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Page 4 of 9 Gholami et al. Mini-invasive Surg 2018;2:44 I http://dx.doi.org/10.20517/2574-1225.2018.44

Figure 1. Illustration of relative sizes of objects

[80]
combinations of inorganic and organic materials . To enable efficient surface modification, increasing the
functionality and stability, the core nanoparticles is coated. The core-shell has different applications in the
medical field such as controlled drug delivery, multimodal-imaging, cell labelling and nuclear medicine
therapy [81,82] . Superparamagnetic iron oxide nanoparticles (SPIONs) are one of the most common core-shell
nanoparticles that are used in medical imaging and therapy [83-93] .

SPIONS
[94]
SPIONs are nanoparticles that have become the focus of nanomedicine research since 1980 , and have
evolved to include SPIONs with a biocompatible polymer coating and core surface modification specifically
for nanomedicine and nuclear medicine applications. The key features of SPIONs include exhibiting
magnetisation only in an applied magnetic field and the ability to load drugs and medical radioisotopes
(due to their highly active surface). Over the past few decades, further developments in radiochemistry
and radiation sciences have led to applying the field of nanomedicine to nuclear medicine for enabling
multimodal medical imaging (radiolabelled nanoparticles with imaging isotopes) and radionuclide therapy
(radiolabelled nanoparticles with therapeutic isotopes) of different types of cancer. This has significantly
[95]
improved cancer diagnosis and therapy . Currently nanoparticle-based magnetic resonance imaging
(MRI) is utilised in cancer medicine for enhancing the MR image contrast. There are key advantages of
SPION drug delivery including longer circulation half-lives, improved pharmacokinetics, capability to
carrying a large amount of drugs, reduction in side effects and targeting the drug to a specific location in
the body [26,38] .

Additionally, the doped gold-SPIONs have been developed for targeted photothermal therapy for
[96]
destruction of CRC . The developed gold-SPIONs were also functionalised with a single chain antibody to
enable active targeting of the A33 antigen, which is overexpressed in CRC cells. Results demonstrated that
the internalisation of gold-SPIONs was five times faster for cells expressing the A33 antigen than cells not
expressing the antigen. Furthermore, this study has shown that upon 6 min of laser radiation exposure (with
-2
an 800 nm laser at 5.1 W·cm ), 53% A33-expressing cells died whereas only 5% of A33 non-expressing cells
died. These results demonstrated an excellent selectivity for targeting and killing CRC.

Moreover, SPION-based MRI has emerged as a common approach in medical imaging specifically of
[97]
lymph nodes in solid cancers, including CRC . This caused by a preferential uptake of SPIONs in lymph
[96]
node as well as the ability of SPIONs to produce high contrast between cancerous and healthy tissues .
Due to the physical and chemical properties (e.g., highly reactive surface and magnetisation) of SPIONs,
they have attracted enormous attention in cancer diagnosis and therapy [83-93] . SPIONs in vivo can perform
actively (targeting a tissue or an organ) or passively. Peptide or antibody labelled SPIONs act as an active
carrier for targeting the organ or tissue of interest. However, passive SPIONs mainly rely on the polymer
type and particle size to achieve accumulation at the target site. Hydrophilic SPIONs with dextran and