Characterization of magnetic relaxation when biofunctionalized magnetic nano-particles are associated with biomarkers in the liquid state in biomedical applications

Shu Hsien Liao, Han Sheng Huang, Jean Hong Chen, Yu Kai Su, Yuan Fu Tong

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This study determined the characteristics of the time-dependent effective relaxation time τeff and magnetization M when biofunctionalized magnetic nanoparticles (BMNPs) associated with biomarkers in a liquid immunoassay. Carcinoembryonic antigen (CEA) was used as the biomarker. BMNP is an anti-CEA that was coated onto dextran-coated Fe3O4 and labeled as Fe3O4-anti-CEA. The phase lag θ of M with respect to the applied field H was measured using a sensitive homemade alternative-current susceptometer, and θ was measured using lock-in detection. The results were used to estimate τeff using the relationship tanθ(t) = ωτeff(t), where 2πf = ω and f is the excitation frequency. Δτeff increased with ΦCEA, where Δτeff was the increment of τeff after Fe3O4-anti-CEA associated with CEA, and ΦCEA was the concentration of CEA. Additionally, M enhanced when ΦCEA increased. We attributed these enhancements to magnetic dipole-dipole interactions among MNPs that contributed extra M and in turn enhanced τeff. Magnetic clusters after the association were verified using a transmission electron microscope. This study established the relationship between Δτeffeff,0 and ΦCEA, where τeff,0 = τeffCEA = 0), allowing the assay of an unknown amount of CEA molecules.

Original languageEnglish
Pages (from-to)4057-4062
Number of pages6
JournalRSC Advances
Issue number8
Publication statusPublished - 2018 Jan 1


ASJC Scopus subject areas

  • Chemistry(all)
  • Chemical Engineering(all)

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