The design of small interfering RNA (siRNA) delivery materials showing efficacy in vivo is at the forefront of nanotherapeutics research. Polyurea (PURE-type) dendrimers, are ‘smart’ biocompatible 3D polymers that unveil a dynamic and elegant back-folding mechanism involving hydrogen bonding between primary amines at the surface and tertiary amines and ureas at the core. Similarly to a biological proton pump, they are able to automatically and reversibly rework their conformation in response to pH stimulus. Herein, we show that PURE-G4 is an useful gene silencing platform showing no cellular toxicity. As a proof-of-concept we investigated the PURE-G4-siRNA dendriplex, which showed to be an attractive platform with high transfection efficacy. The simplicity associated to the complexation of siRNA with polyurea dendrimers makes them a powerful tool for efficient cytosolic siRNA delivery.