Figure 1.
Effective relaxation rate constant R1 ( = 1/T1) as a function of magnetite concentration of five different MLNP formulations.
The letters correspond to the formulations in Table 1.
Figure 2.
T1 histogram (dotted line) of a rat brain.
Triple Gaussian fitting allowed for separation of white matter (circles), gray matter (diamonds) and cerebrospinal fluid (squares).
Figure 3.
SEM images (Tescan MIRA XMU with YAG BSE-detector and SE-detector) of HSA nanoparticles labeled with magnetite (8 nm).
The light spots show the incorporated magnetite. Upper image: 20,000-fold magnification with 5.78 μm field of view, lower image: 60,000-fold magnification with 1.93 μm field of view.
Table 1.
Relaxivity of the different magnetically labeled nanoparticle formulations.
Figure 4.
Uptake of MLNPs in the rat body.
Two coronal MRI slices through the rat body are shown. Following MLNP injection, a significant and long lasting signal increase (arrows) was mostly observed in the liver L (row A) and in the spleen S (row B).
Figure 5.
Fluorescence images from a piece of the left liver lobe (bile duct) obtained from the red (A), blue (B), green (C), and the sum of these three channels (D). Only MLNP agglomerations (arrows) are best seen in the green and red channel with the latter having the lowest background fluorescence.
Figure 6.
Histogram analysis revealed a significant MLNP induced shift of the gray matter peak towards shorter T1 values after 26 and 39 minutes of the injection.
Figure 7.
MLNP uptake corresponded to significant T1 shortening and an increase in fluorescence signal intensity.
GM T1 values in rats treated with MLNPs were significantly decreased in comparison with control group after 26 minutes (A) and after 39 minutes (B). (C) The fluorescence signal in the hippocampus (HC) was significantly increased in the red channel after MLNP administration when compared to the control group (saline solution instead of MLNPs). * p<0.05; ** p<0.01.
Figure 8.
Prussian Blue staining of fluorescencing MLNP accumulations close to the intracerebroventricular injection site.
(A) The magnetite in MLNPs shows emission in the green and red (insert) spectrum with blue and green excitation. It was imaged before doing the Prussian Blue staining from an untreated cryo-slice from PFA fixed brain. (B) shows the Prussian Blue staining, whereas blue color derives from the hexacyanoferrat complex. (C) is a maximum difference projection of (A) and (B), showing the overlap of MLNP fluorescence and Prussian Blue staining. (D) The fluorescence totally vanishes after Prussian Blue staining, indicating that binding the iron in the complex alters the excitability of the magnetite molecules. Abbreviations: F = fluorescence; LV = lateral ventricle; CC = corpus callosum. Magnification = 20x.
Figure 9.
Prussian Blue staining close to the injection site of the rat shown in Figure 8 in a vehicle control rat.
(A) Slice fluorescence levels are generally low in the cryo slices and in most cases restricted to vasculature as shown here for some ependymal cells of the chorioid plexus. (B) shows the Prussian Blue staining, whereas in healthy rats iron accumulations (from micro bleedings) in the brain are typically absent (C) is a maximum difference projection of (A) and (B). (D) The slice fluorescence vanishes during Prussian Blue staining and brightfield imaging. Abbreviations: F = fluorescence; LV = lateral ventricle; CC = corpus callosum. Magnification = 20x.
Figure 10.
T1 changes in gray matter (GM) of the 16 MLNP treated rats versus fluorescence signal in the hippocampus (HC) of the red channel.
Table 2.
Relationship between MLNP induced T1 changes in white matter (WM) and gray matter (GM) and fluorescence signal in the red channel.