Magnetic and thermal properties of CoFe2O4 nanoparticles for magnetic hyperthermia treatment

© 2018 The Authors. Published by IASE. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).


Introduction
*The magnetic nanoparticles (MNPs) have attracted much interest not only in the field of magnetic recording media such as audio and video tape, but also in the areas of medical applications such as drug delivery systems (DDS), magnetic resonance imaging (MRI), medical diagnostics, cancer therapy and magnetic hyperthermia treatment (MHT).
MNPs can be heated by the energy absorption when it exposure on the alternative current magnetic field (ACMF). The capability of MNPs to effective heating agents for MHT was demonstrated many years ago (Elbeshir et al., 2013;Torres et al., 2010).
MHT is a type of the cancer treatment in which the target is exposed to a temperature ranges 42-46 o C, which is found to be more effective to cancer cells than to normal cells. Thermal effect of MNPs can be used to achieve the above purpose of thawing or recovery of tumor hyperthermia. More importantly, the nanoparticles can be inserted into the tumor cells and kill cancer cells effectively without damaging normal cells after the cells are heated to a certain temperature and maintain certain time in  (Elbeshir et al., 2013;Torres et al., 2010).
MHT can be used alone to cancer tumor treatment or together with the radiotherapy or the chemotherapy or the surgery. The hazard and the side effect of the radiotherapy, chemotherapy and the surgery are greater than the MHT. The MHT depend on two mean branches; the first one depends on the MNPs itself like; the size, the concentration, the magnetic and the thermal properties, while the second one depends on the ACMF like the frequency, the intensity and the power (Elbeshir et al., 2013;El Ghandoor et al., 2012a).

XRD and TEM characterizations
The size of CoFe2O4was characterized by the xray diffraction (XRD) and transmission electron microscopy (TEM) (Torres et al., 2010;El Ghandoor et al., 2012a;b)

Magnetization measurements of CoFe2O4 MNPs
The magnetization measurements were done via the second parts of CoFe2O4 samples at room temperature up to a maximum magnetic field (H) of 9000 (Oe) by using vibrating sample magnetometer (VSM) home-madeand parameters like specific saturation magnetization (Ms), coercive force (Hc) and remanence (Mr) were evaluated.

The thermal properties of CoFe2O4 MNPs
An induction heater operated at low frequencies and low powers (100 kHz and 100 W), was used to study the thermal properties (the maximum temperature T o C, the heating rate T/t o C/min and the specific absorption rate SAR W/g) of CoFe2O4 MNPs which was prepared previously (Elbeshir et al., 2013;Elbeshir, 2015;2016a;b;Motoyama et al., 2008).

XRD and TEM analyses
In this study we used the x-ray diffraction (XRD) and the transmission electron microscopy (TEM) analysis of CoFe2O4 (El Ghandoor et al., 2012b). The results are shown in Figs. 1 and 2 and Table 1.

Magnetic characterizations of CoFe2O4 MNPs
According to Table 1, Ms are obviously smaller than that of their bulk values, Ms bulk = 90 emu/g for CoFe2O4 [240], which can be attributed to the disorder canting spins (spin-glass-like) on the surfaces due to the coordination-number imperfection (Calero-DdelC and Rinaldi, 2007;Kumar et al., 2008).
The present results are compared with the published results in Davis and Mott (1970), where (Ms = 45.3 emu/g, Mr =11 emu/g and Hc= 270 Oe) to have a wider view and a deeper insight into the results, and it is found that the present results similar or nearly similar to the published and are listed in Table 1.
According to Davis and Mott (1970) and by viewing Fig. 3, it is easy considering the sample as soft magnetic materials. MNPs are believed to be promising for wide medical applications, such as drug delivery, bio separation, magnetic resonance imaging and magnetic hyperthermia treatment MHT (Calero-DdelC and Rinaldi, 2007).

The thermal properties of CoFe2O4 MNPs
First, 1 ml of deionizing water (DI) was exposed to the magnetic induction and no change on the temperature is noted. Then, 0.5 mg of MNPs was added to 1ml DI water and exposed to the same magnetic induction. The temperature of the samples is seen to increase with time. After 35 minutes the temperature reached 50 o C and remained constant up to 60 minutes exposure to the magnetic induction heating. Fig. 4 and Table 2 show these results.
The SAR value can be calculated by the following equation: where, C is the sample-specific heat capacity which is calculated as a mass weighed mean value of magnetite and water.is the initial slope of the timedependent temperature curve, mferrite is the magnetite content per mg of the sample tube (Elbeshir et al., 2013;Torres et al., 2010). There are as good as the linear relations in the first rising of the temperature. We used the linear relations in 0 -10 minutes intervals for calculating the SAR value of the sample. The heating rate T/t = 0.027 o C/sec and the SAR= 224 W/g.

Conclusion
The size of CoFe2O4 magnetic nanoparticles (MNPs) synthesized by chemical co-precipitation method after treatment at 100 o C was about 13 nm. XRD and TEM were used to characterize the size of CoFe2O4MNPs.   VSM home-made was used to determine the saturation magnetization, remanent magnetization and coercive force, the results are: (Ms = 48emu/g, Mr = 10.8 emu/g and Hc = 240 Oe) respectively; of the CoFe2O4 MNPs.
The maximum temperature was 50 o C and the needed time to reach this temperature was 35 min. with the concentration of 0.5 mg CoFe2O4/ 1ml of deionizing water. The temperature no longer changed over time when it reached to a certain value. The specific absorption rate SAR and the heating rate ΔT/Δt values of the CoFe2O4MNPs were founded to be 224 W/ g and 0.027 o C/sec respectively.
These values of the size, the thermal (energy absorption) and the magnetic properties of CoFe2O4 MNPs, indicate to use this sample in the magnetic hyperthermia treatment MHT.