Gated Mesoporous SiO2 Nanoparticles Using K+-Stabilized G-Quadruplexes

The K+‐induced formation of G‐quadruplexes provides a versatile motif to lock or unlock substrates trapped in the pores of mesoporous SiO2 nanoparticles, MP‐SiO2 NPs. In one system, the substrate is locked in the MP‐SiO2 NPs by K+‐ion‐stabilized G‐quadruplex units, and the pores are unlocked by the elimination of K+ ions using Kryptofix [2.2.2] (KP) or 18‐crown‐6‐ether (CE) from the G‐quadruplexes. In the second system, the substrate is locked in the pores by means of K+‐stabilized aptameric G‐quadruplex/thrombin units. Unlocking of the pores is triggered by the dissociation of the aptamer/thrombin complexes through the KP‐ or CE‐mediated elimination of the stabilizing K+ ions. In the third system, duplex DNA units lock the pores of MP‐SiO2 NPs, and the release of the entrapped substrate is stimulated by the K+‐ion‐induced dissociation of the duplex caps through the formation of the K+‐stabilized G‐quadruplexes. The latter system is further implemented to release the anti‐cancer drug, doxorubicin, in the presence of K+ ions, from the MP‐SiO2 NPs. Preliminary intracellular experiments reveal that doxorubicin‐loaded MP‐SiO2 NPs lead to effective death of breast cancer cells. K+‐ion‐stabilized G‐quadruplexes act as locks for the entrapment of substrates in mesoporous silica nanoparticles. The pores are unlocked by the Kryptofix [2.2.2] (KP) through the removal of the K+ ions. Also, programmed duplex structures lock the anti‐cancer drug doxorubicin in mesoporous silica nanoparticles. The pores are unlocked by the separation of the duplex through the formation of a G‐quadruplex.