Bionische Rekonstruktion definierter neuronaler Netze aus Insekten und Vertebraten unter Verwendung elektromagnetischer Felder

Under in-vivo conditions it is nearly impossible to monitor all in- and outputs of a neuronal network and to provide stable and controlled conditions. Further, it is not possible to isolate a neuron´s activity from that of adjacent ones, because of the electronic coupling via the surrounding medium. Planar multi-electrode-arrays (MEAs) provide a platform which allows the monitoring of the activity as well as the genesis of small two-dimensional networks under controlled/defined conditions. Furthermore they allow the extracellular monitoring and/or stimulation of the neuronal activity of a neuronal network at many sites simultaneously. In this thesis, the question was addressed, whether and how defined neuronal networks can be reconstructed on MEAs. For this purpose, different methods were investigated in order to isolate defined neurons from the biological system and to position them onto the electrodes of the MEA. The latter is important for the improvement of the bioelectronic coupling between neurons and electrodes, enhancing the signal to noise ratio. In the majority of cases, neurons from the meso- and metathoracic ganglion of locusts (Locusta migratoria) were used because they were part of well studied networks and the somata are quite large and robust. Additionally neurons from the telencephalon of the chick (Gallus gallus domesticus) were used. Initially the isolation and positioning of the cells has been tried mechanically by using suction pipettes. Because this led to a reduction of viability and the chance of outgrowth declined, we decided to use dielectrophoresis (DEP) to position the neurons on the electrodes. This method is contact free and made it possible to position all used cell types. It has also been used by others to separate different cell types. Because glia cells are an important part of the nervous system and tend to undermine the neurons under culture conditions thereby decreasing the bioelectronic coupling, we tried to use dielectrophoresis in order to separate neurons and glia cells spatially. On the one hand we tried to find a frequency of the electromagnetic field capable to simultaneously position neurons on and glia cells between the electrodes, which could not be realized. On the other hand a microfluidic system has been constructed with integrated electrodes providing the possibility to generate traveling electromagnetic fields which have been shown by others to be capable of separating different cell types. First experiments displayed a spatial arrangement of the cells but a macroscopic transport could not be observed so far. Another important step within the reconstruction of defined networks is the realization of defined connections between the neurons. Here two different approaches were studied. On the one side the MEA surface was biofunctionalized in order to create adhesion spots on the electrodes and gradients of adhesion molecules around them. Such gradients are known to be important in vivo as well. The deposition was shown for different substrates (e.g. PDL, ConA) and in some cases gradients around the electrodes were found as well as connection lines between electrodes. On the other hand, we tried to use steady electromagnetic fields in order to guide the axonal outgrowth. This has already been shown by others for neurons of other species/tissues but not for locust neurons or telencephalic embryonic chicken neurons. It could be shown in this thesis that many elementary steps in the reconstruction of neuronal networks on MEAs can be solved by using electromagnetic fields applied via the electrodes of the chip including the biofunctionalization of the MEA-surface to create defined adhesion spots and to guide axonal outgrowth as well as the positioning of cells onto the electrodes. In nature all structures are built up by electromagnetic interactions. This principle can also be found on a higher organization level in biological systems (ontogenesis, regeneration). The transfer of this principle of pattern-generation (cells, substrates) to reconstruct defined neuronal networks on MEAs constitutes a simple, multifunctional, low cost, integrated and immanent solution which can therefore be regarded as a bionic solution.

Grantor dc:publisher

Publikationsserver der RWTH Aachen University

Year dc:date

2008

Author dc:creator

• Lautemann, Nico

Contributors dc:contributor

• Bräunig, Peter-Michael

• info:eu-repo/classification/ddc/590
• Zellkultur
• Bionik
• Tiere (Zoologie)
• Microelektroden Array
• Biohybridtechnologie
• Dielektrophorese
• Galvanotropismus
• Biofunktionalisierung
• Microelectrode array
• Biohybrid technology
• Dielectrophoresis
• Galvanotropism
• Biofunctionalization

Statement dc:rights

• info:eu-repo/semantics/openAccess

Language dc:language

ger

Identifier

https://publications.rwth-aachen.de/search?p=id:%22RWTH-CONV-112652%22

OAI record oai:identifier

https://publications.rwth-aachen.de/oai2d?verb=GetRecord&metadataPrefix=oai_dc&identifier=oai%3Apublications.rwth-aachen.de%3A50094