Simulation‐Guided Tracer Optimization for Magnetic Particle Spectroscopy: Interplay of Core, Shell and Anisotropy Across Physiological‐Range Viscosities for Single‐ and Dual‐Frequency Excitation

Small, pp. e76201

Abstract

ABSTRACT Detection of magnetic nanoparticles (MNP) relies on their nonlinear magnetic response, changing with the local environment in vivo. Employing an effective viscosity model within stochastic coupled Néel–Brownian simulations, we quantify how viscosity (0.8–50 000 mPa·s) affects signal intensity of single‐frequency magnetic particle spectroscopy (MPS, 25 kHz) and frequency‐mixing MPS (FM‐MPS; f H = 40.5 kHz, f L = 0.063 kHz). We investigate single‐core, non‐interacting MNP with various core sizes (12–28 nm), hydrodynamic shell thicknesses (5–100 nm), and anisotropy (4–200 kJ m − 3 ), using dominant readouts (MPS: third‐harmonic; FM‐MPS: f H + 2 f L mixing‐term). Increasing viscosity progressively suppresses Brownian rotation, with thicker shells affected at lower viscosities, and drives signals toward an immobilization plateau. Under the simulated conditions, MNP appear distinguishable in blood‐associated viscosities using MPS, whereas distinguishability is pronounced in cellular/tissue‐like viscosities with FM‐MPS. Moderate anisotropy (∼20–40 kJ m − 3 ) enhances signals by ∼10%, whereas higher anisotropies suppress relaxation, finally collapsing the signal. While large cores maximize the signal at fixed particle number, dosage‐normalized conditions suggest favorable performance for intermediate cores (∼15–18 nm). These results propose a cohesive framework linking particle properties, excitation scheme, and physiological environment, thereby providing insight into MNP tracer optimization for biosensing, cell tracking, imaging, and in vivo diagnostics.

Authors 6

1. Mohamad Bilal Abbas Aachen

   FH Aachen

   Affiliation as printed

   Department of Medical Engineering and Applied Mathematics FH Aachen University of Applied Sciences Jülich Germany

2. Mohamad Alaa Abbas Aachen

   FH Aachen

   Affiliation as printed

   Department of Medical Engineering and Applied Mathematics FH Aachen University of Applied Sciences Jülich Germany

3. Timur Bikulov

   Forschungszentrum Jülich

   Affiliation as printed

   Institute of Biological Information Processing—Bioelectronics (IBI‐3) Forschungszentrum Jülich Jülich Germany

4. Ali Mohammad Pourshahidi

   Forschungszentrum Jülich

   Affiliation as printed

   Institute of Biological Information Processing—Bioelectronics (IBI‐3) Forschungszentrum Jülich Jülich Germany

5. Hans‐Joachim Krause

   Forschungszentrum Jülich

   Affiliation as printed

   Institute of Biological Information Processing—Bioelectronics (IBI‐3) Forschungszentrum Jülich Jülich Germany

6. U. Engelmann corresponding Aachen

   FH Aachen

   Affiliation as printed

   Department of Medical Engineering and Applied Mathematics FH Aachen University of Applied Sciences Jülich Germany