Patients with retinal degeneration lose sight due to gradual demise of photoreceptors. Electrical stimulation of the surviving retinal neurons provides an alternative route for delivery of visual information. We demonstrate that subretinal arrays with 70 μm photovoltaic pixels provide highly localized stimulation, with electrical and visual receptive fields of comparable sizes in rat retinal ganglion cells. Similarly to normal vision, retinal response to prosthetic stimulation exhibits flicker fusion at high frequencies, adaptation to static images and non-linear spatial summation. In rats with retinal degeneration, these photovoltaic arrays provide spatial resolution of 64 ± 11 μm, corresponding to half of the normal visual acuity in pigmented rats. Ease of implantation of these wireless and modular arrays, combined with their high resolution opens the door to functional restoration of sight.

Zeolitic Zn-imidazolate cross-linked framework nanoparticles, ZIF-8 NMOFs, are used as "smart" glucose-responsive carriers for the controlled release of drugs. The ZIF-8 NMOFs are loaded with the respective drug and glucose oxidase (GOx), and the GOx-mediated aerobic oxidation of glucose yields gluconic acid and HO. The acidification of the NMOFs' microenvironment leads to the degradation of the nanoparticles and the release of the loaded drugs. In one sense-and-treat system, GOx and insulin are loaded in the NMOFs. In the presence of glucose, the nanoparticles are unlocked, resulting in the release of insulin. The release of insulin is controlled by the concentration of glucose. In the second sense-and-treat system, the NMOFs are loaded with the antivascular endothelial growth factor aptamer (VEGF aptamer) and GOx. In the presence of glucose, the ZIF-8 NMOFs are degraded, leading to the release of the VEGF aptamer, which acts as a potential inhibitor of the angiogenetic regeneration of blood vessels by VEGF. As calcination of the VEGF-generated blood vessels leads to blindness of diabetic patients, the functional NMOFs might act as "smart" materials for the treatment of macular diseases. The potential cytotoxicity of the NMOFs originated from the GOx-generated HO is resolved by the co-immobilization of the HO-scavanger catalase in the NMOFs.

We have previously developed a wireless photovoltaic retinal prosthesis, in which camera-captured images are projected onto the retina using pulsed near-IR light. Each pixel in the subretinal implant directly converts pulsed light into local electric current to stimulate the nearby inner retinal neurons. Here we report that implants having pixel sizes of 280, 140 and 70μm implanted in the subretinal space in rats with normal and degenerate retina elicit robust cortical responses upon stimulation with pulsed near-IR light. Implant-induced eVEP has shorter latency than visible light-induced VEP, its amplitude increases with peak irradiance and pulse duration, and decreases with frequency in the range of 2-20Hz, similar to the visible light response. Modular design of the arrays allows scalability to a large number of pixels, and combined with the ease of implantation, offers a promising approach to restoration of sight in patients blinded by retinal degenerative diseases.

Glaucoma is the second most common cause of blindness in the world. It is a multifactorial disease with several risk factors, of which intraocular pressure (IOP) is a primary contributing factor. IOP measurements are used for glaucoma diagnosis and patient monitoring. IOP has wide diurnal fluctuation and is dependent on body posture, so the occasional measurements done by the eye care expert in the clinic can be misleading. Here we show that microfluidic principles can be used to develop an implantable sensor that has a limit of detection of 1 mm Hg, high sensitivity and excellent reproducibility. This device has a simple optical interface that enables IOP to be read with a smartphone camera. This sensor, with its ease of fabrication and simple design, as well as its allowance for IOP home monitoring, offers a promising approach for better care of patients with glaucoma.