Cornelius S. Bausch

Guided neuronal growth on arrays of biofunctionalized GaAs/InGaAs semiconductor microtubes

We demonstrate embedded growth of cortical mouse neurons in dense arrays of semiconductor microtubes. The microtubes, fabricated from a strained GaAs/InGaAs heterostructure, guide axon growth through them and potentially enable electrical and optical probing of propagating action potentials. The coaxial nature of the microtubes—similar to myelin—is expected to enhance the signal transduction along the axon. We present a technique of suppressing arsenic toxicity and prove the success of this technique by overgrowing neuronal mouse cells.

Ultra-fast cell counters based on microtubular waveguides

We present a radio-frequency impedance-based biosensor embedded inside a semiconductor microtube for the in-flow detection of single cells. An impedance-matched tank circuit and a tight wrapping of the electrodes around the sensing region, which creates a close, leakage current-free contact between cells and electrodes, yields a high signal-to-noise ratio. We experimentally show a twofold improved sensitivity of our three-dimensional electrode structure to conventional planar electrodes and support these findings by finite element simulations. Finally, we report on the differentiation of polystyrene beads, primary mouse T lymphocytes and Jurkat T lymphocytes using our device.

Guided Growth and Electrical Probing of Neurons on Arrays of Biofunctionalized GaAs/InGaAs Semiconductor Microtubes

We demonstrate embedded growth of cortical mouse neurons in dense arrays of semiconductor microtubes (see Figure (a,b)). The microtubes, fabricated from a strained GaAs/InGaAs heterostructure, guide axon growth through them and thus, enable the outgrowth of complex, artificial neuronal networks (see Figure (c)). At the same time, in situ electrical sensing is made possible. We present methods of stimulating and sensing action potentials, where electrodes are embedded inside the microtubes (see Figure d)). The wrapping of these electrodes around the axon greatly increases the contact area, and, with the fabrication of multiple electrodes along the tube length allow for the measurement of action potential propagation along single axons. The coaxial nature of the microtubes - similar to myelin - is expected to enhance the signal transduction along the axon.Our choice of GaAs, an optical III-V semiconductor, offers a variety of advantages over Si despite its toxicity: Its electron velocity and mobility is generally higher than, resulting in lower noise levels of possible electronic devices. We present a technique of suppressing arsenic toxicity and prove its efficiency by the results of neuronal cell culture.View Large Image | View Hi-Res Image | Download PowerPoint Slide

Designer Neural Networks with Embedded Semiconductor Microtube Arrays

Here we present a designers approach to building cellular neuronal networks based on a biocompatible negative photoresist with embedded coaxial feedthroughs made of semiconductor microtubes. The diameter of the microtubes is tailored and adjusted to the diameter of cerebellum axons having a diameter of 2-3 μm. The microtubes as well as the SU-8 layer serve as a topographical cue to the axons. Apart from the topographical guidance, we also employ chemical guidance cues enhancing neuron growth at designed spots. Therefore, the amino acid poly-l-lysine is printed in droplets of pl volume in the front of the tube entrances. Our artificial neuronal network has an extremely high yield of 85% of the somas settled at the desired locations. We complete this by basic patch-clamp measurements on single cells within the neuronal network.