Biohybrid approaches to interface with the nervous system: the best of both worlds

Synthetic materials and devices that interact with light, ultrasound, or magnetic fields can be used to modulate neural activity with high spatial and temporal precision; however, these approaches often lack the ability to target genetically defined cell types and signaling pathways. Genetically encoded proteins can be expressed to modify the host tissue and provide cellular and molecular specificity, but compared to synthetic materials, these proteins often interact weakly with externally applied energy sources. Synthetic materials can respond to optical, acoustic, and magnetic stimuli to focus, convert, and amplify forms of energy to ones that are more accessible to engineered cells and proteins. By combining the devices, synthetic materials, and genetically encoded proteins or cells, researchers can gain the ability to interface with the nervous system with improved spatiotemporal, cell-type and molecular precision. Here we review recent advances in these 'biohybrid' approaches that use optical, acoustic, and magnetic energy sources.