Fig. 1. Ballistic injection and tracking of nanoparticles embedded in the cytoplasm of adherent cells. (A) Schematic of the method of ballistic injection used to efficiently transfer nanoparticles to the cytoplasm of adherent cells. (1) Macrocarriers coated with 100 nm fluorescent nanoparticles are placed into a hepta adapter. (2) Pressurized helium gas (2200 psi) flows through the adapter, and (3) accelerate the macrocarriers toward a stopping screen. (4) Macrocarriers are stopped by the screen and (5) nanoparticles cross the plasma membrane and penetrate the cytoplasm of adherent cells. Typical mean squared displacements (MSD) of nanoparticles in unsheared (B) and sheared (C) serum-starved Swiss 3T3 fibroblasts. Ensemble average MSD is overlaid for unsheared (red) and sheared (blue) fibroblasts. The insets show typical trajectories of the centroids of nanoparticles imbedded in the cytoplasm of cells before (B) and after (C) the application of 40 minutes of shear flow (shear stress, 9.4 dyn/cm²). Bars in insets, 50 nm.