Differences in cell death mechanism after magnetic hyperthermia treatment depending on the nanoparticle location

Abstract

Magnetic hyperthermia is a promising therapy for the localized treatment of cancer. Under the exposure to an external alternating magnetic field, magnetic nanoparticles (MNPs) act as heating agents inducing cell death in the treated region. Understanding the molecular mechanisms involved in the cellular damage generated by this treatment is crucial for the successful application of this therapy. In this study, 12 nm spherical MNPs coated with PMAO (poly (maleic anhydride-alt-1-octadecene) and functionalized with glucose were prepared by thermal decomposition. In order to evaluate the influence of the nanoparticle location in the treatment efficacy, two different 3D cell culture models, based on collagen gels, were prepared using a macrophage cell line, RAW264.7, (Figure 1). The first model (Model 1) kept all the particles inside the cells while the second model (Model 2) had particles both inside and outside the cells. The first model mimics a scenario where MNPs are administered intravenously with an active targeting, and the second one mimics intratumoral administration. The MNPs uptake and cell death mechanisms induced after the hyperthermia treatment (377 kHz, 13kA/m and 30 minutes, DM100-DM3 nB nanoscale Biomagentics,) were evaluated by flow cytometry. Interestingly, the cell death pathway was different depending on the MNPs location. Necrosis was observed 24h after magnetic hyperthermia application in the model where the nanoparticles are located just inside the cells. In contrast, apoptosis was detected in the model where the particles are inside and outside the cells. In addition, in the second model, our results evidenced an enhancement of the nanoparticles uptake after the exposure to the alternating magnetic field. This observation could justify the repetition of the treatment to obtain a better antitumor effect.Our results demonstrate the potential efficacy of magnetic hyperthermia in the treatment of malignant tumours. In addition, the use of 3D cell culture models for the optimization of hyperthermia treatments (type and dose of MNPs, repetition cycles, field amplitude and frequency, etc) presents several advantages, allowing the obtention of information in a more realistic way than monolayer cell cultures and reducing the number of animals required for preclinical tests.