Image created by Dr. Michael J. Miller
Scientists at Washington University in St. Louis have designed a new type of sensor that could transform the way we detect pathogens that spread through the air. Their invention is able to quickly and accurately identify harmful viruses and bacteria, such as H5N1 and the bacteria E. coli.
Airborne transmission is one of the most common ways people and animals get sick. Right now, the most common way to test for viruses or bacteria is through polymerase chain reaction (PCR), a method that can detect genetic material. PCR is highly accurate, but it takes a lot of time, effort, and specialized equipment. Because of this, results are often delayed, which can slow down important health decisions.
The new biosensor offers a much faster option. It can provide results in under five minutes. This kind of speed is critical for stopping the spread of disease before it gets out of control. If health workers or farmers can detect dangerous pathogens right away, they can take action to keep people and animals safe.
The sensor works by using a tiny electrode that is coated with special materials. These include graphene oxide, which is made from very thin sheets of carbon, and Prussian blue, a type of crystal. These materials create a highly sensitive surface. When pathogens are present, the sensor produces an electrical signal that can be measured at extremely small levels, called nanofarads.
During tests in the lab, the sensor showed remarkable accuracy. For the H5N1 virus, it could detect as few as 56 viral particles in a milliliter of liquid. For E. coli, it could detect as few as five bacterial cells in the same amount. These levels are much lower than what many existing methods can identify, making the sensor especially powerful.
The research team also wanted to make sure the sensor could work with real air samples, not just in liquid form. To do this, they built a special air sampler called a wet cyclone. This device pulls in air, traps particles in a liquid, and sends the sample to the sensor. Using this system, the researchers were able to detect very small amounts of pathogens in the air. 93 copies of viral RNA or eight bacterial cells in a cubic meter of air. Accuracy stayed above 90 percent, showing the system has strong potential for real world use.
The scientists believe the sensor can be adapted to detect many different pathogens at the same time. Because it is small, portable, and quick, it could be useful in hospitals, farms, airports, and other high risk areas.
Before the sensor can be widely used, more testing is needed outside the lab. Real environments are more complicated, with changing air quality and temperatures that may affect performance. The research team is working with biotech companies to improve the design and prepare it for larger scale use.
Reference
Capacitive Biosensor for Rapid Detection of Avian (H5N1) Influenza and E. coli in Aerosols. Joshin Kumar, et al. ACS Sensors 2025 10 (5), 3381-3389. DOI: 10.1021/acssensors.4c03087.
Abstract
Airborne transmission via aerosols is a dominant route for the transmission of respiratory pathogens, including avian H5N1 influenza A virus and E. coli bacteria. Rapid and direct detection of respiratory pathogen aerosols has been a long-standing technical challenge. Herein, we develop a novel label-free capacitive biosensor using an interlocked Prussian blue (PB)/graphene oxide (GO) network on a screen-printed carbon electrode (SPCE) for direct detection of avian H5N1 and E. coli. A single-step electro-co-deposition process grows GO branches on the SPCE surface, while the PB nanocrystals simultaneously decorate around the GO branches, resulting in an ultrasensitive capacitive response at nanofarad levels. We tested the biosensor for H5N1 concentrations from 2.0 viral RNA copies/mL to 1.6 × 105 viral RNA copies/mL, with a limit of detection (LoD) of 56 viral RNA copies/mL. We tested it on E. coli for concentrations ranging from 2.0 bacterial cells/mL to 1.8 × 104 bacterial cells/mL, with a LoD of 5 bacterial cells/mL. The detection times for both pathogens were under 5 min. When integrated with a custom-built wet cyclone bioaerosol sampler, our biosensor could detect and quasi-quantitatively estimate H5N1 and E. coli concentrations in air with spatial resolutions of 93 viral RNA copies/m3 and 8 bacterial cells/m3, respectively. The quasi-quantification method, based on dilution and binary detection (positive/negative), achieved an overall accuracy of >90% for pathogen-laden aerosol samples. This biosensor is adaptable for multiplexed detection of other respiratory pathogens, making it a versatile tool for real-time airborne pathogen monitoring and risk assessment.