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

Abstract

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.

Core–shell bioprinting as a strategy to apply differentiation factors in a spatially defined manner inside osteochondral tissue substitutes

“…Recently, OCT has gained more and more interest for the field of biomaterials by allowing observation of implants after in situ placement [47], or with additional image processing for automated assessment of the outer geometry and channel networks of bioprinted gelatin/alginate fibers [48] offering the option of a direct feedback during printing [49]. The contrast for cell visualization/tracking, in addition to the applied MTT staining of viable cells, can be enhanced by magnetic labelling of cells prior to application as shown for agar scaffolds [50] or by leveraging the dynamics of living cells. A combination with confocal or multi-photon techniques for depth-resolving fluorescence imaging might allow the overlay with detailed information about the state and phenotype of the cells.…”

Special Feature Development and Application of Optical Coherence Tomography (OCT)

“…The corresponding technique is referred to as magnetomotive-OCT (MM-OCT). In their paper, P. Cimalla et al [9] present an improved method for MM-OCT and provide first imaging results in cells. Doppler OCT enables the non-invasive quantification of flow in tissue by measuring the axial velocity component.…”

Magnetic Field-Modulated Plasmonic Scattering of Hybrid Nanorods for FFT-Weighted OCT Imaging in NIR-II

“…Active contrast agents have thus been introduced to enhance image quality, , which can change their properties in response to external stimuli, such as heat, light, and magnetic field. − Magnetomotive OCT, for example, takes advantage of the dynamic responses of magnetic particles to magnetic fields for imaging contrast . The lateral displacement of magnetic particles or rotation of anisotropic magnetic nanostructures under applied magnetic fields induces stresses within the viscoelastic biological medium, creating locoregional scattering changes for imaging contrast. , Suppression of noncontrast agent background can be achieved by pixel subtraction between actively modulated OCT images. , The use of magnetic particles also enables multimodal imaging, such as magnetic resonance imaging (MRI) and magnetic particle imaging, and synergistic cancer treatment by magnetothermal therapy. − However, magnetomotive OCT is facing a few challenges during its development. First, the reversible lateral displacement and retrieval of magnetomotive signals are highly reliant on the restoring force of the elastic tissue so that its imaging performance is attenuated by the pathophysiological heterogeneity of tissues and interpatient variations of tissue elasticity. − Second, in most cases, magnetic nanoparticles need to be first labeled on cells or functionalized by biological molecules for strong particle–tissue interactions, considerably large displacement, and detectable optical changes under magnetic fields .…”

“…19 The lateral displacement of magnetic particles or rotation of anisotropic magnetic nanostructures under applied magnetic fields induces stresses within the viscoelastic biological medium, creating locoregional scattering changes for imaging contrast. 19,20 Suppression of noncontrast agent background can be achieved by pixel subtraction between actively modulated OCT images. 21,22 The use of magnetic particles also enables multimodal imaging, such as magnetic resonance imaging (MRI) and magnetic particle imaging, and synergistic cancer treatment by magnetothermal therapy.…”