Improved Imaging of Magnetically Labeled Cells Using Rotational Magnetomotive Optical Coherence Tomography

Peter Cimalla,Michael Brand,Seba Almedawar,Edmund Koch,Julia Walther,Marius Ader,Mike Karl,Claudia Mueller,Bernd Rellinghaus,Richard Funk,Dierk Wittig

doi:10.3390/app7050444

Abstract

In this paper, we present a reliable and robust method for magnetomotive optical coherence tomography (MM-OCT) imaging of single cells labeled with iron oxide particles. This method employs modulated longitudinal and transverse magnetic fields to evoke alignment and rotation of anisotropic magnetic structures in the sample volume. Experimental evidence suggests that magnetic particles assemble themselves in elongated chains when exposed to a permanent magnetic field. Magnetomotion in the intracellular space was detected and visualized by means of 3D OCT as well as laser speckle reflectometry as a 2D reference imaging method. Our experiments on mesenchymal stem cells embedded in agar scaffolds show that the magnetomotive signal in rotational MM-OCT is significantly increased by a factor of ~3 compared to previous pulsed MM-OCT, although the solenoid’s power consumption was 16 times lower. Finally, we use our novel method to image ARPE-19 cells, a human retinal pigment epithelium cell line. Our results permit magnetomotive imaging with higher sensitivity and the use of low power magnetic fields or larger working distances for future three-dimensional cell tracking in target tissues and organs.

Highlights

Magnetomotive optical coherence tomography (MM-OCT) is a promising imaging method for noninvasive three-dimensional (3D) tracking of magnetically labeled cells in target tissues or organs [1,2,3]
At a achieved by addingwe a small in anprovides off-axis configuration to the magnetomotive optical coherence tomography (MM-OCT)
The thickness of thehave permanent magnet only 2 mm; reduction of working distance achieved by adding small permanent magnet inMM-OCT

Summary

Introduction

Magnetomotive optical coherence tomography (MM-OCT) is a promising imaging method for noninvasive three-dimensional (3D) tracking of magnetically labeled cells in target tissues or organs [1,2,3]. To expand MM-OCT to applications and environments where no elastic restoring force is present, such as in liquids, dual-coil configurations were introduced, in which the particles are attracted alternately by a primary and an opposite secondary coil on a common axis [4]. Such a setup would be convenient for cell imaging, since cells are characterized by viscoelastic properties rather than a true elastic behavior [5]. This off-axis configuration allows the generation of modulated longitudinal and transverse magnetic fields, which cause magnetomotion by the alignment and rotation of anisotropic magnetic particles in the sample volume

Methods

Results

Conclusion