Development and optimisation of esculin-loaded chitosan microspheres for intravitreal injection

This study was to prepare the esculin-loaded chitosan microspheres for intravitreal injection and explore the feasibility of the treatment of macular degeneration. The microspheres were fabricated using an emulsification crosslinking technique. The drug loading, encapsulation efficiency, and mean particle diameter of the optimised esculin-loaded chitosan microspheres were 8.03 ± 1.30%, 93.03 ± 2.16%, and 4.81 ± 1.60 μm, respectively. The thermal stability evaluation at 25 °C demonstrated consistent particle diameter maintenance, with microspheres retaining sizes of 4.73 ± 1.75 μm and 4.89 ± 1.55 μm after 15 and 30 days' storage periods, respectively. The <i>in vitro</i> release profile demonstrated 80% cumulative drug release from the microspheres over a 72 h period. Subsequent pharmacokinetic analysis revealed significantly enhanced parameters in the vitreous humour following intravitreal administration, with the half-life (<i>t</i>_1/2) reaching 879.88 ± 44.00 min and the area under curve (<i>AUC</i>) attaining 150.18 ± 2.28 × 10³ mg·min/mL. Intravitreal injection of esculin-loaded chitosan microspheres offers a promising drug delivery system for the treatment of macular degeneration.