A silk-based self-adaptive flexible opto-electro neural probe

The combination of optogenetics and electrophysiological recording enables high-precision bidirectional interactions between neural interfaces and neural circuits, which provides a promising approach for the study of progressive neurophysiological phenomena. Opto-electrophysiological neural probes with sufficient flexibility and biocompatibility are desirable to match the low mechanical stiffness of brain tissue for chronic reliable performance. However, lack of rigidity poses challenges for the accurate implantation of flexible neural probes with less invasiveness. Herein, we report a hybrid probe (Silk-Optrode) consisting of a silk protein optical fiber and multiple flexible microelectrode arrays. The Silk-Optrode can be accurately inserted into the brain and perform synchronized optogenetic stimulation and multichannel recording in freely behaving animals. Silk plays an important role due to its high transparency, excellent biocompatibility, and mechanical controllability. Through the hydration of the silk optical fiber, the Silk-Optrode probe enables itself to actively adapt to the environment after implantation and reduce its own mechanical stiffness to implant into the brain with high fidelity while maintaining mechanical compliance with the surrounding tissue. The probes with 128 recording channels can detect high-yield well-isolated single units while performing intracranial light stimulation with low optical losses, surpassing previous work of a similar type. Two months of post-surgery results suggested that as-reported Silk-Optrode probes exhibit better implant-neural interfaces with less immunoreactive glial responses and tissue lesions. A silk optical fiber-based Silk-Optrode probe consisting of a natural silk optical fiber and a flexible micro/nano electrode array is reported. The multifunctional soft probe can modify its own Young's modulus through hydration to achieve accurate implantation into the brain. The low optical loss and single-unit recording abilities allow simultaneous optogenetic stimulation and multichannel readout, which expands the applications in the operation and parsing of neural circuits in behavioral animals.

Automated summary

The combination of optogenetics and electrophysiological recording allows for high-precision bidirectional interactions between neural interfaces and neural circuits, offering a promising approach for studying progressive neurophysiological phenomena. In this study, a hybrid probe (Silk-Optrode) composed of a silk protein optical fiber and flexible microelectrode arrays is reported. The Silk-Optrode exhibits accurate implantation into the brain and enables synchronized optogenetic stimulation and multichannel recording in freely behaving animals. By utilizing the hydration of the silk optical fiber, the Silk-Optrode adapts to the environment after implantation and reduces its own mechanical stiffness to ensure high fidelity implantation while maintaining mechanical compliance with the surrounding tissue. The probe with 128 recording channels can detect well-isolated single units and perform intracranial light stimulation with low optical losses, surpassing previous similar work. Results from a two-month post-surgery evaluation suggest that the Silk-Optrode probe exhibits improved implant-neural interfaces with less immune response and tissue damage.