Damage mechanisms and electrode behavior during electrical stimulation must be better understood to address the demands of new electrode technologies. Here, we studied the influence of gel electrolytes on electrode polarization and charge injection. We show that agar gels do not change electrode behavior significantly

Lancashire, Henry

Niederhoffer, Thomas

Vanhoestenberghe, Anne

English

UCL Discovery

pH 1H2SO4pH 11NaClpH 7.4PBSpH 7.4PBSpH 11NaClpH 1H2SO4Influence of Extracellular Matrix-Mimicking Gel Electrolyte on Electrode Charge Injection Thomas Niederhoffer†, Anne Vanhoestenberghe‡ and Henry Lancashire†† Department of Medical Physics and Biomedical Engineering, University College London, London, UK‡ School of Biomedical Engineering and Imaging Science, King’s College London, London, UKContact: thomas.niederhoffer.19@ucl.ac.ukReferences1. R.V. Shannon. A model of safe levels for electrical stimulation. IEEE Transactions on biomedical engineering, 39(4):424–426, 1992.2. D.W. Kumsa et al. Electron transfer processes occurring on platinum neural stimulating electrodes: pulsing experiments for cathodic-first/charge-balanced/biphasic pulses for 0.566≤ k≥ 2.3 in oxygenated and deoxygenated sulfuric acid. JNE, 13(5):056001, 2016.3. S. F. Cogan. Neural stimulation and recording electrodes. Annu. Rev. Biomed. Eng, vol. 10, p. 275-309., 2008.IntroductionPatient safetySafe stimulation guidelines, including Shannon’s parameter k [1]Understanding underlying mechanisms for kk = 1.75 corresponds to platinum oxidation [2]Understanding larger polarisation in vivo [3] Tortuous diffusion path increasing polarisation ?AIM: Study the influence of gellified electrolyte on charge injection and possible damagek = log D – log QD, charge densityQ, charge/phase Material & MethodsResultsK-S result (95%) pEa0 (not statistically significant) 1.00Ec0 (not statistically significant) 0.43Figure 2: Bland-Altman plot of peak anodic potentials for all k, for each electrolyte.Figure 3: Bland-Altman plot of peak cathodic potentials for all k, for each electrolyte.Linear regressiongel = solLinear regression parametersy = mx + b Ea Ecm 0.988 1.549b 0.009 0.011R2 0.96 0.90Linear regressiongel = solFigure 1: Evolution of potential with Shannon’s parameter k for PBS solution versus PBS gel.Figure 4: Direct comparison of peak anodic potentials for all k, for each electrolyte.Figure 5: Direct comparison of peak cathodic potentials for all k, for each electrolyte.Table 2: Linear regression parameters of direct comparisons of gel vs solution electrolytes peak anodic and cathodic potentials.Table 1: Parameters two-sample Kolmogorov-Smirnov test of gel vs solution electrolytes peak anodic and cathodic potentials.Statistical analysisElectrochemical measurementsFigure 6: Comparison of a typical CV cycle of solution electrolyte and gel electrolyte for PBS, H2SO4 and pH 11 saline.Conclusionv Peak anodic potentials are not significantly different for solution and gel electrolytes.v Peak cathodic potentials are not statistically significantly different but do show a substantially different trend at extreme pH.v Lower pH correlates with larger cathodic excursions in gels and higher pH with larger cathodic excursions in solutions.SCAN MESCAN MEPlatinum electrodes show similar behaviours in gelelectrolytes and solution electrolytes, however, cathodicpotential excursions during repeated pulsing exhibitsubstantial differences, which are not statisticallysignificant.A combined effect of pH and gellification is shown,with oxide reduction onset delay possibly explaining thediscrepancy.Poster No. 1570890204pH 7.4 PBSpH 1 H2SO4pH 11 NaClShannon’s limitk = 1.75SolutionGelPeak anodic pot. (Ea)End pot.Peak cathodic pot. (Ec)!(=log'−log))pH 11NaCl mm + 1.96 sm - 1.96 spH 1H2SO4pH 7.4PBSmm + 1.96 sm - 1.96 spH 11NaClpH 1H2SO4pH 7.4PBSVWE - VRE100 µs100 µsttICE (carbon) WE (Pt)RE (Ag|AgCl)Faradaic cageGamryReference600+Customstimulator PBS / H2SO4 / pH 11 salinet(pH 11, NaCl + NaOH)anodiccathodic0(pH 1)(pH 7.4)The authors acknowledge funding from the Institute of Physics and Engineering in Medicine.

Influence of Extracellular Matrix-Mimicking Gel Electrolyte on Electrode Charge Injection

https://discovery.ucl.ac.uk/10175490/1/NER23_poster_V2.pdf

Influence of Extracellular Matrix-Mimicking Gel Electrolyte on Electrode Charge Injection

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