Abstract3D nanostructures on top of planar multielectrode array (MEA) electrodes increase the surface area and can offer a tight and stable cell–electrode interface, thus leading to a crucial increase of the signal‐to‐noise ratio during measurement. However, each individual cell type might need specific dimensions and an arrangement of nanostructures that fits ideally to a specific cell type. Therefore, a fabrication method of 3D nanostructured MEA chips based on nanoimprint lithography, gold electroplating, and microstructuring techniques is presented which allows the fabrication of a whole set of MEA chips with different nanostructure layouts in one single approach. The chips are characterized using electrochemical methods, atomic force, and scanning electron microscopy. Furthermore, an impedance measurement method is presented to quantify cell–electrode adhesion of nanostructured and unstructured electrodes using the human embryonic kidney cell line (HEK 293). Double‐layer capacitance, transferred charge, and impedance values of different nanostructure layouts revealed a significant improvement compared to unstructured electrodes. The improvement strongly correlates with the increase of the electrochemical active surface area. Impedance measurement with impedance‐stable HEK 293 cells allows discriminating differences of cell adhesion between the individual nanostructure layouts. A significant increase or decrease of cell–electrode coupling depending on the nanostructure layout is demonstrated.

Since the advent of biosensing, structuring of electrode surfaces for the improvement of cell-coupling and electrophysiological properties has been extensively investigated. Most of these methods result in structures with predefined dimensions and regular organization. Nevertheless, natural adhesion surfaces of the cells are hardly uniform. Therefore, this study focusses on fabricating randomly organized nanostructures mimicking the irregular distribution of natural collagen fibers coated on a planar surface. Fiber geometries are replicated by using a spincoating process followed by thermal nanoimprint lithography and gold electroplating. Microscopic studies reveal the width of these biomimetic collagen-like gold nanostructures ranging between 200 nm and 5 µm, with a uniform height of ≈35 nm. In comparison to unstructured gold surfaces, nanostructured surfaces display a decrease in impedance magnitude by 50% for frequencies below 1 kHz and show an increase in critical free surface energy by 35%, the latter translating to an increased surface wettability. Culturing enteric neurons from postnatal mice, a relative hard to handle type of neurons, results in an improved spreading of the neural networks on the nanostructured surfaces.

Nanostructuring is a promising and successful approach to tailor functional layers and to improve the characteristics of biosensors such as signal transmission and tighter cell-surface coupling. One of the major objectives in biosensing and tissue engineering is the development of interfaces that mimic the natural environment of biosystems composed of extracellular matrix biomolecules. Nevertheless, effective techniques to reconstruct the random distribution of these biomolecules are still not well established. For this reason, the presented work demonstrates different methods based on nanoimprint lithography to replicate randomly distributed natural nanostructures with complex geometries into different polymers and metals. The fidelity of the replicated nanostructures has been evaluated by atomic force microscopy and the attributes of the fabrication processes have been discussed. Finally, different replication techniques have been combined for the biomimetic nanostructuring of the dielectric passivation layer as well the metal electrode surface to develop novel whole-surface-nanostructured microelectrode arrays.

Microelectrode surfaces covered with nanostructures derived from components of extracellular matrix, such as collagen fibers, have shown immense beneficial effects in promoting neuronal growth and cellular signaling. Synthetic nanostructures mimicking the features of biological nanostructures with durable conductive materials could promote the cell adhesion on microelectrode surfaces by providing topographical cues and simultaneously improve the charge transfer properties by reducing its global impedance. Therefore, an advanced nanostructuring method mimicking the structural and organizational features of natural collagen fibers onto metallic microelectrode surfaces has been presented here, which is adapted from previous technological achievements of the group and is based on nanoimprint lithography and gold electroplating. Surface characterization methods reveal an increase in surface area between 20% and 68% on the microelectrodes fabricated with two different nanostructure heights. Impedance spectroscopy measurements reveal reduction in impedance magnitude (at 1 kHz) between 22% and 41%, depending upon the nanostructure height and density on the microelectrode, which should subsequently modulate its charge transfer properties for biosensing application. Cell adhesion analysis performed with seal impedance measurements reveals a tighter coupling of enteric neurons on the nanostructured microelectrodes. Finally, extracellular recordings from enteric neurons exhibit a significant improvement in spike detection properties of the nanostructured microelectrodes.

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