Fig. 4

a A model of adding oral pathogen P. gingivalis proteins K2 and fluorescent dye (Alexa Fluor dextran 647, red colour) to confluent gingival epithelial monolayers, to track pathological changes of epithelial integrity at a time course. Paracellular pathway of movement of the labelled dextran (red) was shown at 15 and 30 min observation times. b and c 2D z-stacking images in the beginning (T = 15 min) and end of the exposure time-lapse period (T = 1.5 h): left panels were the overlay images of cells (green nuclei) with far-red dye channel; right panels were far-red dye channel only. d 3D reconstruction time lapse images from (b-c) on live cells challenged with bacterial protein (K2) (green colour: cell nuclei; red colour: dye). e Another example of projection of 2D z-stack imaging plus a position point. f A 3D reconstruction image with a position point (e) on live cells challenged with P. gingivalis bacterial protein (Ka) at 30 min (green colour: Ka protein; red colour: nuclei)