Formulation and Evaluation of Topically Retained Hydrogels Loaded with Timolol Maleate Microspheres for Extended Release in Treating Glaucoma

Abstract

Conventional aqueous eye drop formulations have a shorter retention period and wash out of the precorneal region more easily. In this study, biodegradable microsphere-loaded hydrogels were developed to extend the time of residence and improve the drug bioavailability. The prepared microspheres were fabricated using PLGA as the biodegradable polymer and PVA as the surfactant. Hydrogels were prepared using Carbopol 940 and Gellan gum as gelling agents. Methods: The microspheres were created through a technique known as double emulsion solvent evaporation method. Evaluation included for its percentage yield, entrapment efficiency, particle size and surface morphology of the prepared microspheres. Timolol Maleate microsphere loaded hydrogel underwent assessments for pH, spreadability, rheological behaviour, sterility, antimicrobial efficacy, in vitro release studies, drug release kinetics and ocular irritation. Results: FTIR analysis confirmed compatibility between the drug and polymer. SEM observations indicated spherical microspheres with sizes ranging from 1 to 12 µm, suitable for ocular application. All formulations exhibited pH values between 4.2 and 5.0, with gelation occurring at 35°C to 38°C. Formulation F3 demonstrated optimal viscosity (1486 – 1850 cps) and good spreadability. Sterility tests were successful, and F3 displayed a drug release of 82.6% after 24 hours. Antimicrobial studies exhibited inhibition zones, and ocular tests on rabbits revealed no irritation. Stability analysis indicated no significant changes in pH or clarity. Conclusion: Based on physiological, rheological, and in vitro evaluations F3 was identified as the most suitable formulation for extended Timolol Maleate release via hydrogel, holding promise for effective glaucoma treatment.