Magnetic hyperthermia is currently an EU-approved clinical therapy against
tumor cells that uses magnetic nanoparticles under a time varying magnetic
field (TVMF). The same basic principle seems promising against trypanosomatids
causing Chagas disease and sleeping sickness, since therapeutic drugs available
display severe side effects and drug-resistant strains. However, no
applications of this strategy against protozoan-induced diseases have been
reported so far. In the present study, Crithidia fasciculata, a widely used
model for therapeutic strategies against pathogenic trypanosomatids, was
targeted with Fe_{3}O_{4} magnetic nanoparticles (MNPs) in order to remotely
provoke cell death using TVMFs. The MNPs with average sizes of d approx. 30 nm
were synthesized using a precipitation of FeSO_{4}4 in basic medium. The MNPs
were added to Crithidia fasciculata choanomastigotes in exponential phase and
incubated overnight. The amount of uploaded MNPs per cell was determined by
magnetic measurements. Cell viability using the MTT colorimetric assay and flow
cytometry showed that the MNPs were incorporated by the cells with no
noticeable cell-toxicity effects. When a TVMF (f = 249 kHz, H = 13 kA/m) was
applied to MNP-bearing cells, massive cell death was induced via a
non-apoptotic mechanism. No effects were observed by applying a TVMF on control
(without loaded MNPs) cells. No macroscopic rise in temperature was observed in
the extracellular medium during the experiments. Scanning Electron Microscopy
showed morphological changes after TVMF experiments. These data indicate (as a
proof of principle) that intracellular hyperthermia is a suitable technology to
induce the specific death of protozoan parasites bearing MNPs. These findings
expand the possibilities for new therapeutic strategies that combat parasitic
infections.Comment: 9 pages, four supplementary video file
