Image created by Dr. Michael J. Miller
Researchers at Worcester Polytechnic Institute (WPI) have developed a solid polymer coated with harmless viruses to detect the bacteria Salmonella enterica (S. enterica), an advance that could lead to new ways of finding contamination in the food supply.
The group, led by Yuxiang “Shawn” Liu, an associate professor in the Department of Mechanical and Materials Engineering, reports that the technology can rapidly capture and visualize foodborne bacterial contaminants in tiny fluid samples. With no need for incubation or complicated equipment in research centers, the technology has the potential to be used as a rapid biosensor in field applications and in areas with few resources.
“We have a solid surface that can be used anywhere in the food supply chain, from farm to fridge, to detect foodborne bacteria with minimum human intervention,” Liu says.
Foodborne diseases cause millions of illnesses and an estimated 420,000 deaths worldwide annually. S. enterica, a leading cause of foodborne illness, can spread through fecal matter and has been found in raw and undercooked foods, such as eggs, meat, milk, and fresh produce. The bacterium infects the intestines, causing diarrhea, fever, and abdominal cramps.
Conventional tests for foodborne bacteria typically involve lab techniques that require special equipment and training. Samples may need to be incubated to allow bacteria to grow so they can be counted, and tests at research centers can take 24 to 48 hours. Other approaches involve amplifying segments of genetic material in samples or detecting antibacterial antibodies in a sample, but those tests may not differentiate live pathogens from dead pathogens. Testing devices with antibodies also tend to have a limited shelf life at room temperature.
The WPI researchers went a different route, starting with a flat, textured, and flexible polymer. They attached bacteriophages (phages), which are viruses that develop through natural processes, to the polymer using a chemical process. Phages can identify and trap specific bacteria that are passing by.
The polymer, about the size of a small fingernail, was then placed on the bottom of a channel in a palm-size microfluidic device, and the channel was sealed from the top by a piece of biocompatible plastic tape. The researchers pumped small drops of fluid containing S. enterica through the channel, and the phages concentrated the bacteria on the solid polymer for detection.
As a final step, the researchers used a microscope and a light technique called fluorescence imaging to examine the polymers for bright spots where phages had concentrated the bacteria. Overall, the researchers found that the phage-coated polymers inside a portable device successfully captured S. enterica so the bacteria could be seen and assessed at a low concentration level that is still dangerous to human beings but challenging to detect when using existing in-field methods.
The research was published in ACS Applied Bio Materials, a peer-reviewed journal of the American Chemical Society. Co-authors with Liu were PhD student Seyed Hamed Ghavami; Teaching Professor Christopher R. Lambert from the Department of Chemistry and Biochemistry; and Jessica Drozd ’26. The work was supported, in part, with funding from the Gapontsev Family Collaborative Venture Fund.
Liu’s research focuses on applications that use light to interact with matter at microscopic and nano scales. Some of his work concentrates on positively impacting the quality and safety of food. In collaboration with other WPI researchers, Liu also has worked on using light to image blood clots with fiber-optic technology and a flexible endoscope that can bend in a patient’s voice box to reach and destroy tiny tumors.
Liu says the S. enterica detection device outlined in the paper will need more work but could be developed to detect multiple pathogens simultaneously and to detect pathogens in groundwater as well as food. Eventually, the technology might be incorporated into food packaging where it could detect contaminants by coming into direct contact with food.
“To translate these findings to practical use, more work is needed on the best ways to prepare samples for testing,” Liu says. “We also want to transition from microscopes to portable readers, such as smartphones, to simplify the process of detecting bacteria. The goal is to create a technology so simple and easy to use that inspectors, retailers, consumers, and others can simply use an app to scan a package and detect pathogens.”
Reference
Phage-Loaded Microfluidic Device for Selective Bacterium Detection with a High Potential for in-the-Field Applications. Hamed Ghavami, Christopher R. Lambert, Jessica Drozd, and Yuxiang Liu. ACS Applied Bio Materials 2026 9 (9), 4002-4012. DOI: 10.1021/acsabm.5c01652
Abstract
Detection of foodborne bacteria is critical because these pathogens cause foodborne outbreaks, which is a major public health concern worldwide. Conventional microbiological methods include plating and colony counting, molecular techniques such as polymerase chain reaction (PCR), and enzyme-linked immunosorbent assays (ELISA). These methods can be quite sensitive and specific, but they are also slow, require labor work, and often involve complex sample preparation. These limitations drive the development of faster and point-of-use detection techniques. In this study, we present a microfluidic biosensor platform based on P22 bacteriophage-loaded PDMS surfaces for rapid detection of Salmonella enterica. The PDMS surface had microscale topographical roughness, which helps improve immobilized phage concentration and promotes their capabilities to capture target bacteria. The system allows rapid bacteria detection with an experimentally demonstrated limit of detection of 9.15 × 103 cells/mL and a demonstrated specificity for Salmonella enterica over Staphylococcus aureus employed as a non-target control. Such detection was achieved under continuous flow conditions without the need of incubation, which implies its high potential for in-field applications and in resource-limited locations. This work demonstrates a rapid and selective approach for bacterial detection with strong potential for real-world food and water safety applications.