Blink Activated Healing: Design of a pH-triggered In Situ Catechin Ophthalmic Gel

Background: Ocular drug delivery poses significant challenges due to rapid precorneal drug elimination, poor bioavailability and patient non-compliance arising from frequent instillations. To overcome these limitations, a gel system activated by pH variation was successfully prepared. Aim: The current research emphasises the development and assessment of a pH-responsive in situ ophthalmic gel formulated with catechin. Method: An ophthalmic in situ gel sensitive to pH was formulated using HPMC-K4M and Carbopol 940, which transforms from a liquid to a gel when exposed to tear fluid. Result: The developed formulations were analysed to determine their drug content, physiological pH compatibility, refractive index and gelling capacity. In vitro drug release studies demonstrated sustained release over 12 hours. Stability studies confirmed that the formulation remains stable at room temperature by retaining its gel integrity and drug potency. Sterility testing showed that the formulation remains sterile over an extended period. The MTT assay on Y-79 retinoblastoma cells revealed dose-dependent cytotoxicity of the catechin-loaded in situ gel, with an IC50 value of 18.47 μg/mL, significantly lower than that of pure catechin. Conclusion: These findings suggest that the developed formulation offers enhanced therapeutic potential and sustained ocular delivery of catechin for effective eye disease management. Major Findings: The pH-sensitive in situ ophthalmic gel of catechin achieved sustained drug release with good stability and sterility. It significantly enhanced anticancer activity, showing a lower IC50 than pure catechin, indicating improved ocular therapeutic efficacy.