Smart nanoparticles for the treatment of ocular degenerative diseases

Retinal degeneration refers to the pathological conditions affecting the ocular posterior segment, including age-related macular degeneration, glaucoma, retinopathies and inherited retinal diseases. This pathological process represents the leading cause of partial or complete blindness, which stands as an extremely debilitating condition. At the end of 2019, it has been estimated that at least 2.2 billion people suffering from vision deficit or loss and this number is dramatically set to increase. Among the several endogenous and exogenous stress stimuli have been identified as factors contributing to retinal degeneration, the oxidative stress plays a key role in the pathogenesis of these diseases. Currently, no treatment is available to restore vision and the lack of effective therapeutical options is related to difficulties in targeting the ocular posterior segment and preventing the rapid degradation and clearance of delivered drugs. The present Ph.D. thesis focused on the development of a nanomedicine-based approach for delivering neuroprotective drugs to the posterior segment of the eye as a strategy to counteract retinal dysfunction. Particularly, we synthesised an organic polymer-based nanoformulation (ANPs), which was functionalised with peanut agglutinin (PNA) and nerve growth factor (NGF). The neuroprotective activity of our smart nanocarrier ANP:PNA:NGF was assessed in vitro on human retinal pigment epithelial cells and further investigated in vivo using the teleost zebrafish as animal model. Hence, we demonstrated that PNA not only improved the targeting of the posterior segment of the eye, thanks to its specific and high affinity for cone photoreceptors, but also prolongs the residence time of the NGF-based nanoformulation, thus resulting in a neuroprotective effect against retinal dysfunction induced by oxidative stress. Indeed, only the preventive administration of nanoformulated NGF, but not the free neurotrophin, improved the visual function of zebrafish larvae and provided a reduction of apoptotic cells in the retina in a model of oxidative damage induced through the intravitreal injection of hydrogen peroxide. Finally, two novel models of retinal degeneration in zebrafish have been developed. Particularly, the effect of exogenous administration of cigarette smoke extract and all-trans retinal, an oxidized form of retinol, was studied to investigate their negative contribution on visual function in zebrafish larvae, also exploring the possible neuroprotective activity of ANP:PNA:NGF. Hence, data related to visual behaviour and differential expression of antioxidant genes were collected to provide insight into retinal degeneration caused by environmental factors, such as smoking and prolonged light exposure. In conclusion, our multifunctional polymeric nanoformulation represents a promising strategy for implementing targeted treatment against retinal degeneration, also confirming the zebrafish as an extremely useful model organism for pre-clinical validations of nanomedicine-based drug delivery systems.