A study on culturing of neurons on micro-electrode array in hybrid retinal implant

We are developing a visual prosthesis named a “hybrid retinal implant” for blind patients. In this prosthesis, it is necessary to develop a stimulating micro-electrode array which is implanted into the eyes, to culture the neurons on it and to guide their axons toward the central nervous system (CNS). We have developed electrodes which were fabricated using micro-machining technology. In a culture experiment, the dorsal root ganglion neurons of an adult rat were cultured on the array, and the axon guidance was tested by means of the concentration gradient of the nerve growth factor (NGF). The results showed that the neurons on the array extended their processes, and the NGF facilitated the extension. However, it failed to guide the axons toward the particular direction. Because the proper gradient was not organized in a low-viscosity collagen, the NGF could spread over the dish. Therefore, in future, a high-viscosity collagen will be used in order to make a suitable gradient