Build a better lab gauge test

Graduate student Dohwan Lee (foreground) tests the new improved fluid flow test developed in the lab of Fatih Sarioglu (left). Postdoctoral researcher Tevhide Ozkaya-Ahmadov (center) is co-author of the team’s recently published study. Credit: Allison Carter

Lateral flow tests (LFAs, often referred to as “oil gauges”) have been a standard point-of-service testing platform for decades and are steadily growing in popularity, particularly in developing countries. These disposable paper diagnostic devices are affordable, widely available, have a long shelf life and are fast, typically providing test results in less than 20 minutes.

They are also easy to use at home. The user adds a few drops of a sample – saliva, blood or urine, for example – to one end of the gauge, and within minutes reads the results at the other end.

The technology has been widely used to determine the presence or absence of biomarkers in humans, as well as contaminants in water or food. Most often, LFA technology is used for home pregnancy tests. And more recently, LFA technology has been used successfully in home tests for COVID-19.

“These tests have been extremely popular for years, mainly because they are so easy to use. You do not send anything to the lab or clinic because these tests do not require any external equipment to function. That’s an advantage, ”said engineering researcher Fatih Sarioglu, who heads the Biomedical Microsystems Laboratory at the Georgia Institute of Technology. “But there is also a downside. There is only so much they can do.

Recognizing the widespread popularity and convenience of test strips, especially in resource-constrained environments, Sarioglu and his research team overcome these limitations by developing flow control technology, transforming these simple tests into complex biomedical tests.

They explain their research and focus on flow technology in two recently published journal articles Scientists progress and ACS sensors. One explains the development of their technology and the other applies the technology in a toolbox to diagnose the novel coronavirus, as well as the flu.

The new user-friendly, disposable liquid flow test includes a heater unit (outfit) and the paper-based test (“gauge”) with built-in flow controller (loaded with dye solutions for demonstration purposes), showing the sequential release of different fluids at reaction points. Credit: Allison Carter

Control the flow

LFAs use capillary liquid flow to detect analytes – capillary flow is the process of passing liquid through a narrow passage (such as a capillary); analytes are substances or chemicals of interest, such as antibodies or proteins, in an analytical procedure (such as an LFA).

Sarioglu explained that conventional LFAs are impractical for performing multistage testing – capillary flow prevents them from coordinating a complex process that includes the application of multiple reagents in a specific sequence with specific delays in between.

In recently published studies, the team describes a technique to control capillary flow by printing roadblocks on laminated paper with water-insoluble ink. The blocked liquid flow is thus handled in a vacuum formed at the interface of the ink infused paper and the polymer tape laminate. By modifying roadblocks, researchers can essentially set the time it takes for a vacuum to form, thereby creating timers that maintain capillary flow for a desired period of time.

“By strategically printing these timers, we can schedule the tests to coordinate different capillary flows,” said Sarioglu, a professor in the School of Electrical and Computer Engineering. “This makes it possible to introduce several liquids and to proceed in several stages chemical reactions, with optimal incubation times, allowing us to perform complex automated tests that otherwise would normally have to be performed in the laboratory. This takes us beyond the conventional LFA.

Build a better gauge
This is the fully assembled liquid flow test developed in the Sarioglu laboratory. Credit: Allison Carter

Disposable laboratory

For the user, the new gauge test works the same as the reliable standard: a sample is added at one end and the results show up a few minutes later in live color (s) at the other end. Sarioglu and his colleagues simply improved and extended the process between the two.

Basically, they drew models on paper – a test strip – and created immunoassays that rival other diagnostic tests requiring laboratories and additional equipment, in the efficient detection of pathogenic targets like Zika virus, HIV. , hepatitis B virus or malaria, among others.

The paper ACS sensors describes a PCR-based point-of-service toolkit based on laboratory flow technology. The test is programmed to perform a sequence of chemical reactions to detect SARS-CoV-2 (Severe Respiratory Syndrome-Coronavirus 2) and / or Influenza A and Influenza B. Traditionally laborious genetic testing can now be performed on a platform. – disposable shape. which will allow frequent and on-demand self-testing, meeting a critical need to monitor and contain epidemics.

The lab is studying the technology’s application for further tests targeting other pathogens, with plans to publish in the coming months. Sarioglu is optimistic that the work will have implications in the current healthcare challenge with COVID-19, and beyond.

“We believe that this flow Technology research will have a widespread impact, ”he said. “This type of strip test is so commonly used by the public for biomedical testing, and now it can be translated into other applications that we do not traditionally consider to be made for these simple tests.”

Researchers develop two new COVID-19 rapid diagnostic tests

More information:
Dohwan Lee et al, Control of capillary flow in lateral flow assays via delamination timers, Scientists progress (2021). DOI: 10.1126 / sciadv.abf9833

Dohwan Lee et al, Point-of-Care Toolkit for Multiplex Molecular Diagnosis of SARS-CoV-2 and Influenza A and B Viruses, ACS sensors (2021). DOI: 10.1021 / acssensors.1c00702

Building a Better Lab Gauge Test (2021, October 18)
retrieved October 19, 2021

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