Hydrogel-Embedded\nPolydimethylsiloxane Contact Lens\nfor Ocular Drug Delivery

Topical administration is the commonly preferred method\nof administering\nophthalmic formulations, with the majority of available medications\nin the form of eye drops or ointments. However, the topical application\nof ophthalmological medications has less bioavailability and a short\nresidence time because of the physiological and anatomical constraints\nof the eye, making efficient ophthalmic drug delivery a challenging\ntask. Microfluidic contact lenses have the advantage of delivering\ndrugs into the eye in a controlled and on-demand manner. Here, we\nshowcase the use of hydrogel-embedded microcavities on PDMS-based\ncontact lenses for ocular drug delivery applications. The fabrication\ntechnique adopted here is the spontaneous formation of the spherical\ncavity by hydrogel monomer droplet, followed by the simultaneous thermal\ncuring of hydrogel and PDMS, creating a spherical cavity as small\nas 150 μm. The spherical cavity is embedded with pH-responsive\nhydrogel for on-demand drug delivery. The drug loaded in the hydrogel\nmatrix is released into the ocular environment by diffusion. The spherical\ncavity with a narrow opening restricts the diffusion to a minimum\nunder normal ocular pH conditions(pH > 6). When the ocular pH reduces\n(pH < 6), the pH-responsive hydrogel inside the spherical cavity\ndeswell and accelerates the drug release.