Simultaneous detection and differentiation of common foodborne pathogens using tri-metallic magnetic microspheres as an aluminium foil based SERS substrate

Abstract

Foodborne bacteria can enter the human body through food, water, and air, potentially causing infections and foodborne illnesses that pose significant health risks, particularly for vulnerable populations. Recent technological advancements have paved the way for new methods for the early detection of these foodborne pathogens. Surface-enhanced Raman scattering (SERS) has emerged as one of the most powerful tools for the rapid and sensitive identification of pathogens. In this work, we fabricated tri-metallic magnetic microspheres (Fe₃O₄@PEI@Ag) and developed a potential SERS substrate in combination with aluminum (Al), which is used for the simultaneous detection and differentiation of three common foodborne pathogens: E. coli, S. aureus, and P. aeruginosa, at a concentration of 10⁵ cells per mL. These microspheres contain a magnetic core–shell structure encapsulated by gold (Au) and silver (Ag) layers. The SERS-active properties were confirmed using standard dyes as analytes. At each step of the preparation process, the morphology and elemental composition were confirmed via structural and morphological measurements. The magnetic strength of the microspheres was evaluated using isothermal magnetization measurements. All three lab-grown bacteria were successfully detected using the SERS substrates, as confirmed by SERS measurements. The stability of the microspheres was examined by evaluating their effective sensitivity through SERS measurements of each pathogen over a period of 40 days. Additionally, the reproducibility of the microspheres was verified by calculating the relative standard deviations (RSDs) from SERS results across 12 batches of tri-metallic magnetic microspheres. Furthermore, the statistical technique Principal Component Analysis (PCA) was used for strain differentiation.