Foodborne diseases result in millions of illnesses and approximately 420,000 deaths worldwide each year. Salmonella enterica (S. enterica) is a leading cause of foodborne illness and is transmitted through contaminated food. Conventional detection methods for foodborne bacteria require specialized equipment and trained personnel and can take 24 to 48 hours. Also, alternative tests may not differentiate between live and dead bacteria, and antibody-based devices typically have limited shelf life at room temperature.
Researchers at Worcester Polytechnic Institute (WPI) have developed a solid-polymer biosensor coated with nonpathogenic viruses to detect S. enterica, potentially providing innovative methods for identifying food contamination. The WPI team employed a flexible, textured polymer to which viruses that specifically target bacteria were chemically bonded.
Associate Professor Yuxiang “Shawn” Liu and his team demonstrated that their technology rapidly captures and visualizes foodborne bacterial contaminants in small fluid volumes. As this method does not require incubation or complex laboratory equipment, it could function as a rapid biosensor in field settings or resource-limited environments. According to Liu, the solid surface can be utilized throughout the food supply chain, from production to storage, to detect foodborne bacteria with minimal human intervention.
The polymer, approximately the size of a fingernail, was placed at the base of a channel within a compact, handheld microfluidic device. The channel was sealed with biocompatible plastic tape. Researchers introduced droplets of fluid containing S. enterica, allowing the phages on the polymer to capture the bacteria for subsequent detection.
To complete the detection process, the team utilized a microscope and fluorescence imaging to identify regions where the phages had accumulated bacteria. The portable, phage-coated polymer device consistently captured S. enterica, enabling detection at low yet hazardous concentrations that are challenging to identify with existing field methods.
Liu’s research employs light-based technologies for applications at the microscopic and nanoscale, with a focus on enhancing food safety. He has also developed tools for imaging blood clots and treating tumors. Liu notes that while the S. enterica detection device requires further development, it could eventually be adapted to detect multiple pathogens in food or water and may be integrated into food packaging to directly monitor contamination.
“To translate these findings to practical use, more work is needed on the best ways to prepare samples for testing,” said Liu. “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.”
