Bird flu (H5N1) can spread quickly when infectious respiratory droplets are inhaled by birds and other animals, and the virus’s frequent mutations make airborne transmission to humans a concern. Current methods to detect H5N1 often require extensive sample preparation in a lab, such as polymerase chain reaction (PCR)-based tests. Therefore, a sensor that quickly detects airborne viral particles without sample preparation could help identify transmission before an outbreak occurs.
Rajan K. Chakrabarty, Washington University in St. Louis, MO, USA, and colleagues have developed a prototype sensor that detects the type of influenza virus that causes bird flu (H5N1) in air samples. The low-cost, handheld sensor detects the virus at levels below an infectious dose and could enable rapid aerosol testing for airborne avian influenza.
The researchers previously developed an electrochemical biosensor to detect SARS-CoV-2 particles in breath using an electrochemical capacitive biosensor (ECB) [1]. They have now adapted their ECB technology to detect and measure levels of H5N1 viruses in the air.
The new ECB consists of a thin network of Prussian blue nanocrystals and graphene oxide branches on a screen-printed carbon electrode. To make the sensor detect H5N1 viruses, the researchers attached probes (aptamers or antibodies) sensitive to these pathogens onto the network.
The biosensor detects pathogens by measuring changes in capacitance, which result from the binding of pathogens to a composite of graphene oxide (GO) and Prussian blue (PB) on the electrode. The total capacitance is determined by the smallest of three capacitances (redox, double-layer, and diffusion layer), with the PB/GO composite enhancing sensitivity for rapid, label-free detection.
The researchers paired the sensor with a custom-built air sampler that pulls in droplets from the air and creates a liquid sample. When liquid samples containing H5N1 viruses were applied to the sensor, the viral particles bound to the probes and changed the sensor’s capacitance. By measuring the total change in capacitance, the researchers could determine the levels of H5N1 in the liquid sample.
In demonstrations with aerosolized samples containing known quantities of inactivated H5N1 viruses, the ECB produced results within five minutes. The sensor’s detection limit for avian influenza was 93 copies/m³ (93 viral copies per 1 m³of air)—a level that the researchers say should be “sensitive enough to detect the presence of H5N1 below the virus’s infectious dose.” The sensor’s overall accuracy exceeded 90% when compared with measurements from a digital PCR test, according to the researchers.
- Capacitive Biosensor for Rapid Detection of Avian (H5N1) Influenza and E. coli in Aerosols,
Joshin Kumar, Meng Xu, Yuezhi August Li, Shu-Wen You, Brookelyn M. Doherty, Woodrow D. Gardiner, John R. Cirrito, Carla M. Yuede, Ananya Benegal, Michael D. Vahey, Astha Joshi, Kuljeet Seehra, Adrianus C. M. Boon, Yin-Yuan Huang, Joseph V. Puthussery, Rajan K. Chakrabarty,
ACS Sensors 2025.
https://doi.org/10.1021/acssensors.4c03087
[1] Dishit P. Ghumra, Nishit Shetty, Kevin R. McBrearty, Joseph V. Puthussery, Benjamin J. Sumlin, Woodrow D. Gardiner, Brookelyn M. Doherty, Jordan P. Magrecki, David L. Brody, Thomas J. Esparza, Jane A. O’Halloran, Rachel M. Presti, Traci L. Bricker, Adrianus C. M. Boon, Carla M. Yuede, John R. Cirrito, Rajan K. Chakrabarty, Rapid Direct Detection of SARS-CoV-2 Aerosols in Exhaled Breath at the Point of Care, ACS Sens. 2023, 8(8), 3023–3031. https://doi.org/10.1021/acssensors.3c00512
