Timolol-eluting graphene oxide laden silicone contact lens: Control release profile with improved critical lens properties

Glaucoma is a chronic ocular disease characterized by increase in intraocular pressure (IOP). Currently, it is managed by high drug concentration eye drop solutions. The dosage form present <5% ocular bioavailability, due to ocular static and dynamic barriers. Ocular drug delivery using contact lens can ameliorate the disadvantages of conventional eye drop treatment. However, drug loading by traditional method using drug-packaging solution showed low drug uptake, burst released with altered swelling and optical properties. The direct drug loading method during lens fabrication show high drug loss during mandatory extraction and sterilization steps. Graphene oxide (GO), a single monomolecular layer nano-sheets, exhibit high drug loading capacity for hydrophobic drugs due to its π-conjugated stratum. In the present study, GO was incorporated into the contact lenses during fabrication step, to control the release profile of timolol along with improvement in opto-physical properties. These GO-laden contact lenses (SM-GO-TB) as well as blank contact lenses (SM-TB) were soaked in the solution of timolol. Alternatively, direct timolol-GO-lenses (DL-TB-GO) and direct timolol-lenses (DL-TB) were fabricated by adding timolol-GO and timolol during polymerization, respectively. GO improved the swelling of both soaked and direct laden contact lenses due to formation of hydrogen bounds between GO and water molecules. A significant improvement in the transmittance of GO-laden contact lenses was observed because of molecular dispersion of drug on the surface of GO. The addition of GO in the soaked and direct timolol-laden contact lenses showed significant decrease in burst release and improvement in the release profiles compared to respective contact lenses without GO. Thus, the study demonstrated that GO-laden contact lenses could improve the critical lens properties like swelling and transmittance with controlled release of timolol.