Application of magnetically induced hyperthermia in the model protozoan Crithidia fasciculata as a potential therapy against parasitic infections

Abstract

Background: Magnetic hyperthermia is currently a clinical therapy approved in the European Union for treatment of tumor cells, and uses magnetic nanoparticles (MNPs) under time-varying magnetic fields (TVMFs). The same basic principle seems promising against trypanosomatids causing Chagas disease and sleeping sickness, given that the therapeutic drugs available have severe side effects and that there are 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 MNPs in order to provoke cell death remotely using TVMFs. Methods: Iron oxide MNPs with average diameters of approximately 30 nm were synthesized by precipitation of FeSO 4 in basic medium. The MNPs were added to C. fasciculata choanomastigotes in the exponential phase and incubated overnight, removing excess MNPs using a DEAE-cellulose resin column. The amount of MNPs uploaded per cell was determined by magnetic measurement. The cells bearing MNPs were submitted to TVMFs using a homemade AC field applicator (f = 249 kHz, H = 13 kA/m), and the temperature variation during the experiments was measured. Scanning electron microscopy was used to assess morphological changes after the TVMF experiments. Cell viability was analyzed using an MTT colorimetric assay and flow cytometry. Results: MNPs were incorporated into the cells, with no noticeable cytotoxicity. When a TVMF was applied to cells bearing MNPs, massive cell death was induced via a nonapoptotic mechanism. No effects were observed by applying TVMF to control cells not loaded with MNPs. No macroscopic rise in temperature was observed in the extracellular medium during the experiments. Conclusion: As a proof of principle, these data indicate that intracellular hyperthermia is a suitable technology to induce death of protozoan parasites bearing MNPs. These findings expand the possibilities for new therapeutic strategies combating parasitic infection.

Microswimmers with Heat Delivery Capacity for 3D Cell Spheroid Penetration

“…We would like to note that although the observed temperature increase Δ T ≈ 3.5 °C might seem insufficient for inducing a therapeutic effect, this temperature change represented an average bulk effect and not the temperature of the particle surface. Indeed, several recent studies demonstrated large local temperature gradients in the proximity of particles, which can surpass the average heating by more than an order of magnitude. − Furthermore, local heating effects have been demonstrated to negatively affect the cell viability even in cases when the bulk temperature was not seen to measurably increase. − …”

Nanoparticle-mediated magnetic hyperthermia is an effective method for killing the human-infective protozoan parasite Leishmania mexicana in vitro

“…It has also shown promise when treating a cutaneous infection of Staphylococcus aureus , a major pathogen that often infects soft tissue wounds 17 . Magnetic hyperthermia has also been shown to kill Crithidia fasciculata , a non-pathogenic protozoan species 18 , but to our knowledge, no report of the use of this technology against human-infective protozoan species such as Leishmania spp has been shown. Harnessing heat generated by magnetic hyperthermia to target pathogens is therefore an attractive, non-chemotherapeutic and novel alternative approach to treating CL that could offer a convenient, cost effective solution to the issues associated with conventional thermotherapy.…”

Influence on cell death of high frequency motion of magnetic nanoparticles during magnetic hyperthermia experiments

“…Surprisingly, it was recently appreciated in several in-vitro experiments using low concentration of MNPs in cell culture dishes that there is no need of global increase in the cell temperature to induce tumor cell death. [7][8][9][10][11][12][13] Different hypotheses have been proposed to explain cancer cell death in MH. One of them is based on recent experimental results showing that the temperature rises in the immediate vicinity of the MNPs.…”