An Automated Device for Pathogen Detection in Milk Integrating Magnetic Nanoprobes with the Lateral-Flow Immunoassay

Foodborne illnesses, particularly in milk, pose significant public health risks, especially in low-income regions where access to reliable testing is limited. Lateral-flow immunoassays (LFAs) offer rapid detection but suffer from small volume capacity and low sensitivity. To address these challenges, we developed a fully automated device that utilizes immunomagnetic separation (IMS), where magnetic nanoprobes (MNPs) selectively capture Escherichia coli (E. coli) in large volumes of milk. The device then removes excess sample and adds a buffer to minimize matrix effects before LFA application. Our device achieves a limit of detection (LOD) of 5 × 10³ colony-forming units per milliliter (cfu/mL), a 20-fold improvement over the standard LFA setup. The device is composed of inexpensive 3D-printed materials and hobby electrical components and has a time to result of 40 min, requiring only sample input and a single button press to complete the entire workflow. This novel device offers a widely accessible and user-friendly solution for small-scale milk distributors for mitigating food contamination outbreaks.