditions and geographic location (Black vs White adjusted Odds Ratio 1.93, 95% CI 1.85-2.01, p<0.001; Hispanic vs White 1.84, 1.74-1.94, p<0.001).

For positive test rates, the disparity between White and Black patients was greatest in the Midwest and decreased slightly overall during the study. The positive-test disparity between Hispanic and White patients was consistent across regions and over time. Among the cohort of 5.8 million people, although those from minority backgrounds appeared to have a higher burden of COVID-19, for those who tested positive, no racial or ethnic disparities in 30-day death rates were seen.

These findings suggest that Black and Hispanic individuals experience a disproportionate risk of COVID-19 infection, even when accounting for where they live and underlying medical conditions. The authors call for urgent state- and local-level strategies to reduce COVID-19 spread in minority communities.

Dr. Rentsch says: “Minority individuals who received a positive COVID-19 test did not appear to have worse outcomes. However, Black and Hispanic individuals were still twice as likely to testing positive for COVID-19, even after accounting for underlying health conditions, other demographics, and geographic location. Taken together, these findings suggest a substantial excess burden of COVID-19 infection in US minority communities.” He adds: “Understanding what is driving these disparities is vital so that strategies can be tailored to curb the disproportionate epidemics in minority communities…going forward, we are exploring whether racial and ethnic disparities exist at other key stages in the clinical course of COVID-19, from hospitalization to intubation. We appeal to other researchers who have the necessary testing data to investigate disparities in testing and testing positive. This will provide essential information to design effective interventions.”

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