🔬 Introduction
Delivering therapeutic agents to the posterior segment of the eye remains one of the greatest challenges in ophthalmology. Diseases such as glaucoma, age-related macular degeneration (AMD), and diabetic retinopathy primarily affect the retina and optic nerve, often leading to irreversible vision loss. Conventional delivery methods—including intravitreal injections and systemic administration—are either invasive or associated with significant side effects. Epoetin-β (EPOβ), a recombinant form of erythropoietin, has demonstrated strong neuroprotective and neuroregenerative properties in retinal tissues. However, its large molecular size limits its ability to cross ocular barriers when administered topically.
To address this challenge, we developed a mucoadhesive nanoparticulate liposomal system for the noninvasive topical delivery of EPOβ to the retina.
🧪 Materials and Methods
1️⃣ Synthesis of Thiolated Hyaluronic Acid (HA-SH)
Hyaluronic acid was chemically modified through carbodiimide-mediated conjugation to introduce thiol groups. The thiolation enhanced:
Mucoadhesion
Stability
Interaction with ocular mucosa
The degree of thiolation was confirmed via NMR and UV spectroscopy.
2️⃣ Microfluidic Preparation of Cationic Liposomes
Cationic liposomes were produced using microfluidic technology with controlled:
Flow rate ratio (FRR)
Lipid composition
Particle size optimization
The optimized formulation resulted in:
Mean size: 144 ± 1.3 nm
PDI: 0.09 ± 0.01
Uniform morphology (confirmed by TEM and FE-SEM)
EPOβ was encapsulated during liposome formation to ensure high entrapment efficiency.
3️⃣ Post-Microfluidic HA-SH Coating
The liposomes were coated with thiolated hyaluronic acid via electrostatic interaction to create:
EPOβ/HA-SH@liposomes
This modification improved:
Mucoadhesive properties
Ocular surface retention
Stability
4️⃣ In Vitro Evaluation
Cell Line: RGC-5 retinal ganglion cells
Assays: MTS viability assay & Live/Dead staining
Results showed:
No significant cytotoxicity
Excellent biocompatibility
5️⃣ In Vivo Studies
Animal model: C57/BL6 mice
Evaluations included:
Immunofluorescence staining
ELISA quantification of retinal EPOβ
Optokinetic response (OKR) behavioral test
Optic nerve crush (ONC) injury model
📊 Results
✅ Efficient Retinal Delivery
Immunofluorescence imaging confirmed successful transcorneal transport of EPOβ into:
Retina
Choroid
📈 Enhanced Penetration
ELISA results demonstrated:
1.9× higher retinal penetration compared to free EPOβ
👁️ Visual Function Assessment
OKR testing showed:
Slight improvement in visual acuity in the liposome-treated group
Neuroprotective potential without statistical toxicity
🧫 Stability & Mucoadhesion
The HA-SH coating improved:
Surface charge stability
Resistance to aggregation
Lipid oxidation resistance
Mucoadhesive index
💡 Discussion
This study demonstrates that combining:
Cationic liposomes
Thiolated hyaluronic acid
Microfluidic fabrication
Creates a stable, reproducible, and scalable nanocarrier system capable of delivering large biologics such as EPOβ to the posterior eye segment via topical administration.
The enhanced mucoadhesion increases ocular residence time, overcoming rapid tear clearance and epithelial barriers.
🎯 Conclusion
Topical administration of EPOβ/HA-SH@liposomes significantly improves retinal drug delivery compared to free EPOβ.
Key achievements:
Noninvasive delivery route
Enhanced retinal penetration (1.9×)
High biocompatibility
Neuroprotective support in optic nerve injury model
This mucoadhesive liposomal platform represents a promising strategy for future ocular therapies targeting retinal neurodegeneration.
📄 Full Article Reference
Title: Topical Administration of Mucoadhesive Liposomes−Epoetin‑β for
Targeting the Ocular Posterior Segment
Journal: Molecular pharmaceutics, March 2025
DOI: https://doi.org/10.1021/acs.molpharmaceut.5c00079
