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Denso, Japanese Universities Using Semiconductor, Aptamer Technology to Develop SARS-CoV-2 Biosensor


NEW YORK ─ Automotive components manufacturer Denso is collaborating with Japanese universities to develop a SARS-CoV-2 biosensor they believe can be more sensitive than antigen tests and provide results in about 10 minutes.

The automotive firm, based in Kariya, Japan, is collaborating with Tokai University, Toyohashi University of Technology, and Chubu University as part of a program funded with an undisclosed amount by the Japanese government's Japan Agency for Medical Research and Development.

So far, according to Kazuhisa Nakagawa, one of the biosensor developers in the Material Research and Innovation division at Denso, the researchers have devised a proof-of-concept prototype that has provided promising results in preliminary clinical studies.

The testing platform consists of a small instrument and disposable cartridge that can be used to conduct a single test or be aligned in parallel to conduct many tests at once at the point of care, Nakagawa said.

It uses an aptamer, an artificially synthesized nucleic acid molecule that binds with proteins, to detect the SARS-CoV-2 spike protein. "A semiconductor sensor subsequently measures changes in an electric current when the SARS-CoV-2 viral infection is present in a sample and has the potential to provide a quantitative measurement of viral loads," Nakagawa said.

Testing for SARS-CoV-2 has relied primarily on RT-PCR- and antigen-based technologies but each modality has its issues, Nakagawa noted.

Antigen tests are more affordable and generally more suitable for point-of-care and at-home use than RT-PCR tests, but they lack sensitivity which can lead to inaccurate test results. Meanwhile, PCR tests in general are the most sensitive available but they are also expensive, require training to operate them, and can provide positive results for individuals that are not contagious.

With much COVID-19 testing worldwide remaining slow, expensive, and inaccessible to some, the aptamer-based biosensor has the potential to add another testing modality to current methods to detect SARS-CoV-2 active infection.

According to Nakagawa, Denso and its collaborators believe they can fill a gap in current testing with a platform that is affordable and easy to use, while providing high levels of sensitivity and specificity. The researchers are seeing limits of detection of 100 copies per microliter, which is better than current antigen tests but less sensitive than RT-PCR, Nakagawa said, adding the researchers are fine-tuning the platform to improve the performance of the biosensor. They are aiming for sensitivity levels that are equivalent to or better than that of RT-PCR, he noted.

The proof-of-concept prototype provides test results in about 30 minutes, but the researchers believe that they can reduce that to 10 minutes, a time-to-result that is equivalent to or better than current antigen tests. In early testing, they observed no cross-reactivity with influenza A, influenza B, human coronavirus-229E, and rhinovirus, Nakagawa added.

Denso said that as the researchers continue to improve the current prototype, they are doing additional testing to assess its performance using clinical samples. Further, they are applying for a patent for the test and instrument, and plan in the future to pursue publications in peer-reviewed journals that describe studies to evaluate the test.

Still, without such evidence, it is currently difficult to assess the researchers' claims, said Pawan Jolly, biosensors and diagnostics team lead at Harvard University's Wyss Institute.

"If the virus is present, the test will detect it by binding to the spike protein," and that is similar to the way current antigen tests operate, said Jolly who is not associated with the Japanese biosensor project but is leading the development of an electrochemical detection technology to detect SARS-CoV-2 and other infections at the point of care.

However, a potential advantage of using aptamers, which could differentiate the test from others, is that they could "increase the sensitivity" of the semiconductors, he added.

"The idea of using aptamers to replace antibodies for diagnostics use has been around for more than a decade, but that promise has yet to be realized," said Katleen Verleysen, CEO of Leuven, Belgium-based MiDiagnostics, which is developing a breath test that catches aerosols carrying SARS-CoV-2 viral particles for testing by a qPCR instrument.

"Specificity will always be a concern and the right aptamer design is key," she said.

Still, "measuring changes through electrical current holds a lot of promise and could allow for more sensitive direct detection," said Verleysen, who is not affiliated with the Japanese biosensor project.

Numerous diagnostic test developers are exploring aptamers, which have the potential to eliminate such issues as lot-to-lot variation in the supply of antibodies, which can lead to performance issues in tests that use the antibodies.

For example, in March, UK-based reagent provider Aptamer Group announced a partnership with Mologic to develop a rapid aptamer-based lateral flow antigen test, which detects the SARS-CoV-2 spike protein antigen in anterior nasal swabs.

Additionally, biosensor test developers are pursuing assays that they believe could add variety to currently available SARS-CoV-2 tests and improve on the performance of some of them.  

In April, Greensboro, North Carolina-based biosensor test developer Qorvo Biotechnologies received US Food and Drug Administration Emergency Use Authorization for its bulk acoustic wave SARS-CoV-2 test. Other biosensor groups are developing tests with the intention of getting regulatory authorizations or approvals including Madrid-based startup Mecwins and Boston-based InnoTech Precision Medicine, which is collaborating with the Massachusetts Institute of Technology.

The prototype developed by the Japanese research team uses nasopharyngeal swabs but the group is working to develop the test for use with saliva, a more convenient sample type.

The future price of the test and instrument have not yet been determined, but the semiconductor and aptamer can be produced at high volumes and low cost, Nakagawa said.

Given the platform's early stage of development, when it might be ready for commercialization is unclear, Nakagawa said, adding that the group is sourcing a manufacturing partner to work with it to obtain regulatory authorizations or approvals and launch the test.

Though the researchers' main focus is a test that detects SARS-CoV-2, their platform is amenable to being developed to diagnose numerous medical conditions, the firm said. The aptamers can be designed to bind to protein biomarkers for many indications, and the semiconductor sensor can detect electrical signals from various aptamers, Nakagawa said.