Characterization of Fe3O4 nanoparticles for liquid phase immunoassay using brownian relaxation time and magnetic susceptibility

Md. Anwarul Kabir Bhuiya, Raihana Ferdaws, Md. Abdul Halim, Takeshi YOSHIDA, Keiji Enpuku, Edmund Soji Otabe

Key Words:

• AC susceptibility
• Biosensor
• Brownian relaxation
• Magnetic marker
• Magnetic moment
• Singular value decomposition (SVD)
• Size distribution

Int. J. Biosci.13( 6), 176-185, December 2018

DOI: http://dx.doi.org/10.12692/ijb/13.6.176-185

Certification:

Abstract

This article describes the detail characterization of the magnetic properties of magnetic markers (Fe₃O₄₎ in solution for biosensor application. Frequency dependence of the AC susceptibility and the magnetization curve, which were dominated by the Brownian rotation of the marker, Brownian relaxation time were measured. The effect of the viscosity of the carrier liquid on the AC susceptibility was also clarified. The experimental results were analyzed by the singular value decomposition (SVD) method. The distribution of marker size d was obtained from the frequency dependence of the AC susceptibility.  The distribution of magnetic moment m was obtained from the magnetization curve. The relationship between m and d was also discussed.  The present estimation method using SVD technique will be useful to obtain the distribution of particle size d and magnetic moment m, which are the important parameters of the magnetic marker for biomedical application. We also obtained the distributions of magnetic moment m and anisotropy energy barrier E_B, and their relationship. From the obtained result, we could classify the particles into three types: Type-I particles with very small m and very short τ_N, Type-II particles with medium values of m and τ_N, and Type-III particles with large m and very long τ_N.