The use of magnetite-doped polymeric microspheres in calibrating cell tracking velocimetry

Lee R. Moore, MacIej Zborowski, Masayuki Nakamura, Kara McCloskey, Sigalit Gura, Merav Zuberi, Shlomo Margel, Jeffrey J. Chalmers

Research output: Contribution to journalArticlepeer-review

22 Scopus citations


Continuous magnetic separation, in which there is no accumulation of mass in the system, is an inherently dynamic process, requiring advanced knowledge of the separable species for optimal instrument operation. By determining cell magnetization in a well-defined field, we may predict the cell trajectory behavior in the well-characterized field environments of our continuous separators. Magnetization is determined by tracking the migration of particles with a technique known as cell tracking velocimetry (CTV). The validation of CTV requires calibration against an external standard. Furthermore, such a standard, devoid of the variations and instabilities of biological systems, is needed to reference the method against day-to-day shifts or trends. To this end, a method of synthesizing monodisperse, magnetite-doped polymeric microspheres has been developed. Five sets of microspheres differing in their content of magnetite, and each of approximately 2.7 μm diameter, are investigated. An average gradient of 0.18 T/mm induces magnetic microsphere velocities ranging from 0.45 to 420 microns/s in the CTV device. The velocities enable calculation of the microsphere magnetization. Magnetometer measurements permit the determination of magnetization at a flux density comparable to that of the CTV magnet's analysis region, 1.57 T. A comparison of the results of the CTV and magnetometer measurements shows good agreement. Copyright (C) 2000.

Original languageEnglish
Pages (from-to)115-130
Number of pages16
JournalJournal of Biochemical and Biophysical Methods
Issue number1-2
StatePublished - 10 Jul 2000

Bibliographical note

Funding Information:
This work is supported by grants from the NIH (number CA62349 to M.Z.), from the U.S.–Israel Binational Science Foundation (number 96-00486 to S.M. and M.Z.), and the NSF (number BES-9731059 to J.J.C.).


  • Cell/particle tracking velocimetry
  • Magnetic microspheres


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