Chemically facilitated microinjection of proteins into intact monolayers of tissue culture cells

Microinjection of physiologic quantities of macromolecules into tissue culture cells can facilitate the study of the biological effects of such macromolecules. In this communication, we describe a chemical technique which can be used to microinject proteins into monolayers of intact cells. Protein is loaded into erthrocyte ghosts, and the ghosts are then fused to the monolayer with polyethylene glycol 1000. Receipient cells can be injected with an efficiency of greater than 90% and contain an average of 3.8 X 10(6) microinjected molecules per cell. This technique circumvents certain problems encountered in virus-induced microinjection.