Application Note

Cells:
Tools:HeLa Cells
CardioExcyte 96, SOL

Inducing cell death using a photostatin on
the CardioExcyte 96 and SOL
Nanion Technologies GmbH, Munich.
Cells and compound PST-1 were kindly provided by LMU Munich/CytoSwitch

Summary

Results

Microtubules are important for cell support, acting

The impedance signal recorded on the CardioExcyte

as a kind of internal scaffold providing both shape

96 changes as a result of alterations in confluency, celland

contact

anorganizedstructure.

Anotherimportant(morphologicalrole of microtubules is the formation of the mitoticof adherent

spindle which is critical in cell division1. For this reason,of toxicity.

cancer therapeutics and biological research tools .
2,3e.g.

combretastin

A-4

conductivity

Compound Light
additionpulse

as Taxol and Vinca alkaloids are important as anticompounds

andcells and thereby provides a measurecompounds which control microtubule dynamics such

Othershape)(CA4),

have been shown to be powerful inhibitors of tubule
polymerization4. Until now, the use of such compounds

1

has been limited because of their non-specificity; theirbioactivity cannot be spatially or temporally directed,
e.g. against particular tissues or cells. As an anti-cancer
agent, CA4 was taken into Phase III clinical trials but
was discontinued due to the cardio- or neurotoxic sideeffects at high doses as healthy organs were affected.
The use of light to control the activity of microtubule
inhibitors may offer a solution to combat the specificity

Normalized Impedancein both biological research and as anti-cancer agents

01 nM
0.9

10 nM
100 nM
1 µM
10 µM

0.8

problem by controlling the activation of the compoundusing visible light in a spatial, temporal and reversible
fashion3.

The CytoSwitch startup project at the LMU

Munich is developing photostatins as anti-cancer agentswith reduced side-effects. Furthermore, CytoSwitch
will commercialize photostatins as research tools forbiological research.
In this study, HeLa cells were used on the CardioExcyte
96 equipped with the SOL and blue light was used
to activate the photostatin PST-1, a photoswitchable
analog of CA43. When activated by light, PST-1 caused
cytotoxicity indicated by a change in impedance.

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15:00 20:00

25:00 30:00 35:00 40:00 45:00 50:00
Time / hh:mm

Figure 1: Effect of low concentrations of the photostatin PST-1 on HeLa cells
before and after light pulses using the SOL. The compound was addedat the timepoint shown (red arrow) at the concentrations indicated.
The compound had no effect on the impedance signal before the lightpulse was switched on for 75 ms repeated every 1 s for the remainderof the experiment, but the impedance signal reduced at the highest
concentration (10 µM) after a delay of approximately 5 hours. No effectwas seen at lower concentrations in either dark or light.

Application Note
The photostatin, PST-1, was applied to HeLa cells at lowInconcentrations. No effect was seen before the SOL wasconcentrations of PST-1 was investigated (Figure 2). In

switched on. Light pulses of 75 ms every 1 s were thenthese experiments, application of concentrations 30 µM

provided by the SOL. After a delay of approximatelyor 100 µM to the HeLa cells caused a moderate decrease

5 hours, a decrease in the normalized impedance sig-in the impedance signal even before exposure to light,

nal at 10 µM was observed indicating a change in cell

indicating a change in cell shape as expected3. Whenmorphology (Figure 1).

the light was applied, the impedance signal decreased

Compoundaddition

Light
pulse

subsequentexperiments,

theeffectof

higherin all concentrations after a delay of approximately 4-5hours as shown in the previous experiment.

1.1

In summary, the CardioExcyte 96 in combination with
the SOL can be used to activate photoswitchable

Normalized Impedancecompounds, such as PST-1, which cause disruption ofmicrotubules upon application of light even at low
concentrations of the compound. The disruption ofmicrotubules results in a morphological change which

1can be measured using impedance. Furthermore,cytotoxicity can be determined using this impedancemeasurement.

1 µM
10 µM
30 µM
100 µM

0.9
15:00 20:00 25:00
30:00
Time / hh:mm
Figure 2: Effect of higher concentrations of PST-1 on the impedance
signal of HeLa cells. At higher concentrations (30 - 100µM),
the impedance signal is reduced even before exposure to thelight pulse (75 ms every 1 s). After exposure to light, the decline
in the impedance signal is accelerated and is seen at allconcentrations. This is in good agreement with the literature3.
00:00 05:00

10:00

Impedance measurements

References
1. Jordan, A., et al. 1998. Med. Res. Rev., 18(4): 259–296
2. Peterson, J.R., & Mitchison, T.J. 2002. Chem. Biol. 1275–1285
3. Borowiak, M. et al. 2015. Cell. 162: 403-411
4. Pettit, G.R. et al. 1989. Experientia 45: 209–211

Impedance measurements were conducted according
to Nanion’s standard procedures for the CardioExcyte
96. HeLa cells were thawed, seeded on the Sensor Plate
at an appropriate density to provide the desired
confluency and cultured under propriety conditions for
24 hours prior to exposure to PST-1. The SOL was switched

Methods

on for 75 ms every 1 s at a wavelength of 390 nm. AllCells

measurements (n=5-11) on the same plate.

signals

HeLa cells kindly provided by LMU Munich/Cytoswitch
were used.

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Ganghoferstr. 70A.

fax

80339 Munich, Germany

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