Surface functionalized iron oxide nanoparticles for applications in biomedical sciences

Abstract

This thesis focuses on the functionalization of iron oxide nanoparticles (Fe3O4) and their applications in biomedical sciences. Each chapter represents an independent research project that has been conducted within a different collaboration. For each project, magnetic Fe3O4 iron oxide nanoparticles have been functionalized or modified to suit its requirements. This thesis aims to show how versatile and most promising Fe3O4 iron oxide nanoparticles are, and how their unique properties in size, shape, and magnetism can be utilized for a broad range of applications in biomedicines. Chapter 2 focuses on magnetic resonance (MR), computed tomography (CT), and intravascular ultrasound (IVUS) as essential diagnostic imaging techniques and how iron oxide nanoparticles can potentially be used as contrast agents across all three imaging modalities. Contrast agents are commonly used to enhance the imaging quality and thus provide more detail for assessment. However, previous studies using nanoparticles for MR and CT were prepared with surface coating stabilizers, which in turn can compromise the use in clinical studies. In this chapter, gold-iron oxide nanoparticles (Au*MNP) are presented as a multi-modal contrast agent. Using a chemically grafting method without stabilizers, presenting nanoparticles with pristine surfaces that allow for further functionalization in molecularly targeted theragnostic applications. In Chapter 3, the response of HepaRG liver cells to nanoparticles is examined in two methods, 2D and 3D cell culturing. By analyzing the cell response in 2D and 3D cultures an accurate estimation of the toxicity of nanoparticles can be made. The toxicity of iron oxide was assessed using commercially available cell assays (CellTiter-Glo and PrestoBlue), however, the experiments suggested some restrictions that could alter the data and therefore resemble inaccurate results. For this purpose, non-invasive imaging techniques based on impedance (xCELLigence system) and Coherent Anti-Stokes Raman Scattering (CARS) were used to analyze the cell toxicity. The results showed that those methods provided a much deeper insight into the cell viability and proliferation of HepaRG cells. Furthermore, valuable data on the immediate effects in real-time and long-term exposures can be captured of the same culture. Chapter 4 presents the cell internalization process of iron oxide nanoparticles, captured using the unique holographic cell imaging technique of a HoloMonitor M4 microscope. In most cases where the cell internalization process is monitored, only one or two cells can be visualized and tracked at the same time. This is not the case with this technique, where hundreds of cells can be simultaneously visualized, analyzed, and monitored over time. Unlike single-cell observation, the system takes pictures of the cell culture at a high capture rate, allowing to observe and interpret the cell dynamics, cell morphologies, and cell reactions to nanoparticles (e.g., toxicity and apoptosis). Measuring the kurtosis and skewness of MCF-7 cancer cells for 72 hours after nanoparticle exposure, showed that cell splitting and proliferation took place, and no extraordinary damages or cell death was caused by the internalization of the particles. Furthermore, every step of the internalization process was monitored and captured in visible data for the first time. Chapter 5 demonstrates magnetic molecularly imprinted polymer networks and spheres (MMIPs) for the selective binding of antibiotics. MIPs are polymers that can be synthesized with highly selective and reusable binding sites. Their combination with magnetic iron oxide can be used as a useful tool to monitor and remove antibiotic pollutants from freshwater sources and food products. MMIPs are prepared using a microemulsion technique containing vinyl-functionalized iron oxide to selectively bind the model antibiotics erythromycin (ERY) and ciprofloxacin (CPX). The results show that MMIPs prepared using this technique are highly selective towards their respective template molecule in methanol/water and milk matrix, are recyclable, and most importantly open to modification. In Chapter 6, zebrafish larvae are exposed to polyethylene glycol coated iron oxide supported gold nanoparticles for further toxicity assessment. In general, toxicological data is gathered in vivo, however, the translational values from in vitro to in vivo are sometimes questionable due to the complexity of the organism. Zebrafish larvae are used as an intermediate method for in vivo experiments, as they can be used 96 hours after hatching, unlike larger animals such as mice, rats, or rabbits which take a much longer time to reach adulthood, sometimes up to 3 months. Also, a single female zebrafish can spawn about 200-300 eggs per week, which can generate an extensive data set from a small-scale experimental setup. The results presented in this chapter showed a 100% survival rate of all exposed zebrafish larvae between a range of concentrations from 0 - 2mM (0 - 463.1 mg/L). Chapter 7 summarizes the key findings and developments presented in this thesis, suggestions for future work within each research project, and proposes future applications. Chapter 8 includes a list of journal publications produced from this thesis.