Figure 15.

Mechanical membrane permeabilization by direct contact. (A) Scrape loading, where a rubber spatula or similar scraping object can be used to simultaneously dislodge cells and permeabilize them. (B) Bead loading, wherein micron-scale beads can be rolled across a cell monolayer for controlled cell injury via collisions. (C) Filtroporation, where a solution of cells is passed through holes in filter membranes, such as a track-etched polycarbonate filter. (D) Microfluidic cell squeezing, where cells membranes are disrupted by rapid deformation that occurs with passage through microfabricated constrictions. (E) Permeabilization with nanoneedle arrays. (i) The array is first centrifuged or otherwise pressed against cells adhered to a rigid substrate. (ii) The array is then removed to enable cargo influx through membrane disruptions in the target cells.