# Magnetic Nanoparticles: Synthesis, Characterization, and Their Use in Biomedical Field
## 4 Biomedical Applications  
Magnetic nanoparticles (MNPs) have become a crucial tool in the biomedical area, significantly transforming different diagnostic and therapeutic methods. Due to their distinctive magnetic properties, as well as their compatibility with biological systems and capacity to be modified on the surface, these materials are highly suitable for a wide range of applications, including magnetic resonance imaging (MRI) [115], targeted drug administration, and cancer therapy [116; 117]. The adaptability of MNPs resides in their capacity to react to external magnetic fields, allowing for accurate regulation and manipulation inside biological systems. This characteristic is especially beneficial for targeted therapies, as it allows for the direct administration of medications or therapeutic agents to specific locations, hence reducing the occurrence of adverse effects throughout the entire body [118]. Moreover, their use in diagnostic imaging, namely in augmenting MRI contrast, facilitates enhanced and more intricate vision of internal body structures, resulting in enhanced diagnostic precision [20].  
The potential of MNPs in biomedical applications is extensive, and current research is investigating novel and effective methods to employ these NPs. Future prospects involve the advancement of multifunctional MNPs with the ability to perform both diagnosis and treatment simultaneously, commonly known as 'theranostics' [119; 120; 121]. This integration holds the potential to improve personalized medicine, wherein treatment approaches can be customized to meet the specific needs of each patient. Furthermore, the investigation of MNPs in the field of regenerative medicine and tissue engineering offers a fresh and promising direction for scientific inquiry, with the potential to facilitate innovative approaches to tissue repair and regeneration [121].  
MNPs have a significant benefit in their large surface area-to-volume ratio, enabling various functionalization and alterations that respond to specific biomedical requirements. The ability to adapt allows for the creation of magnetic nanoparticles (MNPs) with tailored characteristics, suitable for a range of uses including hyperthermia cancer treatment [122] and molecular detection. However, a notable disadvantage is the potential toxicity and biocompatibility. In this regard, the physical properties of NPs, such as the size, concentration, shape, and coatings, together with exposure time, the number of exposed cells, and chemical compositions are of major importance [93]. For example, iron oxide nanoparticlesenter the cell usually through endocytoses. The internalization process is highly dependent on their size [92; 102] and coating [95]. At high doses, MNPs can lead to the generation of reactive oxygen species, affecting the cells' fate [96; 97].  
It is essential to ensure that MNPs do not cause negative immune reactions or gather in important organs in order to safely use them in medical treatments. Furthermore, the ongoing investigation of the enduring stability and deterioration of MNPs in biological systems is being conducted to address any possible health hazards.  
Based on the unique magnetic properties of these nanoparticles, they are suitable for diverse applications as can be seen in Figure 2.