Topical application of choline-calix[4]arene nanocarrier of silibinin reduces retinal damage in a model of Age-Related Macular Disease.

Age-Related Macular Disease (AMD) is a multifactorial neurodegenerative disease that affects the macula, leading cause of blindness (1). A pivotal role in AMD pathogenesis is played by dysregulation of iron homeostasis and currently no effective cure exists; controversial effects are indeed reported by treatments with anti-VEGF intraocular injections (2). An important goal for the treatment of AMD is to obtain therapeutic drug concentrations in the eye posterior segment by a topical drug administration. Due to blood-ocular barriers and lacrimal drainage it is difficult to design non-invasive ocular formulations for the treatment of AMD. Nanoparticles have gained attention because of their ability to penetrate through the ocular tissues, enhancing drug bioavailability. As a possible treatment for AMD, we here investigated a new topical ophthalmic formulation based on choline-calix[4]arene (Ch-Cx) nanoparticles loaded with silibinin (Slb), a flavonoid extract of silymarin (Silybum Marianum), which has multiple biological activities including anti-inflammatory, antiangiogenic and antioxidant properties (3). The synthesized Ch-Cx-Slb formulation showed to have good chemical, chemo-physical and pre-industrialization requirements for a drug delivery system: size smaller than 100 nm, low polydispersity index, stability, appropriate drug loading capacity, suitability of common sterilization and lyophilization processes and, finally, a positively charged surface that may increase eye adhesion and surface permanence (4). In vitro screening was performed to analyze the cell viability and pharmacological effects of Ch-Cx-Slb using the human retinal pigment epithelial cells (ARPE-19) exposed or not to FeSO4. In vivo assays were carried out using a rat model of AMD-like degeneration induced by a single intravitreal injection of FeSO4 and following topical ocular application as collyrium of Ch-Cx-Slb, Ch-Cx uncomplexed with Slb or free Slb, once daily for a period of 10 days. Immunofluorescence and biochemical analyses demonstrated that Ch-Cx-Slb has a higher protective action against RPE/choroid alteration and retinal degeneration by reducing oxidative stress, inflammation and VEGF-induced proliferation, when compared to the free components. All data support the Ch-Cx as a potential drug delivery system of silibinin or other compounds for the treatment of AMD 1. J. Ambati, BJ. Fowler, Neuron, 2012, 75, 26. 2. 2. KG. Falavarjani, Q. D. Nguyen, Eye, 2013, 27, 787. 3. R .Gazák , D. Walterová D, V. Kren V, Current Medicinal Chemistry, 2007, 14, 315. 4. International Patent, WO 2016/055976A1, 14.04. 2016. Acknowledgements: This work was supported by HIPPOCRATES Project PON02_00355 to ARB, GMLC and PG, and by "PNR-CNR Aging Program 2012-201 PI.P02 to PG.