Antibody tests are important in helping determine how many cases of COVID-19 have gone undetected and whether those who have had the virus might now be immune. However, conventional immunosensor antibody tests are slow and have a tendency to display inaccurate results.
A number of researchers are creating SoCs to remedy the design-level issues associated with these essential tests.
Lab-on-a-Chip Detects Antibodies in Minutes
A new antibody test being developed by researchers at Carnegie Mellon University (CMU) is said to detect COVID-19 antibodies in a matter of seconds.
The test is based on an advanced nanomaterial-based biosensing platform, and it could lead to the ultra-rapid diagnosis of COVID-19, something that is critical for the treatment of the disease and slowing down its spread throughout populations.
In research published in October, the scientists present a so-called lab-on-a-chip (LoC) test that is said to detect immune responses to COVID-19 in two to three minutes.
A prototype of the researchers’ rapid COVID-19 antibody test powered by a microfluidic chip. Image used courtesy of Carnegie Mellon University
The device was built by using aerosol jet 3D printing. Tiny gold micropillar electrodes were printed at nanoscale by thermally sintering aerosol droplets together, causing an irregular surface that increases the micropillars’ surface area and leads to an enhanced electrochemical reaction. This reaction causes antibodies to latch to antigens coated on the electrode, enabling detection.
Using a tiny drop of blood, the LoC platform can identify the presence of two key antibodies: the spike S1 protein and receptor-binding domain (RBD), even in low concentrations of antibodies as small as 0.15 nanograms per milliliter. The test works by relying on an electrochemical reaction inside the microfluids to send a signal to a nearby computer.
A schematic of the microfluidic chip’s manufacturing process. Image used courtesy of Carnegie Mellon University
The materials used to build the test are inexpensive, enabling the microfluidic LoC test to be mass-produced at a low cost. The researchers also claim that because the sensing platform itself is generic, it could be used for the rapid detection of different infectious diseases such as HIV and Zika.
Chip-on-a-Card Detects Multiple Viruses at Once
The University of Rochester reported in early January that it’s creating an optical chip embedded on a disposable card that will detect more than one virus, including SARS-CoV-2, within a minute.
Rochester researchers are developing a “chip on a card” that can detect exposure to multiple viruses—including SARS-CoV-2. Image used courtesy of Miller Lab of the University of Rochester Medical Center
The heart of this technology—the small optical chip—is “no larger than a grain of rice,” according to researchers. In different areas of the chip, sensors can detect the proteins linked to eight different viruses. If somebody has been exposed to any of these eight viruses, antibodies to those viruses found in the patient’s blood sample will be drawn to the proteins and thus detected.
“This is a completely new diagnostic platform,” comments Benjamin Miller of the University of Rochester Medical Center, the lead researcher for the project.
The chip on a card device will enable clinicians to quickly detect COVID-19 and understand relationships between COVID-19 and previous infections. The researchers hope to have a validated prototype by early spring at the latest and plan to use blood drawn from 100 consenting COVID-19 patients to test the device’s effectiveness.
Microfluidic Chip Relies on Light for Highly-Accurate Results
In September, research reported by the Okinawa Institute of Science and Technology (OIST) described a device from a proof-of-concept study that uses portable lab-on-a-chip technology to accurately measure the concentration of antibodies present in blood plasma.
The antibody testing platform developed by researchers at OIST. Image used courtesy of Okinawa Institute of Science and Technology
While many accurate platforms exist for antibody testing, they are invariably expensive and need to be carried out in the lab. As we’ve seen during the COVID-19 pandemic, this means that it can take hours (or days in the case of high workloads) to obtain results. This is an obvious disadvantage when there’s a deadly virus in general circulation that can easily be transmitted. And while there are other antibody tests that are easy to use, fast, and portable, they’re not as accurate, which hinders testing efforts.
The Okinawa researchers avoided this disadvantageous trade-off between accessibility and accuracy by developing an alternative testing platform. It combines light-sensing technology with a microfluidic chip to provide accurate results within 30 minutes, even when antibody concentrations are very low.
Each lab-on-a-chip is cheap to produce and eliminates the need for lab-based processing by trained operators, making widespread nationwide testing by general workers and volunteers much more feasible.
Here, green arrows show the direction that the sample moves through the chip. Image used courtesy of Okinawa Institute of Science and Technology
The platform’s microfluidic chip, which is made from a gold-covered glass slide with an embedded microfluidic channel, is integrated with a fiber-optic light probe. Using voltage, the researchers created tens of thousands of spiky gold structures on a glass slide. These structures were then modified by attaching a fragment of the SARS-CoV-2 spike protein, which is crucial for helping the virus infect cells and causes a strong immune response.
In their proof-of-concept study, the researchers demonstrated the workings behind how the test detects antibodies by using artificial plasma spiked with COVID-19 antibodies.
Using a syringe pump, the sample was drawn through the chip past the protein-coated gold nano spikes that bind to the spike protein fragments. This binding is then detected by the fiber optic light probe. When more antibodies bind, the fiber optic light probe picks up larger shifts in the wavelength of absorbed light.
Using this information, it’s possible to determine the concentration of antibodies present within a blood plasma sample. The Okinawa researchers predict that the widespread rollout of its quantitative COVID antibody test could greatly impact how the disease is treated.
