Model p 2000

The piezo scanner of the SICM setup
has been reported in our previous work.^{45 (link)} The glass nanopipettes (aperture inner radius, 50 nm) were fabricated
from borosilicate glass capillaries (GC100F-15, Harvard Apparatus)
using a CO₂ laser puller (Model P-2000, Sutter Instruments).
The SICM uses a nanopipette probe containing 1 M LiClO₄ in a 1:2 volumetric mixture of ethylene carbonate (EC) and diethylene
carbonate (DEC). Li metal-coated Cu wire was inserted into the nanopipette
and used as the SICM working electrode. For the operando SICM measurement, sample potential, or current control during SICM
current detection is essential. The potential and current of the sample
LIB material (composite graphite electrode) were controlled by a potentiostat
(TM-3000, EC Frontier) and a homemade Labview program. Li metal was
used as reference and counter electrodes. The surface area of the
sample was 0.50 cm². The potentials of SICM working and
LIB material working electrodes were controlled individually. The
reference electrode was shared by the potentiostat and the current
amplifier. The potential between the potentiostat working electrode
and the current amplifier working electrode was controlled using the
external bias input function of the current amplifier and Labview
program. The detail of the electric circuit is described in the Supporting
Information (Figure S1).

HEK-hERG cells were cultured on ∅ 12 mm glass coverslips coated with poly-l-lysine (Sigma-Aldrich, Germany). I_hERG was recorded in whole-cell voltage mode. Pipettes (Harvard apparatus, Holliston, USA) were pulled and polished (Model P-2000, Sutter instruments Co., Novato, USA) and had a resistance of 2–4 MΩ once filled with solution. Potassium currents were measured with Axopatch 200B (Axon Instruments, USA) and Clampex 10.0 software.⁵⁹ The following protocol was used: holding potential was −80 mV, a hyperpolarizing step was applied for 50 ms at −120 mV to correct for leak currents. Thereafter 4 s test pulses between −80 mV and +60 mV in 10 mV increments were applied. And it was followed by a 5 s deactivation pulse at −50 mV. After 3.5 min when the current had stabilized a control measurement was done. Subsequently, acute treatment with 4, 5, 6, 7, 8 or 9 (1 μM) was applied with a flow of ∼1 mL min⁻¹. Currents were measured at 3.5, 7 and 15 min. All measurements were obtained at room temperature (22 °C). Bath solution consisted of 140 mM NaCl, 4 mM KCl, 10 mM HEPES, 2 mM CaCl₂, 1 mM MgCl₂ and adjusted to pH 7.4 (NaOH). Pipette solution consisted of 10 mM EGTA, 110 mM KCl, 10 mM HEPES, 4 mM K₂-ATP, 5.17 mM CaCl₂, 1.42 mM MgCl₂, 15 mM sucrose and adjusted to pH 7.2 (KOH). The data were quantified by Clampfit software.⁶⁰