Topical Administration of Mucoadhesive Liposomes–Epoetin-β for Targeting the Ocular Posterior Segment

Delivering drugs to the posterior eye segment is a complex task, particularly for treating retinal diseases. Neuroprotective approaches to maintain neuronal integrity have garnered significant attention in recent research. Here, we developed a mucoadhesive nanoparticulate system based on thiolated hyaluronic acid-modified cationic liposomes (HA-SH@liposomes) for topical administration. To fabricate these liposomes, we utilized microfluidic technology with a toroidal mixer to ensure consistent size and stability. Cationic liposomes were prepared by using the microfluidic method, and Epoetin-β (EPOβ), a neuroprotective agent, was loaded into the liposomes. Following this, HA-SH was conjugated to the EPOβ/HA-SH@liposomes using a postmicrofluidics conjugation method, wherein HA-SH was added dropwise to facilitate electrostatic interactions between the cationic liposomes and the anionic polymer. The resulting liposomes exhibited a mean size of 144 ± 1.3 nm and a polydispersity index (PDI) of 0.09 ± 0.01, indicating their uniformity. We evaluated the biocompatibility of the EPOβ/HA-SH@liposomes in vitro using live/dead and MTS assays on the RGC-5 cell line, demonstrating no notable cytotoxicity compared to the controls. To assess the in vivo performance, we conducted extensive ophthalmological examinations in C57/BL6 mice, including immunofluorescence staining to track the distribution of EPOβ and EPOβ/HA-SH@liposomes within the eyeball. Additionally, we quantified EPOβ levels in the retina using an enzyme-linked immunosorbent assay (ELISA) kit after the topical application of free EPOβ and the EPOβ/HA-SH@liposome formulation. The immunofluorescence staining revealed efficient delivery of EPOβ into the retina and choroid via the transcorneal route when administered as EPOβ/HA-SH@liposomes. ELISA results showed that the liposomal formulation achieved approximately 1.9× greater penetration efficiency than free EPOβ. Furthermore, optokinetic response (OKR) assays indicated that animals treated with EPOβ/HA-SH@liposomes exhibited slightly improved visual acuity compared with those treated with free EPOβ, though the difference was not statistically significant. In conclusion, the topical ocular administration of EPOβ/HA-SH@liposomes facilitated the efficient delivery of EPOβ to the retina, promoting retinal recovery and confirming its neuroprotective properties. This preclinical study provides a foundation for innovative strategies in the topical delivery of neuroprotective agents in ocular therapy.