Elevation of plasma membrane permeability upon laser irradiation of extracellular microbubbles

Laser-mediated gene transfection has received much attention as a new method for targeted gene therapy because of the high controllability of laser energy and direction. In this report, we describe a combination laser-microbubble system that enables membrane-impermeable molecules to penetrate cell membranes. The main theories we apply are optical breakdown and photoacoustic generation, which are induced by laser irradiation. Firstly, different types of laser light (Ar-green, Novus Varia poly-wavelength and Nd:YAG laser) were adopted to blast liposome microbubble contrast medium; subsequently, the Nd:YAG laser (1064 nm, 4 ns), which could successfully blast microbubbles, and ultrasound were used in combination to irradiate a mixture of liposome microbubbles and retinoblastoma (Rb) cells. After irradiation, membrane permeability was evaluated by flow cytometric assay using propidium iodide (PI) and fluorescein diacetate (FDA). The proportion of permeabilized resealed cells was affected by changes in the light energy. All of the Nd:YAG laser, Nd:YAG combination laser-microbubble and combination ultrasound-microbubble systems were able to permeabilize the Rb cells. These results suggest that this combination laser-microbubble system is a new means of delivering exogenous materials into living cells.