Spatial variation of evoked potentials in porcine retinas characterized by multi electrode array upon stimulation via 3D pyrolytic carbon electrodes

Introduction Visual restoration using photovoltaic retinal implants to alleviate vision loss has recently seen substantial progress. Most devices being developed are reliant upon rare earth metals, such as iridium, but their use in connection with highly immunoactive retinal tissue may pose an issue. Typical electrodes are fabricated as thin films and as such they are two-dimensional. Ideally, stimulating electrodes should be patterned into 3D topologies to optimize the electrode-tissue interface. It is currently not possible to achieve complex 3D electrode geometries with metal-based materials, which could potentially improve stimulation efficiency and resolution. Methods This study utilizes multi electrode array analysis of the spatial variation of evoked potentials in porcine retinal explants stimulated electrically via newly developed 3D carbon electrodes. Results Nine out of 10 explants showed significantly higher tissue activity during stimulation using the electrode, supplied with a direct current pulse with a voltage of +0.5 V typical for single-junction silicon photovoltaics. Discussion We report no spatial biases or patterns in tissue activation. The electrode significantly activated tissue above spontaneous activity levels and did not produce spatial patterns or biases, confirming the electrode as an alternative for metallic electrodes and for further development and in vivo testing.