A diagnostic technique for the Ebola virus uses a micro-ring resonator and a biomarker to quickly identify the presence of the virus in blood samples. Researchers at Washington University School of Medicine developed the technique, in collaboration with colleagues at the University of Michigan and biotech company Integrated Biotherapeutics. In tests, the micro-ring resonator sensor detected the biomarker for the virus — soluble glycoprotein (sGP) — in less than 40 min and at low ng/mL concentrations. Micro-ring resonators operate on the principle of whispering-gallery mode (WGM) sensing. Light at a specific resonant wavelength is confined in small micro-ring cavities and, as light circulates within the micro-ring, it interacts with biomolecules deposited on the surface of the ring. This results in a shift in the ring’s resonant wavelength that is proportional to the amount of the surface-adsorbed material. In the work, the researchers used their method to trap light in the resonators. Resonance boosted the signal they obtained. Monitoring where the resonance wavelength occurred indicated how much of the molecule was present. A colorized scanning electron microscopic image depicts Ebola particles budding from the surface of a cell. A study from researchers at Washington University School of Medicine and colleagues at other institutions details a tool that can quickly identify the presence of the virus in blood samples. The research group said that the technology has the potential to be developed into a rapid diagnostic test. Courtesy of the National Institute of Allergy and Infectious Diseases. The researchers developed a highly sensitive antibody to detect the sGP molecule at low levels and integrated the antibody into the sensor. On tests of the device using blood from infected animals, they detected the sGP biomarker as early or earlier than the most sensitive test for viral genetic material. Additionally, they quantified the amount of sGP in the blood. The higher the level of sGP, the more serious the disease. “Looking at these data, we can say, ‘If you’re above these levels, your chance of survival is low; if you’re below it, your chance of survival is high,’” researcher Abraham Qavi said. The team needs to validate its research and approach in infected individuals, he said. If the approach is validated, Qavi said that doctors could use information acquired via the method to tailor treatment plans for individual patients and allocate medications that might be scarce to patients most likely to benefit. With 128 active sensors per chip, the micro-ring resonator platform showed high multiplexing potential. These multiplexing capabilities will enable the current sensor design to be adapted for use with a broader range of pathogens, and will make it possible to incorporate other biomarkers relevant to infection detection, the researchers said. In addition to multiplexing, WGM devices offer high analytical sensitivity, quick time to result, and ease of integration with microfluidics. Another advantage of the WGM-based platform is the addition of unfunctionalized thermal control micro-rings, which negate any environmental fluxes that could influence measurements. Current diagnostic tests for Ebola are not reliable until the virus has multiplied to high levels in the body — a process that can take days. A rapid, early diagnostic could help public health workers track the virus’ spread and implement strategies to limit outbreaks. “Using a biomarker of Ebola infection, we’ve shown that we can detect Ebola infection in the crucial early days after infection,” Qavid said. “A few days makes a big difference in terms of getting people the medical care they need and breaking the cycle of transmission.” The research was published in Cell Reports Methods (www.doi.org/10.1016/j.crmeth.2022.100234).