Eye-mimicked neural network composed of photosensitive neural spheroids with human photoreceptors

Abstract An in vitro model of an eye-to-brain circuit, composed of human photoreceptors that are the short-wavelength opsins and rhodopsins, was created. Two types of photosensitive neural spheroids were transfected for selective reaction under bluish-purple and green lights. These samples were applied to two devices with intact neuron and neural-spheroid to study the interaction. By photostimulation, the photosensitive spheroid initiated photoactivation and phototransduction, and the signal generated from its body was transmitted to adjacent neural networks. Specifically, the signal traveled two millimeters through the axon bundle in the narrow gap from the photosensitive spheroid to the intact spheroid as the eye-to-brain model including optic nerves. The whole process with the photosensitive spheroid was monitored by calcium assay fluorescence images and analyzed by several immunostaining imaging methods. The results of this study can be applied to examine and understand vision restoration and novel photosensitive biological systems with spectral sensitivity.