Design of magnetic iron oxide nanoparticles for the therapy of adiposopathy by low-frequency alternative current magnetic field application

The capability to shape the morphology and size of magnetic nanoparticles (MNPs) has garnered significant interest in the last decade, thanks to the possibility of tuning the magnetic properties of the final system. Among the several applications (e.g. sensors, catalysis, data storage, energy conversion, electronics, pharmacology) in which MNPs can be exploited, biomedicine is one of the most investigated fields. Particle shapes other than spherical have attracted strong interest in biomedical applications, since different shapes define different cellular uptake, different circulation time within the blood or lymphatic vessels, and different residency time within the cytoplasm. Moreover, the shape is responsible for various magnetic properties, which can result in considerably higher values of the effective magnetic anisotropy, greatly influencing the behavior of the particles under AMF. Hence, Fe3O4 nanorods, nanodiscs, and nano-octapods have demonstrated the ability to cause mechanical damage to cancer cells, whereas cubes and nanoflowers appear to be optimal mediators for inducing hyperthermia. Nevertheless, synthesizing various shapes of Fe3O4 MNPs to enhance specific properties remains an ongoing challenge. The main goal of this Ph.D. thesis is to synthesize anisotropic MNPs of various shapes and propose them for the treatment of adiposopathy, one of the most widespread pathologies in EU member states. In particular, we propose a new approach for the treatment of pathological adipose tissue, based on the application of MNPs and the induction of magneto-mechanical stress by applying an external low-frequency alternating current magnetic field (LF-AMF) that activates cell apoptosis, avoiding undesirable side effects associated with standard routes. In this research, in order to evaluate the effect of magneto-mechanical therapy, iron oxide Fe3O4 MNPs with a regular octahedral shape, an average diagonal of 21.7 ± 1.8 nm, and high crystallinity were synthesized and functionalized with DMSA and chitosan. Additionally, to evaluate the magnetic response of MNPs, a device was designed, developed, and implemented to generate an AMF with a frequency below 100 Hz and a suitable field strength. This device can induce a maximum field amplitude of 160 mT with a frequency range of 7-20 Hz, a field gradient of 25 T m-1, and the ability to exert a force of 0.017 fN per MNP. The encouraging preliminary results achieved through the magneto-mechanical treatment mediated by octahedral-shaped Fe3O4 MNPs on adipocyte and macrophage components of adipose tissue allow this treatment to be considered a promising resource for adiposopathy therapy. To enhance the effectiveness of the magneto-mechanical treatment, several shape of Fe3O4 were prepared by exploring different synthetic approaches (nanorods, nanodiscs, nanorhombs and nano-octopods). The deep morphological, structural and magnetic characterization highlighted are promising product for magneto-mechanical application. The cytotoxicity test validates that these nanoparticles are biocompatible for biomedical applications. As a further study, we investigated novel multifunctional magnetic-plasmonic nano-heterostructures (Au@Fe3O4 nanostars and Au-Fe3O4 nano-urchins) to be exploited as magneto-mechanical agents for magneto-mechanical and as heat mediators for photothermal therapy. The biocompatibity tests on RAW 264.7 and ECFCs cells and the viability test by in-vitro experiments on different cancer cell lines (A375M6, MIA PaCa-2, MCF7, and A549) demonstrated the therapeutic potential of these nanosystems. The goals achieved in this Ph.D. thesis demonstrated how using wet chemical methods, the size and shape of high crystalline, anisotropic Fe3O4 MNPs can be effectively tuned within a large spectrum (rod with different size and aspect ratio, disc, rhomb, and octopod). In addition, a similar strategy allowed us to obtain novel multifunctional magnetic-plasmonic nano-heterostructures. In conclusion, the most of these nanosystems represent promising candidates for inducing mechanical damage to cancer cells and adipocytes by applying an LF-AFM.