Maintenance of an intact mucosal barrier is critical to preventing damage to and infection of wet-surfaced epithelia. The mechanism of defense has been the subject of much investigation, and there is evidence now implicating O-glycosylated mucins on the epithelial cell surface. Here we investigate a new role for the carbohydrate-binding protein galectin-3 in stabilizing mucosal barriers through its interaction with mucins on the apical glycocalyx. Using the surface of the eye as a model system, we found that galectin-3 colocalized with two distinct membrane-associated mucins, MUC1 and MUC16, on the apical surface of epithelial cells and that both mucins bound to galectin-3 affinity columns in a galactose-dependent manner. Abrogation of the mucin-galectin interaction in four different mucosal epithelial cell types using competitive carbohydrate inhibitors of galectin binding, beta-lactose and modified citrus pectin, resulted in decreased levels of galectin-3 on the cell surface with concomitant loss of barrier function, as indicated by increased permeability to rose bengal diagnostic dye. Similarly, down-regulation of mucin O-glycosylation using a stable tetracycline-inducible RNA interfering system to knockdown c1galt1 (T-synthase), a critical galactosyltransferase required for the synthesis of core 1 O-glycans, resulted in decreased cell surface O-glycosylation, reduced cell surface galectin-3, and increased epithelial permeability. Taken together, these results suggest that galectin-3 plays a key role in maintaining mucosal barrier function through carbohydrate-dependent interactions with cell surface mucins.

In the ocular pharmacology market, there is a noteworthy unmet demand for more efficacious delivery of ocular therapeutics. Contact lenses are emerging as an alternative ophthalmic drug delivery system to resolve the drawbacks of the conventional topical application methods. Thus, contact lenses drug delivery systems have been developed to provide an increased residence time of the drug at the surface of the eye leading to enhanced bioavailability and more convenient and efficacious therapy. Several research groups have already explored the feasibility and potential of contact lenses loading conventional drugs used to treat anterior eye disorders. Drug incorporation to the lens body is achieved with techniques, like simple soaking, inclusion of drug-loaded colloidal nanoparticles, or molecular imprinting. Regardless of the technique used, key properties of the contact lens, such as transparency and oxygen permeability, should be preserved. In this article, we reviewed the different techniques used for drug delivery through contact lenses, analyzing their advantages and disadvantages, and focused on articles describing contact lens-based ophthalmic drug delivery systems with significant potential to use in ocular therapeutics.