such materials may facilitate improved therapeutic efficiency. As functionalized
graphene derivatives are amphiphilic, they are structurally advantageous to play
such versatile roles. While their functional edges are available for molecular conjugation with metal contrast agents or targeting moieties, the basal plane is capable
of loading various hydrophobic drugs at the same time.
In 2014, Wang et al. reported mesoporous silica nanosheets–Fe 3 O 4 –GOs complex as a multifunctional MRI agent [78]. The complex was prepared by coating
Fe 3 O 4 –GOs composite with aminopropyltriethoxysilane and tetraethyl orthosilicate
to form mesoporous silica nanosheets–Fe 3 O 4 –GOs. The complex was further
modified with interleukin-13-based peptide (IP) loaded with doxorubicin for efficient targeting and chemotherapy. After i.v. injection of the complex, T 2 -weighted
image clearly visualized that the targeting was successfully done by IP moiety. The
doxorubicin was released by photothermal heating of GOs, which immediately
weakened the hydrophobic and electrostatic interactions between GOs due to the
presence of highly concentrated hydrogen ions. Similarly, by another group an
analogous multifunctional complex was loaded with 5-FU, a different type of
anticancer drug on Fe 3 O 4 –GOs composite [79].
Based on these progress in developing MRI contrast agents for imaging and
therapy, the use of radiolabeled multimodal graphenes will be detailed in the following section.
4.6 In Vivo Radionuclide Imaging of Radiolabeled
Graphene
Current various imaging modalities have their own unique properties in terms of
sensitivity and resolution, which has been taking advantage of being fit for relevant
experimental purposes. Although MRI provides definite soft tissue structural
information enabling high-resolution images, the low sensitivity in the detection of
interested tissue area still remains inherent limitation of MRI. Also, as for the
fluorescence imaging, fluorescence imaging has been extensively applied in
examining a variety of exquisite biological events with microscopic resolution.
However, the light absorption/scattering in biological tissues of fluorescence
imaging creates high auto-fluorescence background, leading to low target to
background ratio obliterating image quality and data misinterpretation.
Radionuclide imaging, has played crucial roles in practical application including
disease diagnosis, providing high sensitivity in the clinical as well as preclinical
areas. Moreover, greater biological and clinical accuracy are achieved through
quantitative and tomographic imaging, taking radioactivity’s advantage of depth
imaging [80]. Radio-graphene was recently named in a review article, which
focused on the broad usability of radiolabeled graphenes (GOs and GQDs) for
targeted delivery and therapy [81]. Many available functional groups exposed at the
edge of GO has enabled the easy radiolabeling of GOs for in vivo use. Bifunctional
4 Graphene-Based Nanomaterials
95
graphene derivatives are amphiphilic, they are structurally advantageous to play
such versatile roles. While their functional edges are available for molecular conjugation with metal contrast agents or targeting moieties, the basal plane is capable
of loading various hydrophobic drugs at the same time.
In 2014, Wang et al. reported mesoporous silica nanosheets–Fe 3 O 4 –GOs complex as a multifunctional MRI agent [78]. The complex was prepared by coating
Fe 3 O 4 –GOs composite with aminopropyltriethoxysilane and tetraethyl orthosilicate
to form mesoporous silica nanosheets–Fe 3 O 4 –GOs. The complex was further
modified with interleukin-13-based peptide (IP) loaded with doxorubicin for efficient targeting and chemotherapy. After i.v. injection of the complex, T 2 -weighted
image clearly visualized that the targeting was successfully done by IP moiety. The
doxorubicin was released by photothermal heating of GOs, which immediately
weakened the hydrophobic and electrostatic interactions between GOs due to the
presence of highly concentrated hydrogen ions. Similarly, by another group an
analogous multifunctional complex was loaded with 5-FU, a different type of
anticancer drug on Fe 3 O 4 –GOs composite [79].
Based on these progress in developing MRI contrast agents for imaging and
therapy, the use of radiolabeled multimodal graphenes will be detailed in the following section.
4.6 In Vivo Radionuclide Imaging of Radiolabeled
Graphene
Current various imaging modalities have their own unique properties in terms of
sensitivity and resolution, which has been taking advantage of being fit for relevant
experimental purposes. Although MRI provides definite soft tissue structural
information enabling high-resolution images, the low sensitivity in the detection of
interested tissue area still remains inherent limitation of MRI. Also, as for the
fluorescence imaging, fluorescence imaging has been extensively applied in
examining a variety of exquisite biological events with microscopic resolution.
However, the light absorption/scattering in biological tissues of fluorescence
imaging creates high auto-fluorescence background, leading to low target to
background ratio obliterating image quality and data misinterpretation.
Radionuclide imaging, has played crucial roles in practical application including
disease diagnosis, providing high sensitivity in the clinical as well as preclinical
areas. Moreover, greater biological and clinical accuracy are achieved through
quantitative and tomographic imaging, taking radioactivity’s advantage of depth
imaging [80]. Radio-graphene was recently named in a review article, which
focused on the broad usability of radiolabeled graphenes (GOs and GQDs) for
targeted delivery and therapy [81]. Many available functional groups exposed at the
edge of GO has enabled the easy radiolabeling of GOs for in vivo use. Bifunctional
4 Graphene-Based Nanomaterials
95