Then, 2 mL of fluorescent nanoparticles (PT2* and G2*) diluted in growth medium (1 mg.mL -1 ) were added. The plate was incubated at 37 °C with 5% CO 2 . After 2 h or 4 h, the coverslip was placed in a microscopy cell chamber (Attofluor® cell Chamber) and 500 μL of calcein-AM (3