Membrane permeabilization of adherent cells with laser-induced cavitation bubbles

Abstract

Strongly oscillating bubbles close to cells can cause the opening of the cell’s membrane, thus to stimulate the uptake of molecules from the exterior. However, the volume oscillations of bubbles induce complex fluid flows, especially when bubble-bubble interaction takes place. Here, we report on an experiment where a single cavitation bubble is created close to a layer of adherent HeLa cells. The interaction distance between the bubble and the cell layer is controlled by adjusting the focus of the pulsed laser light, which creates the cavitation bubble. The dynamics of the bubble and the cells is recorded with high-speed photography. The poration of the cells is probed with different fluorescent stains to distinguish viable and permanent poration and programmed cell death (apopotosis). Quantitative data are presented as a function of the radial distance from the stagnation point. Our main finding is the importance of the asymmetrical collapse and the high-speed jet flow: After impact of the jet onto the substrate a strong boundary layer flow is responsible for shearing the cells.