Dorzolamide-loaded PLGA/vitamin E TPGS nanoparticles for glaucoma therapy: Pharmacoscintigraphy study and evaluation of extended ocular hypotensive effect in rabbits

•TPGS was employed to improve the entrapment of dorzolamide hydrochloride into NPs.•Effect of excipients and process variables on size and entrapment was assessed.•Comparative transcorneal permeation as well as corneal uptake was performed.•Reduction in corneal clearance as well as naso-lachrymal drainage was achieved.•NPs showed better intraocular pressure lowering potential than drug solution. Poor drug penetration and rapid clearance after topical instillation of a drug formulation into the eyes are the major causes for the lower ocular bioavailability from conventional eye drops. Along with this, poor encapsulation efficiency of hydrophilic drug in polymeric nanoparticles remains a major formulation challenge. Taking this perspective into consideration, dorzolamide (DZ)-loaded PLGA nanoparticles were developed employing two different emulsifiers (PVA and vitamin E TPGS) and the effects of various formulation and process variables on particle size and encapsulation efficiency were assessed. Nanoparticles emulsified with vitamin E TPGS (DZ-T-NPs) were found to possess enhanced drug encapsulation (59.8±6.1%) as compared to those developed with PVA as emulsifier (DZ-P-NPs). Transcorneal permeation study revealed a significant enhancement in permeation (1.8–2.5 fold) as compared to solution. In addition, ex vivo biodistribution study showed a higher concentration of drug in the aqueous humour (1.5–2.3 fold). Histological and IR-camera studies proved the non-irritant potential of the formulations. Pharmacoscintigraphic studies revealed the reduced corneal clearance, as well as naso-lachrymal drainage in comparison to drug solution. Furthermore, efficacy study revealed that DZ-P-NPs and DZ-T-NPs significantly reduced the intraocular pressure by 22.81% and 29.12%, respectively, after a single topical instillation into the eye.