Magnetic hyperthermia in phosphate coated iron oxide nanofluids

We study the magnetic field induced hyperthermia in water based phosphate coated Fe3O4 nanofluids, synthesized by a co-precipitation method using ferrous and ferric salt solutions, ammonia and orthophosphoric acid. The specific absorption rate (SAR) values were measured at a fixed frequency of 126 kHz and at extremely low field amplitudes. The SAR values were determined from the initial rate of temperature rise curves under non-adiabatic conditions. It was observed that the SAR initially increases with sample concentration, attains a maximum at an optimum concentration and beyond which SAR decreases. The decrease in SAR values beyond the optimum concentration was attributed to the enhancement of dipolar interaction and agglomeration of the particles. The system independent intrinsic loss power (ILP) values, obtained by normalizing the SAR values with respect to field amplitude and frequency, were found to vary between 158-125 nHm2 kg−1, which were the highest benchmark values reported in the biologically safe experimental limit of 1.03-0.92×108 Am−1 s−1. The very high value of ILP observed in the bio-compatible phosphate coated iron oxide nanofluids may find practical applications for these nanoparticles in tumor targeted hyperthermia treatment.