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Ultrasensitive bioelectronic devices based on conducting polymers for electrophysiology studies

Gomes, H.L.

Ultrasensitive bioelectronic devices based on conducting polymers for electrophysiology studies, Proc PRAGUE MEETING ON MACROMOLECULES PMM, Prague, Czech Republic, Vol. , pp. - , September, 2017.

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standard electrophysiological methodology for long-term analysis of in vitro neuronal
cells and networks. MEA technology has been optimized to look at electrogenic cells
that generate action potentials. To observe individual signals, spatial resolution is
crucial, this imposes a limit on the size of the electrode that can be used. Typical
electrodes to record an individual cell generate noise in the range of 5-20 microvolts.
Signals below the electrode noise floor remain inaccessible.
Interesting, there is some less known electrical activity produced by cells and
organs with important physiological/functional roles. This activity generates signals
below 1 microvolt inaccessible by the conventional MEA technology. These signals
are caused by ions, and polar molecules or zwitterions that can pass from cell to cell
by gap junctions. These fluctuations are slow changing gradients and they progress
thousands of times more slowly than action potentials. Since this activity is a result of
cell cooperative phenomena, spatial resolution is not required and large area
electrodes are adequate.
In this contribution we show that large area conducting polymer electrodes are
ideally suited record ultra-week bioelectrical activity generated by populations of
cells. Conducting polymers can easily be processed in large area, offer soft surfaces
large interfacial capacitances for signal coupling and above all have a very low
polymer/electrolyte interfacial resistance that minimizes the thermal noise. We
demonstrate that the conducting polymer based electrodes can detect extracellular
signals with amplitudes of 150 nanovolts in a noise level of 20 nanovolts (peak-topeak)
with a SNR >7. To obtain this high sensitivity, large area electrodes were used
(4 mm2). The electrode surface is also micro-structured with an array of polymer
mushroom-like shapes to further enhance the active area. The polymer microstructured
electrodes were electrically characterized and their performance
demonstrated by recording spontaneous activity generated by a primary culture of
astrocytes cells.
The polymer based electrodes and the methodology developed here can be used as an
ultrasensitive electrophysiological tool to reveal the synchronization dynamics of
ultra-slow ionic signalling between non-electrogenic cells.