Impedance Of 3D Nanostructured MEAs: Influence of Coating and Cell Cultivation
-
1
Hochschule Kaiserslautern University of Applied Sciences, Germany
-
2
RWTH Aachen Universität, Germany
Motivation
In order to improve recording performances MEA electrodes can be optimized by three dimensional nanostructures ensuring a tight cell electrode coupling by partly engulfing the nanosized MEA features by the cells [1]. Nevertheless an additional coating is often needed to promote cell adhesion on the electrode. In this work impedance measurement is used to evaluate the effect of surface coating with gelatin and poly d lysine (PDL) on the characteristics of nanostructured electrodes, respectively. In addition coupling of HEK 293 cells on nanostructured electrodes are investigated.
Materials and Methods
To fabricate customized 8x8 MEA chips nanoimprint lithography, electroplating and microstructuring techniques are used. On the MEA chip one half of all electrodes are provided with nanostructures while the other half is kept unstructured. The nanostructure shape, diameter and pitch length vary by chip, having a broad range of different nanostructures under investigation (figure 1).
Before usage the MEAs were cleaned with 1% Terg-A-Zyme solution (Sigma-Aldrich), threatened with 20% sulfuric acid, rinsed with DI water and sterilized under UV light. In a first set of experiments the MEA chips were coated with either 0.2% gelatin solution or 0.1 g/l PDL solution (MW 30,000-70,000, Sigma). Impedance measurement was done using the MEA-IT device (Multi Channel Systems) and 1x PBS solution in a two-electrode setup calculating the impedance at 1 kHz. These results were compared with impedance measurements of the same chip without coating layer. In a second test series cells of the HEK 293 cell line were cultured on top of the chips without coating layer. After three days of cultivation impedance measurement was performed and results were related to measurements without cells. Nanostructured and unstructured electrodes were compared to reveal the difference in cell adhesion.
Results and Discussion
Impedance measurement shows clear differences in magnitude of the impedance at different surface coatings (figure 2 left). Highest values were measured with gelatin while the increase is markedly reduced with PDL coating. Nevertheless the surface coatings displayed no additional effect to the impedance on nanostructured electrodes.
Confluent growing of HEK 293 cells on the surface of MEA chips also results in an impedance increase on nanostructured and unstructured electrodes compared to uncultured chips. To grade the quality of the cell-electrode adhesion the increase of the impedance ΔZ after cell cultivation compared to the impedance before cell cultivation was ascertained. The higher the increase the closer the cell attaches to the electrode. By comparing the values for nanostructured electrodes ΔZnano and unstructured electrodes ΔZunstr it is possible to evaluate the influence of the nanostructures on cell coupling (figure 2 right). Tube-like nanostructures with a diameter of 300 nm and a pitch length of 5 µm show the best results. The total increase of the impedance of nanostructured electrodes is about 130 % higher than for unstructured electrodes meaning a good cell-electrode-coupling.
Conclusion and Outlook
With the study design we presented here, the influence of different surface coating types on the impedance of customized nanostructured and unstructured electrodes can be measured and quantified. It is possible to make a statement of how the coating influences the nanostructures. In this case the positive effect of the nanostructures regarding the impedance is not affected by the coating layer. In the second approach it was shown that different nanostructure shapes, dimensions and arrangements having obvious influences on cell adhesion. With impedance measurement it is possible to figure out whether the nanostructures promote or hinder cell adhesion which enables to choose the ideal nanostructures for cell signal recordings which will be the framework of future experiments.
Figure Legend:
Figure 1: Left: SEM picture of a nanostructured MEA electrode with tube-like nanostructures, a stalk diameter of400 nm and a pitch length of 1 µm (Inset: Magnification of a tube-like nanostructure, scale bar: 200 nm). Right: SEM picture of a nanostructured MEA electrode with mushroom-like nanostructures, a stalk diameter of 200 nm and a pitch length of 5 µm (Inset: Magnification of a mushroom-Like nanostructure, scale bar: 200 nm).
Figure 2: Impedance measurements of MEA chips. Left: Representative example of a recording showing the dependence of the magnitude of the impedance on different coating types comparing nanostructured and unstructured electrodes. Right: Normalized relation of the increase of the impedance ΔZ for nanostructured and unstructured electrodes showing the influence of different nanostructure types on cell coupling.
References
[1] A. Fendyur, N. Mazurski, J. Shappir and M. E. Spira, “Formation of essential ultrastructural interface between cultured hippocampal cells and gold mushroom-shaped MEA - toward “IN-CELL” recordings from vertebrate neurons”, Frontiers in Neuroengineering, published online: www.frontiersin.org, Jerusalem, 2011, pp.1-14.
Keywords:
impedance,
nanostructured MEAs,
coating,
Gelatin,
PDL,
HEK 293,
cell-electrode-coupling
Conference:
MEA Meeting 2018 | 11th International Meeting on Substrate Integrated Microelectrode Arrays, Reutlingen, Germany, 4 Jul - 6 Jul, 2018.
Presentation Type:
Poster Presentation
Topic:
Microelectrode Array Technology
Citation:
Decker
DM,
Pirrung
M,
Gries
M,
Ingebrandt
S,
Schäfer
K,
Saumer
M and
Rabe
H
(2019). Impedance Of 3D Nanostructured MEAs: Influence of Coating and Cell Cultivation.
Conference Abstract:
MEA Meeting 2018 | 11th International Meeting on Substrate Integrated Microelectrode Arrays.
doi: 10.3389/conf.fncel.2018.38.00094
Copyright:
The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers.
They are made available through the Frontiers publishing platform as a service to conference organizers and presenters.
The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated.
Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed.
For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions.
Received:
18 Mar 2018;
Published Online:
17 Jan 2019.
*
Correspondence:
Mr. Dominique M Decker, Hochschule Kaiserslautern University of Applied Sciences, Kaiserslautern, Germany, dominique.decker@hs-kl.de