Throat and nose swab tests for SARS-CoV-2 establish if someone is infected with the virus that causes coronavirus disease 2019 (COVID-19). These tests are highly sensitive — capable of detecting very low viral RNA levels — and are optimal for the early detection of the virus. The performance of these tests depends on the time the sample is collected, with viral load declining after the first week of symptoms. By contrast, antibody tests can determine whether someone has had the virus in the past. For diagnosis later in disease, or in delayed-onset syndromes, antibody tests could form an important part of hospital diagnostic capabilities. In the new study, the researchers developed their own sensitive and specific antibody assay and used it to conduct unbiased, head-to-head comparisons of ten commercial antibody test kits on an identical panel of 110 SARS-CoV-2-positive blood samples from patients admitted to hospitals with COVID-19 and 50 pre-pandemic negatives.

There was a broad range of performance among the tests, with specificity — the ability of the test to correctly identify those without the disease (true negative rate) — ranging from 82% to 100%, and overall sensitivity — the ability of a test to correctly identify those with the disease (true positive rate) — ranging from 60.9% to 87.3%. But all gave the best results when used 20 days or more after the start of symptoms, with most tests reaching a sensitivity value greater than 95%. In addition, antibody levels were higher in individuals with severe illness compared to those with asymptomatic or mild disease. When all commercial tests were compared, lateral flow immunoassays called Accu-Tell, SureScreen and Spring demonstrated highest sensitivity at earlier time points, while maintaining specificities of 98% or above. Such lateral flow immunoassays are affordable, quick and easy to use, and if they are deployed appropriately, could have considerable usefulness in healthcare settings.

Co-author Jonathan Edgeworth notes, “We found that some of the quick single-use kits (LFIAs) are as accurate as our sophisticated laboratory technologies. Encouraged by these findings we are piloting LFIAs in the hospital to give doctors a quick reliable answer in a range of clinical settings.”

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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.