Abstract
Posterior segment eye diseases (PSEDs) including age macular degeneration (AMD) and diabetic retinopathy (DR) are amongst the major causes of irreversible blindness worldwide. Due to the numerous barriers encountered, highly invasive intravitreal (IVT) injections represent the primary route to deliver drugs to the posterior eye tissues. Thus, the potential of a more patient friendly topical route has been widely investigated. Mucoadhesive formulations can decrease precorneal clearance while prolonging precorneal residence. Thus, they are expected to enhance the chances of adherence to corneal and conjunctival surfaces and as such, enable increased delivery to the posterior eye segment. Among the mucoadhesive polymers available, chitosan is the most widely explored due to its outstanding mucoadhesive characteristics. In this review, the major PSEDs, their treatments, barriers to topical delivery, and routes of topical drug absorption to the posterior eye are presented. To enable the successful design of mucoadhesive ophthalmic drug delivery systems (DDSs), an overview of mucoadhesion, its theory, characterization, and considerations for ocular mucoadhesion is given. Furthermore, chitosan-based DDs that have been explored to promote topical drug delivery to the posterior eye segment are reviewed. Finally, challenges of successful preclinical to clinical translation of these DDSs for posterior eye drug delivery are discussed.
Highlights
In terms of triamcinolone acetonide (TA), previous research has supported that due to the large particle size of TA, it has a longer duration of action in the vitreous compared to DEX [72,73]
The results demonstrated a stable mean visual acuity in the photodynamic therapy (PDT) plus intravitreal TA
Is assumed that the mucoFracture theory theory bond failure occurs at the interface; failure typically adhesive bond failure occurs at the interface; failure occurs at the weakest point couldpoint be any of the adhering typically occurs at which the weakest which could be any of surfaces as well the adhering surfaces as well [107,110]
Summary
Several approaches including nanotechnology drug delivery systems, mucoadhesion, and permeation-enhancement based techniques have been investigated to potentiate topical drug absorption to the posterior eye segment tissues [11,12,13,14]. Owing to the ability of mucoadhesion to prevent rapid precorneal clearance and increase precorneal residence time, it is currently being explored for its potential in increasing chances of corneal and conjunctival absorption to the posterior segment, i.e., promoting non-invasive drug delivery to the posterior eye segment following topical administration. The major posterior eye diseases, their main treatments, the potential benefits of exploring topical ophthalmic drug delivery, and the barriers that need to be overcome for enabling topical drug delivery to the posterior eye segment will be presented. Cs based mucoadhesive DDSs for posterior eye drug delivery will be presented
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