Porous silicon: towards an optimized system for anticancer therapy

Porous silicon (pSi) is a sponge-like material that is commonly obtained through electrochemical etching of a crystalline silicon wafer in hydrofluoric acid-based electrolyte medium. pSi particles of different size distribution can be obtained through fragmentation of the porous layer by means of ultrasounds or ball-milling. Due to quantum confinement effects, this material was discovered to be photoluminescent at room temperature The anodization technique produces a po-rosification of the material, resulting in elevated porosity, high surface-to-volume ratio and a large surface area, thus making pSi very attractive as a carrier in the perspective of drug loading and release in the field of NanoMedicine. Fur-thermore, the surface enables the binding of a broad range of different molecules (e.g., polymers, drugs, dyes, magnetic nanoparticles, antibodies) leading to novel biomedical features, such as pH-responsiveness, magnetic properties and cell targeting. Its unique properties, together with biocompatibility, biodegradability and absence of immunogenicity, make this multifunctional platform perfectly suitable for nanomedicine applications that involve the delivery of drugs and the diagnostics. This thesis work was aimed at developing novel strategies to improve the per-formances of pSi, starting from the achievements already accomplished, for ap-plications in the anticancer therapy. To do that, on the one hand surface modifications through coating and encapsula-tion (with polymers and cationic surfactant) as well as by decoration with mag-netic nanoparticles were investigated. On the other hand, pSi particles were loaded with a variety of anticancer agents and tested on human cancer cell lines and cells of the immune system to explore their potential as valuable tools in support of clinically-established anticancer therapies. Several experimental procedures have been successfully implemented, including magnetic nanoparticles decoration, surface charge modifications and coating with polymers with different properties. The prepared materials were thoroughly investigated by means of different techniques, among all photoluminescence spectroscopy, UV-Vis spectrophotometry, dynamic light scattering, HPLC, FT-IR. Several imaging techniques have been exploited, such as confocal microsco-py, transmission and scanning electron microscopy, optical microscopy and in vitro test were done also by means of biological assays. The results here presented, associated with an acquired deep knowledge of the material, contribute to the improvement of a promising nanomedicine platform, adding a step towards its application in chemotherapy, immunotherapy and gene therapy.