Systematic magnetic fluid hyperthermia studies of carboxyl functionalized hydrophilic superparamagnetic iron oxide nanoparticles based ferrofluids.

We have systematically studied heating efficiencies (via specific absorption rate-SAR/intrinsic loss power-ILP) of carboxyl (terephthalic acid-TA) functionalized hydrophilic SPIONs based ferrofluids (with good biocompatibility/high magnetization) and influence of following key factors in magnetic fluid hyperthermia (MFH): (i) alternating magnetic fields (AMFs - H)/frequencies (f) - chosen below/above Hergt's biological safety limit, (ii) concentrations (0.5-8 mg/ml) and (iii) dispersion media (water, a cell-culture medium and triethylene glycol (TEG)) for in vitro cancer therapy. In calorimetric MFH, aqueous ferrofluids have displayed excellent time-dependent temperature rise for the applied AMFs, which resulted in high SAR ranging from 23.4 to 160.7 W/gFe, attributed to the enhanced magnetic responses via π-conjugations of short-chained TA molecules on the surface of SPIONs. Moreover, ILP values up-to 2.5 nHm2/kg (higher than the best commercial ferrofluids) are attained for the aqueous ferrofluids when excited below the recommended safety limit. Besides, the SPIONs dispersed in high viscous TEG have exhibited the highest SAR value (178.8 W/gFe) and reached therapeutic temperatures at faster rates for the lowest concentration due to prominent Neel relaxations. Moreover, these SPIONs have higher killing efficiency towards MCF-7 cancer cells in in vitro studies. Thus, the TA-based ferrofluids have great potential for in vivo/clinical MFH cancer therapies.