Methods for electrical cell analysis

Question 1

Electrochemical Impedance Spectroscopy (EIS)

procedure

Answer 1

classical technique: 3 electrodes

• apply sinosoidal potential to electrochemical cell
• -> measure response signal (voltage or current)
• calculate impedance Z
• evaluate amplitude and phase shift of response signal
• repeat measurement for a frequency spectrum

Question 2

Resistance - Real part vs. imaginary part

Answer 2

Real part: measure for energy consumption of the system (heat)

Imaginary part: phase-shifted, measure for electrical energy, which is stored in form of an electric field

Question 3

size of stimulation voltage

Answer 3

stimulation voltage must be small

Question 4

Methods to measure passive electronic properties of cells

Answer 4

1) Transepithelial electrical resistance (TEER)
2) Electric Cell-substrate impedance sensing (ECIS) on metal electrodes
3) FET Cell-substrate Impedance Sensing (FETCIS)

Question 5

TEER

Answer 5

measurement technique for in vitro barrier model systems

• 2 electrodes, layer of cells on a semipermeable membrane in the middle
• -> extract impedance

Question 6

ECIS

working principle

Answer 6

• impedance measurement between metal microelectrodes
• small gold electrode with cells
• large gold counter electrode

Question 7

ECIS - extractable parameters

Answer 7

Resistance between cells

membrane capacitance

impedance from cell-adhesion sites

Question 8

Cytometer

Answer 8

for exact single cell analysis individualized cell flow is needed
–> hydrodynamic focussing

• measurement of size and volumina of cells by impedance spectroscopy

Question 9

Cell adhesion probing with FETCIS

current pathways

Answer 9

• stimulation voltage applied at reference electrode –> two current pathways to the sensor
  1st: capacitive current through cell
  2nd: resistive path through cleft

Question 10

FETCIS

advantages

Answer 10

advantages:
- lower impedance –> good for single cell
- large bandwidth
- cell migration can be measured

Question 11

Cell migration mechanism

Answer 11

repetitive sequence: membrane protrusion and adhesion, concentration of cytoskeleton and detachment of the cell’s rear

–> gradual dislocation of the adhesion strength is generating the movement

Question 12

Liquid junction potential

Answer 12

• interface between two solutions with different components or concentrations
• -> small potentials may develop at junctions
• a large concentration difference between the liquid phases results in a high liquid junction potential
• rate of diffusion of each ion is proportional to its speed in an electric field

Question 13

Sharp microelectrode recordings

Answer 13

• technique needs tiny flexible glass needles with openings below 1 um
• -> special, high-impedance amplifiers are needed

only for membrane potential recordings

Question 14

passive electronic properties of cells

Answer 14

1) Barrier functions of cells and tissues
- cell growth
- cell integrity
- carrier function
- -> TEER, ECIS

2) Cell Substrate adhesion
- cell growth
- proliferation
- migration
- invasion
- -> ECIS, FETCIS