Measurement of bio-impedance on an isolated rat sciatic nerve obtained with specific current stimulating pulses

Abstract

In this study we designed and tested a four-probe, bio-impedance measurement set-up for peripheral nerves, based on the Red Pitaya open-source measurement and control tool. The set-up was tested on an isolated rat sciatic nerve (RSN) while it was stimulated with specific current stimulating pulses. The measurements tested the hypothesis that the specific waveform of a stimulating pulse elicits current differences at the double layer (DL) interface between the platinum (Pt) stimulating electrode and the nerve tissue. Impedance spectroscopy was used to electrically characterize the interface between the Pt electrode and the nerve tissue and measure the interface electrical impedance (Z). An analysis of the frequency response and the impedance, with specific current stimulating pulses, characterised the structure and the composition-related electrical properties of the RSN. An analysis of the voltage responses (VRs), measured at the same time, showed that the maximum negative polarization across the electrode-electrolyte interface (Emc) and the maximum positive polarization across the electrode-electrolyte interface (Ema) did not exceed the safety limits for water electrolysis. We conclude that the voltage and current changes, elicited at the DL of the interface between the Pt stimulating electrode and the nerve tissue, do not lead to tissue damage. Based on the obtained electrophysiological results we conclude that the developed stimulating electrodes and the stimulus pattern could act as a useful tool for developing nerve-stimulating electrodes. Keywords: electrical impedance, electrical impedance spectroscopy, bio-impedance, voltage response, current source, platinum, rat sciatic nerve, electrode-nerve tissue interface Izdelali in preizkusili smo napravo za {tiri-to~kovno merjenje elektri~ne impedance (Z) perifernih`ivcev, katere osnova je odprtokodna merilna in kontrolna konzola (Red Pitaya). Naprava je bila preizku{ana na izoliranem`ivcu ischiadicus pri podgani (RSN) tako, da smo`ivec lahko dra`ili z izbranimi tokovnimi stimulacijskimi impulzi. Preverili smo hipotezo, da izbrani stimulacijski impulzi izzovejo razlike na dvojni plasti (DL) prehoda med platinovo (Pt) stimulacijsko elektrodo in`iv~nim tkivom. Z metodo impedan~ne spektroskopije smo izmerili Z na prehodu med Pt elektrodo in`iv~nim tkivom. Analiza frekven~nega odgovora RSN, medtem ko je bil stimuliran s posebnimi tokovnimi stimulacijskimi impulzi, je podala od sestave in zgradbe odvisne elektri~ne lastnosti`ivca. Nadalje je analiza so~asno merjenega napetostnega odgovora (VR) pokazala, da nobena od obeh, tako najve~ja negativna polarizacija Emc kot tudi najve~ja pozitivna polarizacija Ema, na prehodu med elektrodo in elektrolitom, ni presegla varne meje pri kateri lahko pride do elektrolize vode. Zaklju~ujemo, da napetostne in tokovne razlike, ki so nastale na DL prehodu med Pt stimulacijsko elektrodo in`iv~nim tkivom, nimajo {kodljivega u~inka na`iv~no tkivo. Kon~ni sklep raziskave je, da je mogo~e pridobljene elektrofiziolo{ke rezultate koristno u...

Fabrication and Characterization of Gelatin/Carbon Black–Based Scaffolds for Neural Tissue Engineering Applications

“…It was found that the impedance spectra of G-CB-GPTMS samples were consistent with those observed by others in the main neural tissues. 40,41 As it can be observed in figure 8, pure cross-linked gelatin samples showed a higher electrical impedance as compared with composite ones in all the analyzed frequencies' spectrum. The impedance of the G-CB-GPTMS films exhibited a decreasing impedance trend with the increase in through the CB network within the gelatin matrix, improving its electrical conductibility.…”