Figure 2: Death of MCF7 cells induced by two-photon excitation of TPAs.

Living MCF7 cells pre-treated with TP3Bzim (a) or TP2Py (b) were exposed to two-photon illumination using a pulsed IR laser as an excitation source (irradiance, 1.25 W.cm−2). λexc = 760 and 860 nm for TP3Bzim (emission slit: 530–690 nm) and TP2Py (emission slit: 560–720 nm), respectively. Left, initial observation (t = 0). Right, observation after an illumination time of 7 min (TP3Bzim) or 20 min (TP2Py). Corresponding DIC transmission images illustrating membrane blebbing (blue arrows) are shown below fluorescence images. The time of illumination was calculated by taking into consideration the z-stack as indicated in Methods. (c) Two-photon fluorescence images showing the time-dependent re-localization of TP2Py (cytoplasm −>nucleus) as well as the formation of blebs (blue arrows) upon excitation at 860 nm (bottom: DIC transmission image).