Fig. 3

Adherent photoporation of HeLa cells induced by VNB collapse. a Scheme for adherent photoporation: Irradiation of a translating culture dish containing HeLa cells pre-incubated with AuNP by the elliptical nanosecond laser pulse. Permeabilization is monitored with the uptake of fluorescent FITC-Dextran \({10}~{\hbox {kDa}}\). The position of cells is compared to the laser intensity profile during the translation of the laser beam. b Global results of the adherent photoporation of HeLa cells with FITC-Dextran. Viability (\(N^\text {after}/N^\text {before}\)) and positive fraction (\(N^\text {fluo}/N^\text {total}\)) for the photoporation and control conditions are measured over the whole cell population of each sample. c Comparison between the laser control experiment (top) and the AuNP-mediated photoporation sample (bottom). Samples are imaged, reconstructed and divided into zones. In each zone, a local positive fraction is computed (\(\tau _{xy}^\text {pos} = N_{xy}^\text {fluo}/N_{xy}^\text {total}\)) and mapped over the reconstructed sample (example using a \(I_\text {max} \simeq {2.6}~{\hbox {J cm}^{-2}}\)). From left to right: Phase contrast images (scale bars \({500 }{\upmu {\hbox {m}}}\)), FITC-fluorescence microscopy images, maps of the local positive fraction (\(\tau _{xy}^\text {pos}\)) computed from both images and finally the plot of the local positive fraction \(\tau _{xy}^\text {pos}\) (red) and the mean uptake efficiency \(\tau _{xy}^\text {fluo}\) (green) versus the intensity along the laser profile. \(\tau _{xy}^\text {fluo}\) is measured with intra-cellular FITC fluorescence intensity. \(\tau _{xy}^\text {pos}\) and \(\tau _{xy}^\text {fluo}\) are eventually averaged along the direction perpendicular to the long axis of the laser beam to obtain the correlation with the different values of \(I_\text {max}\) (resp. red and green) showing an onset between \({0.25}~{\hbox {J cm}^{-2}}\) to \({0.3}~{\hbox {J cm}^{-2}}\) for \(\tau _{xy}^\text {pos}\), which can be related to the VNB onset