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Cement-free concrete beats corrosion and gives fatbergs the flush

Researchers from RMIT University have developed an eco-friendly zero-cement concrete, which all but eliminates corrosion.

Concrete corrosion and fatbergs plague sewage systems around the world, leading to costly and disruptive maintenance.

But now RMIT engineers have developed concrete that can withstand the corrosive acidic environment found in sewage pipes, while greatly reducing residual lime that leaches out, contributing to fatbergs.

Fatbergs are gross globs of congealed mass clogging sewers with fat, grease, oil and non-biodegradable junk like wet wipes and nappies, some growing to be 200 metres long and weighing tonnes.

Billion-dollar savings

These build-ups of fat, oil and grease in sewers and pipelines, as well as general corrosion over time, costs billions in repairs and replacement pipes.

The RMIT researchers, led by Dr Rajeev Roychand, created a concrete that eliminates free lime — a chemical compound that promotes corrosion and fatbergs.

Roychand said the solution is more durable than ordinary Portland cement, making it perfect for use in major infrastructure, such as sewage drainage pipes.

“The world’s concrete sewage pipes have suffered durability issues for too long,” Roychand said.

“Until now, there was a large research gap in developing eco-friendly material to protect sewers from corrosion and fatbergs.

“But we’ve created concrete that’s protective, strong and environmental — the perfect trio.”

The perfect blend

By-products of the manufacturing industry are key ingredients of the cement-less concrete — a zero cement composite of nano-silica, fly-ash, slag and hydrated lime.

Not only does their concrete use large volumes of industrial by-products, supporting a circular economy, it surpasses sewage pipe strength standards set by ASTM International.

“Though ordinary Portland cement is widely used in the fast-paced construction industry, it poses long term durability issues in some of its applications,” Roychand said.

“We found making concrete out of this composite blend — rather than cement — significantly improved longevity.”

Sustainable benefits

Replacing underground concrete pipes is a tedious task, ripping up the ground is expensive and often has a ripple effect of prolonged traffic delays and neighbourhood nuisances.

The Water Services Association of Australia estimates maintaining sewage networks costs $15 million each year, billions worldwide.

The environmental cost is greater — ordinary Portland cement accounts for about 5% of the world’s greenhouse gas emissions.

However, the RMIT study has proven certain by-products can be up to the job, replacing cement and able to withstand the high acidity of sewage pipes.

“Our zero-cement concrete achieves multiple benefits: it’s environmentally friendly, reduces concrete corrosion by 96% and totally eliminates residual lime that is instrumental in the formation of fatbergs,” Roychand said.

“With further development, our zero-cement concrete could be made totally resistant to acid corrosion.”

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A cheaper, faster COVID-19 test

Researchers at Karolinska Institutet have developed a method for fast, cheap, yet accurate testing for COVID-19 infection. The method simplifies and frees the testing from expensive reaction steps, enabling upscaling of the diagnostics. This makes the method particularly attractive for places and situations with limited resources. It is equally interesting for repeated testing and for moving resources from expensive diagnostics to other parts of the care chain. The study is published in Nature Communications.

“We started working on the issue of developing a readily available testing method as soon as we saw the developments in Asia and southern Europe, and before the situation reached crisis point in Sweden,” says principal investigator Bjorn Reinius, research leader at the Department of Medical Biochemistry and Biophysics at Karolinska Institutet. “Our method was effectively finished already by the end of April, and we then made all the data freely available online.”

The spread of the new coronavirus at the end of 2019 in China’s Wuhan region quickly escalated into a global pandemic. The relatively high transmission rate and the large number of asymptomatic infections led to a huge, world-wide need for fast, affordable and effective diagnostic tests that could be performed in clinical as well as non-clinical settings.

Established diagnostic tests for COVID-19 are based on the detection of viral RNA in patient samples, such as nasal and throat swabs, from which RNA molecules must then be extracted and purified. RNA purification constitutes a major bottleneck for the testing process, requiring a great deal of equipment and logistics as well as expensive chemical compounds.

Making the current methods simpler without markedly compromising their accuracy means that more and faster testing can be carried out, which would help to reduce the rate of transmission and facilitate earlier-stage care.

The cross-departmental research group at Karolinska Institutet has now developed methods that completely circumvent the RNA-extraction procedure, so that once the patient sample has been inactivated by means of heating, rendering the virus particles no longer infectious, it can pass straight to the diagnostic reaction that detects the presence of the virus.

According to the researchers, the most important keys to the method’s success are both the above virus inactivation procedure and a new formulation of the solution used to collect and transport the sample material taken from the patients.

“By replacing the collection buffer with simple and inexpensive buffer formulations, we can enable viral detection with high sensitivity directly from the original clinical sample, without any intermediate steps,” says Dr Reinius.

Institutions and research groups around the world have shown great interest in the method since a first version of the scientific article was published on the preprint server medRxiv. The article was read more than 15,000 times even before it was peer-reviewed by other researchers in the field and officially published in Nature Communications.

“Thanks to the low cost and the simplicity of the method, it becomes a particularly attractive option at sites and in situations with limited resources but a pressing need to test for COVID-19,” he says and adds: “I would certainly like to see that this test used in Sweden too, for example for cheap periodic testing of asymptomatic people to eliminate the spread of infection.”

The study was supported by grants from the Wallenberg Foundations via the SciLifeLab/KAW National COVID-19 Research Program and from the Ragnar Soderberg Foundation.

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Chemists make cellular forces visible at the molecular scale

Scientists have developed a new technique using tools made of luminescent DNA, lit up like fireflies, to visualize the mechanical forces of cells at the molecular level. Nature Methods published the work, led by chemists at Emory University, who demonstrated their technique on human blood platelets in laboratory experiments.

“Normally, an optical microscope cannot produce images that resolve objects smaller than the length of a light wave, which is about 500 nanometers,” says Khalid Salaita, Emory professor of chemistry and senior author of the study. “We found a way to leverage recent advances in optical imaging along with our molecular DNA sensors to capture forces at 25 nanometers. That resolution is akin to being on the moon and seeing the ripples caused by raindrops hitting the surface of a lake on the Earth.”

Almost every biological process involves a mechanical component, from cell division to blood clotting to mounting an immune response. “Understanding how cells apply forces and sense forces may help in the development of new therapies for many different disorders,” says Salaita, whose lab is a leader in devising ways to image and map bio-mechanical forces.

The first authors of the paper, Joshua Brockman and Hanquan Su, did the work as Emory graduate students in the Salaita lab. Both recently received their PhDs.

The researchers turned strands of synthetic DNA into molecular tension probes that contain hidden pockets. The probes are attached to receptors on a cell’s surface. Free-floating pieces of DNA tagged with fluorescence serve as imagers. As the unanchored pieces of DNA whizz about they create streaks of light in microscopy videos.

When the cell applies force at a particular receptor site, the attached probes stretch out causing their hidden pockets to open and release tendrils of DNA that are stored inside. The free-floating pieces of DNA are engineered to dock onto these DNA tendrils. When the florescent DNA pieces dock, they are briefly demobilized, showing up as still points of light in the microscopy videos.

Hours of microscopy video are taken of the process, then speeded up to show how the points of light change over time, providing the molecular-level view of the mechanical forces of the cell.

The researchers use a firefly analogy to describe the process.

“Imagine you’re in a field on a moonless night and there is a tree that you can’t see because it’s pitch black out,” says Brockman, who graduated from the Wallace H. Coulter Department of Biomedical Engineering, a joint program of Georgia Tech and Emory, and is now a post-doctoral fellow at Harvard. “For some reason, fireflies really like that tree. As they land on all the branches and along the trunk of the tree, you could slowly build up an image of the outline of the tree. And if you were really patient, you could even detect the branches of the tree waving in the wind by recording how the fireflies change their landing spots over time.”

“It’s extremely challenging to image the forces of a living cell at a high resolution,” says Su, who graduated from Emory’s Department of Chemistry and is now a post-doctoral fellow in the Salaita lab. “A big advantage of our technique is that it doesn’t interfere with the normal behavior or health of a cell.”

Another advantage, he adds, is that DNA bases of A, G, T and C, which naturally bind to one another in particular ways, can be engineered within the probe-and-imaging system to control specificity and map multiple forces at one time within a cell.

“Ultimately, we may be able to link various mechanical activities of a cell to specific proteins or to other parts of cellular machinery,” Brockman says. “That may allow us to determine how to alter the cell to change and control its forces.”

By using the technique to image and map the mechanical forces of platelets, the cells that control blood clotting at the site of a wound, the researchers discovered that platelets have a concentrated core of mechanical tension and a thin rim that continuously contracts. “We couldn’t see this pattern before but now we have a crisp image of it,” Salaita says. “How do these mechanical forces control thrombosis and coagulation? We’d like to study them more to see if they could serve as a way to predict a clotting disorder.”

Just as increasingly high-powered telescopes allow us to discover planets, stars and the forces of the universe, higher-powered microscopy allows us to make discoveries about our own biology.

“I hope this new technique leads to better ways to visualize not just the activity of single cells in a laboratory dish, but to learn about cell-to-cell interactions in actual physiological conditions,” Su says. “It’s like opening a new door onto a largely unexplored realm — the forces inside of us.”

Co-authors of the study include researchers from Children’s Healthcare of Atlanta, Ludwig Maximilian University in Munich, the Max Planck Institute and the University of Alabama at Birmingham. The work was funded by grants from the National Institutes of Health, the National Science Foundation, the Naito Foundation and the Uehara Memorial Foundation.

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A computer predicts your thoughts, creating images based on them

Researchers at the University of Helsinki have developed a technique in which a computer models visual perception by monitoring human brain signals. In a way, it is as if the computer tries to imagine what a human is thinking about. As a result of this imagining, the computer is able to produce entirely new information, such as fictional images that were never before seen.

The technique is based on a novel brain-computer interface. Previously, similar brain-computer interfaces have been able to perform one-way communication from brain to computer, such as spell individual letters or move a cursor.

As far as is known, the new study is the first where both the computer’s presentation of the information and brain signals were modelled simultaneously using artificial intelligence methods. Images that matched the visual characteristics that participants were focusing on were generated through interaction between human brain responses and a generative neural network.

The study was published in the Scientific Reports journal in September. Scientific Reports is an online multidisciplinary, open-access journal from the publishers of Nature.

Neuroadaptive generative modelling

The researchers call this method neuroadaptive generative modelling. A total of 31 volunteers participated in a study that evaluated the effectiveness of the technique. Participants were shown hundreds of AI-generated images of diverse-looking people while their EEG was recorded.

The subjects were asked to concentrate on certain features, such as faces that looked old or were smiling. While looking at a rapidly presented series of face images, the EEGs of the subjects were fed to a neural network, which inferred whether any image was detected by the brain as matching what the subjects were looking for.

Based on this information, the neural network adapted its estimation as to what kind of faces people were thinking of. Finally, the images generated by the computer were evaluated by the participants and they nearly perfectly matched with the features the participants were thinking of. The accuracy of the experiment was 83 per cent.

“The technique combines natural human responses with the computer’s ability to create new information. In the experiment, the participants were only asked to look at the computer-generated images. The computer, in turn, modelled the images displayed and the human reaction toward the images by using human brain responses. From this, the computer can create an entirely new image that matches the user’s intention,” says Tuukka Ruotsalo, Academy of Finland Research Fellow at the University of Helsinki, Finland and Associate Professor at the University of Copenhagen, Denmark.

Unconscious attitudes may be exposed

Generating images of the human face is only one example of the technique’s potential uses. One practical benefit of the study may be that computers can augment human creativity.

“If you want to draw or illustrate something but are unable to do so, the computer may help you to achieve your goal. It could just observe the focus of attention and predict what you would like to create,” Ruotsalo says. However, the researchers believe that the technique may be used to gain understanding of perception and the underlying processes in our mind.

“The technique does not recognise thoughts but rather responds to the associations we have with mental categories. Thus, while we are not able to find out the identity of a specific ‘old person’ a participant was thinking of, we may gain an understanding of what they associate with old age. We, therefore, believe it may provide a new way of gaining insight into social, cognitive and emotional processes,” says Senior Researcher Michiel Spapé.

According to Spapé, this is also interesting from a psychological perspective.

“One person’s idea of an elderly person may be very different from another’s. We are currently uncovering whether our technique might expose unconscious associations, for example by looking if the computer always renders old people as, say, smiling men.”

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Researchers develop simple method to 3D print milk products

Researchers from the Singapore University of Technology and Design (SUTD) developed a method to perform direct ink writing (DIW) 3D printing of milk-based products at room temperature, while maintaining its temperature sensitive nutrients.

3D printing of food has been achieved by different printing methods, including the widely used selective laser sintering (SLS) and hot-melt extrusion methods. However, these methods are not always compatible with temperature-sensitive nutrients found in certain types of food. For instance, milk is rich in both calcium and protein, but as these nutrients are temperature sensitive, milk is unsuitable for 3D printing using the aforementioned printing methods which require high temperature. While the cold-extrusion is a viable alternative, it often requires rheology modifiers or additives to stabilize printed structures. Optimizing these additives is a complex and judicious task.

To tackle these limitations, the research team from SUTD’s Soft Fluidics Lab changed the rheological properties of the printing ink and demonstrated DIW 3D printing of milk by cold-extrusion with a single milk product — powdered milk. The team found that the concentration of milk powder allowed for the simple formulation of 3D-printable milk inks using water to control the rheology. Extensive characterizations of the formulated milk ink were also conducted to analyse their rheological properties and ensure optimal printability.

“This novel yet simple method can be used in formulating various nutritious foods including those served to patients in hospitals for their special dietary needs,” said the lead author and Ph.D. candidate from SUTD, Mr Lee Cheng Pau.

“Cold-extrusion does not compromise heat-sensitive nutrients and yet offers vast potential in 3D printing of aesthetically pleasing, nutritionally controlled foods customized for individual requirements,” added Assistant Professor Michinao Hashimoto, the principal investigator of the study.

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Researchers 3D print tiny multicolor microstructures

Researchers have developed an automated 3D printing method that can produce multicolor 3D microstructures using different materials. The new method could be used to make a variety of optical components including optical sensors and light-driven actuators as well as multimaterial structures for applications such as soft robotics and medical applications.

“Combining multiple kinds of materials can be used to create a function that cannot be realized with a single material,” said research team leader Shoji Maruo from Yokohama National University in Japan. “Methods like ours that allow single-step fabrication of multimaterial structures eliminates assembling processes, allowing the production of devices with high precision and low cost.”

In The Optical Society (OSA) journal Optical Materials Express, Maruo and colleagues describe their new 3D printing method and demonstrate it by creating various multicolor 3D structures. Their technique is based on stereolithography, a 3D printing method that is ideal for making microdevices because it uses a tightly focused laser beam to make intricately detailed features.

“The ability to make multimaterial microscale optical elements using 3D printing could aid in the miniaturization of optical devices used for medical treatments and diagnoses,” said Maruo. “This could improve the ability to use these devices in or on the body while also enabling them to be disposable, which would help provide an advanced and safe medical diagnosis.”

Optimizing color stereolithography

Stereolithography builds up a high-precision 3D structure by using a laser to harden light-activated materials known as photocurable resins in a layer by layer fashion. Microfluidics are often used to hold the liquid resins, but it is challenging to keep the different resins from contaminating each other when switching materials without creating large amounts of waste or forming air bubbles in the printed object.

In the new work, the researchers developed a way to hold the various materials in a droplet state, which allows them to be more easily exchanged in a closed space such as a microchannel without creating waste. To suppress air bubbles, the 3D-printed structure is moved around inside the resin each time a resin is replaced. They also integrated a two-step process for cleaning the 3D printed structure when the resins are changed to completely prevent cross-contamination.

To implement this optimized approach, the researchers created a palette to hold multiple resins and placed it, two cleaning tanks and an air blow nozzle on a motorized stage. “All the processes, including 3D printing, resin replacement, bubble removal and cleaning are sequentially carried out using software we developed,” said Maruo. “This allows multicolor 3D microstructures to be created automatically.”

Creating multicolor 3D structures

The researchers tested the approach by placing various types of photocurable resins in a palette and using them to create 3D microstructures. For one of these demonstration structures, a tiny multicolor cube just 1.5 millimeters across, the 3D printing system exchanged five colors of resin 250 times during a 6-hour fabrication process. The researchers also showed that adjusting the number of layers of multicolor resins made it possible to adjust absorbance of each part of the structure, allowing them to create microstructures with colors such as black by combining layers of red, blue, green and yellow.

“This method can be applied not only to multicolor resins but also to a wider variety of materials,” said Maruo. “For example, mixing various ceramic micro- or nanoparticles with a photocurable resin can be used to 3D print various types of glass. It could also be used with biocompatible ceramic materials to create scaffolds for regenerating bones and teeth.”

The researchers are now working to shorten the time required for processes such as resin replacement and bubble removal to allow for even faster fabrication. They also plan to use technology they previously demonstrated to build a multiscale fabrication system in which the fabrication resolution can be changed from less than a micrometer to several tens of micrometers by modifying the focusing lens and laser exposure conditions.

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World’s smallest ultrasound detector created

Researchers at Helmholtz Zentrum München and the Technical University of Munich (TUM) have developed the world’s smallest ultrasound detector. It is based on miniaturized photonic circuits on top of a silicon chip. With a size 100 times smaller than an average human hair, the new detector can visualize features that are much smaller than previously possible, leading to what is known as super-resolution imaging.

Since the development of medical ultrasound imaging in the 1950s, the core detection technology of ultrasound waves has primarily focused on using piezoelectric detectors, which convert the pressure from ultrasound waves into electric voltage. The imaging resolution achieved with ultrasound depends on the size of the piezoelectric detector employed. Reducing this size leads to higher resolution and can offer smaller, densely packed one or two dimensional ultrasound arrays with improved ability to discriminate features in the imaged tissue or material. However, further reducing the size of piezoelectric detectors impairs their sensitivity dramatically, making them unusable for practical application.

Using computer chip technology to create an optical ultrasound detector

Silicon photonics technology is widely used to miniaturize optical components and densely pack them on the small surface of a silicon chip. While silicon does not exhibit any piezoelectricity, its ability to confine light in dimensions smaller than the optical wavelength has already been widely exploited for the development of miniaturized photonic circuits.

Researchers at Helmholtz Zentrum Mu?nchen and TUM capitalized on the advantages of those miniaturized photonic circuits and built the world’s smallest ultrasound detector: the silicon waveguide-etalon detector, or SWED. Instead of recording voltage from piezoelectric crystals, SWED monitors changes in light intensity propagating through the miniaturized photonic circuits.

“This is the first time that a detector smaller than the size of a blood cell is used to detect ultrasound using the silicon photonics technology,” says Rami Shnaiderman, developer of SWED. “If a piezoelectric detector was miniaturized to the scale of SWED, it would be 100 million times less sensitive.”

Super-resolution imaging

“The degree to which we were we able to miniaturize the new detector while retaining high sensitivity due to the use of silicon photonics was breathtaking,” says Prof. Vasilis Ntziachristos, lead of the research team. The SWED size is about half a micron (=0,0005 millimeters). This size corresponds to an area that is at least 10,000 times smaller than the smallest piezoelectric detectors employed in clinical imaging applications. The SWED is also up to 200 times smaller than the ultrasound wavelength employed, which means that it can be used to visualize features that are smaller than one micrometer, leading to what is called super-resolution imaging.

Inexpensive and powerful

As the technology capitalizes on the robustness and easy manufacturability of the silicon platform, large numbers of detectors can be produced at a small fraction of the cost of piezoelectric detectors, making mass production feasible. This is important for developing a number of different detection applications based on ultrasound waves. “We will continue to optimize every parameter of this technology — the sensitivity, the integration of SWED in large arrays, and its implementation in hand-held devices and endoscopes,” adds Shnaiderman.

Future development and applications

“The detector was originally developed to propel the performance of optoacoustic imaging, which is a major focus of our research at Helmholtz Zentrum München and TUM. However, we now foresee applications in a broader field of sensing and imaging,” says Ntziachristos.

While the researchers are primarily aiming for applications in clinical diagnostics and basic biomedical research, industrial applications may also benefit from the new technology. The increased imaging resolution may lead to studying ultra-fine details in tissues and materials. A first line of investigation involves super-resolution optoacoustic (photoacoustic) imaging of cells and micro-vasculature in tissues, but the SWED could be also used to study fundamental properties of ultrasonic waves and their interactions with matter on a scale that was not possible before.

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Researchers demonstrate record speed with advanced spectroscopy technique

Researchers have developed an advanced spectrometer that can acquire data with exceptionally high speed. The new spectrometer could be useful for a variety of applications including remote sensing, real-time biological imaging and machine vision.

Spectrometers measure the color of light absorbed or emitted from a substance. However, using such systems for complex and detailed measurement typically requires long data acquisition times.

“Our new system can measure a spectrum in mere microseconds,” said research team leader Scott B. Papp from the National Institute of Standards and Technology and the University of Colorado, Boulder. “This means it could be used for chemical studies in the dynamic environment of power plants or jet engines, for quality control of pharmaceuticals or semiconductors flying by on a production line, or for video imaging of biological samples.”

In The Optical Society (OSA) journal Optics Express, lead author David R. Carlson and colleagues Daniel D. Hickstein and Papp report the first dual-comb spectrometer with a pulse repetition rate of 10 gigahertz. They demonstrate it by carrying out spectroscopy experiments on pressurized gases and semiconductor wafers.

“Frequency combs are already known to be useful for spectroscopy,” said Carlson. “Our research is focused on building new, high-speed frequency combs that can make a spectrometer that operates hundreds of times faster than current technologies.”

Getting data faster

Dual-comb spectroscopy uses two optical sources, known as optical frequency combs that emit a spectrum of colors — or frequencies — perfectly spaced like the teeth on a comb. Frequency combs are useful for spectroscopy because they provide access to a wide range of colors that can be used to distinguish various substances.

To create a dual-comb spectroscopy system with extremely fast acquisition and a wide range of colors, the researchers brought together techniques from several different disciplines, including nanofabrication, microwave electronics, spectroscopy and microscopy.

The frequency combs in the new system use an optical modulator driven by an electronic signal to carve a continuous laser beam into a sequence of very short pulses. These pulses of light pass through nanophotonic nonlinear waveguides on a microchip, which generates many colors of light simultaneously. This multi-color output, known as a supercontinuum, can then be used to make precise spectroscopy measurements of solids, liquids and gases.

The chip-based nanophotonic nonlinear waveguides were a key component in this new system. These channels confine light within structures that are a centimeter long but only nanometers wide. Their small size and low light losses combined with the properties of the material they are made from allow them to convert light from one wavelength to another very efficiently to create the supercontinuum.

“The frequency comb source itself is also unique compared to most other dual-comb systems because it is generated by carving a continuous laser beam into pulses with an electro-optic modulator,” said Carlson. “This means the reliability and tunability of the laser can be exceptionally high across a wide range of operating conditions, an important feature when looking at future applications outside of a laboratory environment.”

Analyzing gases and solids

To demonstrate the versatility of the new dual-comb spectrometer, the researchers used it to perform linear absorption spectroscopy on gases of different pressure. They also operated it in a slightly different configuration to perform the advanced analytical technique known as nonlinear Raman spectroscopy on semiconductor materials. Nonlinear Raman spectroscopy, which uses pulses of light to characterize the vibrations of molecules in a sample, has not previously been performed using an electro-optic frequency comb.

The high data acquisition speeds that are possible with electro-optic combs operating at gigahertz pulse rates are ideal for making spectroscopy measurements of fast and non-repeatable events.

“It may be possible to analyze and capture the chemical signatures during an explosion or combustion event,” said Carlson. “Similarly, in biological imaging the ability to create images in real time of living tissues without requiring chemical labeling would be immensely valuable to biological researchers.”

The researchers are now working to improve the system’s performance to make it practical for applications like real-time biological imaging and to simplify and shrink the experimental setup so that it could be operated outside of the lab.

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Antibody test developed for COVID-19 that is sensitive, specific and scalable

An antibody test for the virus that causes COVID-19, developed by researchers at The University of Texas at Austin in collaboration with Houston Methodist and other institutions, is more accurate and can handle a much larger number of donor samples at lower overall cost than standard antibody tests currently in use. In the near term, the test can be used to accurately identify the best donors for convalescent plasma therapy and measure how well candidate vaccines and other therapies elicit an immune response.

Additional uses coming later that are likely to have the biggest societal impact, the researchers say, are to assess relative immunity in those previously infected by the SARS-CoV-2 virus and identify asymptomatic individuals with high levels of neutralizing antibodies against the virus.

The UT Austin research team, led by Jason Lavinder, a research associate in the Cockrell School of Engineering, and Greg Ippolito, assistant professor in the College of Natural Sciences and Dell Medical School, developed the new antibody test for SARS-CoV-2 and provided the viral antigens for this study via their UT Austin colleague and collaborator, associate professor Jason McLellan. Other UT Austin team members are Dalton Towers and Jimmy Gollihar. The work was published this week in The Journal of Clinical Investigation.

“This is potentially game-changing when it comes to serological testing for COVID-19 immunity,” Lavinder said. “We can now use highly scalable, automated testing to examine antibody-based immunity to COVID-19 for hundreds of donors in a single run. With increased levels of automation, limited capacity for serological testing can be rapidly addressed using this approach.”

The gold standard of COVID-19 antibody testing measures the amount of virus neutralizing (VN) antibodies circulating in the blood, because this closely correlates with immunity. However, this kind of antibody testing is not widely available because it’s technically complex; requires days to set up, run and interpret; and needs to be performed in a biosafety level 3 laboratory.

The research team, therefore, looked to another type of test, called ELISA assays, that can be implemented and performed with relative ease in a high-throughput fashion and are widely available and extensively used in clinical labs across the world. The ELISA tests, or enzyme-linked immunosorbent assays, look at whether antibodies against specific SARS-CoV-2 proteins are present and produce a quantitative measure of those antibodies.

The goal of the study was to test the hypothesis that levels of antibodies that target two regions of the virus’s spike protein — spike ectodomain (ECD) and receptor binding domain (RBD) — are correlated with virus neutralizing antibody levels, making these more accessible, easier-to-perform ELISA tests a surrogate marker to identify plasma donors with antibody levels above the recommended U.S. Food and Drug Administration threshold for convalescent plasma donation.

In collaboration with UT Austin, Penn State University and the U.S. Army Medical Research Institute of Infectious Diseases, study authors James M. Musser, M.D., Ph.D., and Eric Salazar, M.D., Ph.D., physician scientists at Houston Methodist, used the new test to evaluate 2,814 blood samples used in an ongoing study of convalescent plasma therapy. Houston Methodist became the first academic medical center in the nation to transfuse plasma from recovered individuals into COVID-19 patients.

The researchers found that the ELISA tests had an 80% probability or greater of comparable antibody level to VN levels at or above the FDA-recommended levels for COVID-19 convalescent plasma. These results affirm that all three types of tests could potentially serve as a quantitative target for therapeutic and prophylactic treatments.

Ultimately, the study successfully concluded that anti-RBD or anti-ECD antibody levels can serve as a surrogate for VN levels to identify suitable plasma donors and that these alternate ELISA tests may provide critical information about COVID-19 immunity.

“This research required a perfect storm at the university, which included the extraordinary combination of a world-famous coronavirus structural biology lab, a nimble and passionate visiting army scientist, and the highest echelons of the university’s administration who were committed to bringing our extensive research programs to bear on the COVID-19 crisis,” Ippolito said.

This study was supported by funding from the National Institutes of Health, the Fondren Foundation, the National Institute of Allergy and Infectious Diseases, the Army Research Office, Houston Methodist Hospital, Houston Methodist Infectious Diseases Research Fund, Houston Methodist Research Institute and seed funding from the Huck Institutes of the Life Sciences for the studies at Penn State, together with the Huck Distinguished Chair in Global Health award. Funding was also provided through the CARES Act, with programmatic oversight from the Military Infectious Diseases Research Program.

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New ultrafast yellow laser poised to benefit biomedical applications

Researchers have developed a new compact and ultrafast, high-power yellow laser. The tunable laser exhibits excellent beam quality and helps fill the need for a practical yellow light source emitting ultrafast pulses of light.

“The yellow-orange spectral range is highly absorbed by hemoglobin in the blood, making lasers with these wavelengths particularly useful for biomedical applications, dermatology treatments and eye surgery,” said research team member Anirban Ghosh from the Photonic Sciences Lab at the Physical Research Laboratory in India. “A femtosecond, tunable yellow laser source might one day offer medical treatments that produce less thermal damage and are more selective.”

In The Optical Society (OSA) journal Optics Letters, researchers led by Goutam K. Samanta describe how they used an optical phenomenon known as nonlinear frequency conversion to convert mid-infrared laser light into yellow light that can be tuned from 570 nm to 596 nm.

“We demonstrate a robust, high-power, ultrafast, tunable yellow radiation in a rather simple experimental configuration,” said Ghosh. “In addition to biomedical applications, this is a sought-after wavelength range for full-color video projection and could be used for a variety of spectral applications.”

Building a better yellow laser

Although studies have shown that laser emitting in the yellow spectral range are optimal for various medical treatments, such wavelengths are usually created using bulky and inefficient copper vapor lasers, dye lasers and optical parametric oscillators. These sources have been used successfully for various applications, but they suffer from one or more drawbacks such as low average power, lack of good spatial beam profile, limited or no wavelength tunability and broad output pulses.

“Femtosecond lasers are important for many applications because they emit a large number of photons in a short period to provide a very high intensity and extremely high precision without causing any thermal damage,” said Ghosh. “However, there is no commercially available femtosecond yellow laser that can provide all the desired parameters needed for the applications that would benefit from this wavelength range.”

To address these limitations in a single experimental configuration, the researchers used a recently developed ultrafast solid-state Cr2+:ZnS laser emitting in the mid-infrared range along with a two-stage frequency-doubling process. Frequency doubling an ultrafast laser is not an easy process and requires identifying the right crystal to produce a quality laser output with the desired properties.

“We frequency-doubled the ultrafast mid-infrared laser with a peak wavelength at 2360 nm in two different nonlinear crystals and used simple optical components available in any standard optics laboratory to achieve high power, tunable, ultrafast yellow laser source,” said Ghosh. “As a byproduct, our source provides tunable ultrafast near-infrared radiation with substantial average power useful for various fields, including spectroscopy, material processing and imaging.”

Tests of the new laser showed that it can provide a maximum output average power over 1 W with 130 femtosecond pulses at a repetition rate of 80 MHz with an outstanding spatial beam profile. The researchers also observed excellent power stability over a long duration.

The researchers plan to further improve the laser’s pulse duration, efficiency and compactness. They are also working to optimize the laser so that it can operate at room temperature to make it more practical for long-term use.

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Materials provided by The Optical Society. Note: Content may be edited for style and length.

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