Engineering the surface of magnetic nanoparticles with metal-organic framework for hyperthermia and drug delivery applications

The present thesis dissertation presents my doctoral work carried out over the last three years at the Italian Institute of Technology (IIT), University of Genova (UniGe), and University of Santiago de Compostela. The thesis has been conducted within the framework of the Marie Curie ITN project HeatNMof, which aims to combine the highly porous and versatile structure of biocompatible Metal-Organic Frameworks (MOFs) with plasmonic and magnetic nanoparticles (MNPs) to provide a powerful tool to tackle cancer. In this context, my PhD research was mainly focused on synthesizing novel core-shell composites based on MNPs and MOFs and evaluating their effectiveness in cancer treatment through magnetic hyperthermia therapy (MHT) and drug delivery applications. This thesis is organized into three chapters. Chapter 1, Introduction, attempts to provide the reader with a detailed picture of the fundamental concepts of nanomaterials, including metal nanoparticles (NPs) and their hybrids (NPs@MOFs), and how their properties and functionalization have advanced their use as controlled drug delivery systems. Moreover, an overview of the synthesis of MOFs and their composites was presented, with special attention to the combination of iron oxide-based NPs and MOF in a core-shell manner. Multifunctional nanocomposites with a core-shell structure not only exhibit exceptional physical and chemical characteristics inherent to nanomaterials, but they also incorporate outstanding properties from their cores and shells, rendering them highly promising for a wide range of applications, such as absorption and extraction of pollutants, catalysis, and drug delivery. Lastly, since the goal was to apply our proposed nanosystems in nanomedicine, the focus was on the most critical factors influencing nanoparticle interactions in biological environments. These include NP’s integrity, colloidal stability, protein corona formation, uptake, and performance, among others. The last part of Chapter 1 constitutes the description of the prospective objectives of the present PhD thesis and an overview of my work developed in Chapters II and III. Chapter 2, Magnetic-nanoMOF composites, focuses on the synthesis and characterization of different core-shell composites based on MNPs and MOFs, particularly ZIF-8. This chapter is divided into four main experimental sections: i) synthesis of various magnetic cores, ii) their surface modifications to facilitate ZIF-8 growth, iii) synthesis of the final composite by growing ZIF-8 shell, iv) functionalization of the composite surface with an amphiphilic polymer to ensure water stability and prevent degradation. To start with, various MNPs, such as cubic, spherical, and star-like iron oxide (magnetite, Fe3O4), cubic cobalt ferrite (CoFeNPs), cubic zinc ferrite (ZnFeNPs), and Rubik-like maghemite (γ-Fe2O3) NPs were chosen as magnetic cores for the study. Apart from the spherical Fe3O4 and the Rubik-like γ-Fe2O3 received from different collaborators, MNPs were synthesized using two different synthesis methods: thermal decomposition and solvothermal methods. Having ensured the production of the selected NPs, their surfaces were further functionalized with different polymers, to ensure their stability in the media where MOF growth occurs. Thus, surfactants such as cetyltrimethylammonium bromide (CTAB), gallic-polyethylene glycol (Ga-PEG), α-nitrodopamine-ω-carboxy-poly (ethylene glycol) (ND-PEG-COOH), and tetramethyl ammonium hydroxide (TMAOH), were used. Following the surface functionalization, the colloidal stability, possible morphological changes, structural and chemical integrity, and heating efficiencies of NPs were investigated. Next, the CTAB-coated NPs in cubic, spherical, and star-like shapes (magnetite, Fe3O4), cubic zinc ferrite (ZnFeNPs), and Rubik-like maghemite (γ-Fe2O3) were chosen to control ZIF-8 growth, by a simple procedure in aqueous media. The final size and morphology of MNPs@ZIF-8 composites were tailored by controlling different reaction parameters, such as time or concentration of CTAB. Finally, the developed core-shell nanostructures were coated with poly (isobutylene-alt-maleic-anhydride)-graft-dodecyl (PMA) amphiphilic polymer to protect ZIF-8 from degradation. The produced novel magnetic@MOF composites were characterized in detail to assess their potential for applications in MHT and drug delivery. The obtained results confirmed the heating abilities of these composites even in viscous media (50% glycerol). Moreover, these nanocomposites showed excellent performances as MRI contrast agents. Chapter 3, Magnetic@ZIF-8 for MHT triggered release, mainly focuses on the encapsulation of drugs and their release from the synthesized Fe3O4@ZIF-8 (cubic core) composites under AMF. Firstly, two of the most used chemotherapeutic drugs Doxorubicin (Doxo) and 5-fluorouracil (5-FU) were used to study their loading efficiencies. Thus, two main strategies were conducted: in-situ and after-synthesis encapsulation, leading to impressive Doxo encapsulation and loading efficiencies when encapsulated in-situ. The Doxo-loaded composites exhibited high stability in DMEM and showed promising performances for alternating magnetic field (AMF)-triggered release. Next, in vitro cellular uptake and subcellular distribution of these composites were assessed with U-87 glioblastoma cells. The results showed that the Doxo-loaded composite in-situ are non-toxic up to 2 mg/L Zn and that are effectively uptaken by cells, as indicated by the increase of Doxo-related fluorescence over time, with most of the composites’s localization within the lysosomes. Finally, the investigation into using the Doxo-loaded composite to exploit MHT for drug release revealed that while AMF application did not immediately trigger Doxo release in complete DMEM, it significantly increased lysosomal permeabilization. Following continuous exposure to an AMF for 1 h resulted in subsequent leakage of the Doxo which resulted in increased cytotoxicity.