Magnetic nanoparticles as bimodal tools in magnetically induced labelling and magnetic heating of tumour cells:: an in vitro study

Localized magnetic heating treatments (hyperthermia, thermal ablation) using superparamagnetic iron oxide nanoparticles continue to be an active area of cancer research. The present study uses magnetic nanoparticles (MNP) as bimodal tools and combines magnetically induced cell labelling and magnetic heating. The main focus was to assess if a selective and higher MNP accumulation within tumour cells due to magnetic labelling (max. 56 and 83 mT) and consequently a larger heating effect occurs after exposure to an alternating magnetic field (magnetic heating: frequency 400 kHz, amplitude 24.6 kAm(-1)) in order to eliminate labelled tumour cells effectively. The results demonstrate that the magnetically based cellular MNP uptake by human adenocarcinoma cells is due to suitable magnetic field gradients in vitro which intensify the temperature increase generated during magnetic heating. A significantly (P <= 0.05) enhanced MNP cell uptake due to 83 mT labelling compared to controls or to 56 mT labelling was observed. Our experiments required the following conditions, namely a cell concentration of 2.5 x 10(7) cells ml(-1), a minimum MNP concentration of 0.32 mg Fe ml(-1) culture medium, and an incubation time of 24 h, to reach this effect as well as for the significantly enlarged heating effects to occur.