Sustained release of brimonidine from polydimethylsiloxane-coating silicone rubber implant to reduce intraocular pressure in glaucoma

Glaucoma is the leading cause of irreversible blindness, affecting 111 million people by 2040 worldwide. Intraocular pressure (IOP) is the only controllable risk factor for the disease and current treatment options seek to reduce IOP via daily taking eye drops. However, shortcomings of eye drops, such as poor bioavailability and unsatisfied therapeutic effects, may lead to inadequate patient compliance. In this study, an effective brimonidine (BRI)-loaded silicone rubber (SR) implant coated with polydimethylsiloxane (BRI@SR@PDMS) is designed and fully investigated for IOP reduction treatment. The in vitro BRI release from BRI@SR@PDMS implant reveals a more sustainable trend lasting over 1 month, with a gradually declined immediate drug concentration. The carrier materials show no cytotoxicity on human corneal epithelial cells and mice corneal epithelial cells in vitro. After administrated into rabbit’s conjunctival sac, the BRI@SR@PDMS implant releases BRI in a sustained fashion and effectively reduces IOP for 18 days with great biosafety. In contrast, BRI eye drops only maintain IOP-lowering effect for 6 h. Therefore, as a substitute of eye drops, the BRI@SR@PDMS implant can be applied as a promising non-invasive platform to achieve long-term IOP-lowering in patients suffering from ocular hypertension or glaucoma.