Multiplexed detection of pathogens using magnetic microparticles encoded by magnetic axes

Pathogenic diseases caused by bacteria, viruses and fungi have become an important global public health concern. Rapid, simple, and accurate detection methods are urgently needed for in-field screening of such pathogens. We developed a sensing method based on microparticles encoded by axes of aligned superparamagnetic nanoparticles (SMNPs) to concurrently detect various pathogens. The encoded microparticles, which were fabricated using photocurable polymer and SMNPs, were arranged according to the respective direction of the external magnetic field. By measuring their respective tilted angles, the microparticles can be decoded and used for multiplexed assays. To verify this multiplexing capability, we simultaneously assayed four types of pathogens: Bacillus subtillis, Salmonella typhimurium, Staphylococcus aureus and Escherichia coli O157:H7. The microparticles, conjugated with corresponding capture antibodies, were used, and the concentrations of target pathogens were analyzed with a single-color fluorescent label. The total assay time was as short as 35 min with 200 μl of sample volume and the achieved limit-of-detections (measured signal-to-noise ratio > 3) were as low as 10 CFU ml⁻¹ for Bacillus subtillis, Salmonella typhimurium, Staphylococcus aureus and 100 CFU ml⁻¹ for Escherichia coli O157:H7, respectively. This sensing method represents a promising tool for preventing various diseases by rapid detection of multiple pathogens.