Stimulation of primary auditory neurons mediated by near-infrared excitation of gold nanorods

Neural stimulation plays an important role in achieving therapeutic interactions with both the central and peripheral nervous systems, and forms the basis of neural prostheses such as cochlear implants and pacemakers. The interactions are commonly based on electrical stimulation delivered by microelectrodes, which are implanted in the vicinity of the target tissue. Electrical stimulation has limited selectivity, as the resolution of the stimulus is degraded by current spread. Moreover, the implantation may cause injury to the target tissue and the host inflammatory response can reduce stability. In order to improve the performance of neural interfaces, optical stimulation is attracting increasing attention, based on techniques such as optogenetics, photoactive molecules, and infrared neural stimulation. However, optical techniques at present tend to rely on visible or infrared wavelengths that have a limited penetration in tissue. Alternatively, the near-infrared region, corresponding to the therapeutic window in tissue, can be accessed by two-photon stimulation with relatively expensive light sources, or by the introduction of extrinsic light absorbers. For the latter approach, gold nanorods have recently been shown to provide efficient stimulation in a range of cell types, when exposed to near infrared light. Given the wide range of surface functionalizations and relatively low toxicity of gold, this approach is expected to draw increasing interest in the field of neural stimulation. This Method describes experimental procedures that have been used to prepare primary auditory neurons with gold nanorods for near-infrared excitation. It is anticipated that these procedures could be adapted to a range of related neural stimulation studies.