Sustained bimatoprost release using gold nanoparticles laden contact lenses

Contact lenses are ideally suited for sustained ocular drug delivery to bypass the issues associated with eye drop therapy. However, drugs such as bimatoprost loaded by the conventional soaking method show poor drug uptake, high burst release, and altered critical lens properties. In this study, the effect of gold nanoparticles (GNPs) on bimatoprost loading/uptake from the soaking solution and its release kinetics from the lens was investigated. In one method, GNP solutions of varying strength were loaded into the bimatoprost soaking solution (mM-SS batches), and in another method, the GNPs were included in the contact lens matrix during casting (mM-GN-L batches). The GNPs were spherical with average size of 21.1 nm and -20.1 mV zeta potential. The swelling, oxygen permeability, and optical transmittance of the lens were improved compared to those of the lens drug-loaded by the conventional soaking method (SM-L). The mM-GN-L batches showed significant improvement in drug uptake from the soaking solution compared to the SM-L and mM-SS batches. The in vitro studies showed relatively low burst and sustained bimatoprost release up to 72 h compared to 24 h with the SM-L batch. The ability to sustain drug release improved proportionally with an increase in the amount of GNPs in the lens. The presence of GNPs lowered protein adherence. The GNP-laden lenses were deemed safe in ocular irritation and histopathology reports (rabbit model). Further, they showed higher drug retention in the rabbit tear fluid compared to the SM-L lens. In conclusion, the presence of GNPs in contact lenses increased drug uptake from the soaking solution, and improved the in vitro and in vivo release kinetics without affecting the critical properties of the contact lenses for therapeutic application.