Third party funded individual grant
Start date : 01.01.2020
End date : 31.12.2021
Excitable tissues, e.g. brain, nerves or muscle, are characterised by their responsiveness to electrical signal transmission. They respond to changes in internal ionic currents or external electric fields with modulation of ion channels, intracellular signaling cascades, even mechanical movement (muscle). Neuroscience research has taught us many concepts of electro-chemical signal reception, processing and transmission that underlie motor control, neurosensory reception and memory in the brain. For neuroscience research, almost all of our knowledge of the cellular and molecular mechanisms of neuro-circuits and systems regulation has emerged from experimental approaches involving isolation of tissue sections (slices) from the brains of animal models and keeping these tissue sections viable for several hours in appropriate bioreactor environments. For decades, electrical signals have been evoked and analysed using micro-pipette based patch and voltage-clamp techniques, where glass capillaries are melted and pulled to fine end tips that can be inserted into, or attached onto, neurons to establish electrical contact for recording of ionic currents. These tedious approaches, while allowing single cellular electrical resolution however, were not capable of allowing high-content recordings from many cells. As a consequence, multi-electrode-arrays (MEAs) were subsequently developed that included fine arrays of wire electrodes embedded in glass chambers with finely scored grooves, building an external wired network that could be electrically stimulated to create a planar electric field to stimulate whole layers of cells within brain slices positioned above the electrodes. Microscope stage-adapted designs of such MEAs allow large scale electrical stimulation of nerve cells and optical recording of cellular reactions in a high content configuration to maximize readouts. However, commercially available MEAs are usually made from die casting or injection moulding techniques using glass materials and wire embedding in a two-stage manufacturing process, rendering such chambers very expensive and delicate in handling. Furthermore, commercial MEAs usually offer little flexibility regarding hardware modifications and are only compatible with the specific interface boards and field generators of the MEA suppliers. Costs of about 400 USD per MEA-chamber are not unusual (https://www.multichannelsystems.com/), limiting parallelization and multi user availability in many labs. This becomes even more of a bottleneck considering the fact that from one brain, usually multiple slices could be processed and recorded at once, if more affordable and modular MEA chambers were available. This would also reduce animal numbers in neuroscience and comply with the 3R concept of reduction, refinement, replacement. An alternative strategy to produce MEAs is reflected by modern additive manufacturing processes, involving rapid prototyping and 3D-printing of transparent polymer materials. As such, polycarbonate with a glass transition temperature of 147 °C can be well printed in a fluidic phase above 155 °C through a nozzle-based cartridge using MakerBots with lower tens of micron accuracy. The German partner’s (OF) Institute of Medical Biotechnology has substantial expertise and experience in design and additive manufacturing of tissue chambers tailored for bioresearch. Apart from acrylonitrile-butadiene-styrol materials, also polycarbonate and other material blends have been fabricated in past projects. A novel development that now even allows to manufacture low resistance electrodes into polycarbonate material is reflected by advanced electro-conductive poly-dimethyl-siloxane elastomers doped with carbon nanotube particles to create electric conduits in solution suitable for external field stimulation (preliminary results). OF has visited the Australian partner (AM) in 2018 to explore possibilities for projects complementing their expertise. AM is a renowned neurophysiologist and has worked in the field of electrophysiology and ion channels to study neurophysiological mechanisms of pain, stroke and learning. More recently, he has used brain slices of rodent brains to study genetic models of epilepsy. The current project idea was born through a shortage of affordable and more modular MEA systems that could be flexibly designed and being of tougher material as compared to glass. Also, the opportunity to include elastomer-based electrodes would reflect a reduction in electrolysis otherwise seen with metal electrodes. Both partners will benefit from each other’s expertise. OF’s team will design and fabricate new low-cost MEA systems to be validated by AM’s team to increase content for multicellular research in brain slices from epileptic mice. OF will reserve one travel slot while planning three travel slots to the partner laboratories for PhD students/young academics. We expect a combined bioengineering-neuroscience publication as basis for follow-up project funding.