Interazione di nanoparticelle di silice con superficie controllata con modelli di membrana naturali e sintetici

In the last few years, a great interest has been developed to the study of interaction between nanomaterials and biological systems due to the increased use of nanotechnology. Among other nanomaterials, silica nanoparticles are promising candidates for several applications, but the multiple aspects that can affect the interaction with environment and biological systems have to be clearly investigated. Predicting all the interactions at the interface between a biomolecule and a nanoparticle is extremely difficult for the complexity of the membrane and particle surfaces (Nel et al., 2009). For this reason, model systems have become necessary to better understand the effects of nanoparticles on biomolecules. The aim of the thesis was the evaluation of the behavior of surface-controlled silica nanoparticles with two membrane models: liposomes and red blood cells (RBC). The interaction of silica nanoparticle with liposomes of different size was also discussed. Two groups of silica nanoparticles were tested: pristine dense silica nanoparticles (DSN-OH) functionalized with aminopropyl groups (DSN-NH2) and pristine mesoporous silica nanoparticles (MSN-OH) functionalized with hyaluronic acid (MSN-200A, MSN-200B, MSN-6400B). Well-characterized amorphous silica (Aerosil50) was used as positive control throughout the experimental work. Calcein-loaded phosphatidylcholine liposomes were synthesized, incubated with silica nanoparticles and the dye leakage measured as an effect of membrane perturbation (Alkammash et l., 2015). The functionalized silica nanoparticles showed lower dye leakage percentages compared to the native ones without functionalization. Functionalized DSN and MSN were less perturbative than pristine silica. To increase the membrane complexity, silica nanoparticles were contacted with RBC and the hemolytic activity was determined measuring hemoglobin release due to membrane damage (hemolysis assay) (Pavan et al., 2013; Ferenc et al., 2015). Pristine DSN and MSN exhibited high percentages of hemolytic activity in a dose dependent pattern. To clarify the lipid-nanoparticle interaction, size distribution and ζ-potential were investigated with dynamic and electrophoretic light scattering (DLS and ELS), respectively. These results indicate that surface charge and functionalization 3 are involved on dye leakage and membrane disruption. Data support the hypothesis that surface modification of silica nanoparticles with hyaluronic acid increases their biocompatibility. As the DLS size distribution of the liposomes used for the assay showed the presence of two species at 160 nm and 5 μm, the vesicles were extruded with a 220 nm filter to obtain a monodisperse population. Extruded and non-extruded liposomes were tested with two well-characterized silica (A50 and the crystalline silica Min-U-Sil 5). Extruded liposomes seemed to be subjected to a lower membrane damage, with respect to non-extruded ones. Further investigation on the dependence of liposome size in the interaction with silica nanoparticles is required.