Lysozyme activated co-delivery of latanoprost–timolol from mucoadhesive chitosan nanocomposite to manage glaucoma†

Abstract

Glaucoma is a leading cause of irreversible blindness, and controlling intraocular pressure is imperative for good clinical outcomes. It is important to use natural stimuli to trigger the release of the drug when it is linked to a nanoparticle/nanocomposite, particularly in ophthalmic applications to maintain sustained release. Herein the preparation and investigation of biocompatible, mucoadhesive dual drug-loaded chitosan (CS)–graphene quantum dot (GQD) nanocomposites are reported. Drug release from the nanocomposite was controlled by the presence of a natural lacrimal fluid enzyme, lysozyme (Lyz). Lyz is efficient at cleaving the β-1,4 glycosidic linkages of CS, thereby releasing the drug of interest. A biocompatible, fluorescent nanomaterial i.e., GQDs, was employed to track drug loading by using simple photoluminescent spectral studies. The optimized nanocomposite encapsulation efficiencies (EEs) were 94.51% and 74.08% for latanoprost (LP) and timolol (TM) and delivered 32.68% and 66.61% of drugs, respectively, in 72 h. Dual drug delivery through the cleavage of β-1,4 glycosidic linkages of CS in the presence of Lyz was confirmed through ¹H-NMR and FE-SEM studies. An increase in the particle size from 490 nm to 1584 nm in the presence of mucin supports the mucoadhesiveness of the nanocomposite. The in vitro cytocompatibility and live/dead staining assays against human corneal epithelial (HCE) cells showed ≥80% cell viability. Ex vivo tests proved that the nanocomposite was non-irritant, and histopathological studies showed normal growth of blood vessels. Molecular docking studies showed the hydrogen bonding and electrostatic interactions between the drug and CS. Hence the developed nanocomposite could be used as an ocular suspension or nanocomposite for further preclinical studies on glaucoma management.