Cell death induced by the application of alternating magnetic fields to nanoparticle-loaded dendritic cells.

In this work, the capability of primary, monocyte-derived dendritic cells (DCs) to uptake iron oxide magnetic nanoparticles (MNPs) is assessed and a strategy to induce selective cell death in these MNP-loaded DCs using external alternating magnetic fields (AMFs) is reported. No significant decrease in the cell viability of MNP-loaded DCs, compared to the control samples, was observed after five days of culture. The number of MNPs incorporated into the cytoplasm was measured by magnetometry, which confirmed that 1-5 pg of the particles were uploaded per cell. The intracellular distribution of these MNPs, assessed by transmission electron microscopy, was found to be primarily inside the endosomic structures. These cells were then subjected to an AMF for 30 min and the viability of the blank DCs (i.e. without MNPs), which were used as control samples, remained essentially unaffected. However, a remarkable decrease of viability from approximately 90% to 2-5% of DCs previously loaded with MNPs was observed after the same 30 min exposure to an AMF. The same results were obtained using MNPs having either positive (NH(2)(+)) or negative (COOH(-)) surface functional groups. In spite of the massive cell death induced by application of AMF to MNP-loaded DCs, the number of incorporated magnetic particles did not raise the temperature of the cell culture. Clear morphological changes at the cell structure after magnetic field application were observed using scanning electron microscopy. Therefore, local damage produced by the MNPs could be the main mechanism for the selective cell death of MNP-loaded DCs under an AMF. Based on the ability of these cells to evade the reticuloendothelial system, these complexes combined with an AMF should be considered as a potentially powerful tool for tumour therapy.

Dendritic cell uptake of iron-based magnetic nanoparticles.

We have investigated the internalization of magnetic nanoparticles (NPs) into dendritic cells (DCs) in order to assess both the final location of the particles and the viability of the cultured cells. The particles, consisting of a metallic iron core covered with carbon, showed no toxic effects on the DCs and had no effect in their viability. We found that mature DCs are able to incorporate magnetic nanoparticles in a range of size from 10 nm to ca. 200 nm, after 24 h of incubation. We describe a method to separate cells loaded with NPs, and analyze the resulting material by electron microscopy and magnetic measurements. It is found that NPs are internalized in lysosomes, providing a large magnetic signal. Our results suggest that loading DCs with properly functionalized magnetic NPs could be a promising strategy for improved vectorization in cancer diagnosis and treatment.