Nanopore System Allows Diagnostic Testing of Viral Diseases As Accurate as Conventional PCR Tests

During the COVID-19 pandemic, people have become accustomed to swab tests which use at-home rapid diagnostic kits. There are more accurate clinic-provided PCR tests, but they typically require longer processing time. Recently, scientists developed a new diagnostic tool to test for viral diseases as accurately as PCR tests.

Challenges in Using PCR Tests

Polymerase chain reaction (PCR) testing identifies the genetic material in a sample to diagnose infectious diseases and genetic changes. It is currently the standard of accuracy for virology testing.

Despite its effectiveness, this method falls short in different ways. First, PCR tests are highly complex and require chemical reactions that skilled operators should carry out. Since they are typically done at a central laboratory, they sometimes take days to provide the testing results. The complex reactions cannot be ignored since they are needed to amplify viral DNA or RNA molecules.

PCR tests can only detect nucleic acids, or the materials that make up DNA and RNA. In the case of some diseases, however, it would be useful to use other biomarkers, like proteins.

Microfluidic Diagnostic Tool

A new diagnostic tool developed by experts from the University of California (UC) Santa Cruz can solve both of these problems. Led by electrical and computer engineering professor Holger Schmidt, the research team designed a system that requires little sample preparation and is completely free of amplification and labeling. This means that it does not require light to identify biomarkers, potentially cutting down the time and complexity of the diagnostic process.

The novel diagnostic tool combines optofluidics, or the control of tiny amounts of fluids with beams of light, with a nanopore for counting simple nucleic acids to read genetic material. The simple lab-on-a-chip system can perform diagnostic testing at a miniature level with the help of silicon chips, microfluidics, and nanopore detection technologies.

In running the test, a biofluid sample in a container is combined with magnetic microbeads. The scientists used saliva and blood taken from baboons and marmosets kept in the Texas Biomedical Research Institute for this research. The microbeads are designed with a matching RNA sequence of the disease for which the test is designed to detect.

The beads are then put into a silicon microfluidics chip, flowing through a long, thin channel covered by an ultra-thin membrane. Then, they get caught in a light beam, which pushes them against a wall in the channel that contains a nanopore. As heat is applied to the chip, the RNA particles come off the beads, get sucked into the nanopore, and finally detect the presence of virus RNA.

The trials revealed that the test detected the virus even at extremely low concentrations. There were even instances where the PCR test did not detect a case of one of the viruses, which the new system did, indicating that it can be more accurate than PCR.

The microfluidics system is much smaller and less complex than a PCR machine. If this concept is introduced to the market, its compact size can easily fit in a researcher's laboratory. As a result, it can increase testing accessibility and speed up the time needed to provide the results.

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