Dual-functionalized mesoporous silica nanoparticles for topical axitinib delivery to the posterior eye segment

Topical drug delivery to the posterior eye segment remains a significant challenge due to ocular anatomical barriers, particularly in diseases such as wet age-related macular degeneration (AMD), where treatment typically relies on frequent intravitreal (IVT) injections of anti-angiogenic agents. In this study, we present a non-invasive eye drop formulation of axitinib (AXT), a potent vascular endothelial growth factor receptor (VEGFR) inhibitor, encapsulated within 25-nm dual-functionalized mesoporous silica nanoparticles (AXT@dual-MSNs) engineered for efficient retinal delivery. The nanoparticles feature sulfonate-functionalized mesopores that enhanced AXT loading and solubilization, along with a PEGylated/quaternary ammonium-modified surface that improved colloidal stability and favored intramesopore drug confinement. Following topical administration, AXT@dual-MSNs achieved retinal accumulation via the conjunctiva-sclera-choroid pathway, effectively bypassing the corneal route. A pharmacokinetic analysis confirmed rapid, transscleral delivery of AXT with therapeutically relevant concentrations in the retina. In a laser-induced choroidal neovascularization (CNV) mouse model, a well-established surrogate for wet AMD, AXT@dual-MSN eyedrops significantly suppressed neovascular lesion formation, outperforming free-drug eyedrops and IVT AXT injection. Notably, the formulation exhibited excellent ocular tolerance, with no evidence of local toxicity or contralateral eye exposure. This work introduces a novel nanocarrier system capable of overcoming the longstanding delivery barrier to the posterior eye segment via eyedrops, offering a safe, effective, and clinically translatable alternative to IVT injections. The modular design of AXT@dual-MSNs also holds promise for expanding topical access to other hydrophobic or labile therapeutics targeting retinal diseases.