Researchers have demonstrated, for the first time, a graphene-based transistor array that is compatible with living biological cells and capable of recording the electrical signals they generate. This proof-of-concept platform opens the way for further investigation of a promising new material. Graphene's distinctive combination of characteristics makes it a leading contender for future biomedical applications requiring a direct interface between microelectronic devices and nerve cells or other living tissue. A team of scientists from the Technische Universitaet Muenchen and the Juelich Research Center published the results in the journal Advanced Materials.
Today, if a person has an intimate and dependent relationship with an electronic device, it's most likely to be a smart phone; however, much closer connections may be in store in the foreseeable future. For example, "bioelectronic" applications have been proposed that would place sensors and in some cases actuators inside a person's brain, eye, or ear to help compensate for neural damage. Pioneering research in this direction was done using the mature technology of silicon microelectronics, but in practice that approach may be a dead end: Both flexible substrates and watery biological environments pose serious problems for silicon devices; in addition, they may be too "noisy" for reliable communication with individual nerve cells.
Of the several material systems being explored as alternatives, graphene – essentially a two-dimensional sheet of carbon atoms linked in a dense honeycomb pattern – seems very well suited to bioelectronic applications: It offers outstanding electronic performance, is chemically stable and biologically inert, can readily be processed on flexible substrates, and should lend itself to large-scale, low-cost fabrication. The latest results from the TUM-Juelich team confirm key performance characteristics and open the way for further advances toward determining the feasibility of graphene-based bioelectronics.
Also, when the cell layer was exposed to a higher concentration of the stress hormone norepinephrine, a corresponding increase in the frequency of spikes was recorded. Separate experiments to determine the inherent noise level of the G-SFETs showed it to be comparable to that of ultralow-noise silicon devices, which as Garrido points out are the result of decades of technological development.
"Much of our ongoing research is focused on further improving the noise performance of graphene devices," Garrido says, "and on optimizing the transfer of this technology to flexible substrates such as parylene and kapton, both of which are currently used for in vivo implants. We are also working to improve the spatial resolution of our recording devices." Meanwhile, they are working with scientists at the Paris-based Vision Institute to investigate the biocompatibility of graphene layers in cultures of retinal neuron cells, as well as within a broader European project called NEUROCARE, which aims at developing brain implants based on flexible nanocarbon devices.
This research is supported by the German Research Foundation (DFG) within Priority Program 1459 "Graphene," the International Helmholtz Research School BioSoft, the Bavarian Graduate School CompInt, the TUM Institute for Advanced Study, and the Nanosystems Initiative Munich (NIM).
Original publication: Graphene Transistor Arrays for Recording Action Potentials from Electrogenic Cells; Lucas H. Hess, Michael Jansen, Vanessa Maybeck, Moritz V. Hauf, Max Seifert, Martin Stutzmann, Ian D. Sharp, Andreas Offenhaeusser, and Jose A. Garrido. Advanced Materials 2011, 23, 5045-5049. DOI: 10.1002/adma.201102990.
Contact: Dr. J. A. Garrido Walter Schottky Institute Technische Universitaet Muenchen Am Coulombwall 4 85748 Garching, Germany Tel: +49 89 289 12766 E-mail: email@example.com Home page: www.wsi.tum.de
Contact: Patrick Regan firstname.lastname@example.org 49-892-891-0515 Technische Universitaet Muenchen