Formulation of α-Linolenic Acid-Based Microemulsions for Age-Related Macular Degeneration: Physicochemical Tests and...

Background and Objectives: Age-related macular degeneration (AMD) is an age-associated retinal disorder characterized by blood-retinal barrier (BRB) breakdown and pathological angiogenesis, leading to vascular leakage. The intravitreal administration of anti-VEGF agents remains the most effective treatment for neovascular AMD. However, repetitive intravitreal injections have risks, causing side effects such as cataracts, bleeding, retina damage, and, in severe cases, post-injection endophthalmitis. Hence, the development of innovative drug delivery systems is essential to minimize the risks and discomfort associated with intravitreal injections. Materials and Methods: We developed a microemulsion (ME)-based topical drug delivery system incorporating α-linolenic acid (ALA). In brief, pseudo-ternary phase diagrams were constructed by the water titration method using different combinations of surfactants and cosurfactants (S_mix-Cremophor RH 40: Span 80: Transcutol P in ratios of 1:1.05, 1:1:1, 1:1:1.5) containing ALA as the oil phase. Three blank microemulsions (ME1, ME2, and ME3) were prepared and characterized based on the optimized pseudo-ternary phase equilibrium with a S_mix ratio of 1:1:1. Results: ME3, with an average particle size of 38.59 nm, was selected as the optimized formulation for developing drug-loaded ME containing Fenofibrate, Axitinib, and Sirolimus. The drug-loaded ME showed particle size (46.94-56.39 nm) and in vitro release displayed sustained and longer time drug release for 240 h. The irritation and antiangiogenic activities were evaluated using the hen's egg chorioallantoic membrane (HET-CAM) assay employing the optimized ME loaded with each drug. Among the three drug-loaded ME, the Sirolimus ME showed a reduction in blood vessel sprouting in the HET-CAM assay, indicating strong antiangiogenic activity. Treatment with the optimized blank ME and Sirolimus ME significantly (p < 0.05) reduced COX-2 protein expression in LPS-stimulated RAW 264.7 cells, suggesting their potential anti-inflammatory effects. Conclusions: Overall, we suggest that the α-linolenic acid-based Sirolimus microemulsion may serve as a promising topical therapeutic approach for managing AMD and offering a potential alternative to invasive intravitreal injections.