Biodegradable Silicon Nanoneedles for Ocular Drug Delivery

Ocular drug delivery remains a challenging task due to the structural barriers of the eye. Commonly used topical administration has extremely low bioavailability requiring repeated treatment of high dosage, which may increase the risks of toxicity, unwanted side effects, and the patient's financial burden. Intraocular injection such as intravitreal, intracameral, or subconjunctival injection has higher efficiency but is accompanied by pain and bleeding with a possible risk of infection or permanent damage. Many of these treatments are for chronic diseases where sustained medication is needed and repeat treatments must be performed. Injectable drug reservoir implants and drug embedded wearable hydrogel lenses have been attempted, but these suffer from painful surgical procedures or limited treatment duration and efficiency. Recently, vertically ordered microneedles have been used to reduce invasiveness with enhanced therapeutic efficiency. However, key challenges still remain in that they are still bulky and stiff to the cornea that is exceptionally soft and sensitive. This discordance inevitably debases the interfacial contact quality, resulting in the patient's discomfort, especially in long-term implantation. Also, its relatively bulky size in the submillimeter region can cause tissue damage with pain, and structural interference with light array may result in visual interference.<br/>To tackle this problem, we introduce a painless and long-term sustained ocular drug delivery platform through the innovation of biodegradable silicon nanoneedles on a tear-soluble contact lens. The silicon nanoneedles provide enough mechanical strength with sharpened tips to penetrate and embed into the cornea in a visually invisible manner and then undergo controlled gradual degradation over a month, enabling a long-term, sustained release of therapeutic ocular drugs. The tear-soluble contact lens provides an optimal curvature to fit the cornea. It undergoes rapid dissolution in tear fluid within less than a minute, enabling the initial short-term release of anti-inflammatory drugs. We show that the ocular drug delivery platform effectively treats corneal neovascularization in an in vivo rabbit model beyond the current gold standard therapy. This platform will help better manage various chronic ocular diseases painlessly and effectively without significant side effects.