In Vitro primary neuron and Ex Vivo retina stimulation with optoelectronic biointerfaces

Progressive vision impairment generally arise due to irreversible photoreceptor damage in retinal degenerative diseases. Although there are applications aimed at improving patients' life quality, the exact treatment of these diseases has not been found. Optoelectronic approaches aim to perceive the incoming light and convert it into electrical signals by performing an artificially similar function of photoreceptors, and to activate retinal neurons to send signals for perceiving light in brain. Development of optoelectronic biointerfaces provides new strategies for therapeutic application in vision-related diseases. This thesis aims to investigate the design of photovoltaic devices, biocompatibility and functional applications. Fabricated novel biointerfaces were tested in in vitro culture conditions and ex vivo retinal stimulation. The final part of the thesis includes the optimization of an in vivo optic nerve injury model for further prosthesis testing in the future. The first part of the results consists of in vitro tests including cell viability, intracellular stress level, mitochondrial health, calcium influx of primary embryonic hippocampal neurons cultured on different photovoltaic device designs based on P3HT:ITIC and AgBiS2 quantum dots. More than 80% cell viability and minimal stress under light illumination made the biointerfaces suitable candidates for further studies. The next part includes the final design of AgBiS2-based devices with return layer of RuO2 and interlayer of ZnO nanowires to improve photocurrent and photovoltage values. In addition to the biocompatibility and functionality tests on primary hippocampal neurons, the stimulation capacity of AgBiS2-based biointerface was validated by ex vivo retinal recordings from rats with retinal degeneration under repetitive near-infrared light illumination. The last part includes the optimization of animal studies for optic nerve crush model. Histological and functional analysis showed that injury-related conditions such as retinal layer deformation, gliosis, fibrosis and decrease in retinal ganglion cell activity progressed with increasing injury duration. The in vivo model provided a new platform to study the neuroprotective and neuroregeneration capacity of photovoltaic devices in the future.