Cell internalization SELEX: in vitro selection for molecules that internalize into cells.

Aptamer technology allows for the selection of nucleic acids that can bind to and enter cells. By establishing conditions during the selection that eliminate cell-surface binders as well as non-internalizing RNAs, only extremely tightly bound aptamers or aptamers that have internalized are recovered. We describe a general scheme for selecting RNA molecules that are capable of internalizing into cells and discuss the factors that can affect a successful selection. Much like standard cell-surface selections, these types of selections should be possible independent of detailed knowledge of the cell surface.