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Magnetic drug targeting 177

are used mainly as contrast agents in target organs such as liver, spleen, nodules nodes,
and gastrointestinal tract. Commercially available contrast agents are Feridex, Rasovist,
Survivor,and Sinere (Wang, 2015).
Several SPION systems—starch-coated and methotrexate functionalized; coated in
polymeric anhydroglucose and functionalized with epirubicin; starch-coated and functio-
nalized with epirubicin; and coated with dextran and functionalized with steptokinase—
were successfully used in experiments and in clinical trials (Neuberger et al., 2005;
Chomoucka et al., 2010). For instance, the chemotherapeutic drug gemcitabine is absorbed
on the magnetite MNPs coated with chitosan and may release the drug into the cancer
cells of the liver, colon and breast (Viota et al., 2013); dexamethasone 21-acetate, which is
part of the corticosteroid class, may be used with SPION and injected into the joints,
where it may be retained with an external magnet for treatment rheumatoid arthritis
(Butoescu et al., 2009).
Whatever their specific medical or biological role, or fabrication, in the following
the MDT is using MNPs (SIONs) as representative entities, and their spatial distribu-
tion is consistent with the continuous media assumptions. As magnetic materials they
are superparamagnetic, linear media. The following sections present concerns, stages
and results of mathematical and numerical modeling for several MDT application
stages—from physical systems and models, to numerical results. The magnetic field
sources are either permanent or coils. Certain aspects regarding time and space scales,
couplings, which are typical to multiphysics problems, are analyzed, with the aim to
produce solvable numerical models consistent with the physics that they represent.

6.3 Several modeling concerns in magnetic drug targeting

MDT therapy utilizes magnetizable particles (SPIONs) as MNPs carriers for the drug.
Injected into the vasculature, the MD travels with the blood flow to the targeted loca-
tion, where an externally produced magnetic field is used to retain and confine it.
Magnetization body forces and the gradient driven transfer process (convection
through the local vasculature and diffusion) act into hauling it towards the magnetic
field source. The MD fabrication and properties (core and coating) (Pankhurst et al.,
2003; Berry, 2009; Sun et al., 2008; An et al., 2015; Heidarshenas et al., 2019), the
knowledge of its transfer inside the human body (Hobbs et al., 1998; Grief and
Richardson, 2005; David et al., 2011), the magnetic field spectrum and the magnets
design (Jones, 1995; Schenck, 2000; Preis et al., 1991; Nedelcu, 2016), the deep-body
real-time MNPs sensing means and control (Martel et al., 2007; Koch and Josephson,
2009; Martel et al,. 2009; Eckert et al., 2013) are some of the concerns that need to
be comprehended and mastered through physical and numerical experiments to the
success of MDT. Along this line, MDT traverses several stages: (1) injection and
the mixing (with the blood), (2) hemodynamic advection through larger vessels to the