# Magnetic Nanoparticles as Mediators for Magnetic Hyperthermia Therapy Applications: A Status Review
## 4 Conclusions
For maghemite nanoparticles and magnetic NiCu nanoparticles synthesized by the microemulsion method in a silica matrix, this temperature is about 45 \({}^{\circ}\)C, and for magnetic NiCu nanoparticles synthesized by the sol-gel method, the \(T_{\text{C}}\) varies depending on the composition and ranged from 51 to 64 \({}^{\circ}\)C; similarly, for NiCu and NiCr nanoparticles synthesized by mechanical milling, in the case of the former \(T_{\text{C}}\) the temperature varies from 24 to 174 \({}^{\circ}\)C, while for NiCr nanoparticles it ranges from 69 to 340 \({}^{\circ}\)C. As the Ni content increases, so does the \(T_{\text{C}}\). Using TEM analysis, we determined the morphology, size, and size distribution of the synthesized nanoparticles. The size of the nanoparticles, which we estimated using Sherrer's equation, was largely confirmed. The morphology of the MNPs is different, they are mostly round nanoparticles, with the best distribution of the size of the nanoparticles in the case of the synthesis of NiCu nanoparticles by sol-gel synthesis; in these nanoparticles, no agglomeration can be detected. For other nanoparticles, homogenization leads to agglomeration and consequently to a larger size of nanoparticles, and the size distribution is also very wide. The synthesized nanoparticles show magnetic properties, which we have confirmed by magnetic measurements. The highest magnetization is observed for the maghemite nanoparticles, but it decreases somewhat when they are coated with CM-dextran. The magnetization is much lower for the magnetic NiCu nanoparticles, and the magnetization increases with increasing nickel content. The difference is also evident in the sol-gel method of magnetic NiCu nanoparticles, where the magnetization is about 2 emu/g for particles in the silica matrix, while the value increases to 20 emu/g when the silica is leached. Measurements of the magnetic heating effect were performed in a conventionally built calorimetric system generating an AMF with a nominal field strength of 2 kA/m up to 42 kA/m in the frequency range from 80 kHz to 800 kHz and equipped with a fiber-optic temperature probe to measure the temperature required to determine SAR. We monitored the temperature response of individually synthesized nanoparticles at different magnetic fields. Depending on the strength of the magnetic field, the nanoparticles showed different temperature responses; all of them mostly reached a heating temperature in the therapeutic range for use in MH, but it varied depending on the composition or strength of the magnetic field. In the case of NiCu nanoparticles synthesized by the microemulsion method, we also calculated the SAR values, which increased with increasing the magnetic field and ranged from 4.3 to 41.6 mW/g, while in the case of magnetic NiCu nanoparticles, the values ranged from 0.12 to 0.60 W/g, depending on the composition. All synthesized MNPs have properties that are necessary for use in MH. A \(T_{\text{C}}\), which is in the therapeutic temperature range, is particularly important because it means that heating in this range is automatically interrupted, which in the case of cancer cells means damage or destruction, while healthy cells remain undamaged. The magnetic NiCu nanoparticles synthesized by the sol-gel method were found to be most suitable for use in MH. They are about 10 nm in size and have a very narrow size distribution. The magnetization is very low in the case of silica, but only this can be removed. \(T_{\text{C}}\) is close to the therapeutic temperature, which can also be adjusted by simply changing the composition or the nickel content. In this short review article, we have shown that it is possible to synthesize MNPs of different compositions with properties for use in MH using various synthetic methods. In addition, it will be necessary to think in the direction of biocompatibility tests, or the use of both in vitro and in vivo tests, especially of the synthesized nanoparticles that have shown the best properties for use in the field MH.