Assaying biomarkers via the saturated magnetization, residual magnetization and magnetic relaxation of biofunctionalized magnetic nanoparticles associated with biotargets
Chih-Yi Wang (王智億)1*, Guan-Min Chen (陳冠名)1, Yu-Ki Su (蘇裕凱)2, Hong-Chang Yang (楊鴻昌)1,2, Li-Min Wang (王立民)1
1Department of physics, National Taiwan Universirty, Taipei, Taiwan
2Institute of Electro-Optical Science and Technology, National Taiwan Normal University, Taipei, Taiwan
* presenting author:王智億,
An assay of biomarkers consisting alphafetaprotein (AFP) via the measurements of saturated magnetization, residual magnetization and magnetic relaxation is reported. The biofunctionalized magnetic nanoparticles (BMNs) were anti-alphafetaprotein (antiAFP) coated onto dextran-coated iron oxide nanoparticles labeled as Fe3O4-antiAFP, and then conjugated with AFP biotargets. After a complete conjugating of AFP and Fe3O4-antiAFP, the BMNs were dried for magnetic measurements. It is found that the saturated magnetization Ms increases as the concentration of associated AFP is increased. The residual magnetization Mr in a field of 100 Oe decreases rapidly as the concentration of AFP is below 2 ppm. Furthermore, the magnetic relaxation time τ also shows a rapid decrease when the concentration of AFP is lower than 2 ppm. Thus, we demonstrate a sensitive platform for detecting biomarkers by characterizing Ms, Mr, and τ with a sensitivity limit of 0.02-ppm AFP. The results can be attributed to the surface effects and the Néel motion of magnetic moments in BMNs.

Keywords: Alternating current power transmission, Biophysical techniques, Magnetic susceptibilities, Relaxation times, Magnetic nanoparticles