Advanced drug delivery systems for cancer treatment: Formulation strategies and biological models

Nanotechnology is emerging as a new tool in cancer fight. Lipidic nanocarriers represent one of the most studied colloidal systems by virtue of their versatility. Hydrophilic or hydrophobic small molecules can be loaded in liposomal vesicles based on their affinity for the inner core or lipid bilayer, respectively. The loading of hydrophobic molecules in liposomes is the most exploited strategy to enhance and overcome the poor biopharmaceutical properties of lipophilic compounds. Indeed, administration through different routes requires suitable aqueous solubility to ensure an adequate dose. Liposomes can address this issue by increasing the water solubility of hydrophobic molecules through their incorporation in the phospholipid bilayer. Lipidic carriers represent a biocompatible and versatile drug delivery system, reducing systemic toxicity and ameliorating the drug distribution profile to the target tissue. The first part of this project was focused on the development of a liposomal formulation for GlaB delivery in the treatment of Medulloblastoma by taking advantage of nose-to-brain delivery. The primary aim of the project was to generate a liposomal carrier that enhances the very low aqueous solubility of GlaB. Liposome composition was selected based on the drug loading efficiency and colloidal stability by producing liposomes using the thin film hydration technique. The production of liposomes was then switched to a microfluidic device to investigate the scalability of the formulation. GlaB-loaded liposomes were fully characterized in terms of size distribution, drug loading efficiency, drug release profiles, colloidal stability, and biocompatibility. With the aim to further increase drug concentration and provide long-term stability, a lyophilized version of the formulation was studied to select the cryoprotectant able to preserve liposomes’ dimensions upon redispersion. The lyophilized formulation proved to be versatile for the increase of the liposomal GlaB concentration by adapting the redispersion volume. With the aim of generating a formulation intended for intranasal administration, GlaB-loaded liposomes were modified with decorating agents to modulate their surface features in terms of charge exposure and stealthiness. The decoration of GlaB-loaded liposomes with oligocationic cell penetration enhancer (OCE), PEG, or PEG-shielded OCE was explored on a mucus-producing cell line as a model to explore the formulation behavior in a nasal-mimicking environment. The second part of the thesis is focused on the development of gold nanoparticles (GNPs) for the selective delivery of Doxorubicin to cancer tissues overexpressing the folate receptor (FR). The synergistic effect between the sonosensitizing properties of GNPs and the anticancer effect of Doxorubicin was exploited as a therapeutic approach for sonodynamic therapy. GNPs were generated by the Turkevich method. A folate-PEG linker was used as an active targeting agent, allowing folate exposure from the GNPs’ surface and the consequent biorecognition from FR. With the aim to identify the optimal ratio for drug loading and colloidal stability, the metallic surfaces were decorated at increasing molar ratios of a Doxorubicin prodrug. In order to generate a prodrug to limit its toxic effects in off-target tissues, Doxorubicin was conjugated to a lipoic acid moiety through a pH-sensitive hydrazone bond. Indeed, the active targeting would provide selective intracellular delivery of the anticancer drug to FR-overexpressing tissues. The focus of the project was to develop infiltrating metallic nanoparticles that i) could access the core of the tumor tissues binding the FR overexpressed in cancer cells, ii) release the anticancer drug molecule in the lysosomal compartment, and iii) be activated by ultrasound irradiation to induce ROS generation.