biocompatibility [168]. Applying their high absorbance in the NIR region, MoS 2
[167], WS 2 [169], and Bi 2 Se 3 [170] nanosheets have been utilized in photothermal
therapy of cancers. In a noteworthy study performed by Cheng et al. [171], FeSe 2 -
decorated Bi 2 Se 3 nanosheets were developed for theranostic purposes, combining
four imaging modalities together with photothermal and radiotherapeutic properties.
FeSe 2 NPs were gradually converted into Bi 2 Se 3 nanosheets, with the addition of Bi
(NO 3 ) 3 and further functionalized with PEG.
64 Cu labeling was straightforwardly
executed by mixing
64 CuCl 2 with FeSe 2 /Bi2Se 3 –PEG at 37 °C for 1 h under
constant shaking, resulting in a labeling yield of 95%. Taking advantage of the
increased r 2 relaxivity of FeSe 2 , the X-ray attenuation capability of Bi 2 Se 3 and its
NIR optical absorbance, together with the chelator-free radiolabeling with
64 Cu,
in vivo multimodal imaging using four different imaging modalities (MR/CT/PA/
PET) was performed showing efficient tumor uptake of the nanosystem. Similarly, a
tetramodal (PET/MR/PAT/PTT),
64 Cu labeled theranostic agent based on iron
oxide decorated self-assembled MoS 2 nanosheets was developed by the same
group, in which strong PAT signals and clear darkening effects in T 2 weighted MR
images indicated passive tumor retention of the nanoconstructs. PET imaging was
also carried out demonstrating the feasibility of visualizing in vivo tumor (approximately 6%ID/g accumulation) with this moiety. Furthermore, after 14 days of
i.v. injection of the nanosystem and irradiation with 808 nm laser, complete tumor
resection was observed [172]. These studies emphasize the potential of using
transitional metal dichalcogenides for multimodal image-guided cancer therapy.
Another emerging example of novel NPs for molecular imaging was reported by
Ai et al. [173] and Zhan et al. [174], utilizing Gd 2 O 2 S:Eu nanophosphors for
dual-modality imaging. Radioluminescent lanthanide-doped nanophosphors
(RLNPs), such as the Eu
3+ doped gadolinium oxysulfides used in these reports,
have gained increased attention in the biological imaging field due to their unique
properties such as high photochemical stability, adjustable fluorescence emission,
low photobleaching and large Stokes shift [175]. Gd 2 O 2 S:Eu
3+ NPs are strongly
UV or X-rays absorbers, and because of their re-emission of red light with a high
quantum yield, they are suitable to be used as optical luminescent and radioluminescent (RL) agents [176]. This type of nanomaterial can also be used as an MRI
contrast agent due to strong transverse relaxivity of Gd [177]. With that in mind, in
the study performed by Ai et al173], Gd 2 O 2 S:Eu NPs of approximately 13 nm in
size were synthesized and chelator free radiolabeled with
89 Zr, by taking advantage
of the oxophilic nature of the isotope and the plenty O 2
− donors on the NP surface
leading to a NP concentration, pH and temperature dependent labeling yield of
*43% at pH 7–8 and *76% at pH 9–10. A proximity between the scintillation
source and the emitter allowed an improved in vivo RL efficiency. The study results
underline the ability in using these nanophosphors in integrated multimodal PET/
RL/MR studies.
A summary of the NPs and references can be found in Table 2.1. For a complete
and in-depth review of multifunctional radiolabeled NPs for imaging or therapy,
please refer to the following papers [2, 22, 27, 178–182].
34
C. A. Ferreira et al.
[167], WS 2 [169], and Bi 2 Se 3 [170] nanosheets have been utilized in photothermal
therapy of cancers. In a noteworthy study performed by Cheng et al. [171], FeSe 2 -
decorated Bi 2 Se 3 nanosheets were developed for theranostic purposes, combining
four imaging modalities together with photothermal and radiotherapeutic properties.
FeSe 2 NPs were gradually converted into Bi 2 Se 3 nanosheets, with the addition of Bi
(NO 3 ) 3 and further functionalized with PEG.
64 Cu labeling was straightforwardly
executed by mixing
64 CuCl 2 with FeSe 2 /Bi2Se 3 –PEG at 37 °C for 1 h under
constant shaking, resulting in a labeling yield of 95%. Taking advantage of the
increased r 2 relaxivity of FeSe 2 , the X-ray attenuation capability of Bi 2 Se 3 and its
NIR optical absorbance, together with the chelator-free radiolabeling with
64 Cu,
in vivo multimodal imaging using four different imaging modalities (MR/CT/PA/
PET) was performed showing efficient tumor uptake of the nanosystem. Similarly, a
tetramodal (PET/MR/PAT/PTT),
64 Cu labeled theranostic agent based on iron
oxide decorated self-assembled MoS 2 nanosheets was developed by the same
group, in which strong PAT signals and clear darkening effects in T 2 weighted MR
images indicated passive tumor retention of the nanoconstructs. PET imaging was
also carried out demonstrating the feasibility of visualizing in vivo tumor (approximately 6%ID/g accumulation) with this moiety. Furthermore, after 14 days of
i.v. injection of the nanosystem and irradiation with 808 nm laser, complete tumor
resection was observed [172]. These studies emphasize the potential of using
transitional metal dichalcogenides for multimodal image-guided cancer therapy.
Another emerging example of novel NPs for molecular imaging was reported by
Ai et al. [173] and Zhan et al. [174], utilizing Gd 2 O 2 S:Eu nanophosphors for
dual-modality imaging. Radioluminescent lanthanide-doped nanophosphors
(RLNPs), such as the Eu
3+ doped gadolinium oxysulfides used in these reports,
have gained increased attention in the biological imaging field due to their unique
properties such as high photochemical stability, adjustable fluorescence emission,
low photobleaching and large Stokes shift [175]. Gd 2 O 2 S:Eu
3+ NPs are strongly
UV or X-rays absorbers, and because of their re-emission of red light with a high
quantum yield, they are suitable to be used as optical luminescent and radioluminescent (RL) agents [176]. This type of nanomaterial can also be used as an MRI
contrast agent due to strong transverse relaxivity of Gd [177]. With that in mind, in
the study performed by Ai et al173], Gd 2 O 2 S:Eu NPs of approximately 13 nm in
size were synthesized and chelator free radiolabeled with
89 Zr, by taking advantage
of the oxophilic nature of the isotope and the plenty O 2
− donors on the NP surface
leading to a NP concentration, pH and temperature dependent labeling yield of
*43% at pH 7–8 and *76% at pH 9–10. A proximity between the scintillation
source and the emitter allowed an improved in vivo RL efficiency. The study results
underline the ability in using these nanophosphors in integrated multimodal PET/
RL/MR studies.
A summary of the NPs and references can be found in Table 2.1. For a complete
and in-depth review of multifunctional radiolabeled NPs for imaging or therapy,
please refer to the following papers [2, 22, 27, 178–182].
34
C. A. Ferreira et al.