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. 2009 May;9(5):1812-7.
doi: 10.1021/nl803757u.

Formation of Ordered Cellular Structures in Suspension via Label-Free Negative Magnetophoresis

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Free PMC article

Formation of Ordered Cellular Structures in Suspension via Label-Free Negative Magnetophoresis

Melissa D Krebs et al. Nano Lett. .
Free PMC article

Abstract

The creation of ordered cellular structures is important for tissue engineering research. Here, we present a novel strategy for the assembly of cells into linear arrangements by negative magnetophoresis using inert, cytocompatible magnetic nanoparticles. In this approach, magnetic nanoparticles dictate the cellular assembly without relying on cell binding or uptake. The linear cell structures are stable and can be further cultured without the magnetic field or nanoparticles, making this an attractive tool for tissue engineering.

Figures

Figure 1
Figure 1
Schematic of process of cell chain formation in ferrofluid. (a) Suspension of cells in ferrofluid assumes a random orientation in the absence of a magnetic field. (b) The suspended cells form linear arrangements in ferrofluid in presence of magnetic field (arrows), where the ferrofluid particles shepherd the cells into chains due to their induced magnetic dipoles. (c) Linear arrangement of cells adherent to cell-adhesive surface survive and grow upon removal of ferrofluid and magnetic field. (d) Schematic of BSA-passivated nanoparticle synthesis.
Figure 2
Figure 2
Confocal microscopy images of HUVECs chained in BSA-ferrofluid. (a-d) rotated images of cells at 30° intervals under magnetic field forming oriented linear chains. The arrow indicates the direction of the magnetic field. Scale bar = 50 μm. (e) Low magnification view of cells under magnetic field. Scale bar = 200 μm. (f) View of cell chains 1 hour after removal of magnetic field. Scale bar = 50 μm.
Figure 3
Figure 3
Kinetics of cell chain formation. (a) Fluorescently-labeled HUVECs without the presence of a magnetic field exhibit no orientation in BSA-ferrofluid. Following magnetic field application, (b) cells cluster and align with field after 1 second, and (c) cell chains grow in length after 5 minutes. Scale bar represents 100 μm. (d) Log-log plot of effective chain length size (S) versus time (t) (◆) following a power law-dependence consistent with the form of general colloidal aggregation models (dotted line).
Figure 4
Figure 4
Cell viability in the presence of ferrofluid. (a) Cell viability of HUVECs is high after culture with 30 mg/mL magnetic nanoparticles for 2 hours as visualized by LIVE/DEAD staining [green = all cells; red = dead cells]. The 2 dead cells in field of view are shown with arrows. Scale bar represents 100 μm. (b) Ferrofluid concentration does not affect cell viability.
Figure 5
Figure 5
Chain structures of HUVECs on collagen-coated dishes. (a) Chains formed with 15 mg/mL and (b) with 30 mg/mL BSA-ferrofluid. Cells were exposed to a 100 Oe magnetic field for 2 hrs, during which time they adhered to the collagen-coated surface. (c) Chain structure of HUVECs on collagen substrates formed with 30 mg/mL BSA-ferrofluid, exposed to magnetic field for 2 hours, and then incubated overnight. Magnetic field was applied in the direction of the arrow in each case. All scale bars represent 100 μm.

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