Thiolated hemicellulose containing mucoadhesive and permeation-enhancing ocular films of levodopa for potential treatment of myopia.

The ocular bioavailability of a drug is inadequate due to physiological constraints. In this study, an ocular film of Levodopa (LD) using thiolated hemicellulose (THC) with improved mucoadhesion and permeation was made. Linseed hemicellulose (LHC) was extracted, and its esterification was done with thioglycolic acid (TGA), L cysteine (LC), and thiourea (TU). Maximum thiolation of LHC was confirmed by Ellman's test, Fourier-transformed infrared spectroscopy (FTIR), scanning electron microscopy (SEM), X-ray diffraction (XRD), thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). Primary eye irritation tests and histopathological studies of different ocular tissues like cornea, conjunctiva, and sclera conducted on rabbit eyes exhibited nontoxic and non-irritant behavior of LHC and optimized derivative of LHC with TGA (THT-960) which was further used for the preparation of LD-containing ocular films i.e., LD-THC, LD-THT960, and LD-THT960-THC, respectively. Ascorbic acid was added to the ocular film to prevent oxidation of LD. Ex-vivo permeation studies from bovine cornea showed a 1.8fold increase in corneal permeation of LD while ocular irritancy by hen egg chorioallantoic membrane (HET-CAM) test and histopathological analysis confirmed nonirritant and nontoxic nature of THT-960. Conclusively, LD-THT960 due to improved mucoadhesion and corneal permeation of LD can be used effectively for the potential treatment of myopia.