Labeling efficiency of FE-Pro.

<p>(A) Light microscopy images of Prussian blue-stained non-labeled and FE-Pro-labeled NSCs at 24, 48 and 96 hours after labeling. (B) Electron micrographs of Fe-Pro-labeled NSCs. (C) Higher magnification image of outlined area in (B). Red arrows point to internalized FE-Pro complex in membrane-bound organelles. (D–E) T2-weighted MR images of labeled (L), non-labeled (N), and an equal mixture (M) of NSCs grown in soft agar. Each phantom contained three different total numbers of NSCs (1×10⁴, 1×10⁵ and 5×10⁵) each in 500 µl of 20% DMEM and 0.8% agar. Coronal view (D) and axial view at 5×10⁵ (E. left) and 1×10⁵ (E. right) of the phantoms. Decrease in T2-w signal strength correlated with the number of labeled cells in the phantom. (F) Graph of T2-w signal intensity vs. number of labeled NSCs. Data were extracted from 5 random fields of each corresponding phantom using ImageJ and shown as mean±SE. MRI conditions: 7.0 Tesla, Gradient-Echo sequence, voxel size = 0.09 mm³, TR/TE = 5402.5/90 ms. Scale bars = 50 µm (A), 2 µm (B) and 200 nm (C).