By Topic

Characterization of Magnetic Markers and Sensors for Liquid-Phase Immunoassays Using Brownian Relaxation

Sign In

Cookies must be enabled to login.After enabling cookies , please use refresh or reload or ctrl+f5 on the browser for the login options.

Formats Non-Member Member
$33 $13
Learn how you can qualify for the best price for this item!
Become an IEEE Member or Subscribe to
IEEE Xplore for exclusive pricing!
close button

puzzle piece

IEEE membership options for an individual and IEEE Xplore subscriptions for an organization offer the most affordable access to essential journal articles, conference papers, standards, eBooks, and eLearning courses.

Learn more about:

IEEE membership

IEEE Xplore subscriptions

7 Author(s)
Bhuiya, A.K. ; Dept. of Electr. & Electron. Eng., Kyushu Univ., Fukuoka, Japan ; Asai, M. ; Watanabe, H. ; Hirata, T.
more authors

We have developed a liquid phase immunoassay technique using the Brownian relaxation of magnetic markers. In order to achieve this, we first characterized the magnetic markers, which are usually agglomerates of magnetic nanoparticles. The magnetic properties of the agglomerates were analyzed, and parameters such as the Brownian and Neel relaxation times and the magnetic moment were obtained. Using these key parameters, we could determine the markers that were suitable for the liquid-phase immunoassay. Then, we performed the detection of a biological target called biotin. In this experiment, biological targets were fixed on the surface of large polymer beads that were a few μm in size. The bound and unbound (free) markers were magnetically distinguished without requiring a washing process to separate them. We used three magnetic sensors for the signal detection: a SQUID, an MR sensor, and a flux gate. The sensitivity of SQUID, MR sensor, and flux gate to the molecular-number concentration was estimated to be as high as 5.6×10-18 mol/ml, 2.8×10-16 mol/ml, and 2.8×10-16 mol/ml , respectively. We also showed that the sensitivity could be improved by using magnetic markers with a large magnetic moment.

Published in:

Magnetics, IEEE Transactions on  (Volume:48 ,  Issue: 11 )