Topical Drug Delivery to the Posterior Segment of the Eye

Topical drug delivery to the posterior segment of the eye is a very complex challenge. However, topical delivery is highly desired, to achieve an easy-to-use treatment option for retinal diseases. In this review, we focus on the drug characteristics that are relevant to succeed in this challenge. An overview on the ocular barriers that need to be overcome and some relevant animal models to study ocular pharmacokinetics are given. Furthermore, a summary of substances that were able to reach the posterior segment after eye drop application is provided, as well as an outline of investigated delivery systems to improve ocular drug delivery. Some promising results of substances delivered to the retina suggest that topical treatment of retinal diseases might be possible in the future, which warrants further research.

Advancement in Ocular Drug Delivery System to Overcome Ocular Barrier

The Ocular drug delivery system (ODDS) is the prominently challenging system faced by pharmaceutical researchers. Ophthalmic preparations are available in buffered, sterile and isotonic solutions. For the ocular delivery of drugs, various types of dosage forms are prepared and dispensed. As the drops are easier for the administration likewise more prescribed dosage form is the eye drop solution. For obtaining prolonged therapeutic effect ointment, suspensions and gelled systems are also used. The presence of various barriers as anatomical, physiological and physiochemical barriers makes difficulties in delivery of drugs in at the intended sites. Scientists invented alternate delivery routes to direct access at intended target sites. Second invention involves development of novel drug delivery systems providing better permeability, treatability and controlled release at target site. The liposomal delivery is beneficial because they have the ability of envelopment and both hydrophobic and hydrophilic drugs are suitable for delivery to both the anterior and posterior segment of the eye. Therefore, the uses of this alternative approach become quite a necessary. This formulation of novel devices will definitely help to the overcome ocular barriers and side effects with conventional topical drops. Current reviews on the conventional formulations of ocular delivery and their advancements followed by current nanotechnology based on the formulation developments. The recent incident with other ocular drug delivery planning consists of in situ gels, implants, contact lens and nano wafers are discussed. Drug delivery at ophthalmic route has been proven significant advancement for the future perspectives.

Cannabidiol-Loaded Mixed Polymeric Micelles of Chitosan/Poly(Vinyl Alcohol) and Poly(Methyl Methacrylate) for Trans-Corneal Delivery

Ocular drug delivery is challenging due to the very short drug residence time and low permeability. In this work, we produce and characterize mucoadhesive mixed polymeric micelles (PMs) made of chitosan (CS) and poly(vinyl alcohol) backbones graft-hydrophobized with short poly(methyl methacrylate) blocks and use them to encapsulate cannabidiol (CBD), an anti-inflammatory cannabinoid. CBD-loaded mixed PMs are physically stabilized by ionotropic crosslinking of the CS domains with sodium tripolyphoshate and spray-drying. These mixed PMs display CBD loading capacity of 20% w/w and sizes of 100–200 nm, and spherical morphology (cryogenic-transmission electron microscopy). The good compatibility of the unloaded and CBD-loaded PMs is assessed in a human corneal epithelial cell line. Then, we confirm the permeability of CBD-free PMs and nanoencapsulated CBD in human corneal epithelial cell monolayers under liquid–liquid and air–liquid conditions. Overall, our results highlight the potential of these polymeric nanocarriers for ocular drug delivery.