“9.61x6.69” b2815 Tissue Engineering and Nanotheranostics
Magnetic Nanohybrids for Magnetic Resonance Imaging 131The signal intensities and relaxivities values (Table 1) of MRI altered
with the size of the thickness of SiO 2.
Chen et al. synthesized pH-responsive T 1 – T 2 * dual-modal MRI
contrast agents based on iron manganese silicate (FeMn(SiO 4 )) hol-
low nanospheres using hydrothermal method.^105 Different pH sys-
tems contribute a significant function not only in the ion release from
the nanoparticles but also in drug delivery. In this investigation, about
32% Mn2+ ions from FeMn(SiO 4 ) released in acidic media and showed
T 1 MR imaging in kidney as well as in tumor area. T 1 and T 2 * MR
images of the tumor can be shown in Fig. 20(b). The circulation of
magnetic nanohybrids such as in liver, lungs and kidneys was also
observed. These MR imaging results manifested the excellent
enhancement in T 1 due to Mn and T 2 because of Fe. Moreover, the
cell viability and histological examinations showed that FeMn(SiO 4 ))
hollow nanospheres are not toxic and developed obvious distinction
between the normal and tumors.
Similar release of MnO nanoparticles from Fe 3 O 4 –MnO Janus
nanoparticles was observed under different biological atmospheres and
produced T 1 and T 2 * MR imaging in vivo. Figure 20(c) revealed
clearly the difference between MR imaging of liver and kidneys using
single Fe 3 O 4 and Janus Fe 3 O 4 –MnO nanoparticles (red arrow
Table 1. Relaxation properties of different hybrid structures.Sample name
Size
(nm)r1 mM–1
S–1r2 mM–1
S–1 r2/r 1 ReferencesFe 3 O4/SiO 2 /Gd 2 O(CO 3 ) 2 NPs 21.5 3.7 312 84.32 104
Fe 3 O 4 /SiO 2 /Gd 2 O(CO 3 ) 2 NPs 29.5 32.9 269.6 8.19 104
Fe 3 O 4 /SiO 2 /Gd 2 O(CO 3 ) 2 NPs 32.5 32.2 208 6.45 104
FeMn(SiO 4 ) hollow
nanospheres (pH = 7.4)
80 1.92 92.39 48.11 105FeMn(SiO 4 ) hollow
nanospheres (pH = 5)
80 0.6 49.43 82.38 105Fe 3 O 4 –MnO core–shell ~10 1.3 35.8 28 82
Fe 3 O 4 –MnO dumbbell ~25 1.4 78.9 56 82
Fe 3 O 4 –MnO flower ~40 0.6 141 235 82