Universität zu Köln

Yuan, Xiaobo ORCID: 0000-0002-7302-7816 (2021). Tailoring neuroelectronic interfaces via combinations of oxides and molecular layers. PhD thesis, Universität zu Köln.

Preview

PDF Tailoring neuroelectronic interfaces via combinations of oxides and molecular layers.pdf - Published Version Download (8MB) | Preview

Abstract

In this work we introduce a novel method to tailor the interface of neuroelectronic devices in a way that (i) it becomes biocompatible and (ii) at the same time allows a guided growth of neurons on the substrate. By using different oxides which are functionalized with the organic molecules 3-aminopropyltriethoxysilane (APTES), we can generate areas onto which neurons either adhere, grow and mature, or preferably don’t adhere. Furthermore, the resulting cell-chip interface is extremely thin (molecular monolayer) and robust, and therefore promises an optimal electronic signal transfer in neuroelectronic devices. In a first step, surface potential analyses are used to record and optimize the gas-phase deposition of self-assembled monolayers (SAMs) of APTES on SiO2 and to determine the resulting change of the electrokinetic potential and charge at the solid-liquid interface. We found that (i) an adequate post-deposition treatment is crucial to the formation of perfect molecular APTES SAMs. (ii) The activation state of the SiO2 surface which determines the amount of binding docking sites for the molecules, and the stability of the APTES coating is characterized by electrokinetic potential measurement. In a second step, we demonstrate that cell adhesion and neuron maturation can be guided by patterned oxide surfaces using different oxides functionalized with an organic molecular layers of APTES. It seems that only physisorbed layers (no chemical binding) can be achieved for some oxides (Ta2O5 and TiO2), whereas self-assembled monolayers (SAM) form on other oxides (SiO2 and Al2O3). As a result of the different types of APTES binding and the difference in the electrokinetic potential, a large cell density contrast is obtained for SiO2 and Ta2O5. The cell density and coverage with dendrites and growth cones are ~ 8 respectively ~ 3.2 times larger on SiO2 compared to Ta2O5 both coated with APTES. Finally, we test the different oxides in multi electrode array (MEA) devices using the different oxides (Al2O3, TiO2, Ta2O5) as passivation and at the same time for the guidance of cell growth. Impedance measurements indicate, that, due to the thinness of the passivation, the feedlines strongly couple into the electrolyte. Nevertheless these novel MEAs work perfectly in HL-1 cell culture experiments showing smaller action potential signals but at the same time a signal-to-noise ratio (SNR≈3) which is comparable to conventional polyimide passivated MEAs. Finally, tests with neuronal cell cultures show guided cell adhesion, however the patterns chosen for the cell guidance in these experiments turn out to be too small to allow the development of neuronal networks. In conclusion, the combination of organic SAMs and patterns of different oxides (especially SiO2 and Ta2O5) allows guided neuron cell growth. Simultaneously the oxide can be used as passivation in neuroelectronic devices. This complete package could represent a promising option for the development of robust neuroelectronic devices that might enable guided neuron growth as well as a good cell-chip communication.

Item Type:	Thesis (PhD thesis)
Creators:	Creators Email ORCID ORCID Put Code Yuan, Xiaobo yuanbobuaa@126.com orcid.org/0000-0002-7302-7816 UNSPECIFIED
URN:	urn:nbn:de:hbz:38-303628
Date:	12 January 2021
Language:	English
Faculty:	Faculty of Mathematics and Natural Sciences
Divisions:	Faculty of Mathematics and Natural Sciences > Department of Physics > Institute of Physics II
Subjects:	Physics
Uncontrolled Keywords:	Keywords Language Neuroelectronics English Interface modification English Self-assembled monolayers English
Date of oral exam:	12 January 2021
Referee:	Name Academic Title Woerdenweber, Roger Prof. Dr. Maier, Berenike Prof. Dr.
Refereed:	Yes
URI:	http://kups.ub.uni-koeln.de/id/eprint/30362