b2815 Tissue Engineering and Nanotheranostics “9.61x6.69”
132 Tissue Engineering and Nanotheranostics
indicated kidney and white is used for liver). In Janus nanoparticles, T 1
single was observed in the kidney because of MnO and T 2 single was
found in the liver after post injection of the magnetic nanohybrids.
The corresponding r1 and r2 relaxation times can be seen in Table 1.
In summary, the superparamagnetic nanoparticles joined with para-
magnetic are excellent candidates for dual T 1 and T 2 MR imaging with
enhancement in signal strength.
3.2. Multifunctional MRI and PDT MNHs
Later, researchers combined magnetic particles and paramagnetic
Gd-based upconversion nanoparticles with photosynthesizers to
obtain MRI and photodynamic therapy. In fact, rare-earth doped
UCNPs can exchange NIR excitation to ultraviolet or light visible to
stimulate photosensitizers which will help produce cytotoxic^1 O 2 for
killing cancerous cells. In this way, we can enhance PDT efficiency
and be able to treat deep-seated tumors.106,107
Folic acid triggered Gd–Si–Ti hybrid nanocrystals were prepared
by Wu et al. and obtained MRI and PDT response. The MR relaxa-
tion time r1 was observed to be 4.53 mM-1s-1, and the ratio of r2/
r1 was about 1.92, demonstrated good T 1 contrast agent. These par-
ticles exhibited good performance and low toxicity in vitro.
Figure 21(a) demonstrated the MR images and normalized tumor
volume in vivo. The obvious brightness enhancement observed in
T 1 -weighted MR images before and after intratumoral injection which
was not observed in T 2 MRI, indicated good T 1 performance in vivo
MR imaging. Later, they performed PDT effect using NIR light
980 nm at the tumor site by injecting FA–Gd–Si–TiNPs and obtained
excellent treatment effect to inhibit tumor growth as shown in
Fig. 21(a3). Shi et al. reported the first example of trimodal synergetic
therapy using UCNPs coupled with hematoporphyrin photosynthe-
sizer. Nanotheranostic system for cancer therapy was achieved by
Gd–UCNPs as the core, HP and Dtxl capsulated inside the
mesoporous silica. The obtained relaxation time r 1 = 5.62 mM–1s–1 is
greater than Gd–UCNPs@SiO 2 @mSiO 2 3.85 mM–1s–1. Later, MRI
was performed by the injected the nanoparticles at tumor site and
