Superparamagnetic magnetite nanoparticles (MNP) of about 10 nm were designed with proper physico-chemical characteristics by an economic, biocompatible chemical coprecipitation of Fe²⁺ and Fe³⁺ in an ammonia solution, for hyperthermia applications. Synthetic methodology has been developed to get a well dispersed and homogeneous aqueous suspension of MNPs. Citric acid was used to stabilize the magnetite particle suspension, it was anchored on the surface of freshly prepared MNPs by direct addition method. Carboxylic acid terminal group not only render the particles more water dispersible but also provides a site for further surface modification. The naked MNPs are often insufficient for their stability, hydrophilicity and further functionalization. To overcome these limitations, citric acid was conjugated on the surface of the MNPs. The microstructure and morphology of the nanoparticles were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM), and the interaction between citric acid and MNPs were characterized by Fourier transform infrared spectroscopy (FTIR), whereas the magnetic properties were investigated by vibrating sample magnetometry (VSM). Magnetic measurement revealed that the saturation magnetization of the nanoparticles was 74 emu/g and the nanoparticles were superparamagnetic at room temperature. We also have analyzed the potential of these particles for hyperthermia by determination of the specific absorption rate, the temperature increase (ΔT) of the particles was 37ºC. These ferrofluids with high self-heating capacity are a promising candidate for cancer hyperthermia treatment

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We developed a novel hyperthermia material for cancer therapy, cationic albumin-conjugated magnetite nanoparticles (MNPs), which absorb the energy of an alternating magnetic field and convert it into heat. MNPs of about 10 nm were synthesised through co-precipitation, and citric acid was used to stabilise the MNP suspension. Then albumin was cationised by replacing anionic side chain groups with cationic groups. The surface modification of the MNPs was provided by cationic albumin, which was covalently conjugated to carboxylic acid functions located at the distal end of the MNPs' surface by carbodiimide chemistry. Finally, we obtained stable superparamagnetic suspensions with particle sizes of 140 nm and saturation magnetisation of 67 emu/g, which do not have the disadvantage of eventual desorption of physical attachment. We also analysed the potential of these particles for magnetic fluid hyperthermia by determination of the specific absorption rate at a constant frequency of 215 kHz; the temperature increase of the particles was 30.8 °C. This study experimentally demonstrates the high efficiency of these nano-heaters.

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