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@PHDTHESIS{Brusius:463850,
author = {Brusius, Janis Sebastian},
othercontributors = {Offenhäusser, Andreas and Wagner, Hermann},
title = {3-dimensionale penetrierende {M}ultielektrodenarrays zur
{S}timulation und {A}bleitung in der {R}etina},
school = {RWTH Aachen University},
type = {Dissertation},
address = {Aachen},
publisher = {Publikationsserver der RWTH Aachen University},
reportid = {RWTH-2015-01074},
pages = {VII, 147 Bl. : Ill., graph. Darst.},
year = {2015},
note = {Aachen, Techn. Hochsch., Diss., 2015},
abstract = {A variety of retinal degenerating diseases leads to the
loss of photoreceptor cells, causing the retina to lose its
light-sensitivity. Several million people worldwide are
suffering from those degenerative diseases.Retinal
prostheses try to replace the functionality of photoreceptor
cells by electrically stimulating the remaining neurons of
the retinal network.Previous retinal implants use planar
multi-electrode arrays (MEAs), covering the retinal network
in a 2–dimensional manner. Those MEAs usually contact only
single layers within the retina and are not capable of
recording the neuronal response and stimulate electrically
through the same device. Relief could derive from
penetrating, bidirectional MEAs, which penetrate the retina
in the vertical direction and are able to both, record
neuronal activity and perform electrical stimulation.The
main aim of this thesis was the development of a
penetrating, bidirectional MEA, with which multiple layers
of the retinal network can be recorded and stimulated
simultaneously. The MEA presented in this thesis consists of
four shanks penetrating the retina in vertical direction.
Every single shank carries four linearly aligned electrodes.
The dimensions of the MEA and the arrangement of the
electrodes were chosen in a way they could serve as the
basis of a retinal implant.Different materials were used for
coating the microelectrodes: iridium, iridiumoxide and the
conductive polymer poly-3,4-ethylendioxythiphene. Their
appropriateness to act as coatings on stimulation and
recording electrodes was tested. Iridiumoxide proved to have
the best mechanical and chemical stability. The lowest
impedances were achieved with PEDOT coatings. Only with
PEDOT-coated electrodes, it was possible to transfer
sufficient charge to elicit neuronal responses. However,
PEDOT coatings were easily degraded by mechanical and
chemical influences during the experiments as shown by
impedance spectroscopy and electron microscopy imaging.In
the second part of this thesis the new penetrating MEAs were
used for the first time to perform experiments in the
extracted retina of rats. A method was established to
reliably position the MEAs, monitoring the electrical
activity of retinal ganglion cells.Different stimulation
parameters were used to successfully stimulate close to the
retinal bipolar cells. The ganglion cells’ reaction to the
electrical stimulation of the network was recorded
extracellularly. The success of electrical stimulation
mainly depended on the absolute amount of charge transferred
to the tissue and the frequency of stimulation patterns. By
pharmacologically blocking the synaptic transmission within
the retina, it could be shown that the stimulation affected
the deeper retinal layers – presumably the bipolar
cells.By means of penetrating MEAs, characteristic
low-frequency oscillations could be measured in the
degenerated retina of rd10 mice. By reversibly blocking the
synaptic transmission, it could be shown that the chosen
MEA-architecture is feasible for the use in a future
bidirectional retinal implant.},
cin = {134210 / 162110 / 130000 / 160000},
ddc = {570},
cid = {$I:(DE-82)134210_20140620$ / $I:(DE-82)162110_20140620$ /
$I:(DE-82)130000_20140620$ / $I:(DE-82)160000_20140620$},
typ = {PUB:(DE-HGF)11},
urn = {urn:nbn:de:hbz:82-RWTH-2015-01074},
url = {https://publications.rwth-aachen.de/record/463850},
}
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