# Magnetic Nanoparticles as Mediators for Magnetic Hyperthermia Therapy Applications: A Status Review
## 3 Results and Discussion
### Thermogravimetric Analysis and Modified Thermogravimetric Analysis  
Figures 8-13 show the TGA/SDTA analysis and thermomagnetic curves, respectively, and the corresponding \(T_{\rm C}\) of CM-dextran-coated maghemite MNPs, (Mg, Ti)-ferrite MNPs, and thermally homogenized NiCu MNPs and ball-milled NiCu and NiCr MNPs. TGA/SDTA analysis was performed using the TGA/SDTA 851\({}^{\circ}\), Mettler Toledo (Columbus, OH, USA). The thermomagnetic (TM) curves and corresponding \(T_{\rm C}\) were determined by thermal demagnetization using a modified TGA on a TGA/SDTA 851\({}^{\circ}\), Mettler Toledo. \(T_{\rm C}\) was measured by placing a permanent magnet on top of the device. Figure 8 shows the amount/concentration of CM-dextran absorbed into the maghemite MNPs [27]. During thermal heating from room temperature to 750 \({}^{\circ}\)C, there is a total weight loss of 21.2%. The weight loss of 16.4% due to the oxidation of the CM-dextran occurs in the first temperature range (150-500 \({}^{\circ}\)C), indicated by an exothermic peak of the simultaneous differential thermal analysis (SDTA). The last step, 500-750 \({}^{\circ}\)C, is associated with a weight loss of 3.1%, which is due to the removal of the CM-dextran covalently bound to the surface of the particles. Figure 9 shows the TM curves and the corresponding \(T_{\rm C}\) of as-calcined (Mg, Ti)-ferrite powders (30 min, 1000 \({}^{\circ}\)C in the air) [26]. The \(T_{\rm C}\) of MNPs was determined using differential thermomagnetic curves (DTMC), which show an apparent change in weight because of a decrease in magnetization due to an increase in temperature (Figure 9a). Figure 9b shows the first derivative in the TM curve of (Mg, Ti)-ferrite MNPs, the maximum of which is attributed to the corresponding \(T_{\rm C}\). Figure 7 shows the samples for three different compositions. The most promising sample was s2 (x = 0.37), which has a \(T_{\rm C}\) of about 46 \({}^{\circ}\)C,  
Figure 8: Thermal analysis of the maghemite MNPs coated with CM-dextran and the corresponding SDTA. Figure 10: TM curve of the thermally homogenized particles Ni\({}_{0.725}\)Cu\({}_{0.275}\). Figure 9: (**a**) TM curves of the ferrite particles s1, s2, s3 and (**b**) the corresponding \(T_{\rm C}\) (the first derivative curve). which is ideal for use in MH. This is the temperature at which the nanoparticles transition from a ferromagnetic to a paramagnetic state, meaning that they no longer heat up under the influence of a magnetic field. Figure 10 shows the TM curve and its derivative for the thermally homogenized for 5 h at 750 \({}^{\circ}\)C under a reducing atmosphere of Ar/H\({}_{2}\) alloy Ni\({}_{0.725}\)Cu\({}_{0.275}\) MNPs (microemulsion method) [41]. For the as-prepared sample, the \(T_{\rm C}\) was about 250 \({}^{\circ}\)C, close to the \(T_{\rm C}\) of Ni, due to the different standard electrode potentials of Cu and Ni or to inhomogeneities in the sample itself. Using homogenization, we then determined the correct \(T_{\rm C}\) for the Cu\({}_{27.5}\)Ni\({}_{27.5}\) composition, which was about 45 \({}^{\circ}\)C, and which is in the therapeutic temperature range when we refer to MH. Figure 12: First derivative curves of TM curves for Cu\({}_{1-x}\)Ni\({}_{x}\) (B–F) alloys. Figure 13: TM curves of Cr\({}_{x}\)Ni\({}_{1-x}\) samples (S1–S7). Figure 11 shows the \(T_{\rm C}\) as the temperature at which half of the magnetization weight gain/loss was recorded during heating [103]. Samples A (Cu\({}_{67.5}\)Cu\({}_{32.5}\)), B (Ni\({}_{62.5}\)Cu\({}_{37.5}\)), and C (Ni\({}_{60}\)Cu40) were analyzed after heat treatment (850 \({}^{\circ}\)C in a reducing atmosphere, 6 h). Nanoparticles synthesized by the sol-gel method have a \(T_{\rm C}\) in the therapeutic range for use in MH. However, homogenization in a reducing atmosphere is required.