# Investigating the Effect of Magnetic Dipole-Dipole Interaction on Magnetic Particle Spectroscopy (MPS): Implications for Magnetic Nanoparticle-based Bioassays and Magnetic Particle Imaging (MPI)

## TL;DR

This study explores how magnetic dipole-dipole interactions among superparamagnetic nanoparticles influence their magnetic response, revealing that concentration changes significantly affect signal strength in magnetic particle spectroscopy, impacting bioassay and imaging applications.

## Contribution

The paper provides new insights into the effects of dipolar interactions on SPION magnetic dynamics through combined simulations and experiments, highlighting their impact on MPS signals.

## Key findings

- Moderate SPION concentration changes significantly alter magnetic dynamics.
- Harmonic signal magnitudes can vary by up to 60%.
- Dipolar interactions influence magnetic response relevant to bioassays and MPI.

## Abstract

Superparamagnetic iron oxide nanoparticles (SPIONs), with comparable size to biomolecules (such as proteins, nucleic acids, etc.) and unique magnetic properties, good biocompatibility, low toxicity, potent catalytic behavior, are promising candidates for many biomedical applications. There is one property present in most SPION systems, yet it has not been fully exploited, which is the dipole-dipole interaction (also called dipolar interaction) between the SPIONs. It is known that the magnetic dynamics of an ensemble of SPIONs are substantially influenced by the dipolar interactions. However, the exact way it affects the performance of magnetic particle-based bioassays and magnetic particle imaging (MPI) is still an open question. The purpose of this paper is to give a partial answer to this question. This is accomplished by numerical simulations on the dipolar interactions between two nearby SPIONs and experimental measurements on an ensemble of SPIONs using our lab-based magnetic particle spectroscopy (MPS) system. Our results show that even moderate changes in the SPION concentration may have substantial effects on the magnetic dynamics of the SPION system and the harmonic signal magnitudes can be increased or decreased by 60%, depending on the values of MPS system parameters.

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Source: https://tomesphere.com/paper/1901.01355