Cell mono-layers were irradiated with nanosecond laser pulses under two distinct scenarios: (a) with culturing medium
positioning the beam waist at different stand-off distances γ and (b) without cell culturing medium, positioning the beam
waist directly on top of the cell mono-layer. Damaged cells were marked with Trypan Blue, a vital cell marker. Three
different zones of damage were identified: (1) a zone of complete cell clearance, surrounded by (2) a ring of dead cells
marked with Trypan Blue and (3) the rest of the cell culture where the cells remain alive and viable. Different
hydrodynamic mechanisms damage cells as it was shown by high speed video for γ=0 and comparison with time
resolved imaging. The cell damage mechanism has its origin on the optical breakdown plasma formation. For the case
with culturing medium, a combination of plasma formation and shear stresses are responsible for cell damage; wheras
for the case without cell culturing medium, the plasma formation is the only mechanism of interaction between laser
pulses and cells. The rapidly expanding plasma generates shock waves whose pressure is most likely responsible for the
cell detachment observed.
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