Fiber Photonics

When using magnetic nanoparticles as heating source for magnetic particle hyperthermia it is of particular interest to know if the particles are free to move in the interstitial fluid or fixed to the tumour tissue. The immobilisation state determines the relaxation behaviour of the administrated particles and thus their specific heating power. To investigate this behaviour, magnetic multicore nanoparticles were injected into experimentally grown tumours on mice and magnetic heating treatment was carried out in an alternating magnetic field (H = 25 kA/m, f = 400 kHz). The tested particles were well suited for magnetic heating treatment as they heated a tumour of about 100 mg by about 22 K within the first 60 seconds. Upon sacrifice, histological tumour examination showed that the particles form spots in the tissue with a mainly homogeneous particle distribution in these spots. The magnetic ex vivo characterisation of the removed tumour tissue gave a clear evidence for the immobilisation of the particles in the tumour tissue because the particles in the tumour showed the same magnetic behaviour as immobilized particles. Therefore, the particles are not able to rotate and a temperature increase due to Brown relaxation can be neglected. To accurately estimate the heating potential of magnetic materials, the respective environments influencing the nanoparticle mobility status have to be taken into account.