Cell loading with laser-generated stress waves: The role of the stress gradient

Purpose. To determine the dependence of the permeabilzation of the plasma m embrane on the characteristics of laser-generated stress waves. Methods. Laser pulses can generate stress waves by ablation. Depending on t he laser wavelength, fluence, and target material, stress waves of differen t characteristics (rise time, peak stress) can be generated. Human red bloo d cells were subjected to stress waves and the permeability changes were me asured by uptake of extracellular dye molecules. Results. A fast rise time (high stress gradient) of the stress wave was req uired for the permeabilization of the plasma membrane. While the membrane w as permeable, the cells could rapidly uptake molecules From the surrounding medium by diffusion. Conclusions. Stress waves provide a potentially powerful tool for drug deli very.