Andreas Offenhaeusser

Multi-electrode arrays (MEAs) with guided network for cell-to-cell communication transduction

Extracellular signals of living cells provide much information of their cellular electrophysiology, which is extremely important for medical diagnosis and drug discovery. Extracting extracellular signal, however, is always difficult due to its small magnitude relative to the noise and apparently random direction of signal propagation. In this work, a low noise multi-electrode array (MEA) system has been developed using the IC fabrication technology to extract the extracellular signals. Cardiac myocytes (heart muscle cells) have been cultured on the chip surface, after proper packaging. The signal propagation of the cardiac myocytes has been captured to demonstrate the effectiveness of the MEA

Synthesis and Structural Characterization of Ultra-thin Flexible Au Nanowires

Au nanowires (AuNWs) were produced by electroless reduction of HAuCl 4 in a micellar structure formed by oleylamine and investigated by means of high-resolution transmission electron microscopy (HRTEM). Micrometer long ultra-thin flexible AuNWs with 1—2 nm diameter and AuNWs with about 12 nm diameter and a few hundred nm length were produced. Their extremities show a characteristic bulging. In contradiction with previous work, the bodies of the 12 nm nanowires are defect-free along the axial direction, their extremities, however, show the presence of twin boundaries. Ultra-thin AuNWs were often found as bundles presenting lengths of few micrometers. Although they are stable in solution for months, they were found to be quite sensitive to electron beam irradiation during HRTEM experiments, with a tendency to break up into face centered cubic (fcc) Au droplets. It is proposed that the micellar configuration of oleylamine plays a fundamental role in the atomic arrangement of nanowires. Finally, we anticipate our results to be a starting point for a more realistic experimental investigation of surface effects on the mechanical properties of ultra-thin nanowires with high aspect ratio, which have been only widely exploited theoretically.

High Current Optogenetic Channels For Stimulation And Inhibition Of Primary Rat Cortical Neurons

ChR2-XXL and GtACR1 are currently the cation and anion ends of the optogenetic single channel current range. These were used in primary rat cortical neurons in vitro to manipulate neuronal firing patterns. ChR2-XXL provides high cation currents via elevated light sensitivity and a prolonged open state. Stimulating ChR2-XXL expressing putative presynaptic neurons induced neurotransmission. Moreover, stable depolarisation block could be generated in single neurons using ChR2-XXL, proving that ChR2-XXL is a promising candidate for in vivo applications of optogenetics, for example to treat peripheral neuropathic pain. We also addressed an anion channelrhodopsin (GtACR1) for the next generation of optogenetic neuronal inhibition in primary rat cortical neurons. GtACR1‘s light-gated chloride conduction was verified in primary neurons and the efficient photoinhibition of action potentials, including spontaneous activity, was shown. Our data also implies that the chloride concentration in neurons decreases during neural development. In both cases, we find surprising applications of these high current channels. For ChR2-XXL inhibition and stimulation are possible, while for GtACR1 the role of Cl−during neural development becomes a new optogenetic target.

Capturing cellular communication with guided electrode network on a silicon integrated circuit chip

This paper describes the development of a multi-electrode array (MEA) with guided network for cell-to-cell communication transduction using a standard integrated circuit (IC) fabrication process. Unlike conventional electronic system, bio-system requires a special handling environment that is uncommon in conventional IC technology. The work presented here demonstrated the interaction between electrically active cells such as neuron and cardiac cells and an IC based system. Through a carefully designed array, and ionic action of a cell, extracellular signals can be captured and imaged

Towards label-free detection of charged macromolecules using field-effect-based structures: Scaling down from capacitive EIS sensor over ISFET to nano-scale devices

The possibility of a label-free electrical detection of charged macromolecules using semiconductor field-effect sensors offers a new approach for the development of DNA chips with fast and direct electrical readout. A deep understanding of the adsorption and interaction of charged biomolecules onto charged surfaces is of great interest also for the fundamental understanding of many key physiological processes. In the present work, two types of field-effect sensors, namely a capacitive EIS (electrolyte-insulator-semiconductor) structure and an ISFET (ion-sensitive field-effect transistor) have been utilised for monitoring layer-by-layer adsorption of polyelectrolytes as well as for the DNA immobilisation and hybridisation detection.