Pathogen Detection using Magnetic Frequency Mixing Technique (PATHMAG)

• Applicants: Professor Dr. Ulrich Michael Engelmann; Professorin Dr. Corinna Kaulen; Dr. Ali Mohammad Pourshahidi
• Subject Area: Biomedical Systems Technology ; Medical Physics, Biomedical Technology
• Term: since 2026
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 574089568

This proposal aims to develop a mobile, wash-free magnetic biosensor platform for rapid, sensitive, and versatile point-of-care (PoC) diagnostics. The system is based on Frequency Mixing Magnetic Detection (FMMD) of superparamagnetic iron oxide nanoparticles (SPIONs). By combining complementary expertise in instrumentation, nanoparticle synthesis, and simulation, the project addresses current limitations in SPIONs based biosensing particularly the lack of quantitative wash free, and field-deployable solutions. Our proposed FMMD based sensor will detect pathogen-specific binding events through changes in magnetic nanoparticle relaxation behavior, especially Brownian relaxation, which is sensitive to hydrodynamic size variations induced by target binding or agglomeration. We propose to synthesize monodisperse SPIONs with core sizes above 20 nm to ensure dominant Brownian relaxation. These will be functionalized with polyelectrolytes, ssDNA, or gold nanoparticles to form model systems for evaluating changes in hydrodynamic diameter and particle agglomeration. The tailored SPIONs will enable detection of molecular interactions without the need for time-consuming washing steps, representing a strategic advance for PoC settings. A predictive simulation framework will guide synthesis and instrumentation development by modeling dynamic magnetic responses under varying field conditions and SPIONs parameters. This includes particle-particle interactions and aggregation scenarios, enabling optimal design for maximal signal generation. Simulations will also help distinguish Néel and Brownian relaxation contributions critical for interpretation of FMMD signals. The work program comprises eight interlinked work packages: from synthesis and surface functionalization of SPIONs, to their physicochemical and magnetic characterization, and optimization of FMMD instrumentation. Experimental validation and simulation-experiment comparisons will culminate in the demonstration of a wash-free DNA detection assay in physiological media. Overall, the project aims to establish a new class of portable magnetic biosensors for future pathogen diagnostics and broader biomedical applications, combining high sensitivity, speed, and quantitative readout in a robust, field-ready format.

• DFG Programme: Research Grants
• Major Instrumentation: Magnetic particle spectrometer
• Instrumentation Group: 3233 Nichtlineare Magnetpartikel Bildgebung, Magnetic Particle Imaging (MPI)