Accurate multiplexed detection with magnetic particle spectroscopy

Abstract

Accurate multiplexed detection of magnetic nanoparticles (MNPs) is essential for bioassays that require simultaneous quantification of multiple biomolecules. This study proposes a dual-frequency magnetic particle spectroscopy (MPS) approach that improves multiplexed detection accuracy by combining MPS signals acquired at two excitation frequencies. The frequency-dependent MPS responses of MNPs dominated by either Brownian or Néel relaxation are investigated and analyzed, with the complex harmonic components serving as the basis for distinguishing different MNP types. In the experiments, commercial bionized nanoferrite and Synomag MNPs—dominated by Brownian and Néel relaxation, respectively—are mixed with different percentages. The accuracy of multiplexed detection is quantitatively assessed and compared between single-frequency and dual-frequency excitation schemes. Experimental results show that combining MPS signals at 0.5 and 32.6 kHz significantly improves the accuracy of multiplexed detection of MNPs. We anticipate that this dual-frequency strategy is of great importance for enabling highly precise multiplexed detection in bioassay applications.