| dc.description.abstract | Neurodegenerative disorders currently are a major burden to society, expected to grow and impact populations world-wide. Access to the brain is strictly controlled by the blood brain barrier (BBB), which allows the permeation of molecules only via specific transport mechanisms, thus the development of nanomaterials as drug carriers has attracted considerable attention. Polymeric covalently crosslinked nanogels have been considered very promising candidates, having physicochemical properties which can be finely tailored by using specific functional monomers and being characterised by high colloidal stability and high drug uploading capability. In particular, N-isopropylacrylamide (NIPAM) based nanogels are attractive because of their thermoresponsive behaviour, which can be exploited to release the drug under specific temperatures. Moreover, the development of charged nanogels, potentially having both a thermo and pH-stimuli responsive behaviour, offers the possibility to further improve the specificity of these systems, thus to minimise therapeutical side effects. Another fundamental aspect to consider for the development of nanomaterials for biomedical applications is their biocompatibility, which requires the investigation within in vitro and in vivo systems. The use of these models is also necessary to evaluate the capability of these carriers to enter the cells and, eventually, to reach the targeted areas. This project contributes to the development of novel nanocarriers able to efficiently permeate the BBB and to delivery therapeutics to the brain. The work focussed on the following objectives: (1) to investigate the impact of charge introduction on NIPAM-based nanogels and their overall stimuli-responsive behaviour, (2) to evaluate how the introduction of different types of charge influences the in vivo response, by using zebrafish as animal model and (3) to verify the potential of optimised nanogels to cross the BBB and accumulate in the brain tissues in vitro and in vivo. The thesis is organised in a total of 5 main chapters. Chapter 1 is the introduction, that discusses the potential of using nanomaterials as drug delivery systems to the brain and the recent advances in this area, including the importance of using human BBB models and the advantages of using zebrafish to evaluate the suitability of brain-targeting nanocarriers. Additionally, an overview of the literature data regarding nanogel-based drug vehicles and the advantages of using stimuli-responsive systems is presented. In Chapter 2, data on the synthesis and characterisation of positively charged NIPAM-based nanogels, including different crosslinker contents and/or different types of functional groups, and the preliminary evaluation of the optimised formulations in early-age zebrafish show that also slight changes in the physicochemical properties of the nanoparticles can cause different in vivo responses. In particular, the distribution of the charged groups, influenced by the amount of crosslinker introduced, and the amount of surface charge, depending on the chemical structures of the charged functional monomers, were observed to play a key role in influencing the nanogels’ biocompatibility profiles. Chapter 3 presents the data regarding the synthesis of fluorescently labelled neutral and negatively charged NIPAM nanogels, and their use to evaluate their biocompatibility and biodistribution in vitro, using a human BBB model, and also in vivo, using zebrafish up to 10 days post fertilisation. The in vitro studies, carried out during a two-month secondment in the laboratory of Prof. Lino Ferreira in Portugal and partly in collaboration with the Blood Brain Barrier Laboratory at the University of Artois in France, revealed no cytotoxicity and a good capability to permeate through the BBB model, mainly by exploiting active transport mechanisms, in case of the negatively charged formulation at 0.1 mg/mL. Additionally, both the biosafety and the brain-permeation of these nanoparticles were further confirmed in zebrafish larvae, as evidenced by the intravital distribution studies. Chapter 4 presents some conclusions of this research project and its future perspectives, followed by a detailed materials and method section in Chapter 5 and the bibliography. | en_US |
