Researchers at Georgia Tech have developed a lateral flow test platform that can perform advanced assays that would otherwise require a laboratory. By controlling the flow of liquid through the lateral flow test, the research team designed it so that it can perform advanced multistep assays that do not require sophisticated lab equipment and significant periods of time. So far, they have designed advanced dipstick tests that can detect both COVID-19 and influenza simultaneously, and others that can perform immunoassays to detect Zika virus, HIV, hepatitis B virus, or malaria.
Lateral flow assays, otherwise known as dipstick tests, are a very convenient way to perform biological measurements just about anywhere. The most commonly used lateral flow assay is the ubiquitous pregnancy test, and during the COVID-19 pandemic lateral flow antigen tests have been used as a quick assessment of COVID status in many countries.
Lateral flow technology is very simple to use, requiring the user to add a few drops of their sample to one end of the device (or dip it into a sample), and this liquid then flows through a matrix because of capillary action, and typically displays the results visually within 15-30 minutes. While the technology is convenient and fast, to date, the types of tests that lateral flow devices can perform have been limited. Advanced assays requiring multiple steps that are performed at specific times, with different incubation periods in between, are typically beyond the abilities of such technology.
“These tests have been extremely popular for years, mainly because they are so simple to use. You don’t send anything to the lab or clinic because these tests don’t require any external equipment to operate. This is an advantage,” said Fatih Sarioglu, a researcher involved in the study, in a Georgia Tech announcement. “But there also is a disadvantage. There are limitations to what they can do.”
To advance the technology further, and allow multistep assays, the researchers used water insoluble ink to introduce “roadblocks” that help to control the capillary flow through the device, creating ‘timers’ that hold the liquid at certain points for a specific time.
“By strategically imprinting these timers, we can program the assays to coordinate different capillary flows,” said Sarioglu. “That enables multiple liquids to be introduced, and multistep chemical reactions, with optimal incubation times – so, we can perform complex, automated assays that otherwise would normally have to be performed in laboratories. This takes us beyond the conventional lateral flow assays.”
Study in Science Advances: Capillary flow control in lateral flow assays via delaminating timers
Via: Georgia Tech