Magnetite/Rhodamine 6G nanoparticles internalization in Neurospora crassa cells: towards the magnetic hyperthermia application

In this work, the study of aqueous media co-precipitation-obtained magnetite nanoparticles (Fe 3 O 4 -NPs) and Rhodamine 6G coating nanoparticles: Fe 3 O 4 /Rh6G-NPs, stabilized with polyethylene glycol is presented. To assess their suitability for magnetic hyperthermia application, cellular internalization of Fe 3 O 4 /Rh6G nanoparticles using the fungus Neurospora crassa as a model system was also explored. The structural characterization by Infrared and Raman spectroscopies, as well as Transmission Electron Microscopy (TEM) of this material showed that the Fe 3 O 4 /Rh6G-NPs are chemically stable with a pure crystalline phase, exhibiting an average particle size of 38.6 ± 6.4 nm and a near-spherical shape; all these properties are desired for nanoparticles that are intended to be used in biomedical applications. Additionally, a marked superparamagnetic behavior in the composite was revealed by the magnetic characterization. The living cells exposed to Fe 3 O 4 /Rh6G-NPs showed fluorescence from the apical dome to the basal zone of the hyphae scanned under confocal microscopy; while TEM observations of ultrathin sections demonstrated the presence of Fe 3 O 4 /Rh6G-NPs throughout the cytoplasm of the fungus, corroborating internalization of the nanocomposite. It is worth mentioning that alteration of fungus growth or cell morphology after exposure to Fe 3 O 4 /Rh6G-NPs were not observed, which represent an important precedent of internalization of inorganic materials-based nanocomposites in cells for further exploration of magnetic hyperthermia applications.