Toxicity Assessment of Iron Oxide Nanoparticles Based on Cellular Magnetic Loading Using Magnetophoretic Sorting in a Trapezoidal Microchannel

To
accurately assess potential nanotoxicity on the basis of cellular
iron content, the precise separation of cells into subpopulations
according to their magnetic nanoparticle loading is of crucial importance.
In this study, we developed a microfluidic magnetophoresis device
consisting of a trapezoidal channel containing five side outlet branches
and a narrow rectangular channel with three outlet branches. This
unique structure enabled the sequential separation of cells loaded
with tiny amounts of iron oxide and cells heavily labeled with iron
oxide, in a single device. As a proof of concept, we attempted the
sequential separation of Raw 264.7 cells with a large heterogeneity
in uptake capabilities (1–50 pg of iron per cell). Consequently,
we were able to differentiate the bulk cell population into seven
subpopulations according to their mean iron oxide loading. We also
evaluated potential nanotoxicity effects using the production of excess
reactive oxygen species (ROS) and the inhibition of proliferation
on the separated subpopulations, and we found that 46.6% of cells
loaded with iron above the threshold value (16.4 pg) had higher ROS
levels than the control group. Cells loaded with more than 3.7 pg
of iron exhibited transiently inhibited cell-cycle progression. In
particular, cells loaded with more than 35.4 pg of iron exerted a
significant effect on cell proliferation. The proposed system could
be useful in the investigation of nanotoxicity effects of iron oxide
nanoparticle-induced cells, based on their iron oxide nanoparticle
loading.