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Magnetic Manipulation of Blood Conductivity with Superparamagnetic Iron Oxide-Loaded Erythrocytes

Philips, Gavin R., Gleich, Bernhard, Paredes-Juarez, Genaro A., Antonelli, Antonella, Magnani, Mauro, Bulte, Jeff W. M.
ACS applied materials & interfaces 2019 v.11 no.12 pp. 11194-11201
electrodes, electrophysiology, erythrocytes, iron, magnetic fields, prototypes
The active and passive electrophysiological properties of blood and tissue have been utilized in a vast array of clinical techniques to noninvasively characterize anatomy and physiology and to diagnose a wide variety of pathologies. However, the accuracy and spatial resolution of such techniques are limited by several factors, including an ill-posed inverse problem, which determines biological parameters and signal sources from surface potentials. Here, we propose a method to noninvasively modulate tissue conductivity by aligning superparamagnetic iron oxide-loaded erythrocytes with an oscillating magnetic field. A prototype device is presented, which incorporates a three-dimensional set of Helmholtz coil pairs and fluid-channel-embedded electrode arrays. Alignment of loaded cells (∼11 mM iron) within a field of 12 mT is demonstrated, and this directed reorientation is shown to alter the conductivity of blood by ∼5 and ∼0.5% for stationary and flowing blood, respectively, within fields as weak as 6–12 mT. Focal modulation of conductivity could drastically improve numerous bioimpedance-based detection modalities.