In vivo use of a nanoknife for axon microsurgery

OBJECTIVE: Microfabricated devices with nanoscale features have been proposed as new microinstrumentation for cellular and subcellular surgical procedures, but their effectiveness in vivo has yet to be demonstrated. In this study, we examined the in vivo use of 10 to 100 μm-long nanoknives with cutting edges of 20 nm in radius of curvature during peripheral nerve surgery. METHODS: Peripheral nerves from anesthetized mice were isolated on a rudimentary microplatform with stimulation microelectrodes, and the nanoknives were positioned by a standard micromanipulator. The surgical field was viewed through a research microscope system with brightfield and fluorescence capabilities. RESULTS: Using this assembly, the nanoknife effectively made small, 50 to 100 μm-long incisions in nerve tissue in vivo. This microfabricated device was also robust enough to make repeated incisions to progressively pare down the nerve as documented visually and by the accompanying incremental diminution of evoked motor responses recorded from target muscle. Furthermore, this nanoknife also enabled the surgeon to perform procedures at an unprecedented small scale such as the cutting and isolation of a small segment from a single constituent axon in a peripheral nerve in vivo. Lastly, the nanoknife material (silicon nitride) did not elicit any acute neurotoxicity as evidenced by the robust growth of axons and neurons on this material in vitro. CONCLUSION: Together, these demonstrations support the concept that microdevices deployed in a neurosurgical environment in vivo can enable novel procedures at an unprecedented small scale. These devices are potentially the vanguard of a new family of microscale instrumentation that can extend surgical procedures down to the cellular scale and beyond.