Tag Archives: enzyme-linked immunosorbent assay (ELISA)

Spotting the difference between dengue and Zika infections with gold nanosensors

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This July 29, 2020 news item on Nanowerk features research from Brazil,

A new class of nanosensor developed in Brazil could more accurately identify dengue and Zika infections, a task that is complicated by their genetic similarities and which can result in misdiagnosis.

The technique uses gold nanoparticles and can “observe” viruses at the atomic level, according to a study published in Scientific Reports (“Nanosensors based on LSPR are able to serologically differentiate dengue from Zika infections”).

Belonging to the Flavivirus genus in the Flaviviridae family, Zika and dengue viruses share more than 50 per cent similarity in their amino acid sequence. Both viruses are spread by mosquitos and can have long-term side effects. The Flaviviridae virus family was named after the yellow fever virus and comes from the Latin word for golden, or yellow, in colour.

“Diagnosing [dengue virus] infections is a high priority in countries affected by annual epidemics of dengue fever. The correct diagnostic is essential for patient managing and prognostic as there are no specific antiviral drugs to treat the infection,” the authors say.

More than 1.8 million people are suspected to have been infected with dengue so far this year in the Americas, with 4000 severe cases and almost 700 deaths, the Pan American Health Organization says. The annual global average is estimated to be between 100 million and 400 million dengue infections, according to the World Health Organization.

Flávio Fonseca, study co-author and researcher at the Federal University of Minas Gerais, tells SciDev.Net it is almost impossible to differentiate between dengue and Zika viruses.

“A serologic test that detects antibodies against dengue also captures Zika-generated antibodies. We call it cross-reactivity,” he says.

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Meghie Rodrigues’ July 29, 2020 article for SciDev.net, which originated the news item, delves further into the work,

Co-author and virologist, Maurício Nogueira, tells SciDev.Net that avoiding cross-reactivity is crucial because “dengue is a disease that kills — and can do so quickly if the right diagnosis is not made. As for Zika, it offers risks for foetuses to develop microcephaly, and we can’t let pregnant women spend seven or eight months wondering whether they have the virus or not.”

There is also no specific antiviral treatment for Zika and the search for a vaccine is ongoing.

Virus differentiation is important to accurately measure the real impact of both diseases on public health. The most widely used blood test, the enzyme-linked immunosorbent assay (ELISA), is limited in its ability to tell the difference between the viruses, the authors say.

As dengue has four variations, known as serotypes, the team created four different nanoparticles and covered each of them with a different dengue protein. They applied ELISA serum and a blood sample. The researchers found that sample antibodies bound with the viruses’ proteins, changing the pattern of electrons on the gold nanoparticle surface.

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Should you check out Rodrigues’ entire article, you might want to take some time to explore SciDev.net to find science news from countries that don’t often get the coverage they should.

Here’s a link to and a citation for the researchers’ paper,

Nanosensors based on LSPR are able to serologically differentiate dengue from Zika infections by Alice F. Versiani, Estefânia M. N. Martins, Lidia M. Andrade, Laura Cox, Glauco C. Pereira, Edel F. Barbosa-Stancioli, Mauricio L. Nogueira, Luiz O. Ladeira & Flávio G. da Fonseca. Scientific Reports volume 10, Article number: 11302 (2020) DOI: https://doi.org/10.1038/s41598-020-68357-9 Published: 09 July 2020

This paper is open access.

Faster diagnostics with nanoparticles and magnetic phenomenon discovered 170 years ago

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A Jan. 19, 2017 news item on ScienceDaily announces some new research from the University of Central Florida (UCF),

A UCF researcher has combined cutting-edge nanoscience with a magnetic phenomenon discovered more than 170 years ago to create a method for speedy medical tests.

The discovery, if commercialized, could lead to faster test results for HIV, Lyme disease, syphilis, rotavirus and other infectious conditions.

“I see no reason why a variation of this technique couldn’t be in every hospital throughout the world,” said Shawn Putnam, an assistant professor in the University of Central Florida’s College of Engineering & Computer Science.

A Jan. 19, 2017 UCF news release by Mark Schlueb, which originated the news item,  provides more technical detail,

At the core of the research recently published in the academic journal Small are nanoparticles – tiny particles that are one-billionth of a meter. Putnam’s team coated nanoparticles with the antibody to BSA, or bovine serum albumin, which is commonly used as the basis of a variety of diagnostic tests.

By mixing the nanoparticles in a test solution – such as one used for a blood test – the BSA proteins preferentially bind with the antibodies that coat the nanoparticles, like a lock and key.

That reaction was already well known. But Putnam’s team came up with a novel way of measuring the quantity of proteins present. He used nanoparticles with an iron core and applied a magnetic field to the solution, causing the particles to align in a particular formation. As proteins bind to the antibody-coated particles, the rotation of the particles becomes sluggish, which is easy to detect with laser optics.

The interaction of a magnetic field and light is known as Faraday rotation, a principle discovered by scientist Michael Faraday in 1845. Putnam adapted it for biological use.

“It’s an old theory, but no one has actually applied this aspect of it,” he said.

Other antigens and their unique antibodies could be substituted for the BSA protein used in the research, allowing medical tests for a wide array of infectious diseases.

The proof of concept shows the method could be used to produce biochemical immunology test results in as little as 15 minutes, compared to several hours for ELISA, or enzyme-linked immunosorbent assay, which is currently a standard approach for biomolecule detection.

Here’s a link to and a citation for the paper,

High-Throughput, Protein-Targeted Biomolecular Detection Using Frequency-Domain Faraday Rotation Spectroscopy by Richard J. Murdock, Shawn A. Putnam, Soumen Das, Ankur Gupta, Elyse D. Z. Chase, and Sudipta Seal. Small DOI: 10.1002/smll.201602862 Version of Record online: 16 JAN 2017

© 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

This paper is behind a paywall.

Faster predictive toxicology of nanomaterials

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As more nanotechnology-enabled products make their way to the market and concerns rise regarding safety, scientists work to find better ways of assessing and predicting the safety of these materials, from an Aug. 13, 2016 news item on Nanowerk,

UCLA [University of California at Los Angeles] researchers have designed a laboratory test that uses microchip technology to predict how potentially hazardous nanomaterials could be.

According to UCLA professor Huan Meng, certain engineered nanomaterials, such as non-purified carbon nanotubes that are used to strengthen commercial products, could have the potential to injure the lungs if inhaled during the manufacturing process. The new test he helped develop could be used to analyze the extent of the potential hazard.

An Aug. 12, 2016 UCLA news release, which originated the news item, expands on the theme,

The same test could also be used to identify biological biomarkers that can help scientists and doctors detect cancer and infectious diseases. Currently, scientists identify those biomarkers using other tests; one of the most common is called enzyme-linked immunosorbent assay, or ELISA. But the new platform, which is called semiconductor electronic label-free assay, or SELFA, costs less and is faster and more accurate, according to research published in the journal Scientific Reports.

The study was led by Meng, a UCLA assistant adjunct professor of medicine, and Chi On Chui, a UCLA associate professor of electrical engineering and bioengineering.

ELISA has been used by scientists for decades to analyze biological samples — for example, to detect whether epithelial cells in the lungs that have been exposed to nanomaterials are inflamed. But ELISA must be performed in a laboratory setting by skilled technicians, and a single test can cost roughly $700 and take five to seven days to process.

In contrast, SELFA uses microchip technology to analyze samples. The test can take between 30 minutes and two hours and, according to the UCLA researchers, could cost just a few dollars per sample when high-volume production begins.

The SELFA chip contains a T-shaped nanowire that acts as an integrated sensor and amplifier. To analyze a sample, scientists place it on a sensor on the chip. The vertical part of the T-shaped nanowire converts the current from the molecule being analyzed, and the horizontal portion amplifies that signal to distinguish the molecule from others.

The use of the T-shaped nanowires created in Chui’s lab is a new application of a UCLA patented invention that was developed by Chui and his colleagues. The device is the first time that “lab-on-a-chip” analysis has been tested in a scenario that mimics a real-life situation.

The UCLA scientists exposed cultured lung cells to different nanomaterials and then compared their results using SELFA with results in a database of previous studies that used other testing methods.

“By measuring biomarker concentrations in the cell culture, we showed that SELFA was 100 times more sensitive than ELISA,” Meng said. “This means that not only can SELFA analyze much smaller sample sizes, but also that it can minimize false-positive test results.”

Chui said, “The results are significant because SELFA measurement allows us to predict the inflammatory potential of a range of nanomaterials inside cells and validate the prediction with cellular imaging and experiments in animals’ lungs.”

Here’s a link to and a citation for the paper,

Semiconductor Electronic Label-Free Assay for Predictive Toxicology by Yufei Mao, Kyeong-Sik Shin, Xiang Wang, Zhaoxia Ji, Huan Meng, & Chi On Chui. Scientific Reports 6, Article number: 24982 (2016) doi:10.1038/srep24982 Published online: 27 April 2016

This paper is open access.