High-Aspect-Ratio Nanoelectrodes for Neuronal Recordings
High-Aspect-Ratio Nanoelectrodes Enable Long-Term Recordings of Neuronal Signals with Subthreshold Resolution. - P. Shokoohimehr, B. Cepkenovic, F. Milos, J. Bednár, H. Hassani, V. Maybeck, A. Offenhäusser, Small 2022, 18, 2200053. DOI: 10.1002/smll.202200053
The further development of neurochips requires high-density and high-resolution recordings that also allow neuronal signals to be observed over a long period of time. Expanding fields of network neuroscience and neuromorphic engineering demand the multiparallel and direct estimations of synaptic weights, and the key objective is to construct a device that also records subthreshold events. Recently, 3D nanostructures with a high aspect ratio have become a particularly suitable interface between neurons and electronic devices, since the excellent mechanical coupling to the neuronal cell membrane allows very high signal-to-noise ratio recordings. In the light of an increasing demand for a stable, noninvasive and long-term recording at subthreshold resolution, a combination of vertical nanostraws with nanocavities is presented. These structures provide a spontaneous tight coupling with rat cortical neurons, resulting in high amplitude sensitivity and postsynaptic resolution capability, as directly confirmed by combined patch-clamp and microelectrode array measurements.
In this work, the authors incorporate the concept of nanocavity (NC) MEAs with vertical nanostraws. High aspect ratio nanostraws (NS) were engineered to initiate tight cell–structure coupling, while the nanocavity reduces the electrode impedance. With the combination of microscopy and molecular biology, it was found that this combination yields a spontaneous tight mechanical coupling. As a result, we acquired long-term recordings with increased signal amplitude, with no poration-inducing external forces or surface functionalization. Moreover, simultaneous patch-clamp and MEA recordings of the coupled neuron directly demonstrated the capability of our device to record postsynaptic potentials. Here we show that PSP resolution persisted throughout the >1 h measurements, indicating a stable and long-term subthreshold amplitude sensitivity. To our knowledge, this is the first time nonporated MEA recordings could consistently be combined with patch-clamp to compare MEA detected PSPs to the ground truth.
FIGURE 1. Characterization of nanoelectrodes and nanostraw-neuron interface. a) SEM images of the fabricated devices. Nanostraws with 2 µm pitch on electrodes with 10 µm diameter opening (left) containing 9 nanostraws and 6 µm diameter opening (right) containing 5 nanostraws. b) Confocal microscopy visualizing neuron–nanostraw coupling. A neuron with soma in the top left interacts with straws in all compartments. Intensity profile plots along the directions indicated by colored arrows are shown in matching color on the right. All plots share the yellow scale bars. c) Top: The cytoskeleton forms actin-rich accumulations around the nanostraw (arrows). Bottom: The cell membrane is pushed upward by the nanostraws (arrows). The red panels in both micrographs represent orthogonal intensity projections of 30, 0.22 µm slices at the position marked by the dotted line for a Lifeact-RFP-transfected neuronal cell (top) and a DiI-stained neuron (bottom) growing on nanostraws. d) High-resolution SEM/FIB of the neuron–nanostraw interface showing the nucleus deformed by the nanostraws.
Publication: P. Shokoohimehr, B. Cepkenovic, F. Milos, J. Bednár, H. Hassani, V. Maybeck, A. Offenhäusser, High-Aspect-Ratio Nanoelectrodes Enable Long-Term Recordings of Neuronal Signals with Subthreshold Resolution, May 2022, Small 2022, 18, 2200053. Pub. by Wiley-VCH GmbH. DOI: 10.1002/smll.202200053