# Magnetic Nanoparticles as Mediators for Magnetic Hyperthermia Therapy Applications: A Status Review
## 1 Introduction  
Magnetic nanoparticles (MNPs) are nanoscale materials with exceptional properties that find applications across diverse fields, including environmental, biomedical, and clinical domains [1; 2; 3; 4; 5; 6]. The size range of MNPs is comparable to that of viruses (20-500 nm), proteins (5-50 nm), or genes (2 nm wide and 10-200 nm long). These nanoparticles possess magnetic characteristics, adhering to Coulomb's law, enabling their manipulation through an external magnetic field. Moreover, their substantial surface area can be effectively utilized for binding diverse biological agents [7; 8; 9]. The synthesis of magnetic nanoparticles (MNPs) plays a pivotal role in enhancing their properties and evaluating their potential applications [10; 11; 12; 13]. It involves a series of carefully designed processes aimed at tailoring their size, shape, composition, and surface characteristics. In the synthesis of MNPs, the main problem is to control the particle size, which results from the high surface energy of these systems. The spontaneous reduction in surface area in magnetic nanoparticles (MNPs) is driven by interfacial tension, particularly during the initial stages of nucleation, growth, and Ostwald ripening. To ensure the stability of MNPs, it becomes crucial to maintain an appropriate surface area while simultaneously implementing effective protection measures [14; 15; 16]. The coating should improve the stability and solubility of MNPs, increase their biocompatibility and target specificity, and prevent agglomeration, oxidation, corrosion, and toxicity [17; 18; 19; 20; 21; 22; 23]. The MNPs can be synthesized through many different methods including coprecipitation [24; 25; 26; 27; 28; 29; 30], thermal decomposition [31; 32; 33; 34; 35], hydrothermal synthesis [36; 37; 38; 39; 40], microemulsion [41; 42; 43; 44], polyol reduction [45; 46; 47; 48; 49], the sol-gel method [50; 51; 52; 53; 54], and others [55; 56; 57; 58; 59; 60; 61; 62; 63]. The synthesized MNPs are usually coated to ensure a proper surface coating and develop some effective protectionstrategies to maintain stability. Depending on the end use of the MNPs, specific surface modification processes are selected [2]. The applied coating strategies can roughly be divided into different groups: synthetic polymer [64; 65], natural polymer [27; 66], organic surfactants [67; 68], inorganic components [69; 70], and bioactive molecules and structures [71; 72]. Magnetic materials serve as highly effective tools for the magnetic separation of small molecules, biomolecules, and cells. Their unique ability to respond to a magnetic field allows for efficient and precise manipulation in separation processes. Additionally, magnetic materials can be coated with various coatings simultaneously, further expanding their versatility and applicability [73]. In the biomedical field, magnetic particles and magnetic composites are utilized as drug carriers [74; 75; 76; 77; 78; 79; 80; 81], as contrast agents for magnetic resonance imaging (MRI) [82; 83; 84; 85; 86; 87], and in magnetic hyperthermia (MH) [88; 89; 90; 26; 77; 80; 86; 87], which is also a focus of this short review. So far, several methods have been discovered to heat the tissue and destroy tumor cells at the increased temperature. Hyperthermia is an alternative and promising method of treating cancer cells, in which the cancer cells die with minimal damage to healthy cells. Hyperthermia is very popularly used together with radiotherapy and chemotherapy, which is why it has attracted great interest from many researchers from different fields. They started with translational research materials arranged to protect the entire tumor. This method requires carefully planned surgery, but it was not possible to control the temperature. The basis of MH is the increased heat sensitivity of cancer cells. It has been found that treatment of the cancer area is most effective at a therapeutic temperature between 41 and 46 \({}^{\circ}\)C, as it kills most cancer cells in the tissue of interest.