Figure 4.

Particle dynamics at the outer cell membrane. (a, c, and e) Confocal microscopy images of particles interacting with the cell membrane and corresponding trajectories. The white arrows denote the particles of interest and the colored lines their trajectories (with the color indicating elapsed time). Scale bars = 2 μm. (b, d, and f), Zoomed-in versions of the trajectories (with the color indicating elapsed time). Scale bars = 1 μm. (a, b) 200 nm particle adsorbed onto a HEK cell membrane. The particle remains adsorbed for over 100 s and does not move substantially (≲ 1 μm) along the membrane. (c, d) 100 nm particle adsorbed onto a HEK cell membrane. In contrast to the previous example, this particle traverses several micrometers along the membrane within a few seconds. (e, f) 100 nm particle interacting with an MDA-MB-231 cell. The particle repeatedly adsorbs and desorbs from the cell membrane before finally adsorbing for 6.36 s, followed by being internalized into the cell.