Abstract: A method and apparatus for promoting the delivery of a molecule across a cell membrane comprises delivering a molecule to a delivery site of a region of tissue surrounding the cell membrane. A suction component applies a suction through a suction tip that surrounds the surface of the delivery site creating a seal to promote delivery of the molecule across the cell membrane. The application of the suction is controlled to create a predetermined negative pressure for a predetermined period of time before releasing the negative pressure. Suction is used to enhance permeabilization and transfection of cells. The technique can be used to enhance the uptake and subsequent transfection and expression of plasmid DNA vaccines, mRNA vaccines and other nucleic acid molecules, that are introduced subcutaneously. It can be used in combination with coated microneedles.