Molecular gates have received considerable attention as drug delivery systems. More recently, aptamer-based gates showed great potential in overcoming major challenges associated with drug delivery by means of nanocapsules. Based on a switchable aptamer nanovalves approach, we herein report the first demonstration of an engineered single molecular gate that directs nanoparticles to cancer cells and subsequently delivers the payload in a controllable fashion. © 2012 The Royal Society of Chemistry.