Figure 1 : Biomimetic nano-edge microelectrode mimicking the morphological structure of a synaptic cleft.

From: A novel bio-mimicking, planar nano-edge microelectrode enables enhanced long-term neural recording

Figure 1

(a) Schematic representation of two synaptically connected neurons (the box depicts a chemical synapse between the cells). The post-synaptic terminal is shown as engulfing the pre-synaptic terminal; thereby enhancing tight physical and dielectric coupling between the neurons. (b) Schematic layout developed further from Spira and Hai10, illustrating an electrode-neuron interface with its analogue passive electrical circuit. Only the junctional membrane (part of the membrane in contact with the microelectrode) of the cell body is represented here (blue) – depicted to be in close contact with the electrode (yellow) and its nano-edges (orange). The non-junctional membrane (not shown in this diagram) refers to the part of the membrane not juxtaposed against the electrode. The electrode was fabricated on a silicon dioxide substrate (green) and connected to a recording system (MEA1060; Multichannel Systems, Reutlingen, Germany). The junctional membrane resistance (Rj) and conductance (Cj) are represented in parallel, similar to the electrode resistance (Re) and impedance (Ce). The sealing resistance (Rseal) was enhanced due to the nano-edges implemented on the electrodes. (c) Characterization of the nano-edge microelectrodes using atomic force microscopy. A three-dimensional representation of a 30 μm microelectrode with a 40° tilt is depicted. The nano-edge is discernable around the microelectrode perimeter (blue arrow), and can be seen continuing along the connecting electrode wire (bottom right). Having the nano-edge along the wire and not limited to the circular area has the advantage that it increases the sealing resistance even when a neuron is not placed exactly on top of the microelectrode. This configuration also increased the surface area of the microelectrode that was in contact with the neuronal cell membrane (when bigger than 30 μm in diameter). (d) Cross-section of the microelectrode height showing the shape of the nano-edge. The microelectrodes are 30 ± 1 μm in diameter, 200 ± 15 nm in height, and the nano-edges varied between 5 and 15 nm in height and 2 to 3 μm in width. Letters ‘A’ and ‘B’ refer to the location of the cross-section taken from (c).