Building a Biosensor to Detect Harmful Bacteria

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.

An experimental microfluidic device containing two rectangular polymers coated with phages and covered with a biocompatible plastic tape was used in the research team's experiments.

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.”