Electrode Selection for Electrostimulation and TEER Using ECSARA

The TransEpithelial/Endothelial Electrical Resistance (TEER) of cells grown in the 24-well electroculture ware of an Electrical Cell Stimulation and Recoding Apparatus (ECSARA) shows well-to-well variation as potentially a function of the electrode material employed in stimulation-interrogation. Six electrode materials were studied; glassy carbon (GCE), graphitic carbon (GrC), titanium (Ti), platinized Type 304 stainless steel (PtSS), platinum (Pt100) and gold (Au). Each unmodified electrode was studied by multiple scan rate cyclic voltammetry (MSRCV) and by electrochemical impedance spectroscopy (EIS) with equivalent circuit analysis (EQCRTA) in PBS and in Fe(II)/Fe(III). MSRCV and Randles-Sevcik analysis of the bare electrodes produced an effective area correction factor γ* that rank-ordered the electrodes GrC=1.58>Pt=1.40>GCE=0.94>Au=0.66>PtSS=0.11>Ti=0.01. Tandem EIS-EQCRTA produced R_CT (Ω)/γ* of 1.20×10² and 5.60×10⁸ for GrC and Ti, respectively and established these two electrode materials as the performance extremes. GrC and Ti were used as electrode materials in the 24-well electroculture ware of ECSARA. The coefficient of variation of the charging capacity extracted from CVs of GrC (22 wells, 10.05 mC) and Ti (22 wells, 1.75 mC) was 51.4 % and 54.6 % respectively, reflective of the difference in surface area. EIS-EQCRTA of GrC and Ti (21 wells) showed both electrodes to faithfully measure the solution resistance, R_S, with CV of 54 % and 28 %, respectively, despite the lower charge transfer resistance, R_CT, of GrC (R_CT=1.08×10³ Ω, CV=125 %) compared to Ti (R_CT=1.20×10⁵ Ω, CV=30 %). Overall, Ti electrodes were shown to be more appropriate for application in cell stimulation and TEER recording.