PMC

Light microscope images of Prussian blue staining of unlabeled (left) and labeled (right) green fluorescent protein cells. Left, No stainable iron is detected within the unlabeled cells. Right, Intracellular iron accumulation is demonstrated by blue coloring (×8 original magnification).

Confocal microscopic view of labeled cells. The left panel shows green fluorescent protein (GFP) expression of labeled cells, and the right panel shows quantitative signal to noise ratio (SNR) analysis with MetaMorph software; no difference was observed in GFP expression between superparamagnetic iron oxide (SPIO)- and ultrasmall superparamagnetic iron oxide (USPIO)-labeled and unlabeled groups, p > .05.

FLAPS images of the same clusters of ultrasmall superparamagnetic iron oxide (USPIO)- and superparamagnetic iron oxide (SPIO)-labeled cells as shown in . There was a notable signal loss compared with the control with unlabeled cells. Positive signal contrast was observed as narrow bands of signal enhancement surrounding the signal voids (top panel) at the USPIO- and SPIO-labeled cell positions. Banding areas (size of regions exhibiting positive contrast) for each group are shown within the lower panel.

Representative gradient echo T₂*-weighted images of the ultrasmall superparamagnetic iron oxide (USPIO), superparamagnetic iron oxide (SPIO), green fluorescent protein cell pellets in the top panel: 2, 1, and 0.5 million labeled cells and 2 million unlabeled cells as a control group. All labeled cell pellets showed a marked susceptibility effect compared with the control group. Measurement of susceptibility-induced signal void area for each group in the T₂*-weighted images is shown in the lower panel.