E plate pet plates

HaCaT cells
(CLS 300493) were seeded the day before treatment in seven technical
replicates for each condition at a density of 1 × 10⁴ per well on E-plate PET plates (ACEA Biosciences Inc., USA). Cells
were grown in a standard humidified incubator at 37 °C and in
a 5% CO₂ atmosphere in DMEM in the xCELLigence real-time
cell analysis (RTCA) device (ACEA Biosciences Inc., USA).^{17 (link)} When cells were estimated to be in the exponential
phase of growth (cell index (CI) = ∼2), the experiment was
conducted. The PS was added to the cells at a concentration of 0,
1, or 10 μM and left for 10 min in the dark incubation at 37
°C. Then, the cells were washed twice with PBS, and the medium
was changed to PS-free. Afterward, light-treated cells were exposed
to 522 nm light (dose of light: 31.8 J/cm²). In the case
of dark-treated cells, plates were incubated for the corresponding
time of irradiation in the dark at room temperature. Then, the plates
were returned to the xCELLigence device, and the cell index was measured
every 10 min and recorded automatically until the cells reached the
plateau phase under each condition.

To investigate the effect of visible blue light (aBL) on the growth rate of HaCaT (CLS 300493) cells, the day before the experiment, cells were seeded in the amount of 1 × 10⁴ cells/well in seven technical repetitions on E-plate PET plates (ACEA Biosciences Inc., San Diego, CA, USA) according to the protocol published by Michalska et al. [14 (link)]. Cells were cultured in the same conditions as described above in Section 2.9.1. and kept in the standard humified incubator with 5% CO₂ for 24 h in the xCELLigence RTCA instrument (ACEA Biosciences Inc., San Diego, CA, USA). The next day, cells in the exponential growth rate (Cell index (CI) ≈ 2) were removed from the RTCA instrument, exposed to the various blue light doses and after the medium exchange, the plates were returned to the device. The CI was measured for each repetition every 10 min until the cells reached the plateau phase under tested conditions or if the cells did not survive post-irradiation.