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New crown test milestone: biosensor may be key to large-scale coronavirus detection

[Read more] Tech startups are scrambling to develop chips that can show the presence of coronavirus RNA, antibodies and antigens.

New crown test milestone: biosensor may be key to large-scale coronavirus detection

You prick your finger or wipe your nose and then dab a tiny sample of liquid on a semiconductor chip. The chip is inserted into an inexpensive handheld reader, and within a minute or so, its small screen displays a list of results. You test negative for the new coronavirus and positive for antibodies. The likelihood of an incorrect result is extremely low. You are allowed to enter your company's building or travel by air.

Such rapid, on-site testing is now only a dream. Most of the tests available today to see if people are infected with viruses are performed using reverse transcription polymerase chain reaction (RT-PCR) technology.

What is real-time reverse transcription-polymerase chain reaction?

Real-time reverse transcription-polymerase chain reaction is a derivative method for the detection of the presence of specific genetic material from any pathogen, including viruses. Initially, the method used radioisotope markers to detect the target genetic material, but later improvements led to the replacement of the isotope markers with special markers, the most common of which are fluorescent dyes. With this technology, scientists can see results almost immediately, even though the process is still in progress; whereas conventional real-time reverse transcription-polymerase chain reaction can only provide results at the end.

Although real-time reverse transcription-polymerase chain reaction is currently the most widely used method for coronavirus detection, many countries still need support in establishing and using this technique.

This process looks for specific RNA sequences in the sample. In this test case, we look for sequences that are specific to the coronavirus. It then replicates that sequence repeatedly by adding different chemicals and cycling the temperature of the solution. Each copy has a fluorescent molecule on it; when enough copies of RNA accumulate, the sample glows when illuminated by light. However, most of these tests require a laboratory to handle. The necessary chemicals are in short supply, and the fastest tests, those that produce results in less than 15 minutes, may have false negatives from time to time.

Then comes the antibody test, also known as the serological test. These tests can only determine if someone has had a virus in the past, not if they are currently sick. They measure whether a patient's immune system has begun to produce antibodies against a specific virus, using a small sample from a standard blood draw or finger prick. The antibodies in the blood bind to proteins embedded in the test strip, triggering a color change as the sample slides along the test strip and finally revealing the result, much like a pregnancy test stick. More than 100 antibody tests for coronaviruses have been introduced, but their accuracy varies.

A newer test for active viral antigens looks for coronavirus-specific spike protein fragments in nasal swab samples. These tests are less sensitive than PCR tests, but the results are much faster. The U.S. Food and Drug Administration just began approving these tests in May.

Each of these tests has its trade-offs. So what does it take to make a test that is fast, accurate and cost effective?

The appeal of biosensor chips

The answer could come from biosensor chips, says Jessica Gomez, co-founder and CEO of Rogue Valley Microdevices, a foundry specializing in microelectromechanical systems (MEMS) and sensors. The company is working with several startups vying to produce biosensors for coronavirus testing, she said.

Two of these companies, Cardea Bio and Hememics, are talking publicly about their work. The chips they are developing have many similarities and some differences.

Biosensors for viral RNA, antibody or antigen detection all rely on semiconductor circuits coated with biomaterials that will attract and bind to the relevant biomaterials in the sample fluid. When this binding occurs, the flow of electrons through the circuit is significantly altered. They are structured much like silicon MOS field-effect transistors, with a source and a drain and a gate between them. However, in the sensor, the gate is controlled by the binding of biomolecules rather than by a voltage signal: the bioFET.

Biosensors do not require any material to be multiplied to produce a signal, nor do they require the biological sample to undergo multiple laboratory processing steps. This means that tests can be performed very quickly, as fast as within 60 seconds. And because a single chip can contain multiple circuits, multiple tests of different kinds (viral RNA, antibodies and antigens) can be run simultaneously on the same chip; the only requirement is to use different biological substances as detectors for the different circuits. This allows the system to look for a wide variety of RNA fragments, antibodies, and antigens, not just the most likely one. This approach could reduce false results and provide additional information about the patient's health, perhaps detecting influenza and new coronaviruses at the same time.

The biosensors being developed by Cardea and Hememics rely on graphene and carbon nanotubes, respectively, and in both cases are used as semiconductors. Unlike silicon, these materials do not degrade when in contact with biological fluids. And they have the advantage of speed, which is a good thing when the signal changes that occur are very small.

Cardea Bio's Crispr on Chip

For RNA detection, Cardea is special because it uses molecules with Crispr technology as biodetectors. cardea CEO Michael Heltzen says the company has been working since 2013 to build a programmable biosensor platform that can detect DNA, RNA, proteins and other molecular signals. In January 2019, Cardea is ready to start working with commercial partners to develop the first products based on its platform; it published a paper on the technology that essentially opened the door to business, Heltzen said.

New crown test milestone: biosensor may be key to large-scale coronavirus detection

Cardea Bio's biosensor is designed to interface with a handheld reader for rapid testing of coronavirus RNA, proteins and antibodies.

Heltzen says Cardea has 88 companies interested by the end of 2019. While most of them are still in the design and development phase, one company, COBO Technologies, has publicly announced that it will use the Cardea platform in a system for quality control of genome engineering for pharmaceutical drug development.

Then, of course, the outbreak of the New Coronavirus caught the attention of the world. "A lot of people contacted us asking if they could use our technology to detect coronaviruses without having to use Crispr for amplification," Heltzen says. Although Cardea had intended to provide a platform for applications developed by others, Heltzen says that with so many companies wanting to build coronavirus biosensors, Cardea decided to develop assays that detect SARS-CoV-2 virus RNA, associated antibodies and the associated antigen itself." By working in our lab, we can distribute it to many partners and get it out the door faster," he says.

If you had asked me six months ago, I would have said that we weren't going to touch anything involving human diagnostics for a few years; we wanted to focus on being a platform and running our production, and we didn't want to get caught up in the regulatory complexities," Heltzen says. But now, everything has been changed."

Cardea has been working on Crispr testing of the virus for several months; work on antibody and antigen testing has only recently begun.

These tests performed well, but "are still being optimized," says Herzen. The biggest hurdle right now is to scale up from mass production (tens of thousands of chips per month) to extreme mass production (tens of millions per month and, over time, hundreds of millions of chips per month). Herzen said the company is in discussions with large companies, investors and government organizations to get funding and other support.

The dry protein is a special formulation of Hememics

The special feature of Hememics is its ability to preserve biological material in a dry form. Launched in 2007, the company developed a technology for drying blood products, using preservatives containing various sugars that keep these substances alive after drying. in 2015, it began applying its preservation technology to other types of proteins, including antibodies and peptides, for use in biosensors.

New crown test milestone: biosensor may be key to large-scale coronavirus detection

Hememics uses a proprietary drying technology to combine biomaterials with electronics for rapid coronavirus detection.

John Warden, CEO of Hememics, explains that dry biomaterials are easier to integrate into biosensors than wet ones, and they remain stable for longer. He says, "Our dry protein mixture sits on top of the semiconductor, waiting for the wet sample, and if you want to marry biology with electronics, preservation is key to that marriage, so this you can keep the device stable at ambient temperatures."

With investment from Inova, a southeastern U.S. hospital network, Hememics has recently been working on a number of small trials using its biosensor technology to detect hospital-acquired infections.

Then the coronavirus happened, Walden says, "and we flipped the chip. We had been putting antibodies on the chip looking for proteins. Now we put proteins on the chip and look for antibodies."

The version of the chip now under development by Hememics will have 32 sensing circuits. The company believes they are five to six weeks away from a final design.

We will be able to test protein number 4 on one circuit, protein number 16 on another, and so on, and change the way the microcontroller absorbs data from all the different channels to optimize sensitivity and specificity," Walden said. The technology could be used to test viruses or antibodies, or in the case of saliva samples, both at the same time, he said.

Bringing any kind of coronavirus biosensor to the mass market requires significant funding. Any testing would need to be done with multiple patients with existing technology and approved by the FDA for emergency use; only then could manufacturing capabilities be improved.

Cardea has raised $10 million to develop its technology and is in the process of raising a new round of funding, and Heltzen said the company's biosensor for the new coronavirus could be ready for mass production in the fourth quarter of 2020, but true mass production will require an infusion of capital from the government or large investors.

Hememics has raised $2.5 million from AMVI Partners and hopes to secure an additional $3 million from the same investment firm. The company likewise believes it can bring a biosensor for coronavirus testing to market by the end of 2020.

Rogue Valley Microdevices has begun producing sensor chips for Cardea and Hememics. Maintaining the surface chemistry of the devices is critical, Gomez said, and the company is working to develop a manufacturing process that can be transferred to other manufacturers to quickly increase capacity if necessary.

Gomez said, "The production of this device requires a very robust supply chain to ensure that health care providers have enough of the tools they need in the field, and we are really pleased with the potential that the biosensor has to bring as many accurate options for coronavirus testing as possible."

Headline (public number): Smart ScienceWorks