TPGS modified nanoliposomes as an effective ocular delivery system to treat glaucoma

The aim of this study is to investigate the potential of D-alpha-tocopheryl poly (ethylene glycol 1000) succinate (TPGS) modified nanoliposomes as an ophthalmic delivery system of brinzolamide (Brz) for glaucoma treatment. The Brz loaded nanoliposomes containing TPGS (T-LPs/Brz) were firstly developed by a thin-film dispersion method. The average particle size was 96.87 ± 4.43 nm. The entrapment efficiency of the Brz was 95.41 ± 3.03% and the drug loading was 4.00 ± 0.13%. T-LPs/Brz exhibited obvious sustained release of Brz; in stark contrast to the normal liposomes of Brz (LPs/Brz) and the commercial formulation AZOPT® (Brz ophthalmic suspension, Brz-Sus). Enhanced trans-corneal transport of Brz was achieved with T-LPs/Brz. Compared with both Brz-Sus and LPs/Brz, the apparent permeability coefficient (P_app) of T-LPs/Brz was 10.2 folds and 1.38 folds higher, respectively. Moreover, T-LPs/Brz extended the cornea residence of Brz. White New Zealand rabbits treated with T-LPs/Brz had 3.18 folds and 1.57 folds Brz concentration 2 h after treatment than Brz-Sus and LPs/Brz, respectively. Further pharmacodynamic studies showed that T-LPs/Brz maintained an effective intraocular pressure (IOP) reduction from 3 h to 11 h after administration, while Brz-Sus and LPs/Brz presented effective IOP decreases from 3 h to 6 h and 3 h to 8 h respectively. The preliminary safety evaluation demonstrated that T-LPs/Brz had no significant side effects; specifically, no cornea damage and eye irritation. All the results indicated that TPGS modified nanoliposomes were a promising ocular delivery carriers for Brz to treat glaucoma. As such, T-LPs/Brz might be worthy of further translational study.