Abstract/Summary

Keratoconus is a progressive condition caused by the thinning of the cornea, which eventually deforms the front surface of the eye into a cone shape leading to ghosting, multiple images, glare and several other vision problems. Currently keratoconus is treated with UV-induced ribofiavin-mediated collagen cross-linking, which requires a physical removal of the corneal epithelium under topical anesthesia. This study reports the penetration of riboflavin (Rb) and its more water-soluble form, riboflavin-5’- monophosphate (RbP), into the bovine cornea ex vivo. Using ex vivo bovine corneal tissues and 0.8 mg/mL drug solutions in phosphate buffer, it was established that RbP penetration into the cornea within 3 hours of diffusion experiment was greater (17.3 ± 0.8 μg) compared to Rb (10.4 ± 4.2 μg). In the cornea RbP was found to convert to Rb, which is mediated with enzymes present in this tissue. Several formulations including the conventional and propylene glycol-containing liposomes with encapsulated RbP have been developed and their effect on the drug penetration into the bovine cornea was evaluated. Encapsulation of RbP into the liposomes did not provide any statistically significant improvement in the penetration of RbP into the cornea.