DESIGN, SYNTHESIS AND CHARACTERIZATION OF MAGNETIC BIO-INORGANIC NANOSYSTEMS WITH THERANOSTIC FEATURES.

The aim of my PhD project is to obtain immune nanosystems having, at the same time, diagnostic and therapeutic functions. To combine these applications, our nanosystems will be constituted by magnetic nanoparticles linked to an antibody fragment. Magnetic nanoparticles , (I will synthesize cubic ferrites mainly of iron, but also of other transition metals such as cobalt), give us both diagnostic properties, because they are already used as contrast agents in magnetic resonance imaging (MRI), and therapeutic properties, because they could be used in hypertemia experiments for cancer treatment. Furthermore they allow us to monitor the response to therapy. Instead the functionalization of magnetic nanoparticles with a specific antibody fragment (in particular we will start with the fragment of Trastuzumab, a monoclonal antibody that binds to human epidermal growth factor receptor 2 (HER2) )first provides us an active targeting. Indeed HER2 receptor is overexpressed in 20-30% of breast cancers and also in some types of adenocarcinoma of the stomach or gastro-oesophageal junction. Then Trastuzumab give us other therapeutic properties because, with different mechanisms of action, modifies cellular proliferation. So we want to overcame the limitation of traditional chemotherapy, improving the treatment specificity and dramatically reducing toxicity and unspecific side effects. We will start to synthesize magnetic nanoparticles by solvothermal methods, that is , a high-temperature decomposition of metal precursors in non-coordinating solvents and in the presence of surfactants . But in order to obtain nanoparticles water soluble, native surfactants like oleic acid will be exchanged with suitable linker. Particular attention will be given to the synthesis of the latter. Hydrophilic linker will be formed by: a catechol moiety to anchor surfactant to magnetic nanoparticles, a maleimide group able to reacting with free thiol group present on the Trastuzumab antibody fragment and a long polyethylene glycol chain (with molecular weight around 5000 KDa) to enhance water solubility and stability. PEG chain also provides magnetic nanoparticles of a “stealth effect” .They are less recognised by circulating plasma proteins opsonins which adsorb onto their surface and then are removed from the blood by the circulating monocytes and fixed macrophages. So the plasma half-life of these nanoparticles is increased together with the probability of arriving to desided target. We have to characterize these immuno-nanosystems under different aspects. The magnetic NPs will be analyzed:- by transmission electron microscopy (TEM) to study shape, dimensions and chemical composition; - by SQUID (Superconducting Quantum Interference Devices )magnetometry, to measure the magnetical properties - by measurements of proton relaxivity and specific absortion rate (SAR) to quantify capacity of NPs to be used as contrast agents and mediators for hyperthermia We will also study water stability of immune nanoparticles in function of time, pH and temperature with DLS analysis. Afterwards we will investigate in vitro toxicity of immune-nanosystems after their uptake from cells overexpressing HER2 receptor.