PHOTOSENS - The interaction of photosensitive proteins with microfabricated sensor arrays

As the population ages there is an increase in degenerative ophthalmic diseases such as age related macular degeneration (AMD) and retinitis pigmentosa (RP). Both AMD and RP results in the loss of photoreceptor cells in the eye and there is currently no c ure for these medical conditions. One alternative that may restore vision is by aid of artificial retinal implants. Most of the retinal implants under development are based on micro- nanoelectronic devices, powered by external sources or incident light, t o activate the neural cells present in the eye. These implants face challenges regarding output power, heat production, biocompatibility and signal transduction efficiency. The use of light sensitive proteins can be the solution for these challenges. Th e BIRGE research group, together with Lambdavision Inc., has been exploring the photochemical properties of photoactive proteins, such as bacteriorhodopsin (BR), in their retinal implants. BR, when exposed to light, undergoes a photocycle that pumps proto ns which results in a pH gradient that can be used to activate the neural cells. BR has a quantum efficiency of 65% for the first photochemical event and, if targeted with a red photon in the O-state, it can reach an intermediate state (Q-state) which is stable for more than 10 years. The Q-state is important to inactivate the BR implant in areas of the retina with working native photoreceptors. Collaborating with the department of micro- and nanosystems technology at Vestfold University College (HiVe) w ill facilitate the construction of a sensor array (eg. CMOS (photo-) pixels) that may simulate the photoreceptor cells in the human eye. This will permit the investigation of a BR based retina system, in the Q-state, prior to clinical trials. This proje ct involves challenges regarding the immobilization of the BR on the surface of the sensor array and the stimulation of the BR into different states of its photocycle (eg. programing of the Q-state).