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This technique is practical, useful and may provide an alternative method both for monitoring of CML patients treatment and preventive purposes.

      Electrolyte iron is recommended by the World Health Organization (WHO) for anemia. Magnetic NPs known for the treatment of iron deficiency anemia are ferumoxytol, which is used in both Europe and the USA for adult patients with chronic kidney disease (CKD). This drug is administered intravenously prepared by coating carbohydrate shells onto superparamagnetic iron oxide NPs. In phase III clinical trials, ferumoxytol was more effective than oral iron in patients with CKD, with minimal mild or moderate adverse effects (Hilty et al. 2010).

      Magnetic NPs have important advantages such as enhancing the signal obtained from magnetic resonance imaging (MRI) techniques, promoting the accumulation and deposition of biotherapeutic compounds such as genes and peptides in rewarding microniches, and mediating the destruction of cancer cells and biofilms through the production of a local thermo‐ablative effect. Additionally, Superparamagnetic Nanoparticles (SPNs) have been used to mediate the delivery of therapeutic proteins promoting their deposition at specific target sites (Veiseh et al. 2009; Kim et al. 2010; Niemirowicz et al. 2015).

      1.2.4 Theranostic Applications of Multifunctional Magnetic NPs

Magnetic NPs have many novel applications in biology and medicine, including protein purification, drug delivery, and medical imaging. Magnetic NPs exhibit several features synergistically and deliver more than one function simultaneously. It exhibits highly selective binding. Because of the prospective benefits of multimodal functionality in biomedical applications, many researchers like to design and fabricate multifunctional magnetic NPs. There are two main strategies to formulate magnetic nanoparticle‐based multifunctional nanostructures. The first is molecular functionalization that involves attaching antibodies, proteins, and dyes to the magnetic NPs, and other method is magnetic NPs integrated with other functional nanocomponents, e.g. quantum dots (QDs) or metallic nanoparticles. Magnetic NPs combine with other nanocomponents to form a hybrid nanostructure that exhibits paramagnetism alongside features such as fluorescence or enhanced optical contrast. These structures could provide a platform for enhanced medical imaging and controlled drug delivery. The combination of unique structural characteristics and integrated functions of multicomponent magnetic NPs will lead to novel opportunities in nanomedicine (Gao et al. 2014).

      Magnetic separations of DNA play a significant role in molecular biology. Shan et al. (2010) demonstrated a novel method of pDNA isolation from Escherichia coli culture. They suggested the bioseparation of pDNA using the multifunctional magnetic nanoparticles (MNPs). Carboxyl‐modified superparamagnetic nanoparticles play a vital role as multifunctional bioadsorbent. They used these nanoparticles, both for cell capture and the consequent removal of genomic DNA/protein complex after lysis. This was attained by taking advantage of properties of nanoparticles such as bioaffinity and magnetic guidance by strong magnetic field. Moreover, the yield and purity of pDNA extracted by magnetic NPs are comparable to those attained using organic solvents or commercial kits. Moreover, the utilization of multifunctional magnetic NPs proved to be a time and cost‐effective pDNA preparation technique, independent on centrifugation and hazardous organic solvents (Niemirowicz et al. 2012).

Theranostic nanomedicine creates “nanoparticle‐based drugs” all together capable of the diagnosis and treatment of a disease. The goal of theranostic nanomedicine is to improve the detection and to increase the efficacy of the treatment of cancers. Also, to limit the systemic toxicity associated with this treatment. Therefore, it is important that the therapeutic agents reach and can be concentrated on the target sites. The most important advantage of theranostic nanomedicine in the treatment of cancer is the potential for a rapid review of the outcome of treatment in an individual patient, in order to plan the next therapy or to decide to repeat the same therapeutic session (for personalized medicine). The usage of magnetic NPs in conjunction with MRI imaging may advance the concept of personalized nanomedical theranostic treatment in cancer for an individual patient (Ahmed et al. 2012). MRI scanners are currently readily available in hospitals, and this seems to be the most appropriate technique for monitoring the effects of cancer nanomedicine therapies (Liu and Zhang 2012). Li et al. (2015) developed a multifunctional theranostic nanoplatforms for tumor imaging and therapy based on the star‐shaped Fe₃O_{4@Au core/shell nanoparticles, which presented an excellent effect in MRI, CT, thermal imaging, and photothermal therapy. The nanostar showed better biocompatibility, stability, and targeting for cancer cells. The representation of the applications of the core and shell of magnetic NPs are shown in Figure 1.22.}

Figure 1.22 A representation of the application of core and shell of magnetic NPs.

1.3 Conclusion

      Bulk ferro‐ and ferrimagnetic materials are generally characterized by the presence of magnetic hysteresis, more or less wide, when they are magnetized in an external magnetic field. Hysteresis can take different forms specific to soft or hard magnetic materials. They have specific saturation magnetizations and coercive fields that are known.

      However, in the case of magnetic nanoparticles, they change significantly, even if the nature of the magnetic material is the same, as an effect of the small size of the nanoparticles.

      The main basic characteristics of magnetic nanoparticles, in the dimensional range considered relevant for them, respectively 1–100 nm, are the following:

      1 At sizes larger than the critical diameter (Dc), the nanoparticles have (i1) a structure of magnetic domains, similar to bulk magnetic material, but having a small number of domains; (i2) surface effects are not very pronounced; (i3) the behavior in the external field is with hysteresis, more or less pronounced, depending on the nature of the magnetic material (soft or hard).

      2 At very small sizes, below the threshold diameter (Dth) (generally below 10 nm), depending on the nature of the material, magnetic nanoparticles behave radically differently, (ii1) lacking the structure of magnetic domains, having only one domain spontaneously magnetized to saturation; (ii2) the surface effects are strong, leading to a pronounced decrease in the saturation magnetization of the nanoparticles in ordinary fields; (ii3) the effect of superparamagnetism is manifested (lack of hysteresis), the nanoparticles being magnetized according to the Langevin function, like paramagnetic atoms.

      Between the two states (i) and (ii), for D_th < D < D_c, the phenomenon of magnetic relaxation (Nèel relaxation) appears. Thus, for D closer to D_th, but with D > D_th, the magnetization of unidominal magnetic nanoparticles will present a deviation from the Langevin function, more or less pronounced, depending on the nature of the nanoparticle material (reflected in the magnetic anisotropy), the size (volume) of the nanoparticle and the temperature at which it is found, or even the appearance of a small, narrow hysteresis, at larger sizes in the considered interval. In the case of magnetic dispersions for biomedical and technical applications, there will be in addition a Brown time relaxation, processes characterized quantitatively by a resulting relaxation time (Nèel–Brown). For D closer to D_c, but with D < D_c, the magnetization of single‐domain nanoparticle is stable, and nanoparticle is magnetized according to the Stoner–Wohlfarth model: with rectangular hysteresis when the magnetization is done along the direction of easy magnetization of the nanoparticle, and linear until magnetic saturation when the magnetization of the nanoparticle is done in a direction perpendicular to that of easy magnetization.

In dynamic conditions, in harmonic alternating magnetic field, the magnetic relaxation process must be viewed in relation to the measurement time, in which the process is observed (quantitatively, the relaxation time related to the measurement time). The situation changes radically depending on the ratio in which the two

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