Detection of E. Coli in the presence of a magnetic field in integrated microfluidic chips

Foodborne pathogens pose a serious threat to public health and are a major cause of foodborne illnesses. Conventional detection methods, including microbiological tests, polymerase chain reaction (PCR), and immunological techniques, often suffer from long analysis times, complex sample preparation steps, and high costs. In particular, rapid and sensitive detection methods are required when the target pathogen concentration is low or when the available sample volume is limited. In this study, a novel microfluidic biosensor system integrated with surface- enhanced Raman scattering (SERS) was developed for the detection of Escherichia coli (E. coli) in food samples. The proposed system is based on a sandwich immunoassay structure formed by antibody-modified magnetic nanoparticles (MNPs) and 4-aminothiophenol-labeled gold nanorods (AuNRs). The designed microfluidic chip enables the integration of interaction, washing, labeling, and SERS measurement steps within a single platform. The analytical performance of the system was evaluated using E. coli concentrations ranging from 10¹ to 10⁸ CFU/mL. The obtained SERS spectra exhibited a characteristic Raman band at approximately 1330 cm⁻ ¹, the intensity of which increased consistently with increasing bacterial concentration. The limit of detection (LOD) of the system was determined to be 1 × 10² CFU/mL, while a linear response was maintained over the concentration range of 10²–10⁸ CFU/mL. Regression analysis yielded a correlation coefficient of R² = 0.99, demonstrating the high analytical reliability of the proposed platform. These results indicate that the developed microfluidic SERS-based biosensor provides a rapid, sensitive, and reliable approach for the detection of E. coli in food samples and represents a promising tool for food safety applications.